Sequence and function of LuxO, a negative regulator of luminescence in Vibrio harveyi

Abstract

Density-dependent expression of luminescence in Vibrio harveyi is regulated by the concentration of extracellular signal molecules (autoinducers) in the culture medium. A recombinant clone that restored function to one class of spontaneous dim mutants was found to encode a function required for the density-dependent response. Transposon Tn5 insertions in the recombinant clone were isolated, and the mutations were transferred to the genome of V. harveyi for examination of mutant phenotypes. Expression of luminescence in V. harveyi strains with transposon insertions in one locus, luxO, was independent of the density of the culture and was similar in intensity to the maximal level observed in wild-type bacteria. Sequence analysis of luxO revealed one open reading frame that encoded a protein, LuxO, similar in amino acid sequence to the response regulator domain of the family of two-component, signal transduction proteins. The constitutive phenotype of LuxO- mutants indicates that LuxO acts negatively to control expression of luminescence, and relief of repression by LuxO in the wild type could result from interactions with other components in the Lux signalling system.

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

“…In V. harveyi, AI-2 detection and transduction rely on a two-component system similar to that of the QS system in gram-positive bacteria [11]. Boron-AI-2 is recognized by a soluble periplasmic protein that interacts with cytoplasmic response regulator proteins, thus triggering a sensor-kinase couple to finally control the expression of the luciferase structural operon (luxCDABE) [4,21,23,24].…”

“…AI-2 QS system was first identified in the marine bacterium Vibrio harveyi as a part of a complex multilayered QS system responsible for regulating bioluminescence and other virulence-associated traits [4,11]. 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].…”

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

“…Neither the structure nor the biosynthetic gene(s) for the system 2 autoinducer (AI-2) has been reported. The sensor proteins that detect AI-1 and AI-2 are members of the bacterial family of two-component adaptive regulatory proteins, and the mechanism of signal transduction is a phosphorylation͞dephosphorylation cascade (11,12). Reporter strains of V. harveyi have been constructed that respond specifically to only AI-1 or AI-2.…”

“…Therefore, system 1 is composed of sensor 1 and it responds to autoinducer 1 (AI-1), and system 2 is composed of sensor 2 and this system detects autoinducer 2 (AI-2) (6). Sensory information from both systems is integrated via a shared regulatory protein to control the output, light emission (7)(8)(9). Genetic analysis of V. harveyi has shown that either system 1 or system 2 is sufficient for the density-dependent expression of luminescence.…”

Alanine-scanning mutagenesis of selected residues in the N-terminal region alters the functionality of LuxO: lessons from a natural variant LuxOPL91

“…There is a preponderance of data suggesting that it is a homologue of two-component response regulator protein NtrC, which activates gene transcription in concert with the alternative sigma factor s 54 (Bassler et al, 1994;Lilley & Bassler, 2000). Sequence analysis documents several conserved residues in the N-terminal as well as C-terminal region of LuxO that are characteristic of s 54 -transcriptional activators (Lilley & Bassler, 2000).…”