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Journal articles on the topic 'Lac Operon'

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Published: 4 June 2021

Last updated: 1 February 2022

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1

Zeng, Lin, Satarupa Das, and Robert A. Burne. "Utilization of Lactose and Galactose by Streptococcus mutans: Transport, Toxicity, and Carbon Catabolite Repression." Journal of Bacteriology 192, no. 9 (February 26, 2010): 2434–44. http://dx.doi.org/10.1128/jb.01624-09.

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ABSTRACT Abundant in milk and other dairy products, lactose is considered to have an important role in oral microbial ecology and can contribute to caries development in both adults and young children. To better understand the metabolism of lactose and galactose by Streptococcus mutans, the major etiological agent of human tooth decay, a genetic analysis of the tagatose-6-phosphate (lac) and Leloir (gal) pathways was performed in strain UA159. Deletion of each gene in the lac operon caused various alterations in expression of a PlacA -cat promoter fusion and defects in growth on either lactose (lacA, lacB, lacF, lacE, and lacG), galactose (lacA, lacB, lacD, and lacG) or both sugars (lacA, lacB, and lacG). Failure to grow in the presence of galactose or lactose by certain lac mutants appeared to arise from the accumulation of intermediates of galactose metabolism, particularly galatose-6-phosphate. The glucose- and lactose-PTS permeases, EIIMan and EIILac, respectively, were shown to be the only effective transporters of galactose in S. mutans. Furthermore, disruption of manL, encoding EIIABMan, led to increased resistance to glucose-mediated CCR when lactose was used to induce the lac operon, but resulted in reduced lac gene expression in cells growing on galactose. Collectively, the results reveal a remarkably high degree of complexity in the regulation of lactose/galactose catabolism.

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2

Cooper, Robert A. "Teaching the Big Ideas of Biology with Operon Models." American Biology Teacher 77, no. 1 (January 1, 2015): 30–39. http://dx.doi.org/10.1525/abt.2015.77.1.5.

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This paper presents an activity that engages students in model-based reasoning, requiring them to predict the behavior of the trp and lac operons under different environmental conditions. Students are presented six scenarios for the trp operon and five for the lac operon. In most of the scenarios, specific mutations have occurred in genetic elements of the system that alter the behavior from the norm. Students are also challenged to relate their understanding of operon behavior to the “Big Ideas” of homeostasis, evolution, information, interactions, and emergent properties. By using operons to teach students to reason with models of complex systems and understand broad themes, we equip them with powerful skills and ideas that form a solid foundation for their future learning in biology.

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3

Andrews, Ken J. "Lac Operon. Lewis J. Kleinsmith." Quarterly Review of Biology 64, no. 4 (December 1989): 543. http://dx.doi.org/10.1086/416577.

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4

Lewis, Mitchell. "Allostery and the lac Operon." Journal of Molecular Biology 425, no. 13 (July 2013): 2309–16. http://dx.doi.org/10.1016/j.jmb.2013.03.003.

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5

Roderick, Steven L. "The lac operon galactoside acetyltransferase." Comptes Rendus Biologies 328, no. 6 (June 2005): 568–75. http://dx.doi.org/10.1016/j.crvi.2005.03.005.

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6

Vaughan, Elaine E., R. David Pridmore, and Beat Mollet. "Transcriptional Regulation and Evolution of Lactose Genes in the Galactose-Lactose Operon of Lactococcus lactisNCDO2054." Journal of Bacteriology 180, no. 18 (September 15, 1998): 4893–902. http://dx.doi.org/10.1128/jb.180.18.4893-4902.1998.

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ABSTRACT The genetics of lactose utilization within the slow-lactose-fermenting Lactococcus lactis strain NCDO2054 was studied with respect to the organization, expression, and evolution of the lac genes. Initially the β-galactosidase gene (lacZ) was cloned by complementation of an Escherichia coli mutant on a 7-kb HpaI fragment. Nucleotide sequence analysis of the complete fragment revealed part of a gal-lac operon, and the genes were characterized by inactivation and complementation analyses and in vitro enzyme activity measurements. The gene order isgalK-galT-lacA-lacZ-galE; the gal genes encode enzymes of the Leloir pathway for galactose metabolism, andlacA encodes a galactoside acetyltransferase. ThegalT and galE genes of L. lactisLM0230 (a lactose plasmid-cured derivative of the fast-lactose-fermenting L. lactis C2) were highly similar at the nucleotide sequence level to their counterparts in strain NCDO2054 and, furthermore, had the same gene order except for the presence of the intervening lacA-lacZ strain NCDO2054. Analysis of mRNA for the gal and lac genes revealed an unusual transcriptional organization for the operon, with a surprisingly large number of transcriptional units. The regulation of the lac genes was further investigated by using fusions consisting of putative promoter fragments and the promoterless β-glucuronidase gene (gusA) from E. coli, which identified three lactose-inducible intergenic promoters in the gal-lac operon. The greater similarity of thelacA and lacZ genes to homologs in gram-negative organisms than to those of gram-positive bacteria, in contrast to the homologies of the gal genes, suggests that the genes within the gal operon of L. lactisNCDO2054 have been recently acquired. Thus, thelacA-lacZ genes appear to have engaged the promoters of thegal operon in order to direct and control their expression.

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7

Stewart, Valley, and Peggy J. Bledsoe. "Substitutions at Auxiliary Operator O3 Enhance Repression by Nitrate-Responsive Regulator NarL at Synthetic lac Control Regions in Escherichia coli K-12." Journal of Bacteriology 190, no. 1 (October 26, 2007): 428–33. http://dx.doi.org/10.1128/jb.01431-07.

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ABSTRACT We constructed monocopy lac operon control regions in which the operators O1-lac and O3-lac were replaced by NarL and NarP binding sites from the nirB or napF operon control regions. The results support the hypothesis that DNA-bound dimers of phospho-NarL can participate in higher-order cooperative interactions.

