Microbial Diversity And Community Structure In Marine Sediments From The Tropical Western Pacific

To identify the diversity and community structure of microbes in deep subsurface sediments from the tropical Western Pacific, eight bacterial and archaeal 16S rRNA gene clone libraries were constructed by using a PCR-based cloning approach, respectively.691 bacterial valid clones, 261 Restriction Fragment Length Polymorphism (RFLP) genotypes and 181 Operational Taxonomic Units (OTUs) were identified by using PCR amplicons, sequencing, chimera-check and 97% similarity analysis. Meanwhile, we obtained 719 archaeal clones, 199 RFLP genotypes and 181 OTUs.Phylogenetic analysis of 16S rDNA sequences indicated the majority of members were most closely related to uncultivated groups and physiologically uncharacterized assemblages from various marine environments. 15 major bacterial lineages were obtained. Chloroflexi, Proteobacteria and Planctomycetes were the dominate phylotypes detected among the clone libraries. The division of contained three subdivisions includingα-,γ- andδ-Proteobateria subdivisions. In this study, all archaeal phylotypes were affiliated with Crenarchaeota (76%) and Euryarchaeota (24%), respectively. Deep-sea Archaeal Group (DSAG) and Miscellaneous Crenarchaeotic Group (MCG) belonging to Crenarchaeota were the most predominant archaeal 16S rDNA phylotypes in clone libraries. By means of the values of Shannon-Weiner (H), Simpson (1/D), and evenness (J) indices, the bacterial and archaeal communities observed in clone libraries obtained from the eight sediment layers were diverse and showed obviously stratified features. 3051bac4 and 3051bac8 layers had the highest diversity of the bacterial OTUs, and TWP1 clone library had the highest archaeal diversity. The difference might be caused by boundary currents of the tropical Western Pacific and frequent volcano and earthquake activities.Phylotypes in this study shared high similarity with those in subsurface sediments from Peru Margin 1227 site in diversity and community structures, which indicated different geographical zones across the eastern and western Pacific might host similar members of archaeal populations based on similar sedimentary environments. In our study, members of DSAG and MCG seemed to dominate certain layers of the nonhydrate sediments, suggesting a wide ecophysiological adaptation than previously appreciated. The spatial distribution and community structure of these groups might vary with the different geochemical gradient of the environments.