Academic literature on the topic 'Mutant library'

An understanding of plant pathogen-host interactions is essential to design efficient strategies to control disease in crops. Magnaporthe oryzae, an ascomyceteous fungus and causal agent of rice blast disease, is a model organism to study host-microbe interactions. The overall aim of this dissertation project was to identify genes involved in pathogenicity through the construction and characterization of a random insertional mutagenesis library. In order to saturate the genome with DNA inserts, a collection of >54,000 insertion lines of the M. oryzae strain 70-15 was generated via two transformation methods, PEG/CaCl2 (polyethylene glycol)-mediated protoplast transformation and Agrobacterium tumefaciens-mediated transformation. The first part of this dissertation describes the optimization of both transformation approaches, compares their efficiency and provides a description of the high-throughput processing and phenotypic analysis of the insertion lines. An in vitro appressorium assay of 12,000 T-DNA insertion strains allowed the identification of 135 lines that were classified as morphologically or functionally different than wild-type. Rice infection assays demonstrated that 112 of these strains exhibited defects in pathogenicity.The second part of this dissertation project analyzed the T-DNA integration patterns in a subset of pathogenicity mutants. This section aimed to identify the disrupted genes via recovery of M. oryzae sequences adjacent to the sites of T-DNA insertion. Genomic mapping of 61 T-DNA insertions in pathogenicity mutants via rescuing M. oryzae chromosomal T-DNA flanking sequences using inverse PCR resulted in the identification of 22 conserved hypothetical genes with predicted function, 11 predicted open reading frames without a GenBank significant match, two unannotated regions of the genome assembly and seven intergenic regions. The final part of this dissertation describes the characterization of a M. oryzae pathogenicity mutant that contains a T-DNA insertion in the upstream region of two divergently transcribed genes that encode the vacuolar type-ATPase subunit c`` and the general transcription factor TFIIA subunit γ. Genetic complementation demonstrated the insertion of the T-DNA in the promoter region of the general transcription factor TFIIA subunit γ is responsible for observed defects in conidiation, appressorium morphogenesis, and appressorium function. This is the first report relating the function of TFIIA subunit γ to pathogenicity.

<p>Evolution of enzymes with novel functional properties has gained much attention in recent years. Naturally evolved enzymes are adapted to work in living cells under physiological conditions, circumstances that are not always available for industrial processes calling for novel and better catalysts. Furthermore, altering enzyme function also affords insight into how enzymes work and how natural evolution operates. </p><p>Previous investigations have explored catalytic properties in the directed evolution of mutant libraries with high sequence variation. Before this study was initiated, functional analysis of mutant libraries was, to a large extent, restricted to uni- or bivariate methods. Consequently, there was a need to apply multivariate data analysis (MVA) techniques in this context. Directed evolution was approached by DNA shuffling of glutathione transferases (GSTs) in this thesis. GSTs are multifarious enzymes that have detoxication of both exo- and endogenous compounds as their primary function. They catalyze the nucleophilic attack by the tripeptide glutathione on many different electrophilic substrates. </p><p>Several multivariate analysis tools, <i>e.g.</i> principal component (PC), hierarchical cluster, and K-means cluster analyses, were applied to large mutant libraries assayed with a battery of GST substrates. By this approach, evolvable units (quasi-species) fit for further evolution were identified. It was clear that different substrates undergoing different kinds of chemical transformation can group together in a multi-dimensional substrate-activity space, thus being responsible for a certain quasi-species cluster. Furthermore, the importance of the chemical environment, or substrate matrix, in enzyme evolution was recognized. Diverging substrate selectivity profiles among homologous enzymes acting on substrates performing the same kind of chemistry were identified by MVA. Important structure-function activity relationships with the prodrug azathioprine were elucidated by segment analysis of a shuffled GST mutant library. Together, these results illustrate important methods applied to molecular enzyme evolution.</p>

