Identification of key functional groups of microbes in the oxygen minimum zone (OMZ) of the NE equatorial Pacific

Abstract

Recently, oceanic oxygen minimum zones (OMZs) are recognized to play an important role in the global carbon and nitrogen cycles of the ocean. So, biological and biogeochemical activities in there have been gotten more attention to be understood. We performed phylogenetic analysis based on bacterial and archaeal 16S rRNA genes in the OMZ of the NE equatorial Pacific. A total of 290 bacterial clones and 261 archaeal clones were sequenced and used to understand microbial diversity of OMZ in July, 2010. Major bacterial groups in the subsurface chlorophyll maximum (SCM) layer (44 m in depth, 171.68 μmol O2) were Cyanobacteria (28.1% of clones), Alphaproteobacteria (25.0%) and Bacterioidetes (6.3%). OMZ core (700m in depth, 12.05μmol O2) was dominated by SAR406 (27.8%), Deltaproteobacteria (19.6%) and Gammaproteobacteria (12.4%) in order. The lower OMZ (800 m in depth, 19.20 μmol O2) had the largest number of Gammaproteobacteria (24.7%), followed by Deltaproteobacteria (19.6%) and SAR406 (10.3%). In case of archaea, euryarchaeal Marine Group Ⅱ (MG Ⅱ) were dominated in the SCM layer (95.2%). However, in the OMZ, Crenarchaeota (MG Ⅰ) were most dominant group (≃70%) and MG Ⅱ were the second group (≃20%). In summary, major bacterial and archael groups of the OMZ layers are different from those of the SCM layer. Aerobic or photosynthetic bacteria and MG Ⅱ were mostly found in the derstood. We performed phylogenetic analysis based on bacterial and archaeal 16S rRNA genes in the OMZ of the NE equatorial Pacific. A total of 290 bacterial clones and 261 archaeal clones were sequenced and used to understand microbial diversity of OMZ in July, 2010. Major bacterial groups in the subsurface chlorophyll maximum (SCM) layer (44 m in depth, 171.68 μmol O2) were Cyanobacteria (28.1% of clones), Alphaproteobacteria (25.0%) and Bacterioidetes (6.3%). OMZ core (700m in depth, 12.05μmol O2) was dominated by SAR406 (27.8%), Deltapr