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8

Malakar, Pushkar. "Pre-induced Lac Operon Effect on Non Specific Sugars: Pre-culture Effect is Dependent on Strength of Induction, Exponential Phase and Substrate Concentration." Open Microbiology Journal 9, no. 1 (June 23, 2015): 8–13. http://dx.doi.org/10.2174/1874285801509010008.

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The source and history of the cell plays an important role in influencing the phenotypic properties of the organism in a particular environmental condition. Pre-induced lac operon provides benefit on lactose environment. During metabolism lactose is broken down into glucose and galactose. The fate of cells with pre-induced lac operon on glucose and galactose milieu is not known. The influence of nutritional status of the medium, level of pre-induction and growth phase on pre-culture effect is not investigated. Effect of pre-induced lac operon on non specific sugars along with the factors that influence this effect was enumerated in the present study. Results of this present study indicate that pre-induced lac operon provide benefit in terms of growth on galactose milieu. This study also suggests that Pre induced lac operon effect depends on the (i) strength of induction in the pre-culture, (ii) nutritional content of the environment and (iii) exponential growth phase of the organism. The above study will help in the better characterization of the pre culture effect. It will also help in the better understanding of the relation between gene expression and growth physiology.

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9

Yang, Xiaoli, Bin Chen, Yifan Cai, and Charles Tseng. "Understanding the lac operon with GeneAct." International Journal of Computational Biology and Drug Design 8, no. 2 (2015): 168. http://dx.doi.org/10.1504/ijcbdd.2015.071127.

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10

Egel, Richard. "The ‘lac’ operon: an irrelevant paradox?" Trends in Genetics 4, no. 2 (February 1988): 31. http://dx.doi.org/10.1016/0168-9525(88)90062-5.

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11

Sharma, Vijay K., and Richard L. Zuerner. "Role of hha and ler in Transcriptional Regulation of the esp Operon of Enterohemorrhagic Escherichia coli O157:H7." Journal of Bacteriology 186, no. 21 (November 1, 2004): 7290–301. http://dx.doi.org/10.1128/jb.186.21.7290-7301.2004.

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ABSTRACT The locus of enterocyte effacement (LEE), which includes five major operons (LEE1 through LEE4 and tir), enables enterohemorrhagic Escherichia coli (EHEC) O157:H7 to produce attaching and effacing lesions on host cells. Expression of LEE2, LEE3, and tir is positively regulated by ler, a gene located in LEE1. Transcriptional regulation of the esp operon (LEE4), however, is not well defined. Transposon mutagenesis was used to identify transcriptional regulators of the esp operon by screening for mutants with increased β-galactosidase activity in an EHEC O157:H7 strain harboring an esp::lac transcriptional fusion. All mutants with significant increases in β-galactosidase activity had transposon insertions in hha (hha::Tn). Specific complementation of the hha::Tn mutation with a plasmid-encoded copy of hha reduced β-galactosidase activity to the level expressed in the parental esp::lac strain. Purified Hha, however, bound poorly to the esp promoter, suggesting that Hha might repress the transcription of a positive regulator of esp. Transposon mutagenesis of a Δhha esp::lac strain expressing elevated levels of β-galactosidase resulted in ler mutants with reduced β-galactosidase activity. Purified Hha bound to the ler promoter with a higher affinity, and complementation of a Δhha mutation in a Δhha ler::lac strain repressed β-galactosidase activity to the level expressed in a ler::lac strain. A positive regulatory role of ler in esp expression was demonstrated by specific binding of Ler to the esp promoter, reduced expression of β-galactosidase in Δler esp::lac strains with and without hha, and severalfold-increased transcription of ler and espA in strains lacking hha. These results indicate that hha-mediated repression of ler causes reduced expression of the esp operon.

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12

Batt, C. A., M. S. Bodis, S. K. Picataggio, M. C. Claps, S. Jamas, and A. J. Sinskey. "Analysis of xylose operon regulation by Mud (Apr, lac) fusion: trans effect of plasmid coded xylose operon." Canadian Journal of Microbiology 31, no. 10 (October 1, 1985): 930–33. http://dx.doi.org/10.1139/m85-174.

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The regulation of the Escherichia coli xylose operon was investigated by Mud (Apr, lac) fusion. β-Galactosidase activity from the xyl::Mud (Apr, lac) fusion was induced by xylose but not by arabinose and repressed by glucose. The chromosomal fusion was used to analyze the trans effect of plasmid borne xyl genes. The xylA gene repressed the expression of the xyl::Mud (Apr, lac) but xylose isomerase activity was not required for this repression. The results suggest that the regulation of the xylose operon may not be exclusively by a separate regulatory element but that the xylA gene may control the expression of the operon.

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13

Lankester, Anna, Shafayeth Ahmed, Lisa E. Lamberte, Rachel A. Kettles, and David C. Grainger. "The Escherichia coli multiple antibiotic resistance activator protein represses transcription of the lac operon." Biochemical Society Transactions 47, no. 2 (March 8, 2019): 671–77. http://dx.doi.org/10.1042/bst20180498.

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AbstractIn Escherichia coli, the marRAB operon is a determinant for antibiotic resistance. Such phenotypes require the encoded transcription factor MarA that activates efflux pump expression. To better understand all genes controlled by MarA, we recently mapped binding of the regulator across the E. coli genome. As expected, many MarA targets were adjacent to genes encoding stress response systems. Surprisingly, one MarA-binding site overlapped the lac operon regulatory region. Here, we show that MarA specifically targets this locus and can block transcription of the lac genes. Repression is mediated by binding of MarA to a site overlapping the lacP1 promoter −35 element. Control of the lac operon by MarA does not impact antibiotic resistance.

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14

Santillán, M., M. C. Mackey, and E. S. Zeron. "Origin of Bistability in the lac Operon." Biophysical Journal 92, no. 11 (June 2007): 3830–42. http://dx.doi.org/10.1529/biophysj.106.101717.

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15

Wang, Xing-Guo, Laurence R. Olsen, and Steven L. Roderick. "Structure of the lac Operon Galactoside Acetyltransferase." Structure 10, no. 4 (April 2002): 581–88. http://dx.doi.org/10.1016/s0969-2126(02)00741-4.

