Quorum‐sensing autoinducer molecules produced by members of a multispecies biofilm promote horizontal gene transfer to Vibrio cholerae
TL;DR: It is demonstrated that comEA transcription and the horizontal acquisition of DNA by V. cholerae are induced in response to purified CAI-1 and AI-2, and also by autoinducers derived from other Vibrios co-cultured with V. Cholerae within a mixed-species biofilm, suggesting that autoinducer communication within a consortium may promote DNA exchange among VibRIos.
Abstract: Vibrio cholerae, the causative agent of cholera and a natural inhabitant of aquatic environments, regulates numerous behaviors using a quorum-sensing (QS) system conserved among many members of the marine genus Vibrio. The Vibrio QS response is mediated by two extracellular autoinducer (AI) molecules: CAI-I, which is produced only by Vibrios, and AI-2, which is produced by many bacteria. In marine biofilms on chitinous surfaces, QS-proficient V. cholerae become naturally competent to take up extracellular DNA. Because the direct role of AIs in this environmental behavior had not been determined, we sought to define the contribution of CAI-1 and AI-2 in controlling transcription of the competence gene, comEA, and in DNA uptake. In this study we demonstrated that comEA transcription and the horizontal acquisition of DNA by V. cholerae are induced in response to purified CAI-1 and AI-2, and also by autoinducers derived from other Vibrios co-cultured with V. cholerae within a mixed-species biofilm. These results suggest that autoinducer communication within a consortium may promote DNA exchange among Vibrios, perhaps contributing to the evolution of these bacterial pathogens.
Citations
More filters
TL;DR: Recent progress in the study of marine microbial surface colonization and biofilm development is synthesized and discussed and questions are posed for targeted investigation of surface-specific community-level microbial features to advance understanding ofsurface-associated microbial community ecology and the biogeochemical functions of these communities.
Abstract: SUMMARY Biotic and abiotic surfaces in marine waters are rapidly colonized by microorganisms. Surface colonization and subsequent biofilm formation and development provide numerous advantages to these organisms and support critical ecological and biogeochemical functions in the changing marine environment. Microbial surface association also contributes to deleterious effects such as biofouling, biocorrosion, and the persistence and transmission of harmful or pathogenic microorganisms and their genetic determinants. The processes and mechanisms of colonization as well as key players among the surface-associated microbiota have been studied for several decades. Accumulating evidence indicates that specific cell-surface, cell-cell, and interpopulation interactions shape the composition, structure, spatiotemporal dynamics, and functions of surface-associated microbial communities. Several key microbial processes and mechanisms, including (i) surface, population, and community sensing and signaling, (ii) intraspecies and interspecies communication and interaction, and (iii) the regulatory balance between cooperation and competition, have been identified as critical for the microbial surface association lifestyle. In this review, recent progress in the study of marine microbial surface colonization and biofilm development is synthesized and discussed. Major gaps in our knowledge remain. We pose questions for targeted investigation of surface-specific community-level microbial features, answers to which would advance our understanding of surface-associated microbial community ecology and the biogeochemical functions of these communities at levels from molecular mechanistic details through systems biological integration.
696 citations
Additional excerpts
...cholerae in multispecies biofilms (558)....
[...]
TL;DR: It is argued that the lack of environment-facing mitigation actions included in existing AMR action plans is likely a function of the authors' poor fundamental understanding of many of the key issues and the science to inform policy is lacking and this needs to be addressed.
Abstract: The environment is increasingly being recognised for the role it might play in the global spread of clinically-relevant antibiotic resistance. Environmental regulators monitor and control many of the pathways responsible for the release of resistance-driving chemicals into the environment (e.g., antimicrobials, metals, biocides). Hence, environmental regulators should be contributing significantly to the development of global and national antimicrobial resistance (AMR) action plans. It is argued that the lack of environment-facing mitigation actions included in existing AMR action plans is likely a function of our poor fundamental understanding of many of the key issues. Here, we aim to present the problem with AMR in the environment through the lens of an environmental regulator, using the Environment Agency (England’s regulator) as an example from which parallels can be drawn globally. The issues that are pertinent to environmental regulators are drawn out to answer: What are the drivers and pathways of AMR? How do these relate to the normal work, powers and duties of environmental regulators? What are the knowledge gaps that hinder the delivery of environmental protection from AMR? We offer several thought experiments for how different mitigation strategies might proceed. We conclude that: 1) AMR Action Plans do not tackle all the potentially relevant pathways and drivers of AMR in the environment; and 2) AMR Action Plans are deficient, in part, because the science to inform policy is lacking and this needs to be addressed.
