scholarly journals AntisocialluxOMutants Provide a Stationary-Phase Survival Advantage in Vibrio fischeri ES114

2015 ◽  
Vol 198 (4) ◽  
pp. 673-687 ◽  
Author(s):  
John H. Kimbrough ◽  
Eric V. Stabb
Keyword(s):  
Stationary Phase ◽  
Vibrio Fischeri ◽  
Current Model ◽  
Homoserine Lactone ◽  
Survival Advantage ◽  
Mutant Library ◽  
Wild Type ◽  
Host Colonization ◽  
Content Type ◽  
Pheromone Signaling

ABSTRACTThe squid light organ symbiontVibrio fischericontrols bioluminescence using two acyl-homoserine lactone pheromone-signaling (PS) systems. The first of these systems to be activated during host colonization, AinS/AinR, produces and responds toN-octanoyl homoserine lactone (C8-AHL). We screened activity of a PainS-lacZtranscriptional reporter in a transposon mutant library and found three mutants with decreased reporter activity, low C8-AHL output, and other traits consistent with lowainSexpression. However, the transposon insertions were unrelated to these phenotypes, and genome resequencing revealed that each mutant had a distinct point mutation inluxO. In the wild type, LuxO is phosphorylated by LuxU and then activates transcription of the small RNA (sRNA) Qrr, which repressesainSindirectly by repressing its activator LitR. TheluxOmutants identified here encode LuxU-independent, constitutively active LuxO* proteins. The repeated appearance of theseluxOmutants suggested that they had some fitness advantage during construction and/or storage of the transposon mutant library, and we found thatluxO* mutants survived better and outcompeted the wild type in prolonged stationary-phase cultures. From such cultures we isolated additionalluxO* mutants. In all, we isolated LuxO* allelic variants with the mutations P41L, A91D, F94C, P98L, P98Q, V106A, V106G, T107R, V108G, R114P, L205F, H319R, H324R, and T335I. Based on the current model of theV. fischeriPS circuit,litRknockout mutants should resembleluxO* mutants; however,luxO* mutants outcompetedlitRmutants in prolonged culture and had much poorer host colonization competitiveness than is reported forlitRmutants, illustrating additional complexities in this regulatory circuit.IMPORTANCEOur results provide novel insight into the function of LuxO, which is a key component of pheromone signaling (PS) cascades in several members of theVibrionaceae. Our results also contribute to an increasingly appreciated aspect of bacterial behavior and evolution whereby mutants that do not respond to a signal from like cells have a selective advantage. In this case, although “antisocial” mutants locked in the PS signal-off mode can outcompete parents, their survival advantage does not require wild-type cells to exploit. Finally, this work strikes a note of caution for those conducting or interpreting experiments inV. fischeri, as it illustrates how pleiotropic mutants could easily and inadvertently be enriched in this bacterium during prolonged culturing.

scholarly journals Cwp19 Is a Novel Lytic Transglycosylase Involved in Stationary-Phase Autolysis Resulting in Toxin Release inClostridium difficile

mBio ◽  
2018 ◽  
Vol 9 (3) ◽  
Author(s):  
Sandra Wydau-Dematteis ◽  
Imane El Meouche ◽  
Pascal Courtin ◽  
Audrey Hamiot ◽  
René Lai-Kuen ◽  
...  
Keyword(s):  
Health Care ◽  
Clostridium Difficile ◽  
Stationary Phase ◽  
Catalytic Domain ◽  
Brain Heart Infusion ◽  
Surface Protein ◽  
Wild Type ◽  
Content Type ◽  
Lytic Transglycosylase ◽  
Cell Autolysis

