Occurrence and expression of luminescence in Vibrio cholerae

University of Maryland Institute for Advanced Computer Studies, University of Maryland, College Park, Maryland; Center of Marine Biotechnology, University of Maryland Biotechnology Institute, Baltimore, Maryland; International Center for Diarrhoeal Disease Research, Bangladesh, Dhaka, Bangladesh; Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland

^* To whom correspondence should be addressed. Email: rcolwell{at}umiacs.umd.edu.

	Abstract

Several species of the genus Vibrio are bioluminescent or contain bioluminescent strains, including Vibrio cholerae. Previous studies have reported only 10% of V. cholerae strains are luminescent. Analysis of 224 isolates of non-O1/non-O139 V. cholerae collected from Chesapeake Bay, MD, revealed that 52% (116/224) were luminescent when an improved assay method was employed and 58% (130/224) of isolates harbored the luxA gene. In contrast, 334 non-O1/non-O139 V. cholerae strains isolated from two rural provinces in Bangladesh yielded only 21 luminescent (6.3%) and 35 luxA⁺ (10.5%) isolates. An additional 270 clinical and environmental isolates of V. cholerae serogroups O1 and O139 were tested and none were luminescent or harbored luxA. These results indicate that bioluminescence may be a trait specific for non-O1/non-O139 V. cholerae that frequently occur in certain environments. Luminescence expression patterns of V. cholerae were also investigated and isolates could be grouped based on expression level. Several strains with defective expression of the lux operon, including natural K variants, were identified.