Chitin induces natural competence in Vibrio cholerae.
16 Dec 2005-Science (American Association for the Advancement of Science)-Vol. 310, Iss: 5755, pp 1824-1827
TL;DR: It was shown that V. cholerae can acquire new genetic material by natural transformation during growth on chitin, a biopolymer that is abundant in aquatic habitats, where it lives as an autochthonous microbe.
Abstract: The mosaic-structured Vibrio cholerae genome points to the importance of horizontal gene transfer (HGT) in the evolution of this human pathogen. We showed that V. cholerae can acquire new genetic material by natural transformation during growth on chitin, a biopolymer that is abundant in aquatic habitats (e.g., from crustacean exoskeletons), where it lives as an autochthonous microbe. Transformation competence was found to require a type IV pilus assembly complex, a putative DNA binding protein, and three convergent regulatory cascades, which are activated by chitin, increasing cell density, and nutrient limitation, a decline in growth rate, or stress.
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TL;DR: It is argued that the Vibrio quorum-sensing systems are optimally designed to precisely translate extracellular autoinducer information into internal changes in gene expression.
Abstract: Quorum sensing is a cell-cell communication process in which bacteria use the production and detection of extracellular chemicals called autoinducers to monitor cell population density. Quorum sensing allows bacteria to synchronize the gene expression of the group, and thus act in unison. Here, we review the mechanisms involved in quorum sensing with a focus on the Vibrio harveyi and Vibrio cholerae quorum-sensing systems. We discuss the differences between these two quorum-sensing systems and the differences between them and other paradigmatic bacterial signal transduction systems. We argue that the Vibrio quorum-sensing systems are optimally designed to precisely translate extracellular autoinducer information into internal changes in gene expression. We describe how studies of the V. harveyi and V. cholerae quorum-sensing systems have revealed some of the fundamental mechanisms underpinning the evolution of collective behaviors.
1,448 citations
Cites background from "Chitin induces natural competence i..."
...cholerae cells in the presence of chitin, which is believed to be important for serogroup conversion (6, 7, 73)....
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TL;DR: It was concluded that safe drinking water for all is one of the major challenges of the 21st century and that microbiological control of drinking water should be the norm everywhere.
Abstract: Water is essential to life, but many people do not have access to clean and safe drinking water and many die of waterborne bacterial infections. In this review a general characterization of the most important bacterial diseases transmitted through water— cholera, typhoid fever and bacillary dysentery—is presented, focusing on the biology and ecology of the causal agents and on the diseases' characteristics and their life cycles in the environment. The importance of pathogenic Escherichia coli strains and emerging pathogens in drinking water-transmitted diseases is also briefly discussed. Microbiological water analysis is mainly based on the concept of fecal indicator bacteria. The main bacteria present in human and animal feces (focusing on their behavior in their hosts and in the environment) and the most important fecal indicator bacteria are presented and discussed (focusing on the advantages and limitations of their use as markers). Important sources of bacterial fecal pollution of environmental waters are also briefly indicated. In the last topic it is discussed which indicators of fecal pollution should be used in current drinking water microbiological analysis. It was concluded that safe drinking water for all is one of the major challenges of the 21st century and that microbiological control of drinking water should be the norm everywhere. Routine basic microbiological analysis of drinking water should be carried out by assaying the presence of Escherichia coli by culture methods. Whenever financial resources are available, fecal coliform determinations should be complemented with the quantification of enterococci. More studies are needed in order to check if ammonia is reliable for a preliminary screening for emergency fecal pollution outbreaks. Financial resources should be devoted to a better understanding of the ecology and behavior of human and animal fecal bacteria in environmental waters.
853 citations
Cites background from "Chitin induces natural competence i..."
...This process was demonstrated in vitro in cell suspensions and in vivo in the gut of the rat [8,13,19,20]....
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TL;DR: It is found that cyclic di-GMP in many bacterial species is sensed by a riboswitch class in messenger RNA that controls the expression of genes involved in numerous fundamental cellular processes.
Abstract: Cyclic di-guanosine monophosphate (di-GMP) is a circular RNA dinucleotide that functions as a second messenger in diverse species of bacteria to trigger wide-ranging physiological changes, including cell differentiation, conversion between motile and biofilm lifestyles, and virulence gene expression. However, the mechanisms by which cyclic di-GMP regulates gene expression have remained a mystery. We found that cyclic di-GMP in many bacterial species is sensed by a riboswitch class in messenger RNA that controls the expression of genes involved in numerous fundamental cellular processes. A variety of cyclic di-GMP regulons are revealed, including some riboswitches associated with virulence gene expression, pilus formation, and flagellum biosynthesis. In addition, sequences matching the consensus for cyclic di-GMP riboswitches are present in the genome of a bacteriophage.
716 citations
TL;DR: It is argued that understanding this balance between competition and cooperation is central to building a complete and predictive model of biofilm formation, and it is concluded that the appearance of organization in biofilms can emerge without active coordination.
Abstract: Biofilms are densely packed communities of microbial cells that grow on surfaces and surround themselves with secreted polymers. Many bacterial species form biofilms, and their study has revealed them to be complex and diverse. The structural and physiological complexity of biofilms has led to the idea that they are coordinated and cooperative groups, analogous to multicellular organisms. We evaluate this idea by addressing the findings of microbiologists from the perspective of sociobiology, including theories of collective behavior (self-organization) and social evolution. This yields two main conclusions. First, the appearance of organization in biofilms can emerge without active coordination. That is, biofilm properties such as phenotypic differentiation, species stratification and channel formation do not necessarily require that cells communicate with one another using specialized signaling molecules. Second, while local cooperation among bacteria may often occur, the evolution of cooperation among all cells is unlikely for most biofilms. Strong conflict can arise among multiple species and strains in a biofilm, and spontaneous mutation can generate conflict even within biofilms initiated by genetically identical cells. Biofilms will typically result from a balance between competition and cooperation, and we argue that understanding this balance is central to building a complete and predictive model of biofilm formation.