ABSTRACTClostridium difficileis the major etiologic agent of antibiotic-associated intestinal disease. Pathogenesis ofC. difficileis mainly attributed to the production and secretion of toxins A and B. Unlike most clostridial toxins, toxins A and B have no signal peptide, and they are therefore secreted by unusual mechanisms involving the holin-like TcdE protein and/or autolysis. In this study, we characterized the cell surface protein Cwp19, a newly identified peptidoglycan-degrading enzyme containing a novel catalytic domain. We purified a recombinant His6-tagged Cwp19 protein and showed that it has lytic transglycosylase activity. Moreover, we observed that Cwp19 is involved in cell autolysis and that aC. difficilecwp19mutant exhibited delayed autolysis in stationary phase compared to the wild type when bacteria were grown in brain heart infusion (BHI) medium. Wild-type cell autolysis is correlated to strong alterations of cell wall thickness and integrity and to release of cytoplasmic material. Furthermore, we demonstrated that toxins were released into the extracellular medium as a result of Cwp19-induced autolysis when cells were grown in BHI medium. In contrast, Cwp19 did not induce autolysis or toxin release when cells were grown in tryptone-yeast extract (TY) medium. These data provide evidence for the first time that TcdE and bacteriolysis are coexisting mechanisms for toxin release, with their relative contributionsin vitrodepending on growth conditions. Thus, Cwp19 is an important surface protein involved in autolysis of vegetative cells ofC. difficilethat mediates the release of the toxins from the cell cytosol in response to specific environment conditions.IMPORTANCEClostridium difficile-associated disease is mainly known as a health care-associated infection. It represents the most problematic hospital-acquired infection in North America and Europe and exerts significant economic pressure on health care systems. Virulent strains ofC. difficilegenerally produce two toxins that have been identified as the major virulence factors. The mechanism for release of these toxins from bacterial cells is not yet fully understood but is thought to be partly mediated by bacteriolysis. Here we identify a novel peptidoglycan hydrolase inC. difficile, Cwp19, exhibiting lytic transglycosylase activity. We show that Cwp19 contributes toC. difficilecell autolysis in the stationary phase and, consequently, to toxin release, most probably as a response to environmental conditions such as nutritional signals. These data highlight that Cwp19 constitutes a promising target for the development of new preventive and curative strategies.

scholarly journals Production of the Antimicrobial Secondary Metabolite Indigoidine Contributes to Competitive Surface Colonization by the Marine Roseobacter Phaeobacter sp. Strain Y4I

2012 ◽  
Vol 78 (14) ◽  
pp. 4771-4780 ◽  
Author(s):  
W. Nathan Cude ◽  
Jason Mooney ◽  
Arash A. Tavanaei ◽  
Mary K. Hadden ◽  
Ashley M. Frank ◽  
...  
Keyword(s):  
Gene Expression ◽  
Secondary Metabolite ◽  
Biosynthetic Pathway ◽  
Wild Type Strain ◽  
Vibrio Fischeri ◽  
Random Mutagenesis ◽  
Blue Pigment ◽  
Wild Type ◽  
Content Type ◽  
Artificial Surface

ABSTRACTMembers of theRoseobacterlineage of marine bacteria are prolific surface colonizers in marine coastal environments, and antimicrobial secondary metabolite production has been hypothesized to provide a competitive advantage to colonizing roseobacters. Here, we report that the roseobacterPhaeobactersp. strain Y4I produces the blue pigment indigoidine via a nonribosomal peptide synthase (NRPS)-based biosynthetic pathway encoded by a novel series of genetically linked genes:igiBCDFE. A Tn5-based random mutagenesis library of Y4I showed a perfect correlation between indigoidine production by thePhaeobacterstrain and inhibition ofVibrio fischerion agar plates, revealing a previously unrecognized bioactivity of this molecule. In addition, igiD null mutants (igiD encoding the indigoidine NRPS) were more resistant to hydrogen peroxide, less motile, and faster to colonize an artificial surface than the wild-type strain. Collectively, these data provide evidence for pleiotropic effects of indigoidine production in this strain. Gene expression assays support phenotypic observations and demonstrate thatigiDgene expression is upregulated during growth on surfaces. Furthermore, competitive cocultures ofV. fischeriand Y4I show that the production of indigoidine by Y4I significantly inhibits colonization ofV. fischerion surfaces. This study is the first to characterize a secondary metabolite produced by an NRPS in roseobacters.