[ES] Las bacterias resistentes a múltiples antibióticos, como el Enterococo resistente a vancomicina (ERV), son un problema creciente en los pacientes hospitalizados, por lo que se necesita estrategias alternativas para combatir estos patógenos. Las infecciones causadas por ERV suelen comenzar con la colonización del tracto intestinal, un paso crucial que se afectado por la presencia de la microbiota. Sin embargo, los antibióticos alteran la microbiota y esto promueve la colonización de ERV. Una vez que el patógeno ha colonizado el intestino, alcanza niveles muy altos pudiendo diseminar a otros órganos y pacientes. A pesar de su importancia, se sabe muy poco sobre los genes que codifica para colonizar el intestino y sobre el mecanismo por el cual la microbiota suprime su colonización intestinal, siendo los dos objetivos principales. En primer lugar hemos utilizado una metodología previamente descrita (Zhang et al., 2017, BMC Genomics), basada en la generación de una librería de mutantes por transposición junto a secuenciación masiva, con el fin de identificar los genes codificados por ERV necesarios para la colonización del intestino en ratones. Además, hemos realizado análisis metatranscriptómicos para identificar aquellos genes más expresados. El análisis ha identificado genes cuya interrupción reduce significativamente la colonización intestinal en el intestino grueso. Los genes que más afectaron a la colonización codifican proteínas relacionadas con la absorción o el transporte de diversos nutrientes como los carbohidratos (subunidad EIIAB del transportador PTS de manosa, el regulador transcripcional de la familia LacI, ácido N-acetilmurámico 6-fosfato eterasa) o iones (proteína transportadora dependiente de ATP (ABC) y proteínas del grupo [Fe-S]). El papel de estos genes en la colonización se ha confirmado mediante experimentos de mutagénesis directa y de competición con la cepa salvaje. Además, estos genes afectan a la colonización intestinal con diferentes antibióticos (clindamicina y vancomicina). Para identificar el mecanismo molecular por el cual cada gen afecta a la colonización, hemos realizado experimentos in vitro y ex vivo además del análisis transcriptómico. Los experimentos in vitro confirman que las proteínas del grupo [Fe-S] están involucradas en el transporte iones de hierro, principalmente Fe3+. Por otra parte, los genes de la subunidad EIIAB del transportador de manosa y del ácido N-acetilmurámico 6-fosfato eterasa son necesarios para la utilización de la manosa y el ácido N-acetilmurámico, respectivamente, azúcares que suelen estar presentes en el intestino. También confirmamos que el regulador transcripcional de la familia LacI es un represor que afecta a proteínas transportadoras ABC, probablemente implicadas en la absorción de carbohidratos. Además, algunos de estos genes están codificados principalmente por cepas clínicas de E. faecium y en menor medida por cepas comensales. En segundo lugar, estudiamos los mecanismos de protección de un consorcio de cinco bacterias comensales, que anteriormente se había demostrado que disminuían la colonización intestinal por ERV en ratones. Mediante transcriptómica, metabolómica y los ensayos in vivo observamos que el consorcio bacteriano inhibe el crecimiento de ERV mediante la reducción de nutrientes, concretamente fructosa. Por último, el análisis ARN-Seq in vivo de cada aislado en combinación con los ensayos ex vivo e in vivo demostraron que una sola bacteria (Olsenella sp.) proporciona protección. En conjunto, los resultados obtenidos han identificado la función de genes específicos requeridos por ERV para colonizar el intestino. Además, hemos identificado un mecanismo mediante el cual la microbiota confiere protección. Estos resultados podrían conducir a nuevos enfoques terapéuticos para prevenir las infecciones causadas por este patógeno multiresistente a los antibióticos.<br>[CA] Els bacteris resistents a múltiples antibiòtics, com el Enterococo resistent a vancomicina (ERV), són un problema creixent en els pacients hospitalitzats, que són resistents a la majoria d'antibiòtics disponibles per la qual cosa es necessita estratègies alternatives per a combatre aquests patògens. Les infeccions causades per ERV solen començar amb la colonització del tracte intestinal, un pas crucial que es veu afectat per la presència de la microbiota. No obstant això, els antibiòtics alteren la microbiota i això promou la colonització de ERV. Una vegada que el patogen ha colonitzat l'intestí, aconsegueix nivells molt alts podent disseminar a altres òrgans i pacients. Malgrat la seua importància, se sap molt poc sobre els gens que codifica ERV per a colonitzar l'intestí i sobre el mecanisme pel qual la microbiota suprimeix la seua colonització intestinal. En primer lloc hem utilitzat una metodologia prèviament descrita (Zhang et al., 2017, BMC Genomics), basada en la generació d'una llibreria de mutants per transposició junt amb seqüenciació massiva, amb la finalitat d'identificar els gens codificats per ERV necessaris per a la colonització de l'intestí en ratolins. A més a més, hem realitzat anàlisi metatranscriptòmics per a identificar aquells gens més expressats. L'anàlisi ha identificat gens quina interrupció redueix significativament la colonització intestinal en l'intestí gros. Els gens que més van afectar la colonització