PMID:17277225

Citation	Nelson, EJ, Tunsjø, HS, Fidopiastis, PM, Sørum, H and Ruby, EG (2007) A novel lux operon in the cryptically bioluminescent fish pathogen Vibrio salmonicida is associated with virulence. Appl. Environ. Microbiol. 73:1825-33
Abstract	The cold-water-fish pathogen Vibrio salmonicida expresses a functional bacterial luciferase but produces insufficient levels of its aliphatic-aldehyde substrate to be detectably luminous in culture. Our goals were to (i) better explain this cryptic bioluminescence phenotype through molecular characterization of the lux operon and (ii) test whether the bioluminescence gene cluster is associated with virulence. Cloning and sequencing of the V. salmonicida lux operon revealed that homologs of all of the genes required for luminescence are present: luxAB (luciferase) and luxCDE (aliphatic-aldehyde synthesis). The arrangement and sequence of these structural lux genes are conserved compared to those in related species of luminous bacteria. However, V. salmonicida strains have a novel arrangement and number of homologs of the luxR and luxI quorum-sensing regulatory genes. Reverse transcriptase PCR analysis suggests that this novel arrangement of quorum-sensing genes generates antisense transcripts that may be responsible for the reduced production of bioluminescence. In addition, infection with a strain in which the luxA gene was mutated resulted in a marked delay in mortality among Atlantic salmon relative to infection with the wild-type parent in single-strain challenge experiments. In mixed-strain competition between the luxA mutant and the wild type, the mutant was attenuated up to 50-fold. It remains unclear whether the attenuation results from a direct loss of luciferase or a polar disturbance elsewhere in the lux operon. Nevertheless, these findings document for the first time an association between a mutation in a structural lux gene and virulence, as well as provide a new molecular system to study Vibrio pathogenesis in a natural host.
Links	PubMed PMC1828807 Online version:10.1128/AEM.02255-06
Keywords	Aliivibrio salmonicida/genetics; Aliivibrio salmonicida/isolation & purification; Aliivibrio salmonicida/pathogenicity; Amino Acid Sequence; Animals; Conserved Sequence; DNA, Bacterial/chemistry; DNA, Bacterial/genetics; Fish Diseases/microbiology; Gadus morhua/microbiology; Luciferases, Bacterial/genetics; Molecular Sequence Data; Mutation; Operon/genetics; RNA, Antisense/biosynthesis; RNA, Bacterial/analysis; RNA, Bacterial/genetics; RNA, Messenger/analysis; RNA, Messenger/genetics; Reverse Transcriptase Polymerase Chain Reaction; Sequence Alignment; Sequence Homology; Survival Analysis; Vibrio Infections/microbiology; Vibrio Infections/mortality; Vibrio Infections/veterinary; Virulence/genetics
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Annotations

Gene product	Qualifier	GO Term	Evidence Code	with/from	Aspect	Extension	Notes	Status
9GAMM:Q4A537	involved_in	GO:0009405: pathogenesis	ECO:0000315: mutant phenotype evidence used in manual assertion		P		Seeded From UniProt	complete
9GAMM:Q4A537		GO:0009405: pathogenesis	ECO:0000315:		P		Figure Five demonstrates the virulence of wild type LuxA versus the EN4 mutant, which displays reduced virulence.	complete CACAO 8742

References

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