Examples Quorum sensing

1 examples

1.1 vibrio fischeri
1.2 escherichia coli
1.3 salmonella enterica
1.4 pseudomonas aeruginosa
1.5 acinetobacter sp.
1.6 aeromonas sp.
1.7 yersinia

examples
vibrio fischeri

quorum sensing first observed in aliivibrio fischeri, bioluminescent bacterium lives mutualistic symbiont in photophore (or light-producing organ) of hawaiian bobtail squid. when a. fischeri cells free-living (or planktonic), autoinducer @ low concentration, and, thus, cells not luminesce. however, when highly concentrated in photophore (about 10 cells/ml), transcription of luciferase induced, leading bioluminescence.

escherichia coli

in gram-negative bacterium escherichia coli (e. coli), cell division may partially regulated ai-2-mediated quorum sensing. species uses ai-2, produced , processed lsr operon. part of encodes abc transporter, imports ai-2 cells during stationary (latent) phase of growth. ai-2 phosphorylated lsrk kinase, , newly produced phospho-ai-2 can either internalized or used suppress lsrr, repressor of lsr operon (thereby activating operon). transcription of lsr operon thought inhibited dihydroxyacetone phosphate (dhap) through competitive binding lsrr. glyceraldehyde 3-phosphate has been shown inhibit lsr operon through camp-capk-mediated inhibition. explains why, when grown glucose, e. coli lose ability internalize ai-2 (because of catabolite repression). when grown normally, ai-2 presence transient.

e. coli , salmonella enterica not produce ahl signals commonly found in other gram-negative bacteria. however, have receptor detects ahls other bacteria , change gene expression in accordance presence of other quorate populations of gram-negative bacteria.

gram positive bacteria quorum sensing


salmonella enterica

salmonella encodes luxr homolog, sdia, not encode ahl synthase. sdia detects ahls produced other species of bacteria including aeromonas hydrophila, hafnia alvei, , yersinia enterocolitica. when ahl detected, sdia regulates rck operon on salmonella virulence plasmid (pefi-srgd-srga-srgb-rck-srgc) , single gene horizontal acquisition in chromosome srge. salmonella not detect ahl when passing through gastrointestinal tracts of several animal species, suggesting normal microbiota not produce ahls. however, sdia become activated when salmonella transits through turtles colonized aeromonas hydrophila or mice infected yersinia enterocolitica. therefore, salmonella appears use sdia detect ahl production of other pathogens rather normal gut flora.

pseudomonas aeruginosa

the opportunistic pathogen pseudomonas aeruginosa uses quorum sensing coordinate formation of biofilms, swarming motility, exopolysaccharide production, virulence, , cell aggregation. these bacteria can grow within host without harming it, until reach threshold concentration. become aggressive, developing point @ numbers sufficient overcome host s immune system, , form biofilm, leading disease within host biofilm protective layer encasing bacteria population. form of gene regulation allows bacteria rapidly adapt surrounding changes through environmental signaling. recent studies have discovered anaerobiosis can impact major regulatory circuit of quorum sensing. important link between quorum sensing , anaerobiosis has significant impact on production of virulence factors of organism. garlic , ginseng experimentally block quorum sensing in pseudomonas aeruginosa. hoped therapeutic enzymatic degradation of signaling molecules prevent formation of such biofilms , possibly weaken established biofilms. disrupting signalling process in way called quorum sensing inhibition.

acinetobacter sp.

it has been found acinetobacter sp. show quorum sensing activity. bacterium, emerging pathogen, produces ahls. interestingly, acinetobacter sp. shows both quorum sensing , quorum quenching activity. produces ahls , also, can degrade ahl molecules well.

aeromonas sp.

this bacterium considered fish pathogen, has emerged human pathogen. aeromonas sp. have been isolated various infected sites patients (bile, blood, peritoneal fluid, pus, stool , urine). isolates produced 2 principal ahls, n-butanoylhomoserine lactone (c4-hsl) , n-hexanoyl homoserine lactone (c6-hsl). has been documented aeromonas sobria has produced c6-hsl , 2 additional ahls n-acyl side chain longer c6.

yersinia

the yenr , yeni proteins produced gammaproteobacterium yersinia enterocolitica similar aliivibrio fischeri luxr , luxi. yenr activates expression of small non-coding rna, yens. yens inhibits yeni expression , acylhomoserine lactone production. yenr/yeni/yens involved in control of swimming , swarming motility.