Study of the bacterioplankton diversity of a feguian peat bog using metagenomic analysis tools

QUIROGA, MA. VICTORIA; VALVERDE, ANGEL; COWAN, D.A.; LLAMES, M.E.; GONZÁLEZ GARRAZA, GABRIELA; MATALONI, GABRIELA

La Plata, Buenos Aires

Congreso; VI Congreso Argentino de Limnología: Agua, Ambiente y Sociedad; 2014

ILPLA, CONICET - FCNyM, UNLP

Rancho Hambre peat bog is located in a protected area in Tierra del Fuego province (54°S 67ºW) and forms part of the southern-most peatland complex in the world. Since 2008, this area has been used as a limnological case-study, in which the abundance, composition and diversity of the plankton communities have been evaluated in relation to abiotic conditions. The present study aims to use modern metagenomic methods to analyze the composition and diversity of the bacterioplankton community in this peat bog. During the spring of 2012, triplicate surface water samples were collected from five pools (RH1 ? RH5) with different morphometric and trophic conditions, filtered in situ through 0.22 µm membranes and stored in RNAlater (Sigma) for transport. Metagenomic DNA was extracted directly from the filters using the MoBio Power Soil DNA kit, and amplified using 16S rRNA gene universal primers 27F and 519R. The purified final products were analysed with the GS FLX (Roche 454) Titanium chemistry. Pyrosequencing data were analyzed using MOTHUR following a previously established pipeline (Schloss et al., 2011). In order to compare the different pools, the same number of reads (2015) per individual sample was subsampled. A total of 962 OTUs (97% cut-off sequence similarity level) were identified, of which 92% were distributed among the phyla Proteobacteria (51%), Actinobacteria (19%), Bacteroidetes (15%) and Verrucomicrobia (7%), while unclassified bacteria accounted for 7%. Noteworthy, no picocyanobacteria were detected, corroborating epifluorescence observations. 16S rRNA gene pyrosequencing analysis revealed highly diverse and specific bacterial communities within each pool. Thus, a total of 775 OTUs were unique to the respective pool: 154 (RH1), 136 (RH2), 165 (RH3), 149 (RH4) and 171 (RH5), whereas only 5 OTUs were shared between the five pools. Moreover, cluster analysis revealed that samples from minerotrophic pools (RH1 and RH4) and those from ombrotrophic ones (RH2, RH3 and RH5) formed two separated groups. These results concur with previous studies of the diversity of planktonic eukaryotes in these habitats and indicate that bacterial species turnover is higher between pools than within pools, which agrees with a dominant role of deterministic processes on bacterial community composition. Therefore, it seems that peat bog associated bacteria show strong habitat associations that have likely emerged through their adaptation to these particular habitats. Schloss PD, Gevers D, Westcott SL. (2011). Reducing the effects of PCR amplification and sequencing artifacts on 16S rRNA-based studies. Plos One 6.