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16

Stefanski, Katherine M., Grant E. Gardner, and Rebecca L. Seipelt-Thiemann. "Development of aLacOperon Concept Inventory (LOCI)." CBE—Life Sciences Education 15, no. 2 (June 2016): ar24. http://dx.doi.org/10.1187/cbe.15-07-0162.

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Concept inventories (CIs) are valuable tools for educators that assess student achievement and identify misconceptions held by students. Results of student responses can be used to adjust or develop new instructional methods for a given topic. The regulation of gene expression in both prokaryotes and eukaryotes is an important concept in genetics and one that is particularly challenging for undergraduate students. As part of a larger study examining instructional methods related to gene regulation, the authors developed a 12-item CI assessing student knowledge of the lac operon. Using an established protocol, the authors wrote open-ended questions and conducted in-class testing with undergraduate microbiology and genetics students to discover common errors made by students about the lac operon and to determine aspects of item validity. Using these results, we constructed a 12-item multiple-choice lac operon CI called the Lac Operon Concept Inventory (LOCI), The LOCI was reviewed by two experts in the field for content validity. The LOCI underwent item analysis and was assessed for reliability with a sample of undergraduate genetics students (n = 115). The data obtained were found to be valid and reliable (coefficient alpha = 0.994) with adequate discriminatory power and item difficulty.

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17

Gosalbes, María José, Vicente Monedero, and Gaspar Pérez-Martínez. "Elements Involved in Catabolite Repression and Substrate Induction of the Lactose Operon in Lactobacillus casei." Journal of Bacteriology 181, no. 13 (July 1, 1999): 3928–34. http://dx.doi.org/10.1128/jb.181.13.3928-3934.1999.

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ABSTRACT In Lactobacillus casei ATCC 393, the chromosomally encoded lactose operon, lacTEGF, encodes an antiterminator protein (LacT), lactose-specific phosphoenolpyruvate-dependent phosphotransferase system (PTS) elements (LacE and LacF), and a phospho-β-galactosidase. lacT, lacE, andlacF mutant strains were constructed by double crossover. The lacT strain displayed constitutive termination at a ribonucleic antiterminator (RAT) site, whereas lacE andlacF mutants showed an inducer-independent antiterminator activity, as shown analysis of enzyme activity obtained from transcriptional fusions of lac promoter (lacp) and lacpΔRAT with the Escherichia coli gusAgene in the different lac mutants. These results strongly suggest that in vivo under noninducing conditions, the lactose-specific PTS elements negatively modulate LacT activity. Northern blot analysis detected a 100-nucleotide transcript starting at the transcription start site and ending a consensus RAT sequence and terminator region. In a ccpA mutant, transcription initiation was derepressed but no elongation through the terminator was observed in the presence of glucose and the inducing sugar, lactose. Full expression oflacTEGF was found only in a man ccpA double mutant, indicating that PTS elements are involved in the CcpA-independent catabolite repression mechanism probably via LacT.

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18

Lapierre, Luciane, Beat Mollet, and Jacques-Edouard Germond. "Regulation and Adaptive Evolution of Lactose Operon Expression in Lactobacillus delbrueckii." Journal of Bacteriology 184, no. 4 (February 15, 2002): 928–35. http://dx.doi.org/10.1128/jb.184.4.928-935.2002.

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ABSTRACT Lactobacillus delbrueckii subsp. bulgaricus and L. delbrueckii subsp. lactis are both used in the dairy industry as homofermentative lactic acid bacteria in the production of fermented milk products. After selective pressure for the fast fermentation of milk in the manufacture of yogurts, L. delbrueckii subsp. bulgaricus loses its ability to regulate lac operon expression. A series of mutations led to the constitutive expression of the lac genes. A complex of insertion sequence (IS) elements (ISL4 inside ISL5), inserted at the border of the lac promoter, induced the loss of the palindromic structure of one of the operators likely involved in the binding of regulatory factors. A lac repressor gene was discovered downstream of the β-galactosidase gene of L. delbrueckii subsp. lactis and was shown to be inactivated by several mutations in L. delbrueckii subsp. bulgaricus. Regulatory mechanisms of the lac gene expression of L. delbrueckii subsp. bulgaricus and L. delbrueckii subsp. lactis were compared by heterologous expression in Lactococcus lactis of the two lac promoters in front of a reporter gene (β-glucuronidase) in the presence or absence of the lac repressor gene. Insertion of the complex of IS elements in the lac promoter of L. delbrueckii subsp. bulgaricus increased the promoter's activity but did not prevent repressor binding; rather, it increased the affinity of the repressor for the promoter. Inactivation of the lac repressor by mutations was then necessary to induce the constitutive expression of the lac genes in L. delbrueckii subsp. bulgaricus.

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19

Gliese, Nicole, Viola Khodaverdi, Max Schobert, and Helmut Görisch. "AgmR controls transcription of a regulon with several operons essential for ethanol oxidation in Pseudomonas aeruginosa ATCC 17933." Microbiology 150, no. 6 (June 1, 2004): 1851–57. http://dx.doi.org/10.1099/mic.0.26882-0.

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The response regulator AgmR was identified to be involved in the regulation of the quinoprotein ethanol oxidation system of Pseudomonas aeruginosa ATCC 17933. Interruption of the agmR gene by insertion of a kanamycin-resistance cassette resulted in mutant NG3, unable to grow on ethanol. After complementation with the intact agmR gene, growth on ethanol was restored. Transcriptional lacZ fusions were used to identify four operons which are regulated by the AgmR protein: the exaA operon encodes the pyrroloquinoline quinone (PQQ)-dependent ethanol dehydrogenase, the exaBC operon encodes a soluble cytochrome c 550 and an aldehyde dehydrogenase, the pqqABCDE operon carries the PQQ biosynthetic genes, and operon exaDE encodes a two-component regulatory system which controls transcription of the exaA operon. Transcription of exaA was restored by transformation of NG3 with a pUCP20T derivative carrying the exaDE genes under lac-promoter control. These data indicate that the AgmR response regulator and the exaDE two-component regulatory system are organized in a hierarchical manner. Gene PA1977, which appears to form an operon with the agmR gene, was found to be non-essential for growth on ethanol.

