Journal articles: 'Lactose operon'

1

Szeberényi, József. "Lactose operon mutants." Biochemistry and Molecular Biology Education 30, no. 6 (November 2002): 420–21. http://dx.doi.org/10.1002/bmb.2002.494030060092.

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Mackey, Michael C., Moisés Santillán, and Necmettin Yildirim. "Modeling operon dynamics: the tryptophan and lactose operons as paradigms." Comptes Rendus Biologies 327, no. 3 (March 2004): 211–24. http://dx.doi.org/10.1016/j.crvi.2003.11.009.

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Szeberenyi, Jozsef. "cAMP Regulation of the lactose operon." Biochemistry and Molecular Biology Education 32, no. 3 (May 2004): 198–99. http://dx.doi.org/10.1002/bmb.2004.494032030349.

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Abranches, Jacqueline, Yi-Ywan M. Chen, and Robert A. Burne. "Galactose Metabolism by Streptococcus mutans." Applied and Environmental Microbiology 70, no. 10 (October 2004): 6047–52. http://dx.doi.org/10.1128/aem.70.10.6047-6052.2004.

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ABSTRACT The galK gene, encoding galactokinase of the Leloir pathway, was insertionally inactivated in Streptococcus mutans UA159. The galK knockout strain displayed only marginal growth on galactose, but growth on glucose or lactose was not affected. In strain UA159, the sugar phosphotransferase system (PTS) for lactose and the PTS for galactose were induced by growth in lactose and galactose, although galactose PTS activity was very low, suggesting that S. mutans does not have a galactose-specific PTS and that the lactose PTS may transport galactose, albeit poorly. To determine if the galactose growth defect of the galK mutant could be overcome by enhancing lactose PTS activity, the gene encoding a putative repressor of the operon for lactose PTS and phospho-β-galactosidase, lacR, was insertionally inactivated. A galK and lacR mutant still could not grow on galactose, although the strain had constitutively elevated lactose PTS activity. The glucose PTS activity of lacR mutants grown in glucose was lower than in the wild-type strain, revealing an influence of LacR or the lactose PTS on the regulation of the glucose PTS. Mutation of the lacA gene of the tagatose pathway caused impaired growth in lactose and galactose, suggesting that galactose can only be efficiently utilized when both the Leloir and tagatose pathways are functional. A mutation of the permease in the multiple sugar metabolism operon did not affect growth on galactose. Thus, the galactose permease of S. mutans is not present in the gal, lac, or msm operons.

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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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Nanavati, Dhaval M., Tu N. Nguyen, and Kenneth M. Noll. "Substrate Specificities and Expression Patterns Reflect the Evolutionary Divergence of Maltose ABC Transporters in Thermotoga maritima." Journal of Bacteriology 187, no. 6 (March 15, 2005): 2002–9. http://dx.doi.org/10.1128/jb.187.6.2002-2009.2005.

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ABSTRACT Duplication of transporter genes is apparent in the genome sequence of the hyperthermophilic bacterium Thermotoga maritima. The physiological impacts of these duplications are not well understood, so we used the bacterium's two putative maltose transporters to begin a study of the evolutionary relationship between a transporter's function and the control of expression of its genes. We show that the substrate binding proteins encoded by these operons, MalE1 and MalE2, have different substrate specificities and affinities and that they are expressed under different growth conditions. MalE1 binds maltose (dissociation constant [KD ], 24 ± 1 μM), maltotriose (KD , 8 ± 0.5 nM), and β-(1→4)-mannotetraose (KD , 38 ± 1 μM). In contrast, MalE2 binds maltose (KD , 8.4 ± 1 μM), maltotriose (KD , 11.5 ± 1.5 μM), and trehalose (KD , 9.5 ± 1.0 μM) confirming the findings of Wassenberg et al. (J. Mol. Biol. 295:279-288, 2000). Neither protein binds lactose. We examined the expression of these operons at both the transcriptional and translational levels and found that MalE1 is expressed in cells grown on lactose or guar gum and that MalE2 is highly expressed in starch- and trehalose-grown cells. Evidence is provided that malE1, malF1, and perhaps malG1 are cotranscribed and so constitute an operon. An open reading frame encoding a putative transcriptional regulatory protein adjacent to this operon (TM1200) is also up-regulated in response to growth on lactose. These evolutionarily related transporter operons have diverged both in function and expression to assume apparently different physiological roles.

