Sulfidogenesis in Low pH (3.8–4.2) Media by a Mixed Population of Acidophilic Bacteria

Abstract

A defined mixed bacterial culture was established which catalyzed dissimilatory sulfate reduction, using glycerol as electron donor, at pH 3.8-4.2. The bacterial consortium comprised a endospore-forming sulfate reducing bacterium (isolate M1) that had been isolated from acidic sediment in a geothermal area of Montserrat (West Indies) and which had 94% sequence identity (of its 16S rRNA gene) to the Gram-positive neutrophile Desulfosporosinus orientis, and a Gram-negative (non sulfate-reducing) acidophile (isolate PFBC) that shared 99% gene identity with Acidocella aromatica. Whilst M1 was an obligate anaerobe, isolate PFBC, as other Acidocella spp., only grew in pure culture in aerobic media. Analysis of microbial communities, using a combination of total bacterial counts and fluorescent in situ hybridization, confirmed that concurrent growth of both bacteria occurred during sulfidogenesis under strictly anoxic conditions in a pH-controlled fermenter. In pure culture, M1 oxidized glycerol incompletely, producing stoichiometric amounts of acetic acid. In mixed culture with PFBC, however, acetic acid was present only in small concentrations and its occurrence was transient. Since M1 did not oxidize acetic acid, it was inferred that this metabolite was catabolized by Acidocella PFBC which, unlike glycerol, was shown to support the growth of this acidophile under aerobic conditions. In fermenter cultures maintained at pH 3.8-4.2, sulfidogenesis resulted in the removal of soluble zinc (as solid phase ZnS) whilst ferrous iron remained in solution. Potential syntrophic interactions, involving hydrogen transfer between M1 and PFBC, are discussed, as is the potential of sulfidogenesis in acidic liquors for the selective recovery of heavy metals from wastewaters.

Diversity of Dissimilatory Sulfite Reductase Genes ( dsrAB ) in a Salt Marsh Impacted by Long-Term Acid Mine Drainage

“…Although it was undetected in environmental samples, X4 represents a species cultivated from marsh sediments that exhibits some degree of tolerance to the copper and salinity concentrations associated with AMD contamination and periodic desiccation. Furthermore, sulfate reduction under acidic conditions (pH 3.8 to 4.2) has been demonstrated for a Desulfosporosinus orientis relative (55).…”

“…Studies of salt marsh dissimilatory sulfite reductase genes (dsrAB), a highly conserved functional phylogenetic marker of prokaryotic sulfate reducers (49,57,102,103,107), have revealed both novel and deeply branching clades (3). Studies of mining-impacted sites at pH 2.0 to 7.8 (5,7,39,70,72,77,84), of soils and geothermal settings at a pH of ϳ4 (55,68), of metal-contaminated estuaries at pH 6.8 to 7.2 (65), and of hypersaline lakes at pH 7.5 (56) further outline the distribution and tolerance of specific groups and species of SRB under geochemically stringent conditions. Other findings point toward the existence of deltaproteobacteria in environments at a pH of ϳ1 (10), although it is unknown if these include SRB.…”

Bacterial glycerol oxidation coupled to sulfate reduction at neutral and acidic pH

“…As we were not able to detect any other organic compounds, it seems that bacteria with the ability to convert glycerol completely to CO 2 or degrade acetate to CO 2 are present in the enrichment. Syntrophic acetate conversion was suggested in glyceroldegrading acidophilic cultures (Kimura et al, 2006). Currently, we do not know which bacterium in the enrichment performs the complete oxidation of glycerol or acetate.…”

Synthesis of Copper Sulfide Nanoparticles Using Biogenic H2S Produced by a Low-pH Sulfidogenic Bioreactor

“…In our work, the sequence analysis of one isolate obtained from the bioreactor revealed the presence of the recently described acidophilic bacterium D. acididurans. The roles and significance of isolates CCA3 and CCA4 in the sulfidogenic bioreactor cannot be ascertained at this stage, although they may be involved in syntrophic interactions with this SRB, given they tend to grow successfully with a "partner" acidophile [22]. D. acididurans has been described as an incomplete oxidizer of glycerol that generates acetic acid as a waste product, which can be highly toxic even at µM concentrations.…”