posted on 2016-01-05, 00:00authored byDina M. Drennan, Robert Almstrand, Ilsu Lee, Lee Landkamer, Linda Figueroa, Jonathan O. Sharp
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.