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7

RAWLS, REBECCA. "LACTOSE OPERON REPRESSOR Elusive structure finally determined." Chemical & Engineering News 74, no. 10 (March 4, 1996): 4. http://dx.doi.org/10.1021/cen-v074n010.p004.

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8

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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9

Michel, Denis. "Kinetic approaches to lactose operon induction and bimodality." Journal of Theoretical Biology 325 (May 2013): 62–75. http://dx.doi.org/10.1016/j.jtbi.2013.02.005.

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10

Reznikoff, William S. "The lactose operon-controlling elements: a complex paradigm." Molecular Microbiology 6, no. 17 (October 27, 2006): 2419–22. http://dx.doi.org/10.1111/j.1365-2958.1992.tb01416.x.

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11

Vaughan, Elaine E., Patrick T. C. van den Bogaard, Pasquale Catzeddu, Oscar P. Kuipers, and Willem M. de Vos. "Activation of Silent gal Genes in thelac-gal Regulon of Streptococcus thermophilus." Journal of Bacteriology 183, no. 4 (February 15, 2001): 1184–94. http://dx.doi.org/10.1128/jb.183.4.1184-1194.2001.

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ABSTRACT Streptococcus thermophilus strain CNRZ 302 is unable to ferment galactose, neither that generated intracellularly by lactose hydrolysis nor the free sugar. Nevertheless, sequence analysis and complementation studies with Escherichia coli demonstrated that strain CNRZ 302 contained structurally intact genes for the Leloir pathway enzymes. These were organized into an operon in the ordergalKTE, which was preceded by a divergently transcribed regulator gene, galR, and followed by a galMgene and the lactose operon lacSZ. Results of Northern blot analysis showed that the structural gal genes were transcribed weakly, and only in medium containing lactose, by strain CNRZ 302. However, in a spontaneous galactose-fermenting mutant, designated NZ302G, the galKTE genes were well expressed in cells grown on lactose or galactose. In both CNRZ 302 and the Gal+ mutant NZ302G, the transcription of thegalR gene was induced by growth on lactose. Disruption ofgalR indicated that it functioned as a transcriptional activator of both the gal and lac operons while negatively regulating its own expression. Sequence analysis of thegal promoter regions of NZ302G and nine other independently isolated Gal+ mutants of CNRZ 302 revealed mutations at three positions in the galK promoter region, which included substitutions at positions −9 and −15 as well as a single-base-pair insertion at position −37 with respect to the main transcription initiation point. Galactokinase activity measurements and analysis ofgusA reporter gene fusions in strains containing the mutated promoters suggested that they were gal promoter-up mutations. We propose that poor expression of the gal genes in the galactose-negative S. thermophilus CNRZ 302 is caused by naturally occurring mutations in the galKpromoter.

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12

Fulcrand, Geraldine, Steven Eichelbaum, and Fenfei Leng. "Lactose Repressor Functions as a DNA Topological Barrier in Escherichia Coli Lactose Operon." Biophysical Journal 104, no. 2 (January 2013): 417a—418a. http://dx.doi.org/10.1016/j.bpj.2012.11.2326.

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13

Gosalbes, María José, Carlos David Esteban, José Luis Galán, and Gaspar Pérez-Martínez. "Integrative Food-Grade Expression System Based on the Lactose Regulon of Lactobacillus casei." Applied and Environmental Microbiology 66, no. 11 (November 1, 2000): 4822–28. http://dx.doi.org/10.1128/aem.66.11.4822-4828.2000.