525 citations
Cites background from "Quorum‐sensing autoinducer molecule..."
...Many additional drivers (e.g., chemical and environmental) of HGT have been identified (Hastings et al., 2004; Antonova and Hammer, 2011), including abiotic sources (Warnes et al., 2012; Kotnik, 2013)....
[...]
TL;DR: A comprehensive review of the discovery and early characterization of AI-2, current developments in signal detection, transduction and regulation, and the major studies investigating the phenotypes regulated by this molecule is presented.
Abstract: Success in nature depends upon an ability to perceive and adapt to the surrounding environment. Bacteria are not an exception; they recognize and constantly adjust to changing situations by sensing environmental and self-produced signals, altering gene expression accordingly. Autoinducer-2 (AI-2) is a signal molecule produced by LuxS, an enzyme found in many bacterial species and thus proposed to enable interspecies communication. Two classes of AI-2 receptors and many layers and interactions involved in downstream signalling have been identified so far. Although AI-2 has been implicated in the regulation of numerous niche-specific behaviours across the bacterial kingdom, interpretation of these results is complicated by the dual role of LuxS in signalling and the activated methyl cycle, a crucial central metabolic pathway. In this article, we present a comprehensive review of the discovery and early characterization of AI-2, current developments in signal detection, transduction and regulation, and the major studies investigating the phenotypes regulated by this molecule. The development of novel tools should help to resolve many of the remaining questions in the field; we highlight how these advances might be exploited in AI-2 quorum quenching, treatment of diseases, and the manipulation of beneficial behaviours caused by polyspecies communities.
433 citations
TL;DR: The recent focus on complex bacterial communities has led to the recognition of interactions across species boundaries, particularly pronounced in multispecies biofilms, where synergistic interactions impact the bacterial distribution and overall biomass produced.
400 citations
TL;DR: A critical review of QS and how it relates to biofilms in engineered water and wastewater treatment systems and identifies needs for future research is provided.
Abstract: Bacteria have their own form of “twitter” communication, described as quorum sensing (QS), where bacteria emit and sense chemical signal molecules as a means to gauge population density and control gene expression. Many QS-controlled genes relate to biofilm formation and function and may be important for some water and wastewater treatment biofilms. There is a need to better understand bacterial QS, the bacteria biofilm aspects influenced by QS in engineered reactors, and to assess how designs and operations might be improved by taking this signaling into account. This paper provides a critical review of QS and how it relates to biofilms in engineered water and wastewater treatment systems and identifies needs for future research.
256 citations
References
More filters
TL;DR: Chitin-induced natural transformation might be a common mechanism for serogroup conversion in aquatic habitats and for the emergence of V. cholerae variants that are better adapted for survival in environmental niches or more pathogenic for humans.
Abstract: The environmental reservoirs for Vibrio cholerae are natural aquatic habitats, where it colonizes the chitinous exoskeletons of copepod molts. Growth of V. cholerae on a chitin surface induces competence for natural transformation, a mechanism for intra-species gene exchange. The antigenically diverse O-serogroup determinants of V. cholerae are encoded by a genetically variable biosynthetic cluster of genes that is flanked on either side by chromosomal regions that are conserved between different serogroups. To determine whether this genomic motif and chitin-induced natural transformation might enable the exchange of serogroup-specific gene clusters between different O serogroups of V. cholerae, a strain of V. cholerae O1 El Tor was co-cultured with a strain of V. cholerae O139 Bengal within a biofilm on the same chitin surface immersed in seawater, and O1-to-O139 transformants were obtained. Serogroup conversion of the O1 recipient by the O139 donor was demonstrated by comparative genomic hybridization, biochemical and serological characterization of the O-antigenic determinant, and resistance of O1-to-O139 transformants to bacteriolysis by a virulent O1-specific phage. Serogroup conversion was shown to have occurred as a single-step exchange of large fragments of DNA. Crossovers were localized to regions of homology common to other V. cholerae serogroups that flank serogroup-specific encoding sequences. This result and the successful serogroup conversion of an O1 strain by O37 genomic DNA indicate that chitin-induced natural transformation might be a common mechanism for serogroup conversion in aquatic habitats and for the emergence of V. cholerae variants that are better adapted for survival in environmental niches or more pathogenic for humans.
183 citations
"Quorum‐sensing autoinducer molecule..." refers background in this paper
...In laboratory microcosms, DNA encoding antigenic determinants and also carrying CTXF occurs via chitin-induced HGT (Blokesch & Schoolnik, 2007; Udden et al., 2008) between V. cholerae....
