Molecular analysis of bacterial diversity in mudflats along the salinity gradient of an acidified tropical Bornean estuary (South East Asia)

摘要: The Brunei River and Bay estuarine system (BES) in the northwest of Borneo is acidic highly turbid. supports extensive intertidal mudflats presents a potentially steep salinity pH gradient along its length (45 km). Temporal variation physical parameters observed diurnally due to seawater flux during tidal forcing, stochastically elevated freshwater inflow after rains, resulting range between 0 34 psu. High velocity run-off from acid sulphate formations monsoon seasons results variable conditions (pH 4) at upper reaches BES, whereas relatively stable (pH 8) seaward extremes, mixing with South China Sea. At their surfaces, BES present microbial ecosystems driven by oxygenic phototrophs. To study effect various on bacterial diversity mudflats, surface samples were collected six sites stretching over 40 km for molecular phylogentic analysis. these was compared community fingerprinting analysis using 16S rRNA gene based denaturing gel electrophoresis sequencing phylogenetic analyses. Results revealed functionally conserved, diatom-driven mudflat communities composed mainly novel, uncultured species. Species composition evaluated as 50-70% unique each site BES. Clustering sequences commonly occurred that proteobacterial related gradient. When considering all phyla, varied consistently (including anthropogenic) are expected influence composition. found comprise typical functional groups microorganisms associated photosynthetic carbon flux, sulfur cycling (Gamma- Deltaproteobacteria), decomposition (Bacteroidetes). From structural perspective, however, constituted discretely distributed largely novel species Bacteria. This provides first insights into patterns structure tropical East Asian coastal threatened increasing variability salinity, line predicted future environmental change.