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ABSTRACT The lactose operon from Lactobacillus casei is regulated by very tight glucose repression and substrate induction mechanisms, which made it a tempting candidate system for the expression of foreign genes or metabolic engineering. An integrative vector was constructed, allowing stable gene insertion in the chromosomal lactose operon of L. casei. This vector was based on the nonreplicative plasmid pRV300 and contained two DNA fragments corresponding to the 3′ end of lacG and the complete lacF gene. Four unique restriction sites were created, as well as a ribosome binding site that would allow the cloning and expression of new genes between these two fragments. Then, integration of the cloned genes into the lactose operon of L. casei could be achieved via homologous recombination in a process that involved two selection steps, which yielded highly stable food-grade mutants. This procedure has been successfully used for the expression of the E. coli gusA gene and the L. lactis ilvBN genes in L. casei. Following the same expression pattern as that for the lactose genes, β-glucuronidase activity and diacetyl production were repressed by glucose and induced by lactose. This integrative vector represents a useful tool for strain improvement in L. casei that could be applied to engineering fermentation processes or used for expression of genes for clinical and veterinary uses.

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14

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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15

Li, Yong, and Sidney Altman. "Polarity Effects in the Lactose Operon of Escherichia coli." Journal of Molecular Biology 339, no. 1 (May 2004): 31–39. http://dx.doi.org/10.1016/j.jmb.2004.03.041.

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16

Barbé, Jordi, Eloi Garí, and Montserrat Llagostera. "Regulation oflac operon in lactose-utilizing mutants ofRhodobacter capsulatus." Current Microbiology 16, no. 4 (July 1988): 185–89. http://dx.doi.org/10.1007/bf01568527.

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17

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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18

Boucher, Isabelle, Christian Vadeboncoeur, and Sylvain Moineau. "Characterization of Genes Involved in the Metabolism of α-Galactosides by Lactococcus raffinolactis." Applied and Environmental Microbiology 69, no. 7 (July 2003): 4049–56. http://dx.doi.org/10.1128/aem.69.7.4049-4056.2003.

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ABSTRACT Lactococcus raffinolactis, unlike most lactococci, is able to ferment α-galactosides, such as melibiose and raffinose. More than 12 kb of chromosomal DNA from L. raffinolactis ATCC 43920 was sequenced, including the α-galactosidase gene and genes involved in the Leloir pathway of galactose metabolism. These genes are organized into an operon containing aga (α-galactosidase), galK (galactokinase), and galT (galactose 1-phosphate uridylyltransferase). Northern blotting experiments revealed that this operon was induced by galactosides, such as lactose, melibiose, raffinose, and, to a lesser extent, galactose. Similarly, α-galactosidase activity was higher in lactose-, melibiose-, and raffinose-grown cells than in galactose-grown cells. No α-galactosidase activity was detected in glucose-grown cells. The expression of the aga-galKT operon was modulated by a regulator encoded by the upstream gene galR. The product of galR belongs to the LacI/GalR family of transcriptional regulators. In L. lactis, L. raffinolactis GalR acted as a repressor of aga and lowered the enzyme activity by more than 20-fold. We suggest that the expression of the aga operon in lactococci is negatively controlled by GalR and induced by a metabolite derived from the metabolism of galactosides.

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Narang, Atul, and Sergei S. Pilyugin. "Bistability of the lac Operon During Growth of Escherichia coli on Lactose and Lactose + Glucose." Bulletin of Mathematical Biology 70, no. 4 (February 2, 2008): 1032–64. http://dx.doi.org/10.1007/s11538-007-9289-7.

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20

Kuhlman, T., Z. Zhang, M. H. Saier, and T. Hwa. "Combinatorial transcriptional control of the lactose operon of Escherichia coli." Proceedings of the National Academy of Sciences 104, no. 14 (March 21, 2007): 6043–48. http://dx.doi.org/10.1073/pnas.0606717104.

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21

Griffin, H. G., and M. J. Gasson. "The regulation of expression of the Lactococcus lactis lactose operon." Letters in Applied Microbiology 17, no. 2 (August 1993): 92–96. http://dx.doi.org/10.1111/j.1472-765x.1993.tb00379.x.

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22

Pinto, Marcelo Cezar, Luciana Foss, José Carlos Merino Mombach, and Leila Ribeiro. "Modelling, property verification and behavioural equivalence of lactose operon regulation." Computers in Biology and Medicine 37, no. 2 (February 2007): 134–48. http://dx.doi.org/10.1016/j.compbiomed.2006.01.006.

