MICROBIAL DIVERSITY OF SIBERIAN PERMAFROST

This study explores diversity of microbial communities with respects to geological origin, age, and depth. Samples collected in Northern Siberia to a maximum depth of 24.6 meters along the Alazeya River are freshwater lake origin. Cores were collected with a slow rotary drill that prevented down-hole contamination using quality assurance and quality control procedures. Collected cores were subsampled with sterile knife into sterile Whirl-Pak bags in the mobile field laboratory for later microbiological and molecular analyses DNA was isolated from these samples using Fast Spin DNA Kit for Soil®. The 16S rRNA gene was amplified using 27F and 1492R with a further nested amplification using 515F and 806R primers. All samples were cleaned and concentrated using DNA Clean & Concentrator® Kit (Zymo Research). DNA concentration was measured ranging from 1.2-83 ng/µL. After confirming DNA presence without contamination using Agilent Automatic Gel Electrophoresis, correct DNA concentration for MiSeq was determined using qPCR. Sequencing data were obtained using Illumina MiSeq at the Center for Environmental Biotechnology, University of Tennessee. Diversity analyses were done using the CLC Genomics Workbench with the Greengenes 16S rRNA gene database as reference. The OTUs were defined at 95% sequence similarity threshold. We observed that the samples in bore hole AL1 at depths 1.75-1.8 m and 2.95-3.0 m have a greater alpha diversity than samples from depths of 22.9 m and 24.5-24.6 m. Shallow depths of 1-3 m dominated by Actinobacteria at 47-60 %, which decreased with depth up to 1-6% in the deeper sediments (23-25 m). On the contrary Firmicutes were more abundant (46-87%) in the deeper sediments then in the shallower depths, 5-35%. We saw changes in bacterial community from shallow permafrost sediments to deeper strata from aerobic non-spore-forming high GC Gram-positive Actinobacteria to anaerobic spore-forming low GC Gram-positive Firmicutes. The deepest permafrost sample was different and we detected a lot of Betaproteobacteria, Burkholderia, which are Gram-negative aerobic bacteria that often found in decaying organic matter. Microbial diversity data from the permafrost strata will add to our understanding of polar microbial ecology.

This research is supported by NSF DEB 1442262 and NSF IIA 1358155.