Whole Genome Sequencing and Analysis of Pseudomonas fragi MS-10 from Thunnus obesus
To analyze the environmental adaptation and spoilage-related genes of Pseudomonas fragi,and to provide a theoretical basis for the subsequent study of its spoilage-causing mechanism,spoilage bacteria were isolated from spoiled frozen tuna,and the isolates with quorum sensing were screened using Agrobacterium tumefaciens KYC55 and then their secreted AHLs were detected by GC-MS.The strain type was determined using 16S rRNA comparison and ANI analysis.Gene function and annotation were determined by sequencing the whole genome.The content of siderophore secreted by the strain at different temperatures was measured by CASAD plate and UV detection.The changes of total viable count and total volatile basic nitrogen in frozen tuna inoculated with MS-10 were detected,and the putrefactive ability of MS-10 was analyzed in combination with the spoilage metabolite yield factor YTVB-N/CFU.Results:The isolated strain was P.fra-gi,named MS-10,secreting quorum sensing signals,mainly C8-HSL and C1o-HSL.Its genome size was 5.25 Mb,with 58.2％ GC.Comparison of multiple databases revealed that the gene functions of MS-10 were mainly focused on biometabolism,signal transduction and environmental stress,including quorum sensing regulatory genes traI/R and a large number of spoilage-related genes.Low temperature conditions were more favorable for strain MS-10 to secrete siderophore.Tuna blocks inoculated with MS-10 showed a significant increase in total viable count and TVB-N values during refrigeration compared to the blank group,with YTVB-N/CFU values measuring 2.77×10-7 mg/CFU.Conclusion:P.fragi MS-10 possessed a quorum sensing system and was a cold-tolerant putrefactive bacterium.It was demonstrated that it had strong putrefactive potential and environmental adaptability at the genetic level,which could help to further investi-gate the regulatory mechanism of MS-10 quorum sensing and to provide data support for future research on its putrefac-tive properties.
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