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23

jacob, Christian, and Ian Burleigh. "Biomolecular swarms ? an agent-based model of the lactose operon." Natural Computing 3, no. 4 (December 2004): 361–76. http://dx.doi.org/10.1007/s11047-004-2638-7.

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24

Arnold, Jason, Joshua Simpson, Jeffery Roach, Jose Bruno-Barcena, and M. Azcarate-Peril. "Prebiotics for Lactose Intolerance: Variability in Galacto-Oligosaccharide Utilization by Intestinal Lactobacillus rhamnosus." Nutrients 10, no. 10 (October 16, 2018): 1517. http://dx.doi.org/10.3390/nu10101517.

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Lactose intolerance, characterized by a decrease in host lactase expression, affects approximately 75% of the world population. Galacto-oligosaccharides (GOS) are prebiotics that have been shown to alleviate symptoms of lactose intolerance and to modulate the intestinal microbiota, promoting the growth of beneficial microorganisms. We hypothesized that mechanisms of GOS utilization by intestinal bacteria are variable, impacting efficacy and response, with differences occurring at the strain level. This study aimed to determine the mechanisms by which human-derived Lactobacillus rhamnosus strains metabolize GOS. Genomic comparisons between strains revealed differences in carbohydrate utilization components, including transporters, enzymes for degradation, and transcriptional regulation, despite a high overall sequence identity (>95%) between strains. Physiological and transcriptomics analyses showed distinct differences in carbohydrate metabolism profiles and GOS utilization between strains. A putative operon responsible for GOS utilization was identified and characterized by genetic disruption of the 6-phospho-β-galactosidase, which had a critical role in GOS utilization. Our findings highlight the importance of strain-specific bacterial metabolism in the selection of probiotics and synbiotics to alleviate symptoms of gastrointestinal disorders including lactose intolerance.

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25

Brabetz, W., W. Liebl, and K. H. Schleifer. "Studies on the utilization of lactose by Corynebacterium glutamicum, bearing the lactose operon of Escherichia coli." Archives of Microbiology 155, no. 6 (June 1991): 607–12. http://dx.doi.org/10.1007/bf00245357.

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26

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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27

Oskouian, B., and G. C. Stewart. "Repression and catabolite repression of the lactose operon of Staphylococcus aureus." Journal of Bacteriology 172, no. 7 (1990): 3804–12. http://dx.doi.org/10.1128/jb.172.7.3804-3812.1990.

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28

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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Flórez, Ana Belén, Pilar Reimundo, Susana Delgado, Elena Fernández, Ángel Alegría, José A. Guijarro, and Baltasar Mayo. "Genome Sequence of Lactococcus garvieae IPLA 31405, a Bacteriocin-Producing, Tetracycline-Resistant Strain Isolated from a Raw-Milk Cheese." Journal of Bacteriology 194, no. 18 (August 28, 2012): 5118–19. http://dx.doi.org/10.1128/jb.00975-12.

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ABSTRACTThis work describes the draft genome sequence ofLactococcus garvieaeIPLA 31405, isolated from a traditional Spanish cheese. The genome contains a lactose-galactose operon, a bacteriocin locus, two integrated phages, a transposon harboring an activetet(M) gene, and two theta-type plasmid replicons. Genes encoding virulence factors were not recorded.

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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

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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Fortina, Maria Grazia, Giovanni Ricci, Diego Mora, Simone Guglielmetti, and Pier Luigi Manachini. "Unusual Organization for Lactose and Galactose Gene Clusters in Lactobacillus helveticus." Applied and Environmental Microbiology 69, no. 6 (June 2003): 3238–43. http://dx.doi.org/10.1128/aem.69.6.3238-3243.2003.

