scholarly journals Loss of the acetate switch in Vibrio vulnificus enhances predation defence against Tetrahymena pyriformis

2021 ◽  
Author(s):  
Viduthalai Rasheedkhan Regina ◽  
Parisa Noorian ◽  
Clarence Sim Bo Wen ◽  
Florentin Constancias ◽  
Eganathan Kaliyamoorthy ◽  
...  
Keyword(s):  
Vibrio Vulnificus ◽  
Anaerobic Respiration ◽  
Tetrahymena Pyriformis ◽  
Central Carbon Metabolism ◽  
Overflow Metabolism ◽  
Defence Mechanisms ◽  
Acetate Excretion ◽  
Control Switch ◽  
Natural Variants ◽  
Opportunistic Human Pathogen

Vibrio vulnificus is an opportunistic human pathogen and autochthonous inhabitant of coastal marine environments, where the bacterium is under constant predation by heterotrophic protists or protozoans. As a result of this selection pressure, genetic variants with anti-predation mechanisms are selected for and persist in the environment. Such natural variants may also be pathogenic to animal or human hosts, making it important to understand these defence mechanisms. To identify anti-predator strategies, thirteen V. vulnificus strains of different genotypes isolated from diverse environments were exposed to predation by the ciliated protozoan, Tetrahymena pyriformis , and only strain ENV1 was resistant to predation. Further investigation of the cell-free supernatant showed that ENV1 acidifies the environment by the excretion of organic acids, which is toxic to T. pyriformis . As this predation resistance was dependent on the availability of iron, transcriptomes of V. vulnificus in iron-replete and iron-deplete conditions were compared. This analysis revealed that ENV1 ferments pyruvate and the resultant acetyl-CoA leads to acetate synthesis under aerobic conditions, a hallmark of overflow metabolism. The anaerobic respiration global regulator, arcA , was upregulated when iron was available. An Δ arcA deletion mutant of ENV1 accumulated less acetate and importantly, was sensitive to grazing by T. pyriformis . Based on the transcriptome response and quantification of metabolites, we conclude that ENV1 has adapted to overflow metabolism and has lost a control switch that shifts metabolism from acetate excretion to acetate assimilation, enabling it to excrete acetate continuously. We show that overflow metabolism and the acetate switch contribute to prey-predator interactions. Importance Bacteria in the environment, including Vibrio spp., interact with protozoan predators. To defend against predation, bacteria evolve anti-predator mechanisms ranging from changing morphology, biofilm formation and secretion of toxins or virulence factors. Some of these adaptations may result in strains that are pathogenic to humans. Therefore, it is important to study predator defence strategies of environmental bacteria. V. vulnificus thrives in coastal waters and infects humans. Very little is know about the defence mechanisms V. vulnificus expresses against predation. Here we show that a V. vulnificus strain (ENV1) has rewired the central carbon metabolism enabling the production of excess organic acid that is toxic to the protozoan predator, T. pyriformis . This is a previously unknown mechanism of predation defence that protects against protozoan predators.

scholarly journals Regulation of acetate metabolism and coordination with the TCA cycle via a processed small RNA

2018 ◽  
Vol 116 (3) ◽  
pp. 1043-1052 ◽  
Author(s):  
François De Mets ◽  
Laurence Van Melderen ◽  
Susan Gottesman
Keyword(s):  
Small Rna ◽  
Posttranscriptional Regulation ◽  
Tca Cycle ◽  
Central Carbon Metabolism ◽  
Growth Defect ◽  
Acetate Metabolism ◽  
Overflow Metabolism ◽  
Acetyl Phosphate ◽  
Rnase E ◽  
The Tca Cycle

Bacterial regulatory small RNAs act as crucial regulators in central carbon metabolism by modulating translation initiation and degradation of target mRNAs in metabolic pathways. Here, we demonstrate that a noncoding small RNA, SdhX, is produced by RNase E-dependent processing from the 3′UTR of thesdhCDAB-sucABCDoperon, encoding enzymes of the tricarboxylic acid (TCA) cycle. InEscherichia coli, SdhX negatively regulatesackA, which encodes an enzyme critical for degradation of the signaling molecule acetyl phosphate, while the downstreamptagene, encoding the enzyme critical for acetyl phosphate synthesis, is not significantly affected. This discoordinate regulation ofptaandackAincreases the accumulation of acetyl phosphate when SdhX is expressed. Mutations insdhXthat abolish regulation ofackAlead to more acetate in the medium (more overflow metabolism), as well as a strong growth defect in the presence of acetate as sole carbon source, when the AckA-Pta pathway runs in reverse. SdhX overproduction confers resistance to hydroxyurea, via regulation ofackA. SdhX abundance is tightly coupled to the transcription signals of TCA cycle genes but escapes all known posttranscriptional regulation. Therefore, SdhX expression directly correlates with transcriptional input to the TCA cycle, providing an effective mechanism for the cell to link the TCA cycle with acetate metabolism pathways.