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20

Hall, B. G., P. W. Betts, and J. C. Wootton. "DNA sequence analysis of artificially evolved ebg enzyme and ebg repressor genes." Genetics 123, no. 4 (December 1, 1989): 635–48. http://dx.doi.org/10.1093/genetics/123.4.635.

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Abstract The ebg system has been used as a model to study the artificial selection of new catalytic functions of enzymes and of inducer specificities of repressors. A series of mutant enzymes with altered catalytic specificities were previously characterized biochemically as were the changes in inducer specificities of mutant, but fully functional, repressors. The wild type ebg operon has been sequenced, and the sequence differences of the mutant enzymes and repressors have been determined. We now report that, contrary to our previous understanding, ebg enzyme contains 180-kD alpha-subunits and 20-kD beta-subunits, both of which are required for full activity. Mutations that dramatically affect substrate specificity and catalytic efficiency lie in two distinct regions, both well outside of the active site region. Mutations that affect inducer specificity of the ebg repressor lie within predicted sugar binding domains. Comparisons of the ebg beta-galactosidase and repressor with homologous proteins of the Escherichia coli and Klebsiella pneumoniae lac operons, and with the galactose operon repressor, suggest that the ebg and lac operons diverged prior to the divergence of E. coli from Klebsiella. One case of a triple substitution as the consequence of a single event is reported, and the implications of that observation for mechanisms of spontaneous mutagenesis are discussed.

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21

Borukhov, Sergei, and Jookyung Lee. "RNA polymerase structure and function at lac operon." Comptes Rendus Biologies 328, no. 6 (June 2005): 576–87. http://dx.doi.org/10.1016/j.crvi.2005.03.007.

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22

La Penna, Giovanni, and Angelo Perico. "Wrapped-Around Models for the Lac Operon Complex." Biophysical Journal 98, no. 12 (June 2010): 2964–73. http://dx.doi.org/10.1016/j.bpj.2010.03.024.

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23

Sendy, Bandar, David J. Lee, Stephen J. W. Busby, and Jack A. Bryant. "RNA polymerase supply and flux through the lac operon in Escherichia coli." Philosophical Transactions of the Royal Society B: Biological Sciences 371, no. 1707 (November 5, 2016): 20160080. http://dx.doi.org/10.1098/rstb.2016.0080.

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Chromatin immunoprecipitation, followed by quantification of immunoprecipitated DNA, can be used to measure RNA polymerase binding to any DNA segment in Escherichia coli . By calibrating measurements against the signal from a single RNA polymerase bound at a single promoter, we can calculate both promoter occupancy levels and the flux of transcribing RNA polymerase through transcription units. Here, we have applied the methodology to the E. coli lactose operon promoter. We confirm that promoter occupancy is limited by recruitment and that the supply of RNA polymerase to the lactose operon promoter depends on its location in the E. coli chromosome. Measurements of RNA polymerase binding to DNA segments within the lactose operon show that flux of RNA polymerase through the operon is low, with, on average, over 18 s elapsing between the passage of transcribing polymerases. Similar low levels of flux were found when semi-synthetic promoters were used to drive transcript initiation, even when the promoter elements were changed to ensure full occupancy of the promoter by RNA polymerase. This article is part of the themed issue ‘The new bacteriology’.

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24

Stewart, Valley, and Peggy J. Bledsoe. "Synthetic lac Operator Substitutions for Studying the Nitrate- and Nitrite-Responsive NarX-NarL and NarQ-NarP Two-Component Regulatory Systems of Escherichia coli K-12." Journal of Bacteriology 185, no. 7 (April 1, 2003): 2104–11. http://dx.doi.org/10.1128/jb.185.7.2104-2111.2003.

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ABSTRACT The NarX and NarQ sensor-histidine kinases control phosphorylation of the NarL and NarP response regulators in response to the respiratory oxidants nitrate and nitrite. Target operon transcription is activated by the Fnr protein in response to anaerobiosis, and it is further activated and/or repressed by the phospho-NarL and phospho-NarP proteins, which bind to heptamer DNA sequences. The location and arrangement of heptamers vary widely among different target operon control regions. We have constructed a series of monocopy lac operon control region constructs in which the primary operator O1-lac has been replaced by 7-2-7 heptamer pairs from the nrfA, nirB, napF, and fdnG operon control regions. These constructs provide tools for dissecting various aspects of ligand interactions with sensor-kinases, sensor interactions with response regulators, and phospho-response regulator interactions with DNA targets. Expression of the lacZ gene from these constructs was repressed to various degrees by nitrate and nitrite. In response to nitrate, the nrfA and nirB operon 7-2-7 heptamer pairs at operator O1 each mediated greater than 100-fold repression of lacZ gene expression, whereas the napF operon 7-2-7 heptamer pair mediated approximately tenfold repression. Introduction of narL, narP, narX, and narQ null alleles in various combinations allowed the in vivo interactions between different sensor-regulator pairs to be evaluated and compared.

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25

Angelova, Maia, and Asma Ben-Halim. "Dynamic model of gene regulation for the lac operon." Journal of Physics: Conference Series 286 (March 1, 2011): 012007. http://dx.doi.org/10.1088/1742-6596/286/1/012007.

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26

Veliz-Cuba, Alan, and Brandilyn Stigler. "Boolean Models Can Explain Bistability in the lac Operon." Journal of Computational Biology 18, no. 6 (June 2011): 783–94. http://dx.doi.org/10.1089/cmb.2011.0031.

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27

Buvinger, W. E., and M. Riley. "Regulatory region of the divergent Klebsiella pneumoniae lac operon." Journal of Bacteriology 163, no. 3 (1985): 858–62. http://dx.doi.org/10.1128/jb.163.3.858-862.1985.

