Response of sediment bacterial assemblages to selenate and acetate amendments

We followed the response of bacterial assemblages in slurries of estuarine sediments to amendments of 100 microM sodium selenate and 10 mM sodium acetate. Selenate was removed from the dissolved phase in all slurries after an initial lag that varied depending on the source of the sediment used in the slurry. Subsequent selenate amendments were removed without a lag but with the appearance of transient peaks of selenite. We documented changes in the composition of bacterial assemblages in the slurries using PCR/DGGE and RT-PCR/DGGE of 16S rDNA and rRNA. Bands of interest were sequenced to identify organisms responding to selenate amendments. The composition of communities from the two sampling sites was different and changed but did not converge during incubations with selenate. Selenate-reducing assemblages had broad phylogenetic diversity. Most bands were related to groups of bacteria known to contain organisms capable of selenate or selenite reduction, except for Acinetobacter species which dominated one of the samples and has not previously been associated with selenium oxyanion reduction.