The Quorum-sensing Regulon of Vibrio Fischeri
The Quorum-sensing Regulon of Vibrio Fischeri

Author: Sean Michael Callahan

Publisher:

Published: 1999

Total Pages: 192

ISBN-13:

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In this study five proteins regulated by quorum sensing are described from the marine bacterium Vibrio fischeri. Each protein is positively regulated by 30C6-HSL and LuxR and negatively regulated at low population density by C8-HSL. Probable LuxR/autoinducer binding sites are found in the promoter regions of the genes encoding each of the proteins. QsrP and RibB are encoded monocistronically, whereas AcfA and QsrV appear to be encoded by a two-gene operon. In competition assays with the parent strain, qsrP and acfA insertion mutants displayed altered colonization phenotypes with the squid symbiotic host. RibB is believed to be an enzyme that catalyzes an initial step of riboflavin synthesis and AcfA is believed to be a pilus subunit protein. The functions of QsrP and QsrV are unknown at this time. Oriented divergently from acfA are open reading frames that code for two putative members of the LysR family of transcriptional regulators. The shared promoter region suggests that transcription of acfA and qsrv may be regulated by one or both of these divergently transcribed proteins. This work defines a quorum-sensing regulon in V. fischeri. A model describing its regulation is presented.

The Quorum-sensing Regulation of Vibrio Fischeri
The Quorum-sensing Regulation of Vibrio Fischeri

Author: Sean Michael Callahan

Publisher:

Published: 1999

Total Pages: 340

ISBN-13:

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In the marine bacterium Vibrio fischeri two intercellular homoserine-Iactone signal molecules (luxI-dependent 30C6-HSL and the ainS-dependent C8-HSL) and the transcriptional activator LuxR regulate the luminescence system in a cell-density dependent manner by a process termed quorum sensing. In this study, five additional proteins whose production is regulated by quorum sensing are described, and the genes encoding four of the five proteins, denoted as QsrP, RibB, QsrV, and AcfA, are analyzed. Each protein is positively regulated by 30C6-HSL and LuxR and negatively regulated at low population density by C8-HSL. Probable LuxR/autoinducer binding sites are found in the promoter region of each. QsrP and RibB are encoded monocistronically, whereas AcfA and QsrV appear to be encoded by a two-gene operon. On the basis of sequence similarity to proteins of known function from other organisms, RibB is believed to be an enzyme that catalyzes the transformation of ribulose 5-phosphate to 3,4-dihydroxy-2- butanone 4-phosphate, a precursor for the xylene ring of riboflavin; AcfA is believed to be a pilus subunit; and the functions of QsrP and QsrV are unknown at this time. A qsrP mutant was reduced in its ability to colonize its symbiotic partner, Euprymna scolopes when placed in competition with the parent strain. On the other hand, a mutant strain of V. fischeri containing an insertion in acfA, which is believed to be polar with respect to qsrV, displayed enhanced colonization competence in a competition assay. A ribB mutant grew well on media not supplemented with additional riboflavin and displayed normal induction of luminescence. Both phenotypes suggest that the lack of a functional ribB gene is complemented by another gene of similar function in the mutant. Oriented divergently from acfA are open reading frames that code for two putative proteins that are similar in sequence to members of the LysR family of transcriptional regulators. Organization of the two divergent sets of genes and the shared promoter region suggests that transcription of acfA and qsrV may be regulated by one or both of these divergently transcribed proteins. This work defines a quorum-sensing regulon in V. fischeri. A model describing its regulation is presented.