scholarly journals Complex Control of a Genomic Island Governing Biofilm and Rugose Colony Development in Vibrio vulnificus

2018 ◽  
Vol 200 (16) ◽  
Author(s):  
Daniel M. Chodur ◽  
Dean A. Rowe-Magnus
Keyword(s):  
Food Chain ◽  
Horizontal Transfer ◽  
Vibrio Vulnificus ◽  
Regulatory Control ◽  
Colony Development ◽  
Dependent Manner ◽  
Human Pathogen ◽  
Content Type ◽  
Regulatory Pathways ◽  
Opportunistic Human Pathogen

ABSTRACT Vibrio vulnificus is a potent opportunistic human pathogen that contaminates the human food chain by asymptomatically colonizing seafood. The expression of the 9-gene brp exopolysaccharide locus mediates surface adherence and is controlled by the secondary signaling molecule c-di-GMP and the regulator BrpT. Here, we show that c-di-GMP and BrpT also regulate the expression of an adjacent 5-gene cluster that includes the cabABC operon, brpT, and another VpsT-like transcriptional regulator gene, brpS. The expression of the 14 genes spanning the region increased with elevated intracellular c-di-GMP levels in a BrpT-dependent manner, save for brpS, which was positively regulated by c-di-GMP and repressed by BrpT. BrpS repressed brpA expression and was required for rugose colony development. The mutation of its consensus WFSA c-di-GMP binding motif blocked these activities, suggesting that BrpS function is dependent on binding c-di-GMP. BrpT specifically bound the cabA, brpT, and brpS promoters, and binding sites homologous to the Vibrio cholerae VpsT binding site were identified upstream of brpA and brpT. Transcription was initiated distal to brpA, and a conserved RfaH-recruiting ops element and a potential Rho utilization (rut) terminator site were identified within the 100-bp leader region, suggesting the integration of early termination and operon polarity suppression into the regulation of brp transcription. The GC content and codon usage of the 16-kb brp region was 5.5% lower relative to that of the flanking DNA, suggesting its recent assimilation via horizontal transfer. Thus, architecturally, the brp region can be considered an acquired biofilm and rugosity island that is subject to complex regulation. IMPORTANCE Biofilm and rugose colony formation are developmental programs that underpin the evolution of Vibrio vulnificus as a potent opportunistic human pathogen and successful environmental organism. A better understanding of the regulatory pathways governing theses phenotypes promotes the development and implementation of strategies to mitigate food chain contamination by this pathogen. c-di-GMP signaling is central to both pathways. We show that the molecule orchestrates the expression of 14 genes clustered in a 16-kb segment of the genome that governs biofilm and rugose colony development. This region exhibits the hallmarks of horizontal transfer, suggesting complex regulatory control of a recently assimilated genetic island governing the colonization response of V. vulnificus.

scholarly journals Survival of and In Situ Gene Expression by Vibrio vulnificus at Varying Salinities in Estuarine Environments

2007 ◽  
Vol 74 (1) ◽  
pp. 182-187 ◽  
Author(s):  
Melissa K. Jones ◽  
Elizabeth Warner ◽  
James D. Oliver
Keyword(s):  
Gene Expression ◽  
Vibrio Vulnificus ◽  
Natural Habitat ◽  
Term Survival ◽  
Long Term Survival ◽  
Wide Range ◽  
Opportunistic Human Pathogen

ABSTRACT The opportunistic human pathogen Vibrio vulnificus survives in a wide range of ecological environments, which demonstrates its ability to adapt to highly variable conditions. Survival and gene expression under various conditions have been extensively studied in vitro; however, little work has been done to evaluate this bacterium in its natural habitat. Therefore, this study monitored the long-term survival of V. vulnificus in situ and simultaneously evaluated the expression of stress (rpoS, relA, hfq, and groEL) and putative virulence (vvpE, smcR, viuB, and trkA) genes at estuarine sites of varying salinity. Additionally, the survival and gene expression of an rpoS and an oxyR mutant were examined under the same conditions. Differences between the sampling sites in the long-term survival of any strain were not seen. However, differences were seen in the expression of viuB, trkA, and relA but our findings differed from what has been previously shown in vitro. These results also routinely demonstrated that genes required for survival under in vitro stress or host conditions are not necessarily required for survival in the water column. Overall, this study highlights the need for further in situ evaluation of this bacterium in order to gain a true understanding of its ecology and how it relates to its natural habitat.