scholarly journals An Expanded Transposon Mutant Library Reveals that Vibrio fischeri δ-Aminolevulinate Auxotrophs Can Colonize Euprymna scolopes

2016 ◽  
Vol 83 (5) ◽  
Author(s):  
Noreen L. Lyell ◽  
Alecia N. Septer ◽  
Anne K. Dunn ◽  
Drew Duckett ◽  
Julie L. Stoudenmire ◽  
...  
Keyword(s):  
Vibrio Fischeri ◽  
Light Organ ◽  
Mutant Library ◽  
Euprymna Scolopes ◽  
Simple Method ◽  
Content Type ◽  
Transposon Insertion ◽  
Rich Media ◽  
Show Evidence

ABSTRACT Libraries of defined mutants are valuable research tools but necessarily lack gene knockouts that are lethal under the conditions used in library construction. In this study, we augmented a Vibrio fischeri mutant library generated on a rich medium (LBS, which contains [per liter] 10 g of tryptone, 5 g of yeast extract, 20 g of NaCl, and 50 mM Tris [pH 7.5]) by selecting transposon insertion mutants on supplemented LBS and screening for those unable to grow on LBS. We isolated strains with insertions in alr, glr (murI), glmS, several heme biosynthesis genes, and ftsA, as well as a mutant disrupted 14 bp upstream of ftsQ. Mutants with insertions in ftsA or upstream of ftsQ were recovered by addition of Mg2+ to LBS, but their cell morphology and motility were affected. The ftsA mutant was more strongly affected and formed cells or chains of cells that appeared to wind back on themselves helically. Growth of mutants with insertions in glmS, alr, or glr was recovered with N-acetylglucosamine (NAG), d-alanine, or d-glutamate, respectively. We hypothesized that NAG, d-alanine, or d-glutamate might be available to V. fischeri in the Euprymna scolopes light organ; however, none of these mutants colonized the host effectively. In contrast, hemA and hemL mutants, which are auxotrophic for δ-aminolevulinate (ALA), colonized at wild-type levels, although mutants later in the heme biosynthetic pathway were severely impaired or unable to colonize. Our findings parallel observations that legume hosts provide Bradyrhizobium symbionts with ALA, but they contrast with virulence phenotypes of hemA mutants in some pathogens. The results further inform our understanding of the symbiotic light organ environment. IMPORTANCE By supplementing a rich yeast-based medium, we were able to recover V. fischeri mutants with insertions in conditionally essential genes, and further characterization of these mutants provided new insights into this bacterium's symbiotic environment. Most notably, we show evidence that the squid host can provide V. fischeri with enough ALA to support its growth in the light organ, paralleling the finding that legumes provide Bradyrhizobium ALA in symbiotic nodules. Taken together, our results show how a simple method of augmenting already rich media can expand the reach and utility of defined mutant libraries.

scholarly journals Novel Reporter for Identification of Interference with Acyl Homoserine Lactone and Autoinducer-2 Quorum Sensing

2014 ◽  
Vol 81 (4) ◽  
pp. 1477-1489 ◽  
Author(s):  
Nancy Weiland-Bräuer ◽  
Nicole Pinnow ◽  
Ruth A. Schmitz
Keyword(s):  
Quorum Sensing ◽  
Vibrio Fischeri ◽  
Quorum Quenching ◽  
Homoserine Lactone ◽  
Signal Molecules ◽  
Lethal Gene ◽  
Reporter Strain ◽  
Content Type ◽  
E Coli ◽  
Autoinducer 2

