Abstract: To explore the cultivable microbial diversity in Antarctic offshore, this study employed traditional agar plate culture methods to isolate bacteria from marine sediment samples collected from 11 sites in the South Shetland Islands, the Cosmonaut Sea, and Prydz Bay during the 39th Chinese Antarctic Research Expeditions. A total of 882 bacterial strains were obtained. Through 16S rRNA gene sequencing and phylogenetic analysis, these strains were classified into 4 phyla, 5 classes, 54 genera, and 95 species, including 7 potential novel species. At five sites on the South Shetland Islands, a total of 39 genera were isolated, with Pseudoalteromonas being the dominant genus at station TY14 and Cellulophaga at station CJW01. The dominant genera of DA04A, DA03 and DA01 stations were all Sulfitobacter. At two sites in Prydz Bay (P1-06 and P1-12), 27 genera were isolated, with Croceibacter as the dominant genus. In the Cosmonaut Sea, 22 genera were isolated from four sites (CA1-10, C5-09, CD1-11, and CA1-09), all dominated by the genus Sulfitobacter. Additionally, 92 representative strains were selected for extracellular enzyme activity assays, including DNAase, amylase, lipase (Tween 20, 40, and 80), gelatinase, cellulase, fucoidanase, and caseinase. The results showed that 57.61% of the isolated strains exhibited activity in two or more kinds of enzymes, and most of the isolated strains had extracellular enzyme activities. These findings provide a reference for the utilization of Antarctic microbial resources and the development of cold-adapted enzymes.

Key words: cultivable microbial, extracellular enzymes, South Shetland Islands, Cosmonaut Sea, Prydz Bay, Antarctic offshore