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28

Montalva-Medel, Marco, Thomas Ledger, Gonzalo A. Ruz, and Eric Goles. "Lac Operon Boolean Models: Dynamical Robustness and Alternative Improvements." Mathematics 9, no. 6 (March 11, 2021): 600. http://dx.doi.org/10.3390/math9060600.

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In Veliz-Cuba and Stigler 2011, Boolean models were proposed for the lac operon in Escherichia coli capable of reproducing the operon being OFF, ON and bistable for three (low, medium and high) and two (low and high) parameters, representing the concentration ranges of lactose and glucose, respectively. Of these 6 possible combinations of parameters, 5 produce results that match with the biological experiments of Ozbudak et al., 2004. In the remaining one, the models predict the operon being OFF while biological experiments show a bistable behavior. In this paper, we first explore the robustness of two such models in the sense of how much its attractors change against any deterministic update schedule. We prove mathematically that, in cases where there is no bistability, all the dynamics in both models lack limit cycles while, when bistability appears, one model presents 30% of its dynamics with limit cycles while the other only 23%. Secondly, we propose two alternative improvements consisting of biologically supported modifications; one in which both models match with Ozbudak et al., 2004 in all 6 combinations of parameters and, the other one, where we increase the number of parameters to 9, matching in all these cases with the biological experiments of Ozbudak et al., 2004.

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29

Kalousek, S., and W. Lubitz. "High-level poly(β-hydroxybutyrate) production in recombinantEscherichia coliin sugar-free, complex medium." Canadian Journal of Microbiology 41, no. 13 (December 15, 1995): 216–21. http://dx.doi.org/10.1139/m95-190.

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The poly(β-hydroxybutyrate) (PHB) biosynthetic genes of Alcaligenes eutrophus that are organized in a single operon (phbCAB) have been cloned in Escherichia coli, where the expression of the genes in the wild-type phb operon from plasmid p4A leads to the formation of 10 or 50–80% PHB/cell dry mass when the cells are grown in Luria–Bertani medium alone or supplemented with 1% glucose (w/v), respectively. To further stimulate PHB formation independent of additional carbon source in Luria–Bertani medium, molecular methods have been applied to provide efficient E. coli transcription and translation signals for the PHB synthase gene (phbC). The lac promoter present upstream of the phbC sequence allows its expression to be controlled depending on the LacI status of the chosen host strain. The T7 gene 10 ribosome binding site is utilized for translational initiation. PHB production in E. coli was compared in strains either harboring plasmid p4A containing the intact phbCAB operon or harboring two compatible plasmids carrying the β-ketothiolase (phbA) and acetoacetyl-CoA-reductase (phbB) genes under transcriptional control of the lac promoter–operator region and also carrying separately the phbC gene with its natural promoter sequence. In addition, plasmid pSYN allowing the phbC gene to be expressed under new transcription and translation conditions combined with plasmid pUMS gave rise to the same amount of PHB formation (70% PHB cell dry mass) in E. coli when grown in Luria–Bertani medium without glucose supplement.Key words: PHB production, engineered phbCAB operon.

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30

Tsai, Yu-Kuo, Hung-Wen Chen, Ta-Chun Lo, and Thy-Hou Lin. "Specific point mutations in Lactobacillus casei ATCC 27139 cause a phenotype switch from Lac− to Lac+." Microbiology 155, no. 3 (March 1, 2009): 751–60. http://dx.doi.org/10.1099/mic.0.021907-0.

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Lactose metabolism is a changeable phenotype in strains of Lactobacillus casei. In this study, we found that L. casei ATCC 27139 was unable to utilize lactose. However, when exposed to lactose as the sole carbon source, spontaneous Lac+ clones could be obtained. A gene cluster (lacTEGF–galKETRM) involved in the metabolism of lactose and galactose in L. casei ATCC 27139 (Lac−) and its Lac+ revertant (designated strain R1) was sequenced and characterized. We found that only one nucleotide, located in the lacTEGF promoter (lacTp), of the two lac–gal gene clusters was different. The protein sequence identity between the lac–gal gene cluster and those reported previously for some L. casei (Lac+) strains was high; namely, 96–100 % identity was found and no premature stop codon was identified. A single point mutation located within the lacTp promoter region was also detected for each of the 41 other independently isolated Lac+ revertants of L. casei ATCC 27139. The revertants could be divided into six classes based on the positions of the point mutations detected. Primer extension experiments conducted on transcription from lacTp revealed that the lacTp promoter of these six classes of Lac+ revertants was functional, while that of L. casei ATCC 27139 was not. Northern blotting experiments further confirmed that the lacTEGF operon of strain R1 was induced by lactose but suppressed by glucose, whereas no blotting signal was ever detected for L. casei ATCC 27139. These results suggest that a single point mutation in the lacTp promoter was able to restore the transcription of a fully functional lacTEGF operon and cause a phenotype switch from Lac− to Lac+ for L. casei ATCC 27139.

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31

Stoebel, Daniel M. "Lack of Evidence for Horizontal Transfer of the lac Operon into Escherichia coli." Molecular Biology and Evolution 22, no. 3 (November 24, 2004): 683–90. http://dx.doi.org/10.1093/molbev/msi056.

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32

Browning, Douglas F., Rita E. Godfrey, Kirsty L. Richards, Colin Robinson, and Stephen J. W. Busby. "Exploitation of the Escherichia coli lac operon promoter for controlled recombinant protein production." Biochemical Society Transactions 47, no. 2 (April 10, 2019): 755–63. http://dx.doi.org/10.1042/bst20190059.

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AbstractThe Escherichia coli lac operon promoter is widely used as a tool to control recombinant protein production in bacteria. Here, we give a brief review of how it functions, how it is regulated, and how, based on this knowledge, a suite of lac promoter derivatives has been developed to give a controlled expression that is suitable for diverse biotechnology applications.