ABSTRACTTwo reporter strains were established to identify novel biomolecules interfering with bacterial communication (quorum sensing [QS]). The basic design of theseEscherichia coli-based systems comprises a gene encoding a lethal protein fused to promoters induced in the presence of QS signal molecules. Consequently, theseE. colistrains are unable to grow in the presence of the respective QS signal molecules unless a nontoxic QS-interfering compound is present. The first reporter strain designed to detect autoinducer-2 (AI-2)-interfering activities (AI2-QQ.1) contained theE. coliccdBlethal gene under the control of theE. colilsrApromoter. The second reporter strain (AI1-QQ.1) contained theVibrio fischeriluxIpromoter fused to theccdBgene to detect interference with acyl-homoserine lactones. Bacteria isolated from the surfaces of several marine eukarya were screened for quorum-quenching (QQ) activities using the established reporter systems AI1-QQ.1 and AI2-QQ.1. Out of 34 isolates, two interfered with acylated homoserine lactone (AHL) signaling, five interfered with AI-2 QS signaling, and 10 were demonstrated to interfere with both signal molecules. Open reading frames (ORFs) conferring QQ activity were identified for three selected isolates (Photobacteriumsp.,Pseudoalteromonassp., andVibrio parahaemolyticus). Evaluation of the respective heterologously expressed and purified QQ proteins confirmed their ability to interfere with the AHL and AI-2 signaling processes.

scholarly journals AinS Quorum Sensing Regulates the Vibrio fischeri Acetate Switch

2008 ◽  
Vol 190 (17) ◽  
pp. 5915-5923 ◽  
Author(s):  
Sarah V. Studer ◽  
Mark J. Mandel ◽  
Edward G. Ruby
Keyword(s):  
Quorum Sensing ◽  
Vibrio Fischeri ◽  
Growth Yield ◽  
Normal Growth ◽  
Homoserine Lactone ◽  
Acetate Metabolism ◽  
Wild Type ◽  
Gene Encoding ◽  
Sensing Systems ◽  
Acetate Utilization

ABSTRACT The marine bacterium Vibrio fischeri uses two acyl-homoserine lactone (acyl-HSL) quorum-sensing systems. The earlier signal, octanoyl-HSL, produced by AinS, is required for normal colonization of the squid Euprymna scolopes and, in culture, is necessary for a normal growth yield. In examining the latter requirement, we found that during growth in a glycerol/tryptone-based medium, wild-type V. fischeri cells initially excrete acetate but, in a metabolic shift termed the acetate switch, they subsequently utilize the acetate, removing it from the medium. In contrast, an ainS mutant strain grown in this medium does not remove the excreted acetate, which accumulates to lethal levels. The acetate switch is characterized by the induction of acs, the gene encoding acetyl coenzyme A (acetyl-CoA) synthetase, leading to uptake of the excreted acetate. Wild-type cells induce an acs transcriptional reporter 25-fold, coincident with the disappearance of the extracellular acetate; in contrast, the ainS mutant did not display significant induction of the acs reporter. Supplementation of the medium of an ainS mutant with octanoyl-HSL restored normal levels of acs induction and acetate uptake. Additional mutant analyses indicated that acs regulation was accomplished through the regulator LitR but was independent of the LuxIR quorum-signaling pathway. Importantly, the acs mutant of V. fischeri has a competitive defect when colonizing the squid, indicating the importance of proper control of acetate metabolism in the light of organ symbiosis. This is the first report of quorum-sensing control of the acetate switch, and it indicates a metabolic connection between acetate utilization and cell density.

scholarly journals Phosphate Transporter PstSCAB of Campylobacter jejuni Is a Critical Determinant of Lactate-Dependent Growth and Colonization in Chickens

2020 ◽  
Vol 202 (7) ◽  
Author(s):  
Ritam Sinha ◽  
Rhiannon M. LeVeque ◽  
Marvin Q. Bowlin ◽  
Michael J. Gray ◽  
Victor J. DiRita
Keyword(s):  
Stationary Phase ◽  
Campylobacter Jejuni ◽  
Phosphate Transporter ◽  
Rna Seq ◽  
Wild Type ◽  
Content Type ◽  
High Affinity ◽  
Polyphosphate Metabolism

