Abstract:

To analyze the diversity of cultured agar-degrading bacteria from the surfaces of six Antarctic macroalgae samples collected from King George Island, a selective medium and Lugol’s iodine staining method were used to screen and purify the agar-degrading bacteria, and the phylogenetic relationships of these strains were then investigated according to their 16S rRNA sequences. Thirty-seven strains of agar-degrading bacteria were screened, purified, and identified as belonging to the Gammaproteobacteria, Flavobacteriia, and Actinobacteria, respectively. At the genus level, the strains were classified as Pseudoalteromonas, Colwellia, Shewanella, Psychrobacter, Pseudomonas, Halomonas, Photobacterium, Flavobacterium, Zobellia, and Salinibacterium, in addition to a strain that was classified as belonging to the family Thiotrichaceae. Among them, Flavobacterium and Zobellia belong to the Flavobacteriia, Salinibacterium belongs to the Actinobacteria, and the remaining genera belong to the Gammaproteobacteria. The most dominant genus of agar-degrading bacteria was Pseudoalteromonas (20/37), followed by Psychrobacter(4/37). Shewanella, Psychrobacter, Pseudomonas, Halomonas, Photobacterium, and the member of the family Thiotrichaceaeare the first reported taxa with agar-degrading activity isolated from the surfaces of macroalgae in Antarctica. The results not only expand our knowledge of the diversity of agar-degrading bacteria, but also contribute to the investigation and exploitation of Antarctic microbial resources.