N-195. Comparative Analysis of Winter and Summer End-Sequence Libraries from Antarctic Bacterioplankton Reveals Major Differences in Diversity of Organisms and Function

J. Grzymski1, S. G. Tringe2, H. Ducklow3, A. Murray1;
1Desert Res. Inst., Reno, NV, 2US DOE Joint Genome Inst., Walnut Creek, CA, 3Marine Biological Lab., Woods Hole, MA.

Background: The International Polar Year (IPY) is an intense scientific campaign focusing on the Polar Regions. The Antarctic Peninsula marine waters (~65°S latitude) are dynamic and productive in the summer, yet little is known about the microbial community composition, metabolic, or genomic differences between this period of maximal productivity and the Antarctic winter. Methods: Two large insert (fosmid) libraries were created from the <2.5um fraction of marine bacterioplankton from a February (summer) sample and an August (winter) sample collected off the Antarctic Peninsula. Bi-directional end-sequencing generated 7 and 9.6 Mb of coding DNA for the summer and winter libraries respectively. Results: About sixty percent of the protein coding regions were assigned to a COG. Then, 74% of the winter sequences and 78% of the summer sequences were assigned to a phylogenetic class using MEGAN. The summer library sequences were less diverse and less evenly distributed among phyla than the winter library. Almost 10% of the sequences from the summer library aligned to the Pelagibacter ubique genome. It was also dominated by Polaribacter, Rosebacter-related sequences, and gammaproteobacteria. Not surprisingly, light driven pathways involving the proteins proteorhodopsin and bacteriochlorophyll were abundant. The winter library sequences were more evenly distributed between Archaea, and Bacteria domains. The Group I marine crenarchaeota, cytophaga, alpha, beta, delta (nitrite oxidizing) and gammaproteobacteria-affiliated sequences were all well represented. A syntenous 300kb region of the Nitrosopumilos maritimus crenarchaeal genome was assembled from the winter library. Sequences in the winter library including RuBisCO were homologous to protein sequences from putative sulfur oxidizing bacteria, suggesting the potential for chemoautotrophy. Conclusion: This examination of winter and summer large insert libraries revealed major differences in the diversity of organisms and functions encoded in these distinct assemblages with the winter being more diverse and more even phylogenetically and functionally.