Regulation of Vibrio Quorum Sensing in Natural and Competitive Environments
Regulation of Vibrio Quorum Sensing in Natural and Competitive Environments

Author: Michaela Jo Eickhoff

Publisher:

Published: 2021

Total Pages: 0

ISBN-13:

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Bacteria have the remarkable ability to rapidly and accurately detect and adapt to fluctuations in the environment. Often, transcriptional and post-transcriptional regulatory mechanisms function in concert to tune gene expression patterns that enhance survival and conserve resources under varying conditions. Among the changes bacteria monitor and respond to is the cell density and species composition of the vicinal community. Bacteria accomplish this using quorum sensing (QS), a cell-cell communication process that alters global gene expression patterns to foster the synchronous execution of collective behaviors. QS involves the production, release, accumulation, and group-wide detection of signaling molecules called autoinducers (AIs). The marine bacterium V. harveyi produces and responds to three AIs, which act in parallel. At low cell-density, AI concentrations are low, and a phosphorelay cascade leads to the activation of five small regulatory RNAs called Qrr1-5 that post-transcriptionally regulate target genes, leading to a downstream QS regulon of over 600 genes. Because Qrr1-5 largely function redundantly, the advantages of encoding five qrr genes are not well-understood. This work explores the transcriptional and post-transcriptional regulatory mechanisms controlling the QS regulon and how the V. harveyi QS response is altered in the presence of competing bacterial species. First, a new QS regulator called LuxT is discovered to repress the transcription of one Qrr small RNA, Qrr1. As a repressor of qrr1, LuxT indirectly regulates Qrr1 target mRNAs, demonstrating how Qrr1 can control gene expression independently of Qrr2-5. Second, LuxT is also identified as a global regulator that functions in parallel to QS to control over 400 genes. Finally, a co-culture model between V. harveyi and its competitor Vibrio fischeri is established to study QS interactions in competitive multi-species environments.

The Physical Basis of Bacterial Quorum Communication
The Physical Basis of Bacterial Quorum Communication

Author: Stephen J. Hagen

Publisher: Springer

Published: 2014-09-29

Total Pages: 257

ISBN-13: 1493914022

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Quorum sensing (QS) describes a chemical communication behavior that is nearly universal among bacteria. Individual cells release a diffusible small molecule (an autoinducer) into their environment. A high concentration of this autoinducer serves as a signal of high population density, triggering new patterns of gene expression throughout the population. However QS is often much more complex than this simple census-taking behavior. Many QS bacteria produce and detect multiple autoinducers, which generate quorum signal cross talk with each other and with other bacterial species. QS gene regulatory networks respond to a range of physiological and environmental inputs in addition to autoinducer signals. While a host of individual QS systems have been characterized in great molecular and chemical detail, quorum communication raises many fundamental quantitative problems which are increasingly attracting the attention of physical scientists and mathematicians. Key questions include: What kinds of information can a bacterium gather about its environment through QS? What physical principles ultimately constrain the efficacy of diffusion-based communication? How do QS regulatory networks maximize information throughput while minimizing undesirable noise and cross talk? How does QS function in complex, spatially structured environments such as biofilms? Previous books and reviews have focused on the microbiology and biochemistry of QS. With contributions by leading scientists and mathematicians working in the field of physical biology, this volume examines the interplay of diffusion and signaling, collective and coupled dynamics of gene regulation, and spatiotemporal QS phenomena. Chapters will describe experimental studies of QS in natural and engineered or microfabricated bacterial environments, as well as modeling of QS on length scales spanning from the molecular to macroscopic. The book aims to educate physical scientists and quantitative-oriented biologists on the application of physics-based experiment and analysis, together with appropriate modeling, in the understanding and interpretation of the pervasive phenomenon of microbial quorum communication.