ABSTRACT Campylobacter jejuni causes acute gastroenteritis worldwide and is transmitted primarily through poultry, in which it is often a commensal member of the intestinal microbiota. Previous transcriptome sequencing (RNA-Seq) experiment showed that transcripts from an operon encoding a high-affinity phosphate transporter (PstSCAB) of C. jejuni were among the most abundant when the bacterium was grown in chickens. Elevated levels of the pstSCAB mRNA were also identified in an RNA-Seq experiment from human infection studies. In this study, we explore the role of PstSCAB in the biology and colonization potential of C. jejuni. Our results demonstrate that cells lacking PstSCAB survive poorly in stationary phase, in nutrient-limiting media, and under osmotic conditions reflective of those in the chicken. Polyphosphate levels in the mutant cells were elevated at stationary phase, consistent with alterations in expression of polyphosphate metabolism genes. The mutant strain was highly attenuated for colonization of newly hatched chicks, with levels of bacteria at several orders of magnitude below wild-type levels. Mutant and wild type grew similarly in complex media, but the pstS::kan mutant exhibited a significant growth defect in minimal medium supplemented with l-lactate, postulated as a carbon source in vivo. Poor growth in lactate correlated with diminished expression of acetogenesis pathway genes previously demonstrated as important for colonizing chickens. The phosphate transport system is thus essential for diverse aspects of C. jejuni physiology and in vivo fitness and survival. IMPORTANCE Campylobacter jejuni causes millions of human gastrointestinal infections annually, with poultry a major source of infection. Due to the emergence of multidrug resistance in C. jejuni, there is need to identify alternative ways to control this pathogen. Genes encoding the high-affinity phosphate transporter PstSCAB are highly expressed by C. jejuni in chickens and humans. In this study, we address the role of PstSCAB on chicken colonization and other C. jejuni phenotypes. PstSCAB is required for colonization in chicken, metabolism and survival under different stress responses, and during growth on lactate, a potential growth substrate in chickens. Our study highlights that PstSCAB may be an effective target to develop mechanisms for controlling bacterial burden in both chicken and human.

scholarly journals Characterization of FlgP, an Essential Protein for Flagellar Assembly inRhodobacter sphaeroides

2018 ◽  
Vol 201 (5) ◽  
Author(s):  
Caleb Pérez-González ◽  
Clelia Domenzain ◽  
Sebastian Poggio ◽  
Diego González-Halphen ◽  
Georges Dreyfus ◽  
...  
Keyword(s):  
Vibrio Fischeri ◽  
Selective Advantage ◽  
Basal Bodies ◽  
Wild Type ◽  
Content Type ◽  
Chemotactic Protein ◽  
Flagellar Assembly ◽  
Basal Disk ◽  
Main Component

ABSTRACTThe flagellar lipoprotein FlgP has been identified in several species of bacteria, and its absence provokes different phenotypes. In this study, we show that in the alphaproteobacteriumRhodobacter sphaeroides, a ΔflgPmutant is unable to assemble the hook and the filament. In contrast, the membrane/supramembrane (MS) ring and the flagellar rod appear to be assembled. In the absence of FlgP a severe defect in the transition from rod to hook polymerization occurs. In agreement with this idea, we noticed a reduction in the amount of intracellular flagellin and the chemotactic protein CheY4, both encoded by genes dependent on σ28. This suggests that in the absence offlgPthe switch to export the anti-sigma factor, FlgM, does not occur. The presence of FlgP was detected by Western blot in samples of isolated wild-type filament basal bodies, indicating that FlgP is an integral part of the flagellar structure. In this regard, we show that FlgP interacts with FlgH and FlgT, indicating that FlgP should be localized closely to the L and H rings. We propose that FlgP could affect the architecture of the L ring, which has been recently identified to be responsible for the rod-hook transition.IMPORTANCEFlagellar based motility confers a selective advantage on bacteria by allowing migration to favorable environments or in pathogenic species to reach the optimal niche for colonization. The flagellar structure has been well established inSalmonella. However, other accessory components have been identified in other species. Many of these have been implied in adapting the flagellar function to enable faster rotation, or higher torque. FlgP has been proposed to be the main component of the basal disk located underlying the outer membrane inCampylobacter jejuniandVibrio fischeri. Its role is still unclear, and its absence impacts motility differently in different species. The study of these new components will bring a better understanding of the evolution of this complex organelle.