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33

Guardabassi, Luca, Bruno Perichon, Jean van Heijenoort, Didier Blanot, and Patrice Courvalin. "Glycopeptide Resistance vanA Operons in Paenibacillus Strains Isolated from Soil." Antimicrobial Agents and Chemotherapy 49, no. 10 (October 2005): 4227–33. http://dx.doi.org/10.1128/aac.49.10.4227-4233.2005.

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ABSTRACT The sequence and gene organization of the van operons in vancomycin (MIC of >256 μg/ml)- and teicoplanin (MIC of ≥32 μg/ml)-resistant Paenibacillus thiaminolyticus PT-2B1 and Paenibacillus apiarius PA-B2B isolated from soil were determined. Both operons had regulatory (vanR and vanS), resistance (vanH, vanA, and vanX), and accessory (vanY, vanZ, and vanW) genes homologous to the corresponding genes in enterococcal vanA and vanB operons. The vanA PT operon in P. thiaminolyticus PT-2B1 had the same gene organization as that of vanA operons whereas vanA PA in P. apiarius PA-B2B resembled vanB operons due to the presence of vanW upstream from the vanHAX cluster but was closer to vanA operons in sequence. Reference P. apiarius strains NRRL B-4299 and NRRL B-4188 were found to harbor operons indistinguishable from vanA PA by PCR mapping, restriction fragment length polymorphism, and partial sequencing, suggesting that this operon was species specific. As in enterococci, resistance was inducible by glycopeptides and associated with the synthesis of pentadepsipeptide peptidoglycan precursors ending in d-Ala-d-Lac, as demonstrated by d,d-dipeptidase activities, high-pressure liquid chromatography, and mass spectrometry. The precursors differed from those in enterococci by the presence of diaminopimelic acid instead of lysine in the peptide chain. Altogether, the results are compatible with the notion that van operons in soil Paenibacillus strains and in enterococci have evolved from a common ancestor.

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34

Oehler, S., E. R. Eismann, H. Krämer, and B. Müller-Hill. "The three operators of the lac operon cooperate in repression." EMBO Journal 9, no. 4 (April 1990): 973–79. http://dx.doi.org/10.1002/j.1460-2075.1990.tb08199.x.

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35

Mahaffy, Joseph M., and Emil Simeonov Savev. "Stability analysis for a mathematical model of the lac operon." Quarterly of Applied Mathematics 57, no. 1 (March 1, 1999): 37–53. http://dx.doi.org/10.1090/qam/1672171.

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36

Sharp, Kim A. "Allostery in the lac operon: Population selection or induced dissociation?" Biophysical Chemistry 159, no. 1 (November 2011): 66–72. http://dx.doi.org/10.1016/j.bpc.2011.05.007.

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37

Karkare, Kedar, Huei-Yi Lai, Ricardo B. R. Azevedo, and Tim F. Cooper. "Historical Contingency Causes Divergence in Adaptive Expression of the lac Operon." Molecular Biology and Evolution 38, no. 7 (March 21, 2021): 2869–79. http://dx.doi.org/10.1093/molbev/msab077.

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Abstract Populations of Escherichia coli selected in constant and fluctuating environments containing lactose often adapt by substituting mutations in the lacI repressor that cause constitutive expression of the lac operon. These mutations occur at a high rate and provide a significant benefit. Despite this, eight of 24 populations evolved for 8,000 generations in environments containing lactose contained no detectable repressor mutations. We report here on the basis of this observation. We find that, given relevant mutation rates, repressor mutations are expected to have fixed in all evolved populations if they had maintained the same fitness effect they confer when introduced to the ancestor. In fact, reconstruction experiments demonstrate that repressor mutations have become neutral or deleterious in those populations in which they were not detectable. Populations not fixing repressor mutations nevertheless reached the same fitness as those that did fix them, indicating that they followed an alternative evolutionary path that made redundant the potential benefit of the repressor mutation, but involved unique mutations of equivalent benefit. We identify a mutation occurring in the promoter region of the uspB gene as a candidate for influencing the selective choice between these paths. Our results detail an example of historical contingency leading to divergent evolutionary outcomes.

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38

Kennardi, Gabriel, Maelita Moeis, and Andreas Andreas. "Operon Construction Containing alsS, ilvC, ilvD and kivd Genes in Esch-erichia coli for Isobutanol Production from Glucose." Jurnal Matematika dan Sains 25, no. 1 (September 2020): 11–17. http://dx.doi.org/10.5614/jms.2020.25.1.3.

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Isobutanol is a biofuel considered to be a potential gasoline substitute. However, isobutanol production is difficult because there is no native organism that can produce isobutanol. A biosynthetic pathway to produce isobutanol had been designed to utilize pyruvate produced from glucose breakdown by glycolysis in Escherichia coli (E. coli). This biosynthetic pathway con-sists of acetolactate-synthase (ALS), ketol-acid reductoisomerase (KARI), dihydroxy-acid dehydratase (DHAD), alpha-ketoisovalerate decarboxylase (KDC) and alcohol dehydrogenase (ADH) enzymes. Since E. coli does not have ALS and KDC, the genes coding for the protein is needed to be cloned and overexpressed in E. coli. KARI and DHAD were overexpressed to increase the accumulation of keto acid to increase isobutanol production. Plasmid contains an operon controlled by lac pro-moter and lac operator consisting of alsS (coded ALS from Bacillus subtilis), ilvC (coded KARI from E. coli MG1655) and ilvD (coded DHAD from E. coli MG1655) genes, obtained from previous research, and operon sequences have been confirmed by DNA sequencing. kivd gene (coding KDC from Lactococcus lactis) was obtained from iGEM 2013 kit. kivd was amplified by PCR and inserted into pJET 1.2 blunt. kivd gene was then added into 3’ end of previous operon using restriction-ligation tech-nique. The plasmid constructed was then transfered into E. coli DH5α using heat shock. The recombinant genes were expressed using IPTG (isopropyl-β-D-1-thiogalactopyranoside) induction. The SDS PAGE results were inconclusive, however isobutanol was detected by Gas Chromatography Mass Spectrometry – Selected Ion Monitoring (GC-MS-SIM) from 48 hours fermenta-tion culture at 30 oC (1,17%). An operon regulated by the lac promoter-operator containing four genes for the biosynthesis of isobutanol has been constructed and cloned in E. coli. The isobutanol production was not optimal due to weak expression and repression by glucose, which was used as substrate.

