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Calcium promotes exopolysaccharide phase variation and biofilm formation of the resulting phase variants in the human pathogen Vibrio vulnificus
Author(s) -
GarrisonSchilling Katherine L.,
Grau Brenda L.,
McCarter Kevin S.,
Olivier Brett J.,
Comeaux Nicole E.,
Pettis Gregg S.
Publication year - 2011
Publication title -
environmental microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.954
H-Index - 188
eISSN - 1462-2920
pISSN - 1462-2912
DOI - 10.1111/j.1462-2920.2010.02369.x
Subject(s) - vibrio vulnificus , phase variation , biofilm , biology , microbiology and biotechnology , virulence , pathogen , vibrio , bacteria , extracellular , genetic variation , extracellular polymeric substance , phenotype , vibrionaceae , gene , genetics
Summary Vibrio vulnificus is a Gram‐negative bacterium found in estuaries and coastal waters and is associated with human disease caused by ingestion of raw shellfish. Pathogenesis is directly related to the presence of capsular polysaccharide (CPS). Encapsulated virulent strains exhibit an opaque colony phenotype, while unencapsulated attenuated strains appear translucent. A third colony type, rugose, is caused by expression of rugose extracellular polysaccharide (rEPS) and forms robust biofilms. Vibrio vulnificus undergoes phase variation associated with altered levels of CPS and rEPS, and we show here that calcium (Ca 2+ ) significantly increases the rate of CPS and rEPS phase variation in this species. Interestingly, multiple phenotypic responses to increased [Ca 2+ ] were observed among strains, which suggests the existence of underlying cognate genetic or epigenetic differences. Certain translucent isolates contained deletions at the group I CPS operon, inferring increased [Ca 2+ ] upregulates existing phase variation mechanisms. Expanding on a previous observation (Kierek and Watnick, Proc. Natl. Acad. Sci. USA 100: 14357–14362, 2003), increased [Ca 2+ ] also enhanced biofilm formation for all phase variants. Our results show that Ca 2+ promotes both polysaccharide phase variation and biofilm formation of the resulting phase variants, thereby likely serving a dual role in persistence of V. vulnificus in the environment.