scholarly journals Interspecific Quorum Sensing Mediates the Resuscitation of Viable but Nonculturable Vibrios

2014 ◽  
Vol 80 (8) ◽  
pp. 2478-2483 ◽  
Author(s):  
Mesrop Ayrapetyan ◽  
Tiffany C. Williams ◽  
James D. Oliver
Keyword(s):  
Quorum Sensing ◽  
Molecular Mechanisms ◽  
Vibrio Vulnificus ◽  
Entry And Exit ◽  
Viable But Nonculturable ◽  
Content Type ◽  
Vbnc Cell ◽  
Opportunistic Human Pathogen ◽  
Survival Mechanisms

ABSTRACTEntry and exit from dormancy are essential survival mechanisms utilized by microorganisms to cope with harsh environments. Many bacteria, including the opportunistic human pathogenVibrio vulnificus, enter a form of dormancy known as the viable but nonculturable (VBNC) state. VBNC cells can resuscitate when suitable conditions arise, yet the molecular mechanisms facilitating resuscitation in most bacteria are not well understood. We discovered that bacterial cell-free supernatants (CFS) can awaken preexisting dormant vibrio populations within oysters and seawater, while CFS from a quorum sensing mutant was unable to produce the same resuscitative effect. Furthermore, the quorum sensing autoinducer AI-2 could induce resuscitation of VBNCV. vulnificus in vitro, and VBNC cells of a mutant unable to produce AI-2 were unable to resuscitate unless the cultures were supplemented with exogenous AI-2. The quorum sensing inhibitor cinnamaldehyde delayed the resuscitation of wild-type VBNC cells, confirming the importance of quorum sensing in resuscitation. By monitoring AI-2 production by VBNC cultures over time, we found quorum sensing signaling to be critical for the natural resuscitation process. This study provides new insights into the molecular mechanisms stimulating VBNC cell exit from dormancy, which has significant implications for microbial ecology and public health.

scholarly journals The Proline Variant of the W[F/L/M][T/S]R Cyclic Di-GMP Binding Motif Suppresses Dependence on Signal Association for Regulator Function

2017 ◽  
Vol 199 (19) ◽  
Author(s):  
Daniel M. Chodur ◽  
Linda Guo ◽  
Meng Pu ◽  
Eric Bruger ◽  
Nico Fernandez ◽  
...  
Keyword(s):  
Vibrio Vulnificus ◽  
Single Point ◽  
Extracellular Polysaccharide ◽  
Single Point Mutation ◽  
Binding Motif ◽  
Content Type ◽  
Bacterial Signaling ◽  
Direct Binding ◽  
Opportunistic Human Pathogen ◽  
The Impact

ABSTRACT Vibrio vulnificus is an estuarine bacterium and potent opportunistic human pathogen. It enters the food chain by asymptomatically colonizing a variety of marine organisms, most notably oysters. Expression of the brp-encoded extracellular polysaccharide, which enhances cell-surface adherence, is regulated by cyclic di-GMP (c-di-GMP) and the activator BrpT. The Vibrio cholerae and Vibrio parahaemolyticus homologs VpsT and CpsQ, directly bind c-di-GMP via a novel W[F/L/M][T/S]R motif, and c-di-GMP binding is absolutely required for activity. Notably, BrpT belongs to a distinct subclass of VpsT-like regulators that harbor a proline in the third position of the c-di-GMP binding motif (WLPR), and the impact of this change on activity is unknown. We show that the brp locus is organized as two linked operons with BrpT specifically binding to promoters upstream of brpA and brpH. Expression data and structural modeling suggested that BrpT might be less dependent on c-di-GMP binding for activity than VpsT or CpsQ. We show that the affinity of BrpT for c-di-GMP is low and that signal binding is not a requisite for BrpT function. Furthermore, a BrpT mutant engineered to carry a canonical WLTR motif (BrpTP124T) bound c-di-GMP with high affinity and its activity was now c-di-GMP dependent. Conversely, introduction of the WLPR motif into VpsT suppressed its dependence on c-di-GMP for activity. This is the first demonstration of reduced dependence on signal association for regulator function within this motif family. Thus, BrpT defines a new class of VpsT-like transcriptional regulators, and the WLPR motif variant may similarly liberate the activity of other subclass members. IMPORTANCE A Vibrio genome may encode nearly 100 proteins that make, break, and bind c-di-GMP, underscoring its central role in the physiology of these bacteria. The activity of the biofilm regulators VpsT of V. cholerae and CpsQ of V. parahaemolyticus is regulated by the direct binding of c-di-GMP via a novel W[F/L/M][T/S]R motif. The V. vulnificus homolog, BrpT, bears an unusual WLPR variant and remains active at low intracellular c-di-GMP levels. This suggests that the WLPR motif may also liberate the activity of other members of this subclass. A single point mutation at the 3rd position of the motif was sufficient to moderate dependence on c-di-GMP binding for activator function, highlighting the simplicity with which complex bacterial signaling networks can be rewired.

