Hexavalent Chromium Reduction under Fermentative Conditions with Lactate Stimulated Native Microbial Communities
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Date
2013-12-23Author
Anil C. Somenahally
Jennifer J. Mosher
Tong Yuan
Mircea Podar
Tommy J. Phelps
Steven D. Brown
Zamin K. Yang
Terry C. Hazen
Adam P. Arkin
Anthony V. Palumbo
Joy D. Van Nostrand
Jizhong Zhou
Dwayne A. Elias
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Microbial reduction of toxic hexavalent chromium (Cr(VI)) in-situ is a plausible bioremediation strategy in electron-acceptor limited environments. However, higher Cr(VI) may impose stress on syntrophic communities and impact community structure and function. The study objectives were to understand the impacts of Cr(VI) concentrations on community structure and on the Cr(VI)-reduction potential of groundwater communities at Hanford, WA. Steady state continuous flow bioreactors were used to grow native communities enriched with lactate (30 mM) and continuously amended with Cr(VI) at 0.0 (No-Cr), 0.1 (Low-Cr) and 3.0 (High-Cr) mg/L. Microbial growth, metabolites, Cr(VI), 16S rRNA gene sequences and GeoChip based functional gene composition were monitored for 15 weeks. Temporal trends and differences in growth, metabolite profiles, and community composition were observed, largely between Low-Cr and High-Cr bioreactors. In both High-Cr and Low-Cr bioreactors, Cr(VI) levels were below detection from week 1 until week 15. With lactate enrichment, native bacterial diversity substantially decreased as Pelosinus spp., and Sporotalea spp., became the dominant groups, but did not significantly differ between Cr concentrations. The Archaea diversity also substantially decreased after lactate enrichment from Methanosaeta (35%), Methanosarcina (17%) and others, to mostly Methanosarcina spp. (95%). Methane production was lower in High-Cr reactors suggesting some inhibition of methanogens. Several key functional genes were distinct in Low-Cr bioreactors compared to High-Cr. Among the Cr resistant microbes, Burkholderia vietnamiensis, Comamonas testosterone and Ralstonia pickettii proliferated in Cr amended bioreactors. In-situ fermentative conditions facilitated Cr(VI) reduction, and as a result 3.0 mg/L Cr(VI) did not impact the overall bacterial community structure.
Citation
Somenahally AC, Mosher JJ, Yuan T, Podar M, Phelps TJ, et al. (2013) Hexavalent Chromium Reduction under Fermentative Conditions with Lactate Stimulated Native Microbial Communities. PLoS ONE 8(12): e83909. doi:10.1371/journal.pone.0083909