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Adaptive response to cold temperatures in Vibrio vulnificus
P J Bryan1, R J Steffan, A DePaola
1Department of Biology, University of Alabama at Birmingham, 1300 University Boulevard, Birmingham, AL 35294-1170, USA.
Current Microbiology
|January 29, 1999
Summary
Oysters contaminated with Vibrio vulnificus can survive cold temperatures if the bacteria adapt first. Pre-adaptation at 15°C helps Vibrio vulnificus remain viable and culturable after chilling or freezing, impacting shellfish safety.
Area of Science:
- Microbiology
- Food Safety
- Bacterial Physiology
Background:
- Vibrio vulnificus poses a significant risk in raw shellfish.
- Rapid chilling and freezing are used to reduce bacterial load.
- Product handling may inadvertently promote bacterial cold adaptation, compromising safety measures.
Purpose of the Study:
- To investigate the phenomenon of cold adaptation in Vibrio vulnificus.
- To determine the mechanisms underlying Vibrio vulnificus survival at low temperatures.
- To assess the implications of cold adaptation for shellfish safety protocols.
Main Methods:
- Exposing Vibrio vulnificus cultures to different temperature shifts (35°C to 6°C, 15°C to 6°C).
- Assessing bacterial viability and culturability after temperature changes and freezing (-78°C).
- Investigating the role of protein synthesis inhibition (chloramphenicol) and iron availability (2,2'-Dipyridyl).
- Analyzing protein expression changes using SDS-PAGE with 35S-methionine labeling.
Main Results:
- Vibrio vulnificus shifted directly to 6°C became non-culturable.
- Cultures adapted at 15°C prior to 6°C remained viable and culturable.
- 15°C-adapted cultures showed enhanced survival after freezing compared to those directly from 35°C.
- Inhibition of protein synthesis blocked cold tolerance; iron removal reduced viability.
- Specific protein expression changes (6-kDa, 40-kDa, 80-kDa) were observed during cold adaptation.
Conclusions:
- Vibrio vulnificus exhibits an inducible cold adaptation response at intermediate temperatures (15°C).
- This adaptation involves the expression of specific cold-protective proteins and is influenced by iron availability.
- Understanding this cold adaptive mechanism is crucial for improving food safety strategies in the shellfish industry to mitigate Vibrio vulnificus risks.