scholarly journals Transcriptional Analysis of an Ammonium-Excreting Strain of Azotobacter vinelandii Deregulated for Nitrogen Fixation

2017 ◽  
Vol 83 (20) ◽  
Author(s):  
Brett M. Barney ◽  
Mary H. Plunkett ◽  
Velmurugan Natarajan ◽  
Florence Mus ◽  
Carolann M. Knutson ◽  
...  
Keyword(s):  
Nitrogen Fixation ◽  
Stationary Phase ◽  
Gene Transcription ◽  
Biological Nitrogen Fixation ◽  
Azotobacter Vinelandii ◽  
Nitrogen Fixing ◽  
Wild Type ◽  
Content Type ◽  
Ammonium Production ◽  
Biological Nitrogen

ABSTRACT Biological nitrogen fixation is accomplished by a diverse group of organisms known as diazotrophs and requires the function of the complex metalloenzyme nitrogenase. Nitrogenase and many of the accessory proteins required for proper cofactor biosynthesis and incorporation into the enzyme have been characterized, but a complete picture of the reaction mechanism and key cellular changes that accompany biological nitrogen fixation remain to be fully elucidated. Studies have revealed that specific disruptions of the antiactivator-encoding gene nifL result in the deregulation of the nif transcriptional activator NifA in the nitrogen-fixing bacterium Azotobacter vinelandii, triggering the production of extracellular ammonium levels approaching 30 mM during the stationary phase of growth. In this work, we have characterized the global patterns of gene expression of this high-ammonium-releasing phenotype. The findings reported here indicated that cultures of this high-ammonium-accumulating strain may experience metal limitation when grown using standard Burk's medium, which could be amended by increasing the molybdenum levels to further increase the ammonium yield. In addition, elevated levels of nitrogenase gene transcription are not accompanied by a corresponding dramatic increase in hydrogenase gene transcription levels or hydrogen uptake rates. Of the three potential electron donor systems for nitrogenase, only the rnf1 gene cluster showed a transcriptional correlation to the increased yield of ammonium. Our results also highlight several additional genes that may play a role in supporting elevated ammonium production in this aerobic nitrogen-fixing model bacterium. IMPORTANCE The transcriptional differences found during stationary-phase ammonium accumulation show a strong contrast between the deregulated (nifL-disrupted) and wild-type strains and what was previously reported for the wild-type strain under exponential-phase growth conditions. These results demonstrate that further improvement of the ammonium yield in this nitrogenase-deregulated strain can be obtained by increasing the amount of available molybdenum in the medium. These results also indicate a potential preference for one of two ATP synthases present in A. vinelandii as well as a prominent role for the membrane-bound hydrogenase over the soluble hydrogenase in hydrogen gas recycling. These results should inform future studies aimed at elucidating the important features of this phenotype and at maximizing ammonium production by this strain.

scholarly journals Vibrio fischeriDarR Directs Responses to D-Aspartate and Represents a Group of Similar LysR-Type Transcriptional Regulators

2018 ◽  
Vol 200 (15) ◽  
Author(s):  
Richard M. Jones ◽  
David L. Popham ◽  
Alicia L. Schmidt ◽  
Ellen L. Neidle ◽  
Eric V. Stabb
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Transcriptional Control ◽  
Vibrio Fischeri ◽  
Transcriptional Response ◽  
Control Mechanisms ◽  
Wild Type ◽  
Acinetobacter Baylyi ◽  
Transcriptional Responses ◽  
Content Type