Quorum Sensing vs Quorum Quenching: A Battle with No End in Sight
Quorum Sensing vs Quorum Quenching: A Battle with No End in Sight

Author: Vipin Chandra Kalia

Publisher: Springer

Published: 2016-08-23

Total Pages: 0

ISBN-13: 9788132235484

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Microbial relationships with all life forms can be as free living, symbiotic or pathogenic. Human beings harbor 10 times more microbial cells than their own. Bacteria are found on the skin surface, in the gut and other body parts. Bacteria causing diseases are the most worrisome. Most of the infectious diseases are caused by bacterial pathogens with an ability to form biofilm. Bacteria within the biofilm are up to 1000 times more resistant to antibiotics. This has taken a more serious turn with the evolution of multiple drug resistant bacteria. Health Departments are making efforts to reduce high mortality and morbidity in man caused by them. Bacterial Quorum sensing (QS), a cell density dependent phenomenon is responsible for a wide range of expressions such as pathogenesis, biofilm formation, competence, sporulation, nitrogen fixation, etc. Majority of these organisms that are important for medical, agriculture, aquaculture, water treatment and remediation, archaeological departments are: Aeromonas, Acinetobacter, Bacillus, Clostridia, Enterococcus, Pseudomonas, Vibrio and Yersinia spp. Biosensors and models have been developed to detect QS systems. Strategies for inhibiting QS system through natural and synthetic compounds have been presented here. The biotechnological applications of QS inhibitors (QSIs) in diverse areas have also been dealt with. Although QSIs do not affect growth and are less likely to impose selective pressure on bacteria, however, a few reports have raised doubts on the fate of QSIs. This book addresses a few questions. Will bacteria develop mechanisms to evade QSIs? Are we watching yet another defeat at the hands of bacteria? Or will we be acting intelligently and survive the onslaughts of this Never Ending battle?

Quorum Sensing in Vibrio Fischeri Cell Density-Dependent Activation of Symbiosis-Related Genes in a Marine Bacterium
Quorum Sensing in Vibrio Fischeri Cell Density-Dependent Activation of Symbiosis-Related Genes in a Marine Bacterium

Author:

Publisher:

Published: 1998

Total Pages: 0

ISBN-13:

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The general objective of the proposed research is to fully elucidate the mechanism of quorum sensing and response in bacteria by continuing investigations of the most well-developed model for this phenomenon, autoinduction of lux genes in Vibrio fischeri. This research should continue to reveal general rules governing regulation of bacterial genes used specifically in symbiotic associations with marine animals. This research program also has recently provided and should continue to provide insights into how bacteria interact with eukaryotic hosts in a more universal way. Little is known about synthesis of the autoinducer, the sensory signal, other than that it is catalyzed by the luxI gene product. Thus, an analysis of the structure and function of LuxI was initiated. This analysis involved the construction of point and deletion mutations in luxI and studies of the activity of the mutant proteins encoded by these defective genes. This analysis also involved studies of autoinducer synthesis in luxI-containing E. coli amino acid biosynthesis mutants, and studies of the biochemistry of purified enzymes.

Quorum Sensing
Quorum Sensing

Author: Giuseppina Tommonaro

Publisher: Academic Press

Published: 2019-04-15

Total Pages: 310

ISBN-13: 0128149051

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Quorum sensing (QS) is a process of bacterial cooperative behaviour that has an effect on gene regulation. This cell-to-cell communication system involves the production of signalling molecules according to cell density and growth stage. Virulence, the ability to infest a habitat and cause disease, is also governed by such communication signals. Quorum Sensing: Molecular mechanism and biotechnological application collects, describes and summarizes the most interesting results obtained from experts working on QS mechanisms. It contributes to the understanding of the molecular basis that regulates this mechanism, and describes new findings in fields of application. This volume describes the QS mechanism from its molecular basis to medical applications such as antibiotic therapy and involvement of QS in pathologies. This reference also analyzes its potential use in biotechnological applications such as food packaging, drug delivery, and marine biofilm. The broad scope of this title will be of significant use to researchers across several fields with interest in QS, including to microbiologists, chemists, biochemists and ecologists. Describes Quorum Sensing (QS) mechanisms from their molecular basis, to their clinical applications Spans several fields in relation to QS, including microbiology, chemistry, biochemistry and ecology Considers QS as an approach to the discovery of new antibiotics Looks at QS as a means to understand the microbial world and towards use of bacteria and their products in biotechnological applications Summarizes key results on QS mechanisms' molecular basis and fields of application