Selection for novel, acid-tolerant Desulfovibrio spp. from a closed Transbaikal mine site in a temporal pH-gradient bioreactor

Abstract

Almost all the known isolates of acidophilic or acid-tolerant sulphate-reducing bacteria (SRB) belong to the spore-forming genus Desulfosporosinus in the Firmicutes. The objective of this study was to isolate acidophilic/acid-tolerant members of the genus Desulfovibrio belonging to deltaproteobacterial SRB. The sample material originated from microbial mat biomass submerged in mine water and was enriched for sulphate reducers by cultivation in anaerobic medium with lactate as an electron donor. A stirred tank bioreactor with the same medium composition was inoculated with the sulphidogenic enrichment. The bioreactor was operated with a temporal pH gradient, changing daily, from an initial pH of 7.3 to a final pH of 3.7. Among the bacteria in the bioreactor culture, Desulfovibrio was the only SRB group retrieved from the bioreactor consortium as observed by 16S rRNA-targeted denaturing gradient gel electrophoresis. Moderately acidophilic/acid-tolerant isolates belonged to Desulfovibrio aerotolerans-Desulfovibrio carbinophilus-Desulfovibrio magneticus and Desulfovibrio idahonensis-Desulfovibrio mexicanus clades within the genus Desulfovibrio. A moderately acidophilic strain, Desulfovibrio sp. VK (pH optimum 5.7) and acid-tolerant Desulfovibrio sp. ED (pH optimum 6.6) dominated in the bioreactor consortium at different time points and were isolated in pure culture.

Solids Retention Times Shift Methanogenic Ethanol Oxidation: Novel Insights into Metabolic Pathways, Microbial Community Dynamics, and Energy Metabolisms

“…summarized that the doubling times of most methanogens with cytochrome (such as Methanosarcina and Methanothrix) were generally longer than 10 h, while those of other methanogens without cytochromes (included Methanobacterium) could be as low as 1 h. Besides, some species of Methanobacterium were reported to be able to grow optimally at low pH (5.6–6.2) . The next most abundant genus in SBR 10-E , Desulfovibrio, was an incomplete sulfate-reducing bacterium (SRB) which also acted as a common acetogenic bacteria in methanogenic reactors. , Similarly, the acid-tolerant ability of Desulfovibrio might be the reason for its enrichment in SBR 10-E . It was reported that in the absence of sulfate, Desulfovibrio species were able to syntrophically grow on ethanol in the presence of H 2 -consuming methanogens. , Together, the relative abundance of Desulfovibrio and Methanobacterium accounted for 95.1%, emphasizing their crucial roles in ethanol oxidation and methanogenesis in SBR 10-E .…”