scholarly journals Cyclo-(L-Phe-L-Pro), a Quorum-Sensing Signal ofVibrio vulnificus, Induces Expression of Hydroperoxidase through a ToxR-LeuO-HU-RpoS Signaling Pathway To Confer Resistance against Oxidative Stress

2018 ◽  
Vol 86 (9) ◽  
Author(s):  
In Hwang Kim ◽  
So-Yeon Kim ◽  
Na-Young Park ◽  
Yancheng Wen ◽  
Keun-Woo Lee ◽  
...  
Keyword(s):  
Oxidative Stress ◽  
Signaling Pathway ◽  
Virulence Factor ◽  
Vibrio Vulnificus ◽  
Transcriptional Regulator ◽  
Oxygen Species ◽  
Human Pathogen ◽  
Content Type ◽  
Opportunistic Human Pathogen ◽  
Bacterial Genes

ABSTRACTVibrio vulnificus, an opportunistic human pathogen, produces cyclo-(l-Phe-l-Pro) (cFP), which serves as a signaling molecule controlling the ToxR-dependent expression of innate bacterial genes, and also as a virulence factor eliciting pathogenic effects on human cells by enhancing intracellular reactive oxygen species levels. We found that cFP facilitated the protection ofV. vulnificusagainst hydrogen peroxide. At a concentration of 1 mM, cFP enhanced the level of the transcriptional regulator RpoS, which in turn induced expression ofkatG, encoding hydroperoxidase I, an enzyme that detoxifies H2O2to overcome oxidative stress. We found that cFP upregulated the transcription of the histone-like proteins vHUα and vHUβ through the cFP-dependent regulator LeuO. LeuO binds directly to upstream regions ofvhuAandvhuBto enhance transcription. vHUα and vHUβ then enhance the level of RpoS posttranscriptionally by stabilizing the mRNA. This cFP-mediated ToxR-LeuO-vHUαβ-RpoS pathway also upregulates genes known to be members of the RpoS regulon, suggesting that cFP acts as a cue for the signaling pathway responsible for both the RpoS and the LeuO regulons. Taken together, this study shows that cFP plays an important role as a virulence factor, as well as a signal for the protection of the cognate pathogen.

scholarly journals Complete Genome Sequence of Oyster Isolate Vibrio vulnificus Env1

2018 ◽  
Vol 6 (20) ◽  
Author(s):  
Parisa Noorian ◽  
Shuyang Sun ◽  
Diane McDougald
Keyword(s):  
Genome Sequence ◽  
Complete Genome Sequence ◽  
Complete Genome ◽  
Vibrio Vulnificus ◽  
Tetrahymena Pyriformis ◽  
Opportunistic Pathogen ◽  
Environmental Isolate ◽  
Marine Animals ◽  
Content Type ◽  
Coastal Marine

ABSTRACT Vibrio vulnificus, a ubiquitous inhabitant of coastal marine environments, has been isolated from a variety of sources. It is an opportunistic pathogen of both marine animals and humans. Here, the genome sequence of V. vulnificus Env1, an environmental isolate resistant to predation by the ciliate Tetrahymena pyriformis, is reported.

Bacterial adherence and biofilm behavior of Vibrio vulnificus

1993 ◽  
Vol 51 ◽  
pp. 378-379
Author(s):  
B. D. Tall ◽  
R. T. Gray ◽  
D. B. Shah
Keyword(s):  
Electron Microscopy ◽  
Biofilm Formation ◽  
Vibrio Vulnificus ◽  
Ruthenium Red ◽  
Human Pathogen ◽  
Normal Microflora ◽  
Microscopic Studies ◽  
Plate Counts ◽  
Opportunistic Human Pathogen ◽  
Phase Variants