[...]
...In this study, we tested the hypothesis that autoinducer molecules made by different bacteria within a mixed-species biofilm induce HGT to V. cholerae (Bartlett & Azam, 2005)....
[...]
...We are currently performing experiments to test a model that autoinducers may promote interspecies HGT and emergence of genetic diversity in Vibrios....
[...]
...It is proposed that HGT among Vibrio species likely explains the current genome structures, but it has yet to be demonstrated whether chitin-induced HGT can promote DNA exchange among different Vibrios in environmental microcosms....
[...]
...HapR represses multiple genes, and also activates others, such as the gene coding for ComEA, a ssDNA-binding protein required for DNA uptake or horizontal gene transfer (HGT) (Meibom et al., 2005) (Fig....
[...]
TL;DR: Evidence for a unique gut flora in laboratory-reared animals is presented and the predominant bacteria were represented by the genus Vibrio; other organisms such as Pseudomonas and Cytophaga were found less abundantly associated with the copepods and not specifically associated withThe gut.
Abstract: Little is known about the nature of bacteria associated with the surface and gut of marine copepods, either in laboratory-reared animals or in the natural environment. Nor is it known whether such animals possess a gut flora. The present report deals with studies of microorganisms isolated from healthy, laboratory-reared copepods of the species Acartia tonsa Dana, from several species of wild copepods collected from a marine or estuarine environment, and from laboratory dishes containing moribund copepods. Evidence for a unique gut flora in laboratory-reared animals is presented; the predominant bacteria were represented by the genus Vibrio. Other organisms such as Pseudomonas and Cytophaga were found less abundantly associated with the copepods and not specifically associated with the gut. Images
182 citations
"Quorum‐sensing autoinducer molecule..." refers background in this paper
...…determine whether additional chitinous materials that support growth of Vibrios and other bacteria in marine environments (Kaneko & Colwell, 1975; Sochard et al., 1979; Davis & Sizemore, 1982; Huq et al., 1983; Bartlett & Azam, 2005; Lyons et al., 2007) also stimulate autoinducer-induced DNA…...
[...]
...Vibrio species can often be found together in marine settings (Kaneko & Colwell, 1975; Kaper et al., 1979; Sochard et al., 1979; Davis & Sizemore, 1982; Huq et al., 1983; Lyons et al., 2007) and can communicate with each other using both CAI-1 and AI2 (Bassler et al., 1997; Henke & Bassler, 2004a;…...
[...]
TL;DR: Vibrio spp.
Abstract: Bacteria were readily isolated from the hemolymph of a majority (88%) of the blue crabs collected from Galveston Bay, Texas. The hemolymph of most crabs contained moderate (greater than 10(3) bacteria/ml) to heavy (greater than (10(5) bacteria/ml) infections. Large variances were observed in the bacterial number associated with individual crabs, but no significant difference was observed between the mean bacterial levels in the hemolymph of crabs collected during different seasons of the sampling year. Vibrio spp. were the predominant bacterial types in the hemolymph of infected crabs and increased in number significantly during the summer season. Warmer water temperatures were thought to be responsible for this increase. Bacterial numbers and the percentage of Vibrio spp. were highest in the interior of the crab bodies, especially in the digestive tract. The exterior of the crabs did not appear to be the source of the hemolymph's bacterial flora. Bacteria taxonomically identical to Vibrio cholerae. V. vulnificus, and V. parahaemolyticus were routinely isolated from the crab hemolymph and external carapace. V. parahaemolyticus was the most prevalent of the pathogenic Vibrio spp. and was isolated from 23% of the hemolymph samples. V. vulnificus (7%) and V. cholerae (2%) occurred less commonly in the hemolymph. The incidences of V. parachaemolyticus and V. vulnificus were related and increased in the summer months. Both organisms were frequently isolated from the same crab.
141 citations
"Quorum‐sensing autoinducer molecule..." refers background in this paper
...…chitinous materials that support growth of Vibrios and other bacteria in marine environments (Kaneko & Colwell, 1975; Sochard et al., 1979; Davis & Sizemore, 1982; Huq et al., 1983; Bartlett & Azam, 2005; Lyons et al., 2007) also stimulate autoinducer-induced DNA uptake (Bartlett & Azam,…...
[...]