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ABSTRACT The nucleotide sequences of the Lactobacillus helveticus lactose utilization genes were determined, and these genes were located and oriented relative to one another. The lacLM genes (encoding the β-galactosidase protein) were in a divergent orientation compared to lacR (regulatory gene) and lacS (lactose transporter). Downstream from lacM was an open reading frame (galE) encoding a UDP-galactose 4 epimerase, and the open reading frame had the same orientation as lacM. The lacR gene was separated from the downstream lacS gene by 2.0 kb of DNA containing several open reading frames that were derived from fragmentation of another permease gene (lacS′). Northern blot analysis revealed that lacL, lacM, and galE made up an operon that was transcribed in the presence of lactose from an upstream lacL promoter. The inducible genes lacL and lacM were regulated at the transcriptional level by the LacR repressor. In the presence of glucose and galactose galE was transcribed from its promoter, suggesting that the corresponding enzyme can be expressed constitutively. Lactose transport was inducible by addition of lactose to the growth medium.

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Newman, Janet, Karine Caron, Tom Nebl, and Thomas S. Peat. "Structures of the transcriptional regulator BgaR, a lactose sensor." Acta Crystallographica Section D Structural Biology 75, no. 7 (June 26, 2019): 639–46. http://dx.doi.org/10.1107/s2059798319008131.

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The structure of BgaR, a transcriptional regulator of the lactose operon inClostridium perfringens, has been solved by SAD phasing using a mercury derivative. BgaR is an exquisite sensor of lactose, with a binding affinity in the low-micromolar range. This sensor and regulator has been captured bound to lactose and to lactulose as well as in a nominal apo form, and was compared with AraC, another saccharide-binding transcriptional regulator. It is shown that the saccharides bind in the N-terminal region of a jelly-roll fold, but that part of the saccharide is exposed to bulk solvent. This differs from the classical AraC saccharide-binding site, which is mostly sequestered from the bulk solvent. The structures of BgaR bound to lactose and to lactulose highlight how specific and nonspecific interactions lead to a higher binding affinity of BgaR for lactose compared with lactulose. Moreover, solving multiple structures of BgaR in different space groups, both bound to saccharides and unbound, verified that the dimer interface along a C-terminal helix is similar to the dimer interface observed in AraC.

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Vaillancourt, Katy, Sylvain Moineau, Michel Frenette, Christian Lessard, and Christian Vadeboncoeur. "Galactose and Lactose Genes from the Galactose-Positive Bacterium Streptococcus salivarius and the Phylogenetically Related Galactose-Negative Bacterium Streptococcus thermophilus: Organization, Sequence, Transcription, and Activity of the gal Gene Products." Journal of Bacteriology 184, no. 3 (February 1, 2002): 785–93. http://dx.doi.org/10.1128/jb.184.3.785-793.2002.

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ABSTRACT Streptococcus salivarius is a lactose- and galactose-positive bacterium that is phylogenetically closely related to Streptococcus thermophilus, a bacterium that metabolizes lactose but not galactose. In this paper, we report a comparative characterization of the S. salivarius and S. thermophilus gal-lac gene clusters. The clusters have the same organization with the order galR (codes for a transcriptional regulator and is transcribed in the opposite direction), galK (galactokinase), galT (galactose-1-P uridylyltransferase), galE (UDP-glucose 4-epimerase), galM (galactose mutarotase), lacS (lactose transporter), and lacZ (β-galactosidase). An analysis of the nucleotide sequence as well as Northern blotting and primer extension experiments revealed the presence of four promoters located upstream from galR, the gal operon, galM, and the lac operon of S. salivarius. Putative promoters with virtually identical nucleotide sequences were found at the same positions in the S. thermophilus gal-lac gene cluster. An additional putative internal promoter at the 3′ end of galT was found in S. thermophilus but not in S. salivarius. The results clearly indicated that the gal-lac gene cluster was efficiently transcribed in both species. The Shine-Dalgarno sequences of galT and galE were identical in both species, whereas the ribosome binding site of S. thermophilus galK differed from that of S. salivarius by two nucleotides, suggesting that the S. thermophilus galK gene might be poorly translated. This was confirmed by measurements of enzyme activities.

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Kercher, M. A., G. Chang, N. C. Horton, P. Lu, J. H. Miller, H. C. Pace, and M. Lewis. "Structure of the lactose operon repressor and its complexes with DNA and inducer." Acta Crystallographica Section A Foundations of Crystallography 52, a1 (August 8, 1996): C156. http://dx.doi.org/10.1107/s0108767396093002.

