Adaptive Response to Cold Temperatures in Vibrio vulnificus |
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Authors: | Patrick J Bryan Robert J Steffan Angelo DePaola John W Foster Asim K Bej |
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Institution: | (1) Department of Biology, University of Alabama at Birmingham, 1300 University Boulevard, Birmingham, AL 35294-1170, USA , US;(2) Envirogen, Inc., 4100 Quakerbridge Road, Lawrenceville, NJ 08648, USA , US;(3) U.S. Food and Drug Administration, Gulf Coast Seafood Laboratory, Dauphin Island, AL 36528, USA , US;(4) Department of Microbiology and Immunology, University of South Alabama, Mobile, AL 36688, USA , US |
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Abstract: | The effectiveness of rapid chilling or freezing of oysters to reduce Vibrio vulnificus levels in shellfish may be compromised by product handling procedures that permit cold adaptation. When a V. vulnificus culture was shifted from 35°C to 6°C conditions, it underwent transition to a non-culturable state. Cells adapted to 15°C
prior to change to 6°C condition, however, remain viable and culturable. In addition, cultures adapted to 15°C were able to
survive better upon freezing at −78°C compared with cultures frozen directly from 35°C. Inhibition of protein synthesis by
addition of chloramphenicol in a V. vulnificus culture immediately prior to the exposure to the adaptive temperature eliminated inducible cold tolerance. These results
suggest that cold-adaptive “protective” proteins may enhance survival and tolerance at cold temperatures. In addition, removal
of iron from the growth medium by adding 2,2′-Dipyridyl prior to cold adaptation decreased the viability by approximately
2 logarithm levels. This suggests that iron plays an important role in adaptation at cold temperatures. Analysis of total
cellular proteins on an SDS polyacrylamide gel electrophoresis, labeled with
35S-methionine during exposure at 15°C, showed elevated expressions of a 6-kDa and a 40-kDa protein and decreased expression
of an 80-kDa protein. These results suggest that, for V. vulnificus, survival and tolerance at cold temperatures could be due to the expression of cold-adaptive proteins other than previously
documented major cold shock proteins such as CS7.4 and CsdA. In this study, for the first time we have shown that exposure
to an intermediate cold temperature (15°C) causes a cold adaptive response, helping this pathogen remain in culturable state
when exposed to a much colder temperature (6°C). This adaptive nature to cold temperatures could be important for shellfish
industry efforts to reduce the risk of V. vulnificus infection from consuming raw oysters.
Received: 30 July 1998 / Accepted: 1 October 1998 |
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