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:

DOWNLOAD EBOOK

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:

DOWNLOAD EBOOK

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:

DOWNLOAD EBOOK

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.

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: Everett Greenberg

Publisher:

Published: 1998

Total Pages: 4

ISBN-13:

DOWNLOAD EBOOK

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.

Implication of Quorum Sensing System in Biofilm Formation and Virulence
Implication of Quorum Sensing System in Biofilm Formation and Virulence

Author: Pallaval Veera Bramhachari

Publisher: Springer

Published: 2019-01-28

Total Pages: 381

ISBN-13: 9811324298

DOWNLOAD EBOOK

This book illustrates the importance and significance of Quorum sensing (QS), it’s critical roles in regulating diverse cellular functions in microbes, including bioluminescence, virulence, pathogenesis, gene expression, biofilm formation and antibiotic resistance. Microbes can coordinate population behavior with small molecules called autoinducers (AHL) which serves as a signal of cellular population density, triggering new patterns of gene expression for mounting virulence and pathogenesis. Therefore, these microbes have the competence to coordinate and regulate explicit sets of genes by sensing and communicating amongst themselves utilizing variety of signals. This book descry emphasizes on how bacteria can coordinate an activity and synchronize their response to external signals and regulate gene expression. The chapters of the book provide the recent advancements on various functional aspects of QS systems in different gram positive and gram negative organisms. Finally, the book also elucidates a comprehensive yet a representative description of a large number of challenges associated with quorum sensing signal molecules viz. virulence, pathogenesis, antibiotic synthesis, biosurfactants production, persister cells, cell signaling and biofilms, intra and inter-species communications, host-pathogen interactions, social interactions & swarming migration in biofilms.