Characterization of the prokaryotic community of Lake Suigetsu, Japan: towards a novel palaeoenvironment

Lake Suigetsu is a small tectonic lake in central Japan containing annually laminated sediment. A recent study combined more than 300 radiocarbon ages on terrestrial leaf macrofossils with varve ages from the core generated a quasi-continuous radiocarbon calibration model to the limit of radiocarbon dating (c.50,000BP). This core chronology provides an ideal basis for quantitative studies of climate change and palaeoenvironmental reconstruction. The present study aimed to identify and elucidate the diversity of the microbial communities down the sediment core to develop novel biomarkers for past climate change, using both culture-dependent and independent (molecular) techniques. Here we report the analysis of eighteen samples of the lake sediment sampled at every 4m of the 73.5m core covering the past 150,000 years using PCr-DGGE for 16S rrNA genes from Eubacteria and Archaea. in addition, two of the eighteen sediment samples, indicative of a salinity shift between 10911BP (freshwater) to 6860BP (brackish) were subjected to a Dispersion and Differential Centrifugation (DDC) culture-based approach. A total of 183 taxa were isolated from freshwater sediment samples and 71 taxa from sediments after the saline infux, respectively. This suggests that environmental shifts impose an effect over the diversity of microbial communities, endorsing their potential as biomarkers.