Comparison of 16S rRNAs samples from three Antartic marine environments reveals a highly diverse bacterioplankton community

LANDONE VESCOVO IA; LEVIN G; DI LELLO FA.; RUBERTO, LUCAS; LÓPEZ JL.; MAC CORMACK WP.

Congreso; XXXI SCAR and Open Science Conference; 2010

Scientific Committee on Antarctic Research

Bacterioplankton community diversity was investigated in sea waters samples taken during two consecutive summers (2008 and 2009) at Potter Cove (25 de Mayo Island, South Shetland Islands). Samples from three oceanographic stations exposed to different natural oceanographic conditions (Stations 1, 2 and 3) were studied by amplification and sequencing of 16S rDNA genes from environmental DNA. Sequence analysis of sixty clones evidenced the presence of bacteria affiliated to the alpha, gamma and beta subdivisions of Class Proteobacteria. Also members of the Cytophaga?Flavobacteria?Bacteroides (CFB)group were detected. Proteobacteria constituted the main fraction (95%) of the obtained sequences [Alpha-proteobacteria (31): Rhizobiales (1), Caulobacterales (1), Rhodospirillales (1), Sphingomonadales (2), Rickettsiales (8), and Rhodobacterales (8); Beta-proteobacteria (2): Methylophilales (1) and Rhodocyclales (1); Gammaproteobacteria (23): Alteromonadales (3), Pseudomonadales (1), family Gammaproteobacteria_incertae_sedis (1), Xanthomonadales (1), Oceanospirillales (11), unclassified_Gammaproteobacteria (6) and unclassified Proteobacteria (1)]; the remaining 5% were affiliated to Bacteroidetes [Flavobacteriales (3)]. Alignment?s entropy values were the following: Station 1/08 (0,281); Station 1/09 (0,419); Station 2/08 (0,309); Station2/09 (0,263); Station 3/08 (0,354) and Station 3/09 (0,351). The open sea station (Station 3) showed the largest and unvariable Shannon?s entropy throughout the time. Instead, river and glacial-ice influenced station (Station 1) was characterised by a more variable bacterial assemblage. Only 15/60 isolates were classified at genus level, evidencing that the major part of the sequences from these antartic environments are not described at present. Finally, as previously described, 8/60 isolates were affiliated to the ubiquitous Pelagibacter genus, confirming their global distribution in the oceans.