The archaeal community in sediments of freshwater lakes of north-east Antarctic Peninsula: Structure and diversity

This research represents the first attempt to study the structure and diversity of the archaeal and methanogenic archaeal community in selected lakes around the Czech polar station J.G. Mendel on James Ross Island (JRI), Antarctica. Sediment samples from a total of 19 of JRI and the nearby Vega Island and Long Island, were analyzed using 16S rRNA and mcrA genes sequencing and real-time qPCR. Contrary to the sequences retrieved by 16S rRNA analysis, many more reads belonging to methanogens were found with mcrA gene sequencing. Generally, archaea represented only a small proportion (0–8.8%) of the total prokaryotic community. With the exception of lakes in the Solorina Valley and Lagoons Mesa area and Lake Esmeralda on Vega Island, methanogenic archaea made up a small proportion of the archaea present in most lakes. The genera Methanothrix and Methanosarcina were identified as the predominant methanogenic representatives in the lake samples. Sequences of representatives belonging to Methanothermobacter sp. and Methanomassiliicoccales and a high proportion of sequences belonging to Methanoperedens-like archaea, methanotrophs that associate anaerobic methane oxidation with denitrification, were recorded for the first time in Antarctica. It is also the first time that the presence of the genus Methanobacterium has been detected to such a large extent. Generally, sequences of the methanogens which might be involved in all three pathways of methane production were found in our samples, indicating the broad metabolic potential of the methanogens present. Individual lakes from one area shared much higher similarity in their methanogenic diversity with the lakes from another area rather than with the lakes within the same area, suggesting that a lake location is probably not the main factor influencing the diversity of the methanogens. Indeed, archaeal and methanogenic community structure and mcrA gene copy numbers varied even within a single lake, suggesting that more sampling within a single lake, preferably at different times of the year, will be necessary in the future for more comprehensive information. Although this is an initial study, our research unambiguously provides evidence that the lakes of the JRI and surrounding islands may be potential sources of new archaeal species or metabolic pathways.