Quorum sensing in Escherichia coli , Salmonella typhimurium , and Vibrio harveyi : A new family of genes responsible for autoinducer production

Abstract

In bacteria, the regulation of gene expression in response to changes in cell density is called quorum sensing. Quorum-sensing bacteria produce, release, and respond to hormone-like molecules (autoinducers) that accumulate in the external environment as the cell population grows. In the marine bacterium Vibrio harveyi two parallel quorum-sensing systems exist, and each is composed of a sensor-autoinducer pair. V. harveyi reporter strains capable of detecting only autoinducer 1 (AI-1) or autoinducer 2 (AI-2) have been constructed and used to show that many species of bacteria, including Escherichia coli MG1655, E. coli O157:H7, Salmonella typhimurium 14028, and S. typhimurium LT2 produce autoinducers similar or identical to the V. harveyi system 2 autoinducer AI-2. However, the domesticated laboratory strain E. coli DH5␣ does not produce this signal molecule. Here we report the identification and analysis of the gene responsible for AI-2 production in V. harveyi, S. typhimurium, and E. coli. The genes, which we have named luxS V.h. , luxS S.t. , and luxS E.c. respectively, are highly homologous to one another but not to any other identified gene. E. coli DH5␣ can be complemented to AI-2 production by the introduction of the luxS gene from V. harveyi or E. coli O157:H7. Analysis of the E. coli DH5␣ luxS E.c. gene shows that it contains a frameshift mutation resulting in premature truncation of the LuxS E.c. protein. Our results indicate that the luxS genes define a new family of autoinducer-production genes.

Monitoring of Vibrio harveyi quorum sensing activity in real time during infection of brine shrimp larvae

“…As brine shrimp larvae are transparent, using bioluminescence as a read-out of quorum sensing activity allowed us to perform this kind of analysis. Quorum sensing-regulated bioluminescence has been used before in many studies investigating the quorum sensing activity of Vibrio harveyi (Bassler et al, 1994;Freeman and Bassler, 1999;Surette et al, 1999;Lilley and Bassler, 2000;Mok et al, 2003;Henke and Bassler, 2004b). We found that the bacteria behave remarkably similar in different larvae, despite the fact that only half of them survive the infection.…”

“…Vibrio harveyi strains and growth conditions Wild-type strain BB120 (ATCC BAA-1116) and quorum sensing mutants BB152 (luxM::Tn5; Bassler et al, 1994), MM30 (luxS::Tn5; Surette et al, 1999), JMH603 (cqsA::Cm R ; Henke and Bassler, 2004b) and JAF548 (luxO D47E linked to Kn R ; Freeman and Bassler, 1999) were grown in Luria-Bertani medium containing 35 g l À 1 Instant Figure 1 The Vibrio harveyi quorum sensing system. The LuxM, LuxS and CqsA enzymes synthesise the autoinducers HAI-1, AI-2 and CAI-1, respectively.…”

Synergy in biofilm formation between Fusobacterium nucleatum and Prevotella species

“…AI-2 levels in the culture supernatants of F. nucleatum, P. intermedia and P. nigrescens were evaluated using the Vibrio harveyi reporter strain BB170 (kindly provided by Dr. Bassler, B.L., Princeton University) as described by Surette et al (27,28). Briefly, after incubation in an anaerobic chamber for 24 hr, each culture broth was centrifuged at 10,000 g for 20 min.…”

LsrR-binding site recognition and regulatory characteristics in Escherichia coli AI-2 quorum sensing

“…When the concentration of the autoinducers reaches a threshold, an alteration of gene expression is induced, allowing the bacteria to adopt behaviors that are only productive when the bacteria are working together as a group [3,4]. Among many different mechanisms for QS by bacteria, one is shared by both gram-negative and gram-positive bacteria, involving the production of autoinducer 2 (AI-2) [5][6][7][8][9][10].…”

“…Subsequently, AI-2 production was verified in a large number of species and the AI-2 QS system was recognized to be involved in the regulation of a range of functions in diverse bacteria [6,7,10,[12][13][14]. In contrast to other autoinducers that are specific for a narrow range of organisms, the widely conserved AI-2 has been hypothesized to be a universal language for interspecies communication [6,9,10,13,15]. In every case, AI-2 is synthesized by LuxS, which functions in the pathway for metabolism of S-adenosylmethionine (SAM), a major cellular methyl donor.…”