| Title | Identification of Proteolytic Bacteria from the Arctic Chukchi Sea Expedition Cruise and Characterization of Cold-active Proteases |
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| Author | Ha Ju Park, Yung Mi Lee, Sunghui Kim, Ah Ram Wi, Se Jong Han, Han-Woo Kim, Il-Chan Kim, Joung Han Yim, and Dockyu Kim* |
| Address | Division of Life Sciences, Korea Polar Reserch Institute, Incheon 406-840, Republic of Korea |
| Bibliography | Journal of Microbiology, 52(10),825-833, 2014, |
| DOI | 10.1007/s12275-014-4226-6 |
| Key Words | Arctic, cold-active enzymes, expedition cruise, protease, Pseudoalteromonas |
| Abstract | Following collection of seawater samples during an Arctic Chukchi Sea expedition cruise of the Korean icebreaker Araon in 2012, a total of 15,696 bacteria were randomly isolated from Marine Broth 2216 agar plates. Of these, 2,526 (16%) showed proteolytic activity and were identified as mainly Alteromonas (31%), Staphylococcus (27%), and Pseudoalteromonas (14%). Among the proteolytic strains, seven were selected based on their significant ability to grow and produce a halo on skim milk plates at low temperatures (<5°C) owing to cold-active proteases. These strains were affiliated with the genus Pseudoalteromonas and were divided into three groups based on phylogenetic analysis of the 16S rRNA genes. Profiling cell membrane fatty acids confirmed the 16S rRNA-based differentiation and revealed the accordance between the two analyses. Seven genes for serine protease precursors were amplified from the corresponding strains, and based on sequence similarities, these genes were divided into three groups that were identical to those identified by the 16S rRNA phylogenetic analysis. Three protease genes from the representative strains of each group were composed of 2,127–2,130 bp, encoding 708–709 amino acids, and these genes yielded products with calculated molecular weights of approximately 72.3–72.8 kDa. Amino acid sequence analysis suggested that the precursors are members of the subtilase serine endo- and exo-peptidase clan and contain four domains (signal peptide, N-terminal prosequence, catalytic domain, and two pre-peptidase C-terminal domains). Upon expression in E. coli, each recombinant protease exhibited proteolytic activity on zymogram gels. |