...Vibrio species can often be found together in marine settings (Kaneko & Colwell, 1975; Kaper et al., 1979; Sochard et al., 1979; Davis & Sizemore, 1982; Huq et al., 1983; Lyons et al., 2007) and can communicate with each other using both CAI-1 and AI2 (Bassler et al., 1997; Henke & Bassler, 2004a;…...
[...]
TL;DR: It is shown that in the absence of Dns, transformation frequencies are significantly higher than in its presence, and the following model is suggested: nuclease production by low-density populations of V. cholerae might foster rapid growth by providing a source of nucleotides for the repletion of nucleotide pools.
Abstract: Free extracellular DNA is abundant in many aquatic environments. While much of this DNA will be degraded by nucleases secreted by the surrounding microbial community, some is available as transforming material that can be taken up by naturally competent bacteria. One such species is Vibrio cholerae, an autochthonous member of estuarine, riverine, and marine habitats and the causative agent of cholera, whose competence program is induced after colonization of chitin surfaces. In this study, we investigate how Vibrio cholerae's two extracellular nucleases, Xds and Dns, influence its natural transformability. We show that in the absence of Dns, transformation frequencies are significantly higher than in its presence. During growth on a chitin surface, an increase in transformation efficiency was found to correspond in time with increasing cell density and the repression of dns expression by the quorum-sensing regulator HapR. In contrast, at low cell density, the absence of HapR relieves dns repression, leading to the degradation of free DNA and to the abrogation of the transformation phenotype. Thus, as cell density increases, Vibrio cholerae undergoes a switch from nuclease-mediated degradation of extracellular DNA to the uptake of DNA by bacteria induced to a state of competence by chitin. Taken together, these results suggest the following model: nuclease production by low-density populations of V. cholerae might foster rapid growth by providing a source of nucleotides for the repletion of nucleotide pools. In contrast, the termination of nuclease production by static, high-density populations allows the uptake of intact DNA and coincides with a phase of potential genome diversification.
141 citations
"Quorum‐sensing autoinducer molecule..." refers background or result in this paper
...…impaired in expression of the comEA gene and in DNA uptake Previous studies with V. cholerae mutants (DhapR and DluxO) documented that in addition to the chitin controlled TfoX pathway, QS is required for the activation of comEA transcription (Meibom et al., 2005; Blokesch & Schoolnik, 2008) (Fig....
[...]
...Thus, wild-type (WT) V. cholerae strains are naturally competent at high cell density, a DhapR mutant does not take up DNA, and a DluxO strain that constitutively expresses HapR is capable of comEA-dependent DNA uptake even at low cell density (Meibom et al., 2005; Blokesch & Schoolnik, 2008)....
[...]
01 Jan 2009
TL;DR: Gene dosage compensation adjusts the total Qrr1–4 sRNA pool and provides the molecular mechanism underlying sRNA redundancy, which is exquisitely sensitive to small perturbations in Qrr levels.
Abstract: Quorum sensing is a mechanism of cell-to-cell communication that allows bacteria to coordinately regulate gene expression in response to changes in cell-population density. At the core of the Vibrio cholerae quorum-sensing signal transduction pathway reside four homologous small RNAs (sRNAs), named the quorum regulatory RNAs 1‐4 (Qrr1‐4). The four Qrr sRNAs are functionally redundant. That is, expression of any one of them is sufficient for wild-type quorum-sensing behaviour. Here, we show that the combined action of two feedback loops, one involving the sRNA-activator LuxO and one involving the sRNAtarget HapR, promotes gene dosage compensation between the four qrr genes. Gene dosage compensation adjusts the total Qrr1‐4 sRNA pool and provides the molecular mechanism underlying sRNA redundancy. The dosage compensation mechanism is exquisitely sensitive to small perturbations in Qrr levels. Precisely maintained Qrr levels are required to direct the proper timing and correct patterns of expression of quorum-sensingregulated target genes.
105 citations
"Quorum‐sensing autoinducer molecule..." refers background in this paper
...At low cell density (low autoinducer levels) the phosphorylated response regulator LuxO activates transcription of multiple small RNAs that base-pair with and alter translation of several mRNAs, most notably repressing the translation of hapR, which encodes the master regulator of QS (Lenz et al., 2004; Hammer & Bassler, 2007; Svenningsen et al., 2009; Rutherford et al., 2011)....
[...]
...…LuxO activates transcription of multiple small RNAs that base-pair with and alter translation of several mRNAs, most notably repressing the translation of hapR, which encodes the master regulator of QS (Lenz et al., 2004; Hammer & Bassler, 2007; Svenningsen et al., 2009; Rutherford et al., 2011)....
[...]