codifiquen proteïnes relacionades amb l'absorció o el transport de diversos nutrients com els carbohidrats (subunitat EIIAB del transportador PTS de manosa, el regulador transcripcional de la família LacI, àcid N-acetilmuràmic 6-fosfat eterasa) o ions (proteïna transportadora dependent d'ATP (ABC) i proteïnes del grup [Fe-S]). El paper d'aquests gens en la colonització s'ha confirmat mitjançant experiments de mutagènesis directa i de competició amb el cep salvatge. A més, aquests gens afecten la colonització intestinal amb diferents antibiòtics (clindamicina i vancomicina). Per a identificar el mecanisme molecular pel qual cada gen afecta a la colonització, hem realitzat experiments in vitro i ex viu a més de l'anàlisi transcriptòmic. Els experiments in vitro confirmen que les proteïnes del grup [Fe-S] estan involucrades en el transport d'ions de ferro, principalment Fe3+. D'altra banda, els gens de la subunitat EIIAB del transportador PTS de manosa i de l'àcid N-acetilmuràmic 6-fosfat eterasa són necessaris per a la utilització de la manosa i l'àcid N-acetilmuràmic, respectivament, sucres que solen estar presents en l'intestí. També confirmem que el regulador transcripcional de la família LacI és un repressor que afecta proteïnes transportadores ABC, probablement implicades en l'absorció de carbohidrats. A més a més, alguns d'aquests gens estan codificats principalment per ceps clínics de E. faecium i en menor mesura per ceps comensals. En segon lloc, estudiem els mecanismes de protecció d'un consorci de cinc bacteris comensals, que adès s'havia demostrat que disminuïen la colonització intestinal per ERV en ratolins. Amb l'ús de transcriptòmica, metabolòmica i els assajos in vivo observem que el consorci bacterià inhibeix el creixement de ERV mitjançant la reducció de nutrients, concretament fructosa. Finalment, l'anàlisi ARN-Seq in vivo de cada aïllat en combinació amb els assajos ex viu i in vivo van demostrar que un sol bacteri (Olsenella sp.) proporciona protecció. En conjunt, els resultats obtinguts han identificat la funció de gens específics requerits per ERV per a colonitzar l'intestí. A més, hem identificat un mecanisme mitjançant el qual la microbiota confereix protecció. Aquests resultats podrien conduir a nous enfocaments terapèutics per a previndre les infeccions causades per aquest patogen multiresistent als antibiòtics.<br>[EN] Multidrug-resistant bacteria, such as vancomycin-resistant-Enterococcus (VRE), are an increasing problem in hospitalized patients. Some VRE strains can be resistant to most available antibiotics, thus, alternative strategies to antibiotics are urgently needed to combat these challenging pathogens. Infections caused by VRE frequently start by colonization of the intestinal tract, a crucial step that is impaired by the presence of the intestinal microbiota. Administration of antibiotics disrupts the microbiota, which promotes VRE intestinal colonization. Once VRE has colonized the gut, it reaches very high levels, which promotes its dissemination to other organs and its transfer to other patients. Despite the relevance of VRE gut colonization, very little is known about the genes encoded by this pathogen to colonize the gut and about the mechanisms by which the microbiota suppresses VRE gut colonization. In this thesis, we have utilized a previously described methodology (Zhang et al., 2017, BMC Genomics), based on the generation of a transposon mutant library coupled with high-throughput sequencing, in order to identify VRE encoded genes required for colonization of the mouse intestinal tract. In addition, we have performed metatranscriptomic analysis in mice to identify VRE genes specifically expressed in the gut. Our analysis has identified genes whose disruption significantly reduces VRE gut colonization in the large intestine. The genes that most affected VRE gut colonization encoded for proteins related to the uptake or transport of diverse nutrients such as carbohydrates (PTS mannose transporter subunit EIIAB, LacI family DNA-binding transcriptional regulator, N-acetylmuramic acid 6-phosphate etherase) or ions (phosphate ABC transporter ATP-binding protein and proteins from [Fe-S] cluster). The role of these genes in gut colonization has been confirmed through targeted mutagenesis and competition experiments against a wild type strain. Moreover, these genes affect gut colonization under different antibiotic treatments (clindamycin and vancomycin). To elucidate the mechanism by which each gene influences gut colonization, we have performed in vitro and ex vivo experiments besides transcriptomic analysis. In vitro experiments confirm that proteins from [Fe-S] cluster are involved in the transport of different forms of iron ions, mostly Fe3+. On the other hand, the PTS mannose transporter subunit EIIAB and N-acetylmuramic acid 6-phosphate etherase genes are required for the utilization of mannose and N-acetyl-muramic acid, respectively, sugars that are usually present in the intestinal environment. We have also confirmed that LacI