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39

Loo, C. Y., K. Mitrakul, I. B. Voss, C. V. Hughes, and N. Ganeshkumar. "Involvement of an Inducible Fructose Phosphotransferase Operon in Streptococcus gordonii Biofilm Formation." Journal of Bacteriology 185, no. 21 (November 1, 2003): 6241–54. http://dx.doi.org/10.1128/jb.185.21.6241-6254.2003.

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ABSTRACT Oral streptococci, such as Streptococcus gordonii, are the predominant early colonizers that initiate biofilm formation on tooth surfaces. Investigation of an S. gordonii::Tn917-lac biofilm-defective mutant isolated by using an in vitro biofilm formation assay showed that the transposon insertion is near the 3′ end of an open reading frame (ORF) encoding a protein homologous to Streptococcus mutans FruK. Three genes, fruR, fruK, and fruI, were predicted to encode polypeptides that are part of the fructose phosphotransferase system (PTS) in S. gordonii. These proteins, FruR, FruK, and FruI, are homologous to proteins encoded by the inducible fruRKI operon of S. mutans. In S. mutans, FruR is a transcriptional repressor, FruK is a fructose-1-phosphate kinase, and FruI is the fructose-specific enzyme II (fructose permease) of the phosphoenolpyruvate-dependent sugar PTS. Reverse transcription-PCR confirmed that fruR, fruK, and fruI are cotranscribed as an operon in S. gordonii, and the transposon insertion in S. gordonii fruK::Tn917-lac resulted in a nonpolar mutation. Nonpolar inactivation of either fruK or fruI generated by allelic replacement resulted in a biofilm-defective phenotype, whereas a nonpolar mutant with an inactivated fruR gene retained the ability to form a biofilm. Expression of fruK, as measured by the β-galactosidase activity of the fruK::Tn917-lac mutant, was observed to be growth phase dependent and was enhanced when the mutant was grown in media with high levels of fructose, sucrose, xylitol, and human serum, indicating that the fructose PTS operon was fructose and xylitol inducible, similar to the S. mutans fructose PTS. The induction by fructose was inhibited by the presence of glucose, indicating that glucose is able to catabolite repress fruK expression. Nonpolar inactivation of the fruR gene in the fruK::Tn917-lac mutant resulted in a greater increase in β-galactosidase activity when the organism was grown in media supplemented with fructose, confirming that fruR is a transcriptional repressor of the fructose PTS operon. These results suggest that the regulation of fructose transport and metabolism in S. gordonii is intricately tied to carbon catabolite control and the ability to form biofilms. Carbon catabolite control, which modulates carbon flux in response to environmental nutritional levels, appears to be important in the regulation of bacterial biofilms.

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40

Scrable, Heidi, and Peter J. Stambrook. "Activation of the lac Repressor in the Transgenic Mouse." Genetics 147, no. 1 (September 1, 1997): 297–304. http://dx.doi.org/10.1093/genetics/147.1.297.

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Abstract We have introduced sequences encoding the lac repressor of Escherichia coli into the genome of the mouse. One sequence was derived from the bacterial lac operon and the other was created by reencoding the amino acid sequence of lacI with mammalian codons. Both versions are driven by an identical promoter fragment derived from the human β-actin locus and were microinjected into genetically identical pronuclear stage embryos. All transgenes utilizing the bacterial coding sequence were transcriptionally silent in all somatic tissues tested. The sequence re-encoded with mammalian codons was transcriptionally active at all transgene loci and expressed ubiquitously. Using methylation-sensitive enzymes, we have determined the methylation status of lac repressor transgenes encoded by either the bacterial or mammalian sequence. The highly divergent bacterial sequence was hypermethylated at all transgene loci, while the mammalian sequence was only hypermethylated at a high copy number locus. This may reflect a normal process that protects the genome from acquiring new material that has an abnormally divergent sequence or structure.

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41

Biard, Denis S. F., Michael R. James, André Cordier, and Alain Sarasin. "Regulation of the Escherichia coli lac operon expressed in human cells." Biochimica et Biophysica Acta (BBA) - Gene Structure and Expression 1130, no. 1 (February 1992): 68–74. http://dx.doi.org/10.1016/0167-4781(92)90463-a.

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42

Dreisigmeyer, D. W., J. Stajic, M. E. Wall, I. Nemenman, and W. S. Hlavacek. "Determinants of bistability in induction of the Escherichia coli lac operon." IET Systems Biology 2, no. 5 (September 1, 2008): 293–303. http://dx.doi.org/10.1049/iet-syb:20080095.

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43

Racine, Valérie. "The mechanistic-holistic divide revisited: The case of the lac operon." Studies in History and Philosophy of Science Part C: Studies in History and Philosophy of Biological and Biomedical Sciences 59 (October 2016): 1–10. http://dx.doi.org/10.1016/j.shpsc.2016.05.001.

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44

Flashner, Y., and J. D. Gralla. "Dual mechanism of repression at a distance in the lac operon." Proceedings of the National Academy of Sciences 85, no. 23 (December 1, 1988): 8968–72. http://dx.doi.org/10.1073/pnas.85.23.8968.

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45

van Hoek, Milan, and Paulien Hogeweg. "The Effect of Stochasticity on the Lac Operon: An Evolutionary Perspective." PLoS Computational Biology 3, no. 6 (June 22, 2007): e111. http://dx.doi.org/10.1371/journal.pcbi.0030111.

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46

Baumberg, Simon, and Margo Roberts. "Anomalous expression of the E. coli lac operon in Proteus mirabilis." Molecular and General Genetics MGG 204, no. 2 (August 1986): 362. http://dx.doi.org/10.1007/bf00425524.

