Organoheterotrophic Bacterial Abundance Associates with Zinc Removal in Lignocellulose-Based Sulfate-Reducing Systems

Abstract

Syntrophic relationships between fermentative and sulfate-reducing bacteria are essential to lignocellulose-based systems applied to the passive remediation of mining-influenced waters. In this study, seven pilot-scale sulfate-reducing bioreactor columns containing varying ratios of alfalfa hay, pine woodchips, and sawdust were analyzed over ∼500 days to investigate the influence of substrate composition on zinc removal and microbial community structure. Columns amended with >10% alfalfa removed significantly more sulfate and zinc than did wood-based columns. Enumeration of sulfate reducers by functional signatures (dsrA) and their putative identification from 16S rRNA genes did not reveal significant correlations with zinc removal, suggesting limitations in this directed approach. In contrast, a strong indicator of zinc removal was discerned in comparing the relative abundance of core microorganisms shared by all reactors (>80% of total community), many of which had little direct involvement in metal or sulfate respiration. The relative abundance of Desulfosporosinus, the dominant putative sulfate reducer within these reactors, correlated to representatives of this core microbiome. A subset of these clades, including Treponema, Weissella, and Anaerolinea, was associated with alfalfa and zinc removal, and the inverse was found for a second subset whose abundance was associated with wood-based columns, including Ruminococcus, Dysgonomonas, and Azospira. The construction of a putative metabolic flowchart delineated syntrophic interactions supporting sulfate reduction and suggests that the production of and competition for secondary fermentation byproducts, such as lactate scavenging, influence bacterial community composition and reactor efficacy.

Sulfide-Induced Dissimilatory Nitrate Reduction to Ammonium Supports Anaerobic Ammonium Oxidation (Anammox) in an Open-Water Unit Process Wetland

“…To better understand the functional implications of these shifts, we utilized this differential abundance analysis to focus a literature synthesis of previously reported attributes of bacterial clades primarily at the taxonomic planes of family and genus where putative functionality can be more effectively inferred (29). This approach, with a caveat of imperfect associations between microbial structure and function, enabled us to identify microbial shifts and infer potential associations with carbon, nitrogen, and sulfur biogeochemical processes between the top and bottom samples of the biomat in an approximate 10-cm vertical stratification ( Fig.…”

Spatial impacts of inorganic ligand availability and localized microbial community structure on mitigation of zinc laden mine water in sulfate-reducing bioreactors

“…Specifics of column construction and design are detailed in Drennan et al, 2017. Experimental details related to inoculation, flow regimes, sampling, and mass loading are provided in (Drennan et al, 2016), which investigated syntrophic microbial associations represented by dotted lines, observations made in these systems are in single lines, and predictions are in double lines. This conceptual model highlights the role of limestone dissolution, carbonate release (red) and subsequent ZnCO 3 formation as an initial removal mechanism.…”

“…Abiotic factors that can affect metal immobilization in SRBRs include pH, dissolved oxygen, temperature, carbon release and bioavailability, and MIW composition (Concas et al, 2006). In addition to water chemistry parameters, it has been shown that the recalcitrance of solid-phase organic substrates is a strong selective driver of resident microbial communities (Drennan et al, 2016). In these systems, metal sulfide precipitation results from syntrophic relationships between fermentative organisms and sulfate-reducing bacteria (SRB).…”

“…In these systems, metal sulfide precipitation results from syntrophic relationships between fermentative organisms and sulfate-reducing bacteria (SRB). The former mediate the process of anoxic cellulose and lignin degradation to simple organic molecules, such as lactate, which in turn are oxidized by the SRB (Drennan et al, 2016;Liamleam and Annachhatre, 2007).…”

“…After oxygen is consumed, redox stratification in SRBRs, as with analogous reducing systems, is strongly influenced by the terminal electron accepting process (TEAP). When a single electron acceptor is in excess, such as sulfate, in combination with an abundance of spatially homogenous electron donors through the fermentative release of species such as lactate from plant detritus, the system is not poised for vertical redox stratification (Drennan et al, 2016;McGuire et al, 2000). Under these conditions prevailing binding efficiencies and the availability of aqueous metals to organic and inorganic ligands may have a greater bearing on spatial and temporal metal(loid) precipitation than localized bacterial community structure.…”