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McCormick, J. R., J. M. Zengel, and L. Lindahl. "Intermediates in the degradation of mRNA from the lactose operon of Escherichia coli." Nucleic Acids Research 19, no. 10 (May 25, 1991): 2767–76. http://dx.doi.org/10.1093/nar/19.10.2767.

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Oskouian, B., and G. C. Stewart. "Cloning and characterization of the repressor gene of the Staphylococcus aureus lactose operon." Journal of Bacteriology 169, no. 12 (1987): 5459–65. http://dx.doi.org/10.1128/jb.169.12.5459-5465.1987.

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Basile, F., K. D. Hughes, P. E. Wisniowski, D. G. Gorenstein, F. E. Lytle, T. S. Mccaybuis, D. M. Huber, and B. C. Hemming. "Fast and Sensitive Laser-Based Enzymatic Detection of the Lactose Operon in Microorganisms." Analytical Biochemistry 211, no. 1 (May 1993): 55–60. http://dx.doi.org/10.1006/abio.1993.1232.

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Robert, Lydia, Gregory Paul, Yong Chen, François Taddei, Damien Baigl, and Ariel B. Lindner. "Pre‐dispositions and epigenetic inheritance in the Escherichia coli lactose operon bistable switch." Molecular Systems Biology 6, no. 1 (January 2010): 357. http://dx.doi.org/10.1038/msb.2010.12.

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van den Bogaard, Patrick T. C., Michiel Kleerebezem, Oscar P. Kuipers, and Willem M. de Vos. "Control of Lactose Transport, β-Galactosidase Activity, and Glycolysis by CcpA in Streptococcus thermophilus: Evidence for Carbon Catabolite Repression by a Non-Phosphoenolpyruvate-Dependent Phosphotransferase System Sugar." Journal of Bacteriology 182, no. 21 (November 1, 2000): 5982–89. http://dx.doi.org/10.1128/jb.182.21.5982-5989.2000.

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ABSTRACT Streptococcus thermophilus, unlike many other gram-positive bacteria, prefers lactose over glucose as the primary carbon and energy source. Moreover, lactose is not taken up by a phosphoenolpyruvate-dependent phosphotransferase system (PTS) but by the dedicated transporter LacS. In this paper we show that CcpA plays a crucial role in the fine-tuning of lactose transport, β-galactosidase (LacZ) activity, and glycolysis to yield optimal glycolytic flux and growth rate. A catabolite-responsive element (cre) was identified in the promoter of the lacSZ operon, indicating a possible role for regulation by CcpA. Transcriptional analysis showed a sevenfold relief of repression in the absence of a functional CcpA when cells were grown on lactose. This CcpA-mediated repression oflacSZ transcription did not occur in wild-type cells during growth on galactose, taken up by the same LacS transport system. Lactose transport during fermentation was increased significantly in strains carrying a disrupted ccpA gene. Moreover, accpA disruption strain was found to release substantial amounts of glucose into the medium when grown on lactose. Transcriptional analysis of the ldh gene showed that expression was induced twofold during growth on lactose compared to glucose or galactose, in a CcpA-dependent manner. A reduced rate of glycolysis concomitant with an increased lactose transport rate could explain the observed expulsion of glucose in a ccpAdisruption mutant. We propose that CcpA in S. thermophilusacts as a catabolic regulator during growth on the preferred non-PTS sugar lactose. In contrast to other bacteria, S. thermophilus possesses an overcapacity for lactose uptake that is repressed by CcpA to match the rate-limiting glycolytic flux.

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Yu, Yang, Martin Tangney, Hans C. Aass, and Wilfrid J. Mitchell. "Analysis of the Mechanism and Regulation of Lactose Transport and Metabolism in Clostridium acetobutylicum ATCC 824." Applied and Environmental Microbiology 73, no. 6 (January 5, 2007): 1842–50. http://dx.doi.org/10.1128/aem.02082-06.