Vibrio vulnificus, an opportunistic human pathogen, is found as member of the normal microflora of shellfish and other seafoods, many of which are eaten raw. Though usually not harmful, V. vulnificus is responsible for causing fulminating septicemia in immunocompromised individuals. In previous light microscopic studies, we showed data suggesting that isogenic unencapsulated phase variants were more adherent to HeLa cells than were counterpart encapsulated phase variants. In this study, we extended our observations by comparing phase variant capsular morphology stained with Alcian blue (AB) and Ruthenium red (RR), and investigated the dynamics of biofilm formation by these organisms to glass coverslips (CS) using quantitative plate counts and scanning electron microscopy (SEM).To characterize the morphology of capsules expressed by these organisms, we stained cells grown on trypticase soy agar containing 1 % NaCl (TSA/NaCl) with AB and then prepared them for electron microscopy (EM) according to the method described by Hendley et al.

scholarly journals The HlyU Protein Is a Positive Regulator of rtxA1, a Gene Responsible for Cytotoxicity and Virulence in the Human Pathogen Vibrio vulnificus

2007 ◽  
Vol 75 (7) ◽  
pp. 3282-3289 ◽  
Author(s):  
Moqing Liu ◽  
Alejandro F. Alice ◽  
Hiroaki Naka ◽  
Jorge H. Crosa
Keyword(s):  
Transcription Initiation ◽  
Vibrio Vulnificus ◽  
Protein A ◽  
Open Reading Frames ◽  
Toxin Gene ◽  
Release Factor ◽  
Rapid Progress ◽  
Human Pathogen ◽  
Opportunistic Human Pathogen ◽  
Reading Frames

ABSTRACT Vibrio vulnificus is an opportunistic human pathogen that preferentially infects compromised iron-overloaded patients, causing a fatal primary septicemia with very rapid progress, resulting in a high mortality rate. In this study we determined that the HlyU protein, a virulence factor in V. vulnificus CMCP6, up-regulates the expression of VV20479, a homologue of the Vibrio cholerae RTX (repeats in toxin) toxin gene that we named rtxA1. This gene is part of an operon together with two other open reading frames, VV20481 and VV20480, that encode two predicted proteins, a peptide chain release factor 1 and a hemolysin acyltransferase, respectively. A mutation in rtxA1 not only contributes to the loss of cytotoxic activity but also results in a decrease in virulence, whereas a deletion of VV20481 and VV20480 causes a slight decrease in virulence but with no effect in cytotoxicity. Activation of the expression of the rtxA1 operon by HlyU occurs at the transcription initiation level by binding of the HlyU protein to a region upstream of this operon.

scholarly journals Experimental Identification and Quantification of Glucose Metabolism in Seven Bacterial Species

2005 ◽  
Vol 187 (5) ◽  
pp. 1581-1590 ◽  
Author(s):  
Tobias Fuhrer ◽  
Eliane Fischer ◽  
Uwe Sauer
Keyword(s):  
Glucose Metabolism ◽  
Sinorhizobium Meliloti ◽  
Bacterial Species ◽  
Building Blocks ◽  
Central Carbon Metabolism ◽  
Pentose Phosphate ◽  
Overflow Metabolism ◽  
Dehydrogenase Reaction ◽  
Tracer Experiments

ABSTRACT The structurally conserved and ubiquitous pathways of central carbon metabolism provide building blocks and cofactors for the biosynthesis of cellular macromolecules. The relative uses of pathways and reactions, however, vary widely among species and depend upon conditions, and some are not used at all. Here we identify the network topology of glucose metabolism and its in vivo operation by quantification of intracellular carbon fluxes from 13C tracer experiments. Specifically, we investigated Agrobacterium tumefaciens, two pseudomonads, Sinorhizobium meliloti, Rhodobacter sphaeroides, Zymomonas mobilis, and Paracoccus versutus, which grow on glucose as the sole carbon source, represent fundamentally different metabolic lifestyles (aerobic, anaerobic, photoheterotrophic, and chemoheterotrophic), and are phylogenetically distinct (firmicutes, γ-proteobacteria, and α-proteobacteria). Compared to those of the model bacteria Escherichia coli and Bacillus subtilis, metabolisms of the investigated species differed significantly in several respects: (i) the Entner-Doudoroff pathway was the almost exclusive catabolic route; (ii) the pentose phosphate pathway exhibited exclusively biosynthetic functions, in many cases also requiring flux through the nonoxidative branch; (iii) all aerobes exhibited fully respiratory metabolism without significant overflow metabolism; and (iv) all aerobes used the pyruvate bypass of the malate dehydrogenase reaction to a significant extent. Exclusively, Pseudomonas fluorescens converted most glucose extracellularly to gluconate and 2-ketogluconate. Overall, the results suggest that metabolic data from model species with extensive industrial and laboratory history are not representative of microbial metabolism, at least not quantitatively.

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