Vibrio cholerae, the pathogen that causes cholera, also survives in aqueous reservoirs, probably in the form of biofilms. Quorum sensing negatively regulates V. cholerae biofilm formation through HapR, whose expression is induced at a high cell density. In this study, we show that the concentration of the quorum-sensing signal molecule CAI-1 is higher in biofilms than in planktonic cultures. By...

The LasR-dependent and RhlR-dependent quorum-sensing systems are global regulators of gene expression in Pseudomonas aeruginosa. Previous studies have demonstrated that promoter elements of the quorum-sensing-controlled genes lasB and hcnABC are important in density-dependent regulation. We have identified LasR- and RhlR-dependent determinants in promoters of quorum-sensing-controlled genes qsc...

The quorum regulatory cascade is poorly characterized in Vibrio parahaemolyticus, in part because swarming and virulence factors--the hallmarks of the organism--are repressed by this scheme of gene control, and quorum sensing seems to be silenced in many isolates. In these studies, we examine a swarming-proficient, virulent strain and identify an altered-function allele of the quorum regulator ...

Cell-to cell communication occurs via a signaling pathway referred to as quorum sensing. There are four main types of these systems according to the chemical nature of signal molecules used by microorganisms to elicit expression of target genes in response to environmental stimuli or need of microbial communities. Type I system acts by using acyl homoserine lactones as signals to trigger the ex...

background and objectives: this study was designed to evaluate the activity of quercus infectoria galls extract (qifge) on virulence factor production and inhibition of quorum sensing (qs) in pseudomonas aeruginosa. materials and methods: minimum inhibitory concentration (mic) of qifge against 5 strains of p. aeruginosa was determined. the extract at sub-mic was used to determine biofilm format...

Quorum sensing is a chemical signaling mechanism used by bacteria to communicate and orchestrate group behaviors. Multiple feedback loops exist in the quorum-sensing circuit of the model bacterium Vibrio harveyi. Using fluorescence microscopy of individual cells, we assayed the activity of the quorum-sensing circuit, with a focus on defining the functions of the feedback loops. We quantitativel...

QoS-constrained policy has an advantage to guarantee QoS requirements requested by users. Quorum systems can ensure the consistency and availability of replicated data despite the benign failure of data repositories. We propose a Quorum based resource management scheme, which resource Quorum includes middleware entity and network entity, both can satisfy requirements of application QoS. We also...

N-acylhomoserine lactone-dependent quorum sensing was first discovered in two luminescent marine bacteria, Vibrio fischeri and Vibrio harveyi. The LuxI/R system of V. fischeri is the paradigm of Gram-negative quorum-sensing systems; however, it is not found in all vibrios. A more complex quorum-sensing regulation is found in V. harveyi. Three parallel systems transmit signals via phosphorelays ...

'Secrete-and-sense cells' can communicate by secreting a signaling molecule while also producing a receptor that detects the molecule. The cell can potentially 'talk' to itself ('self-communication') or talk to neighboring cells with the same receptor ('neighbor communication'). The predominant forms of secrete-and-sense cells are self-communicating 'autocrine cells', which are largely found in...

The expression of certain bacterial genes is regulated in a cell-density dependent way, a phenomenon called quorum sensing. Both Gram-negative and Gram-positive bacteria use this type of communication, though the signal molecules (auto-inducers) used by them differ between both groups: Gram-negative bacteria use predominantly N-acyl homoserine lacton (AHL) molecules (autoinducer-1, AI-1) while ...