Preliminary Research On Quorum Sensing System Of Spoilage Bacteria Isolated From Instant Sea Cucumber

The quorum sensing mechanism of spoilage bacteria is a research focus in the world at present.Instant sea cucumber is convenient to eat,it has rich nutrition,and its function in health care has been recognized more and more widely.At the same time,instant sea cucumber has formed a center of trade and consumer market in a number of countries and regions.In order to solve the increasingly expanding of market demand,instant sea cucumber industry is developing rapidly.However,with the rapid development of instant sea cucumber industry,its preservation is more prominent.Such as unconventional method of sterilization and preservatives chaotic used,and these questions have seriously hampered the healthy development of this industry.And the use of molecular biology techniques to suppress microbial corruption has become the focus research of food preservation at present.This study was to investigate the spoilage bacteria of instant sea cucumber and detect the quorum sensing mediated by N-acyl-homoserine lactones(AHLs).AHLs of gram negative spoilage strains were detected by strain Agrobacterium tumefaciens CF11.The experimental results show that,the dominant spoilage bacteria H-1 and spoilage bacteria H-3 can secret AHLs,and the AHLs activity of H-1 is higher than H-3.Then we do a further research about AHLs of H-1 and H-3.We used n-hexane,ethyl acetate and acidified ethyl acetate(containing 0.5%methanoic acid)to extract strain fermented supernatant,and found that acidified ethyl acetate had the best effect.The Agrobacteriumtumefaciens CFl1 detection showed that both strains produce different concentration of AHLs during different growth period,but reached the highest in stable period.After calculating the concentration of AHLs at this time,the concentration of H-1 was about 7.7 ?g/mL,when H-3 was 9.2 ?g/mL.After mass spectrometry analysis,both of the two strains produced N-hexanoyl homoserine lactone(C6-HSL)molecules.Finally,the correlation between quorum sensing and spoilage characteristic on H-1 and H-3 was studied,the results indicated that,when the exogenous signal molecule(5?mol/L C6-HSL)adding amount was 5?L,the biofilm formation ability of strain H-1 was the strongest,and which H-3 was 3?L.And the degradation of AHLs can block H-1 and H-3 protease.The degradation of AHLs can block the expression of protease gene of H-1 and H-3.The two strains were identified by 16S rDNA gene sequence,and the results indicated that H-1 belong to Aliivibrio fischeri,and H-3 belong to Psychrobacter alimentarius.The above experimental results indicated that,the spoilage of instant sea cucumber bacteria had closely relation with quorum sensing of bacteria mediated by N-acyl-homoserine lactones(AHLs).And this was first study of quorum sensing signal molecule AHLs produced by the Gram-negative spoilage bacteria from instant sea cucumber and layed the foundation for new strategies of food preservation based on interfering in quorum sensing of spoilage bacteria.And this also accumulated basic data for the research of gram negative bacterial quorum sensing system.