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47

Hughes, Kelly T., and John R. Roth. "DIRECTED FORMATION OF DELETIONS AND DUPLICATIONS USING Mud(Ap, lac)." Genetics 109, no. 2 (February 1, 1985): 263–82. http://dx.doi.org/10.1093/genetics/109.2.263.

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ABSTRACT A genetic procedure is directed for the isolation of chromosomal deletions and duplications with predetermined endpoints. These rearrangements are generated in transduction crosses using a mixture of P22-transducing phage lysates grown on two strains, each carrying a Mud-lac insertion. The formation of duplications and deletions was demonstrated in the his operon using insertions of Mud1-8 (a transposition-defectiveMud-lac phage). This technique was also used to make larger chromosomal duplications between Mud1-8 insertions in the thr and leu biosynthetic operons and between Mud insertions in the thr and pyrB operons. Genetic evidence is presented that strongly suggests that inheritance of a single Mud prophage by P22-mediated crosses requires two transduced fragments; each carrying part of the Mud prophage. The two fragments must be involved in three recombinational exchanges; one exchange joins the donor Mud fragments and two exchanges occur between the composite fragment and the recipient chromosome, one on either side of the complete donor Mud element. Since duplications only occur between Mud insertions in the same orientation on the chromosome, the method of duplication formation provides a simple means of determining the orientation of Mud1-8 on the chromosome and, therefore, the direction of transcription of the gene into which Mud is inserted. This method was also used to construct recombinants between a Mud1-8 prophage and Casadaban's protein fusion vector Mud2 and, thereby, isolate Mud2-8, a Mud derivative containing the protein fusion ability of Mud2 and the defective transposition functions of Mud1-8.

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48

Morales, Pilar, Josette Rouviere-Yaniv, and Marc Dreyfus. "The Histone-Like Protein HU Does Not Obstruct Movement of T7 RNA Polymerase in Escherichia coli Cells but Stimulates Its Activity." Journal of Bacteriology 184, no. 6 (March 15, 2002): 1565–70. http://dx.doi.org/10.1128/jb.184.6.1565-1570.2002.

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ABSTRACT In vivo, RNA polymerases (RNAPs) do not transcribe naked DNA but do transcribe protein-associated DNA. Studies with the model enzyme T7 RNAP have shown that, in eukaryotic cells or in vitro, nucleosomes can inhibit both transcription initiation and elongation. We examine here whether the presence of HU, one of the major histone-like proteins in Escherichia coli cells (the genuine milieu for T7 RNAP) affects its activity. An engineered lac operon fused to the T7 late promoter was introduced into the chromosome of T7 RNAP-producing strains that either overexpress HU or lack it. The flows of RNAP that enter and exit this operon were compared with regard to the content of HU. We found that the fraction of T7 RNAP molecules that do not reach the end of the lac operon (ca. 15%) is the same whether the host cells overexpressed HU or lacked it: thus, the enzyme either freely displaces HU or transcribes through it. However, in these cells, the transcript yield was increased when HU is overexpressed and decreased in the hup mutants, presumably reflecting changes in DNA supercoiling. Thus, in contrast to eukaryotic nucleosomes, HU does not impair T7 RNAP activity but has a stimulatory effect. Finally, our results suggest that HU can also influence mRNA stability in vivo.

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49

Eismann, Elis, Brigitte v.Wilcken-Bergmann, and Benno Müller-Hill. "Specific destruction of the second lac operator decreases repression of the lac operon in Escherichia coli fivefold." Journal of Molecular Biology 195, no. 4 (June 1987): 949–52. http://dx.doi.org/10.1016/0022-2836(87)90499-2.

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50

Loo, C. Y., K. Mitrakul, I. B. Voss, C. V. Hughes, and N. Ganeshkumar. "Involvement of the adc Operon and Manganese Homeostasis in Streptococcus gordonii Biofilm Formation." Journal of Bacteriology 185, no. 9 (May 1, 2003): 2887–900. http://dx.doi.org/10.1128/jb.185.9.2887-2900.2003.

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ABSTRACT Pioneer oral bacteria, including Streptococcus gordonii, initiate the formation of oral biofilms on tooth surfaces, which requires differential expression of genes that recognize unique environmental cues. An S. gordonii::Tn917-lac biofilm-defective mutant was isolated by using an in vitro biofilm formation assay. Subsequent inverse PCR and sequence analyses identified the transposon insertion to be near the 3′ end of an open reading frame (ORF) encoding a protein homologous to a Streptococcus pneumoniae repressor, AdcR. The S. gordonii adc operon, consisting of the four ORFs adcR, adcC, adcB, and adcA, is homologous to the adc operon of S. pneumoniae, which plays a role in zinc and/or manganese transport and genetic competence in S. pneumoniae. AdcR is a metal-dependent repressor protein containing a putative metal-binding site, AdcC contains a consensus-binding site for ATP, AdcB is a hydrophobic protein with seven hydrophobic membrane-spanning regions, and AdcA is a lipoprotein permease with a putative metal-binding site. The three proteins (AdcC through -A) are similar to those of the binding-lipoprotein-dependent transport system of gram-positive bacteria. Reverse transcriptase PCR confirmed that adcRCBA are cotranscribed as an operon in S. gordonii and that the transposon insertion in S. gordonii adcR::Tn917-lac had resulted in a polar mutation. Expression of adcR, measured by the β-galactosidase activity of the adcR::Tn917-lac mutant, was growth phase dependent and increased when the mutant was grown in media with high levels of manganese (>1 mM) and to a lesser extent in media with zinc, indicating that AdcR may be a regulator at high levels of extracellular manganese. A nonpolar inactivation of adcR generated by allelic replacement resulted in a biofilm- and competence-defective phenotype. The biofilm-defective phenotype observed suggests that AdcR is an active repressor when synthesized and acts at a distant site(s) on the chromosome. Thus, the adc operon is involved in manganese acquisition in S. gordonii and manganese homeostasis and appears to modulate sessile growth in this bacterium.

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