, Volume 32, Issue 6, pp 66-74
Date: 30 Jan 2013

Phylogenetic diversity of planktonic bacteria in the Chukchi Borderland region in summer

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Abstract

Planktonic bacteria are abundant in the Chukchi Borderland region. However, little is known about their diversity and the roles of various bacteria in the ocean. Seawater samples were collected from two stations K2S and K4S where sea ice was melting obviously. The analysis of water samples with fluorescence in situ hybridization (FISH) showed that DMSP-degrading bacteria accounted for 13% of the total bacteria at the station K2S. No aerobic anoxygenic phototrophic (AAP) bacteria were detected in both samples. The bacterial communities were characterized by two 16S rRNA gene clone libraries. Sequences fell into four major lineages of the domain Bacteria, including Proteobacteria (Alpha, Beta and Gamma subclasses), Bacteroidetes, Actinobacteria and Firmicutes. No significant difference was found between the two clone libraries. SAR11 and Rhodobacteraceae clades of Alphaproteobacteria and Pseudoalteromonas of Gammaproteobacteria constituted three dominant fractions in the clone libraries. A total of 191 heterotrophic bacterial strains were isolated and 76% showed extracellular proteolytic activity. Phylogenetic analysis reveals that the isolates fell into Gammaproteobacteria, Bacteroidetes, Actinobacteria and Firmicutes. The most common genus in both the bacterial isolates and protease-producing bacteria was Pseudoalteromonas. UniFracdata showed suggestive differences in bacterial communities between the Chukchi Borderland and the northern Bering Sea.

Foundation item: The National Natural Science Foundation of China under contract No. 41076131; the Youth Marine Science Foundation of State Oceanic Administration under contract No. 2011104; the Public Science and Technology Research Funds Projects of Ocean under contract No. 201105022; the Chinese Polar Environment Comprehensive Investigation and Assessment Program under contract No. CHINARE2012-02-01; the National High-Tech Research and Development Program of China under contract No. 2012AA021706; supports for SH Lee were provided by grants for the Polar Academic Program (PAP) and Korea Polar Research Institute (KOPRI) under contract No. PM11080.