Screening and phylogenetic analysis of antibacterial strains isolated from Antarctic Krill

Staphylococcus aureus ATCC 27661 and Escherichia coli 35218 were used as indicator strains respectively.Screening of the antibacterial activity strains from the 59 strains isolated from Antarctic Krill was by the method of Oxford cup diffusion.The partial characteristics including growth curve, antibacterial curve, optimum temperature, optimum p H and optimum salinity of the antibacterial strains were also studied by the method of nephelometry and Oxford cup diffusion.And with the method of Mega 5 adjacency, the 16S rRNA gene sequence of the antibacteria strains were blasted and then the phylogenetic tree were constructed.The results showed that thirteen strains of Sa 27661 antibacteria activity and six strains of Ec 35218 antibacteria activity were screened in the preliminary screening.Also three antibacterial strains named as 1A3, A4, 1A5 both of Sa 27661and Ec 35218 antibacteria activities were screened in the dual-frequency screening.The positive rate was 5.08%.And they reach the logarithmic phase when they were cultured 16, 20, 28 hours and reach the stationary phase when they were cultured 36, 48, 60hours respectively.They have the highest antibacterial activities when they were cultured 56, 64, 72 hours respectively.The optimum temperature of the antibacterial activity strains were 15℃, 20℃, 20℃, optimum pH values were 7, 6, 6 and optimum salinity were 1%, 3%, 2%respectively.Phylogenetic analysis indicated that strains of A4, 1A5 belong to genera of Psychrobacter.And the gene sequence similarity of strain 1A5 was up to 100%of the registered Psychrobacter sp.OK1 (AB302184.1) .But the homology of strain 1A3 was only 97%to Uncultured Psychrobacter which need further study.Three strains all have the ability of acid resistance, alkali resistance, salt tolerance, also the antibacteria activity which need further study.