family DNA-binding transcriptional regulator is a repressor that affects the expression of genes encoding for an ABC transporter probably involved in the uptake of carbohydrates. Furthermore, we have confirmed that some of these genes are encoded mainly by E. faecium clinical strains but not or to a lower extent by commensal strains. Secondly, we studied the mechanisms of protection of a consortium of five commensals bacteria, previously shown to restrict VRE gut colonization in mice. Functional transcriptomics in combination with targeted metabolomics and in vivo assays performed in this thesis indicated that the bacterial consortium inhibits VRE growth through nutrient depletion, specifically by reducing the levels of fructose. Finally, in vivo RNA-Seq analysis of each bacterial isolate of the consortium in combination with ex vivo and in vivo assays demonstrated that a single bacterium (Olsenella sp.) could recapitulate the protective effect. Altogether, the results obtained have identified the function of specific genes required by VRE to colonize the gut. In addition, we have identified a specific mechanism by which the microbiota confers protection against VRE colonization. These results could lead to novel therapeutic approaches to prevent infections caused by this pathogen.<br>Flor Duro, A. (2021). Characterization of Genes and Functions Required by Multidrug-resistant Enterococci to Colonize the Intestine [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/166494<br>TESIS

Embryogenesis plays a central role in the plant life cycle. It starts after fertilization. A single zygote divides asymmetrically, giving rise a small apical cell and a larger basal cell. The small apical cell undergoes precise cell divisions, passes through 2, 4 and 8 cell stages, followed by the protoderm, globular, heart, torpedo and cotyledon stage, in the process of forming a mature embryo. In embryo development a large number of genes are estimated to be involved and interact with each other during embryogenesis. We demonstrated that the RSH gene was required for normal embryo development of Arabidopsis. Its essential role was determined by disrupting expression of the gene by the Ac/ DsE two-element transposon system, which caused the embryo mutation. The abnormal phenotype was traced to the first asymmetrical division of the zygote and the embryo development lost its precise programmed cell division pattern. The rsh mutant showed both apical-basal and radial pattern defects. The RSH gene mapped to chromosome I. The gene was cloned and sequenced. It encoded a HRGP-type protein of predicted size, 49 k Dalton. The pre-protein contained a signal peptide and 13 almost identical repeats. Each repeat had 28 amino acids. The rescue of homozygous rsh mutants by complementation with the wild-type RSH gene demonstrated that the rsh mutation is the consequence of the DsE insertion. The gene was found to be expressed through out the developing embryo. It was expressed in a tissue specific manner after embryo germination. The RSH gene expression pattern was first profiled using the GUS reporter gene assay. The Northern and RT-PCR confirmed the results. To localize the RSH protein at the cellular level, an EGFP gene was linked to the C-terminus of the RSH gene and expressed in wild-type Arabidopsis . Confocal microscopy showed that the fusion protein was localized to the cell wall. Wild type transformants expressing RSH-EGFP showed mutant phenotypes. All these results support the conclusion that the RSH protein plays an important role in cell division during embryogenesis.

碩士<br>國立臺灣大學<br>微生物學研究所<br>95<br>Klebsiella pneumoniae is an opportunistic pathogen associated with nosocomial infections such as urinary tract infection, bacteremia and pneumonia. The biofilm formation of bacteria has been known to involve in the increasing resistance to antibiotic, antibacterial, and host immune responses. In order to explore the genes responsible for the biofilm formation in K. pneumoniae, a NTUH-K2044 mutant transposon library was screened by biofilm microtiter plate assay. Three mutants revealed decreased biofilm formation, and three mutants revealed increased biofilm formation compared with wild-type. The interrupted gene of one mutant with increased biofilm formation was similar with sugE in Escherichia coli. Unmarked deletion and chromosomal complementation of sugE demonstrated that sugE was responsible for the biofilm formation. In order to sutudy the role of gene regulation in sugE in biofilm formation, the RNA expression profiles of ΔsugE mutant was compared with those of wild type by microarray. The expressions of twelve clones were up-regulated in ΔsugE mutant. These twelve clones contained genes involved in maltose catabolism and carbohydrate phosphotransferase system (PTS) that had been proven to associate with biofilm formation. These results suggested that sugE might affect the biofilm formation through the regulation of genes in maltose regulon and carbohydrate phosphotransferase system.