vimss hanford
Microbial Community Succession during Lactate Amendment and Electron Acceptor Limitation Reveals a Predominance of Metal-Reducing Pelosinus spp
The determination of the success of in situ bioremediation strategies is complex. By using controlled laboratory conditions, the  influence of individual variables, such as U(VI), Cr(VI), and electron donors and acceptors on community structure, dynamics,  and the metal-reducing potential can be studied. Triplicate anaerobic, continuous-flow reactors were inoculated with Cr(VI)-  contaminated groundwater from the Hanford, WA, 100-H area, amended with lactate, and incubated for 95 days to obtain stable,  enriched communities. The reactors were kept anaerobic with N2 gas (9 ml/min) flushing the headspace and were fed a defined  medium amended with 30mMlactate and 0.05mMsulfate with a 48-h generation time. The resultant diversity decreased  from 63 genera within 12 phyla to 11 bacterial genera (from 3 phyla) and 2 archaeal genera (from 1 phylum). Final communities  were dominated by Pelosinus spp. and to a lesser degree, Acetobacterium spp., with low levels of other organisms, including  methanogens. Four new strains of Pelosinus were isolated, with 3 strains being capable of Cr(VI) reduction while one also reduced  U(VI). Under limited sulfate, it appeared that the sulfate reducers, including Desulfovibrio spp., were outcompeted. These  results suggest that during times of electron acceptor limitation in situ, organisms such as Pelosinus spp. may outcompete the  more-well-studied organisms while maintaining overall metal reduction rates and extents. Finally, lab-scale simulations can test  new strategies on a smaller scale while facilitating community member isolation, so that a deeper understanding of community  metabolism can be revealed.