ABSTRACTMounting evidence suggests thatd-amino acids play previously underappreciated roles in diverse organisms. In bacteria, evend-amino acids that are absent from canonical peptidoglycan (PG) may act as growth substrates, as signals, or in other functions. Given these proposed roles and the ubiquity ofd-amino acids, the paucity of knownd-amino-acid-responsive transcriptional control mechanisms in bacteria suggests that such regulation awaits discovery. We found that DarR, a LysR-type transcriptional regulator (LTTR), activates transcription in response tod-Asp. Thed-Glu auxotrophy of aVibrio fischerimurI::Tn mutant was suppressed, with the wild-type PG structure maintained, by a point mutation indarR. ThisdarRmutation resulted in the overexpression of an adjacent operon encoding a putative aspartate racemase, RacD, which compensated for the loss of the glutamate racemase encoded bymurI. Using transcriptional reporters, we found that wild-type DarR activatedracDtranscription in response to exogenousd-Asp but not upon the addition ofl-Asp,l-Glu, ord-Glu. A DNA sequence typical of LTTR-binding sites was identified betweendarRand the divergently orientedracDoperon, and scrambling this sequence eliminated activation of the reporter in response tod-Asp. In several proteobacteria, genes encoding LTTRs similar to DarR are linked to genes with predicted roles ind- and/orl-Asp metabolism. To test the functional similarities in another bacterium,darRandracDmutants were also generated inAcinetobacter baylyi. InV. fischeriandA. baylyi, growth ond-Asp required the presence of bothdarRandracD. Our results suggest that multiple bacteria have the ability to sense and respond tod-Asp.IMPORTANCEd-Amino acids are prevalent in the environment and are generated by organisms from all domains of life. Although some biological roles ford-amino acids are understood, in other cases, their functions remain uncertain. Given the ubiquity ofd-amino acids, it seems likely that bacteria will initiate transcriptional responses to them. Elucidatingd-amino acid-responsive regulators along with the genes they control will help uncover bacterial uses ofd-amino acids. Here, we report the discovery of DarR, a novel LTTR inV. fischerithat mediates a transcriptional response to environmentald-Asp and underpins the catabolism ofd-Asp. DarR represents the founding member of a group of bacterial homologs that we hypothesize control aspects of aspartate metabolism in response tod-Asp and/or tod-Asp-containing peptides.

scholarly journals TfoX-Based Genetic Mapping Identifies Vibrio fischeri Strain-Level Differences and Reveals a Common Lineage of Laboratory Strains

2015 ◽  
Vol 197 (6) ◽  
pp. 1065-1074 ◽  
Author(s):  
John F. Brooks ◽  
Mattias C. Gyllborg ◽  
Acadia A. Kocher ◽  
Laura E. H. Markey ◽  
Mark J. Mandel
Keyword(s):  
Genetic Mapping ◽  
Vibrio Fischeri ◽  
Natural Populations ◽  
Culture Conditions ◽  
Strain Level ◽  
Wild Type ◽  
Random Mutation ◽  
Genetic Traits ◽  
Content Type ◽  
Glycerol Utilization

Bacterial strain variation exists in natural populations of bacteria and can be generated experimentally through directed or random mutation. The advent of rapid and cost-efficient whole-genome sequencing has facilitated strain-level genotyping. Even with modern tools, however, it often remains a challenge to map specific traits to individual genetic loci, especially for traits that cannot be selected under culture conditions (e.g., colonization level or pathogenicity). Using a combination of classical and modern approaches, we analyzed strain-level variation inVibrio fischeriand identified the basis by which some strains lack the ability to utilize glycerol as a carbon source. We proceeded to reconstruct the lineage of the commonly usedV. fischerilaboratory strains. Compared to the wild-type ES114 strain, we identify in ES114-L a 9.9-kb deletion with endpoints intadB2andglpF; restoration of the missing portion ofglpFrestores the wild-type phenotype. The widely used strains ESR1, JRM100, and JRM200 contain the same deletion, and ES114-L is likely a previously unrecognized intermediate strain in the construction of many ES114 derivatives. ES114-L does not exhibit a defect in competitive squid colonization but ESR1 does, demonstrating that glycerol utilization is not required for early squid colonization. Our genetic mapping approach capitalizes on the recently discovered chitin-based transformation pathway, which is conserved in theVibrionaceae; therefore, the specific approach used is likely to be useful for mapping genetic traits in otherVibriospecies.

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