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ABSTRACT Although the acetone-butanol-ethanol fermentation of Clostridium acetobutylicum is currently uneconomic, the ability of the bacterium to metabolize a wide range of carbohydrates offers the potential for revival based on the use of cheap, low-grade substrates. We have investigated the uptake and metabolism of lactose, the major sugar in industrial whey waste, by C. acetobutylicum ATCC 824. Lactose is taken up via a phosphoenolpyruvate-dependent phosphotransferase system (PTS) comprising both soluble and membrane-associated components, and the resulting phosphorylated derivative is hydrolyzed by a phospho-β-galactosidase. These activities are induced during growth on lactose but are absent in glucose-grown cells. Analysis of the C. acetobutylicum genome sequence identified a gene system, lacRFEG, encoding a transcriptional regulator of the DeoR family, IIA and IICB components of a lactose PTS, and phospho-β-galactosidase. During growth in medium containing both glucose and lactose, C. acetobutylicum exhibited a classical diauxic growth, and the lac operon was not expressed until glucose was exhausted from the medium. The presence upstream of lacR of a potential catabolite responsive element (cre) encompassing the transcriptional start site is indicative of the mechanism of carbon catabolite repression characteristic of low-GC gram-positive bacteria. A pathway for the uptake and metabolism of lactose by this industrially important organism is proposed.

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Lewis, M., G. Chang, N. C. Horton, M. A. Kercher, H. C. Pace, M. A. Schumacher, R. G. Brennan, and P. Lu. "Crystal Structure of the Lactose Operon Repressor and Its Complexes with DNA and Inducer." Science 271, no. 5253 (March 1, 1996): 1247–54. http://dx.doi.org/10.1126/science.271.5253.1247.

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Velkov, Tony, Alun Jones, and Maria L. R. Lim. "Ni2+-Based Immobilized Metal Ion Affinity Chromatography of Lactose Operon Repressor Protein fromEscherichia Coli." Preparative Biochemistry and Biotechnology 38, no. 4 (September 26, 2008): 422–41. http://dx.doi.org/10.1080/10826060802325725.

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Bouffard, Gerard G., Kenneth E. Rudd, and Sankar L. Adhya. "Dependence of Lactose Metabolism upon Mutarotase Encoded in the gal Operon in Escherichia coli." Journal of Molecular Biology 244, no. 3 (December 1994): 269–78. http://dx.doi.org/10.1006/jmbi.1994.1728.

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Maccormick, Caroline A., Hugh G. Griffin, and Michael J. Gasson. "Construction of a food-grade host/vector system forLactococcus lactisbased on the lactose operon." FEMS Microbiology Letters 127, no. 1-2 (March 1995): 105–9. http://dx.doi.org/10.1111/j.1574-6968.1995.tb07457.x.

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Payne, John, Caroline A. MacCormick, Hugh G. Griffin, and Michael J. Gasson. "Exploitation of a chromosomally integrated lactose operon for controlled gene expression in Lactococcus lactis." FEMS Microbiology Letters 136, no. 1 (February 1996): 19–24. http://dx.doi.org/10.1111/j.1574-6968.1996.tb08019.x.

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Gosalbes, María José, Vicente Monedero, Carl-Alfred Alpert, and Gaspar Pérez-Martínez. "Establishing a model to study the regulation of the lactose operon in Lactobacillus casei." FEMS Microbiology Letters 148, no. 1 (January 17, 2006): 83–89. http://dx.doi.org/10.1111/j.1574-6968.1997.tb10271.x.

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Hediger, M. A., D. F. Johnson, D. P. Nierlich, and I. Zabin. "DNA sequence of the lactose operon: the lacA gene and the transcriptional termination region." Proceedings of the National Academy of Sciences 82, no. 19 (October 1, 1985): 6414–18. http://dx.doi.org/10.1073/pnas.82.19.6414.

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Zander, Dominique, Daniel Samaga, Ronny Straube, and Katja Bettenbrock. "Bistability and Nonmonotonic Induction of the lac Operon in the Natural Lactose Uptake System." Biophysical Journal 112, no. 9 (May 2017): 1984–96. http://dx.doi.org/10.1016/j.bpj.2017.03.038.

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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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Journal articles on the topic 'Lactose operon'

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