Characterisation of the spoilage bacterial microbiota in oyster gills during storage at different temperatures.

Background: The spoilage bacterial community in oyster gill was investigated during storage at 4, 10 and 20 °C. Aerobic plate counts and pH values were determined. Total bacterial DNA was extracted from oyster gill and bulk cells of plate count media. The major bacterial species during fresh or different temperatures storage were determined by polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE).

Results: The initial aerobic plate count in oyster gill reached 6.70 log CFU g(-1). PCR-DGGE fingerprinting analysis of the 16S rRNA gene V3 region revealed that most of the strains in fresh oyster gill belonged to the genera Lactococcus and Enterobacter. The major spoilage bacteria at a storage temperature of 20 °C were Leuconostoc pseudomesenteroides, an uncultured bacterium, Cytophaga fermentans, Lactococcus lactis, Pseudoalteromonas sp., Enterococcus mundtii, Clostridium difficile and an uncultured Fusobacteria; those at 10 °C were Lactococcus spp., Lactobacillus curvatus, Weissella confusa and C. difficile; those at 4 °C were Lactococcus, Weissella, Enterobacter and Aeromonas. The other minor species were L. curvatus, Pseudomonas sp. and E. mundtii. Lactococcus spp. was the most common main spoilage bacteria in oyster gill during chilled storage.

Conclusion: PCR-DGGE revealed the complexity of the bacterial microbiota and the major bacteria species in oyster gill for fresh and storage.