615 citations
TL;DR: Excessive use of antimicrobials in aquaculture can potentially negatively impact animal and human health as well as the aquatic environment and should be better assessed and regulated.
Abstract: The worldwide growth of aquaculture has been accompanied by a rapid increase in therapeutic and prophylactic usage of antimicrobials including those important in human therapeutics. Approximately 80% of antimicrobials used in aquaculture enter the environment with their activity intact where they select for bacteria whose resistance arises from mutations or more importantly, from mobile genetic elements containing multiple resistance determinants transmissible to other bacteria. Such selection alters biodiversity in aquatic environments and the normal flora of fish and shellfish. The commonality of the mobilome (the total of all mobile genetic elements in a genome) between aquatic and terrestrial bacteria together with the presence of residual antimicrobials, biofilms, and high concentrations of bacteriophages where the aquatic environment may also be contaminated with pathogens of human and animal origin can stimulate exchange of genetic information between aquatic and terrestrial bacteria. Several recently found genetic elements and resistance determinants for quinolones, tetracyclines, and β-lactamases are shared between aquatic bacteria, fish pathogens, and human pathogens, and appear to have originated in aquatic bacteria. Excessive use of antimicrobials in aquaculture can thus potentially negatively impact animal and human health as well as the aquatic environment and should be better assessed and regulated.
602 citations
Cites background from "Chitin induces natural competence i..."
...Several aquatic bacteria such as Vibrio spp. are naturally competent for DNA uptake, thus also increasing the opportunities for transformation to occur in the aquatic environment (Stewart and Sinigalliano, 1990; Meibom et al., 2005; Baharoglu et al., 2012)....
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References
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TL;DR: Bacterial biofilms are structured communities of cells enclosed in self-produced hydrated polymeric matrix adherent to an inert or living surface that have inherent resistance to antibiotics and host immune attack.
Abstract: Bacterial biofilms are structured communities of cells enclosed in self-produced hydrated polymeric matrix adherent to an inert or living surface ([1][1]). Formation of these sessile communities and their inherent resistance to antibiotics and host immune attack are at the root of many persistent
1,962 citations
TL;DR: The emergence of toxigenic V. cholerae involves horizontal gene transfer that may depend on in vivo gene expression, and is shown here to be encoded by a filamentous bacteriophage (designated CTXΦ), which is related to coliphage M13.
Abstract: Vibrio cholerae, the causative agent of cholera, requires two coordinately regulated factors for full virulence: cholera toxin (CT), a potent enterotoxin, and toxin-coregulated pili (TCP), surface organelles required for intestinal colonization. The structural genes for CT are shown here to be encoded by a filamentous bacteriophage (designated CTXphi), which is related to coliphage M13. The CTXphi genome chromosomally integrated or replicated as a plasmid. CTXphi used TCP as its receptor and infected V. cholerae cells within the gastrointestinal tracts of mice more efficiently than under laboratory conditions. Thus, the emergence of toxigenic V. cholerae involves horizontal gene transfer that may depend on in vivo gene expression.
1,744 citations
TL;DR: The current understanding of the biology of transformation is summarized to provide the platform on which aspects of bacterial transformation in water, soil, and sediments and the habitat of pathogens are discussed.
1,329 citations
TL;DR: It is shown that, in addition to the known components of the ToxR signaling circuit, quorum-sensing regulators are involved in regulation of V. cholerae virulence, and an infant mouse model found that a luxO mutant is severely defective in colonization of the small intestine.
Abstract: The production of virulence factors including cholera toxin and the toxin-coregulated pilus in the human pathogen Vibrio cholerae is strongly influenced by environmental conditions. The well-characterized ToxR signal transduction cascade is responsible for sensing and integrating the environmental information and controlling the virulence regulon. We show here that, in addition to the known components of the ToxR signaling circuit, quorum-sensing regulators are involved in regulation of V. cholerae virulence. We focused on the regulators LuxO and HapR because homologues of these two proteins control quorum sensing in the closely related luminous marine bacterium Vibrio harveyi. Using an infant mouse model, we found that a luxO mutant is severely defective in colonization of the small intestine. Gene arrays were used to profile transcription in the V. cholerae wild type and the luxO mutant. These studies revealed that the ToxR regulon is repressed in the luxO mutant, and that this effect is mediated by another negative regulator, HapR. We show that LuxO represses hapR expression early in log-phase growth, and constitutive expression of hapR blocks ToxR-regulon expression. Additionally, LuxO and HapR regulate a variety of other cellular processes including motility, protease production, and biofilm formation. Together these data suggest a role for quorum sensing in modulating expression of blocks of virulence genes in a reciprocal fashion in vivo.
843 citations
TL;DR: The current knowledge of DNA transport during transformation is reviewed, and proteins related to those involved in the assembly of type IV pili and type II secretion systems are reviewed.
Abstract: Naturally competent bacteria are able to take up exogenous DNA and undergo genetic transformation. The transport of DNA from the extracellular milieu into the cytoplasm is a complex process, and requires proteins that are related to those involved in the assembly of type IV pili and type II secretion systems, as well as a DNA translocase complex at the cytoplasmic membrane. Here, we will review the current knowledge of DNA transport during transformation.
745 citations