Microbial ecology in selenate‐reducing biofilm communities: Rare biosphere and their interactions with abundant phylotypes

Abstract

Selenate (SeO 4 2− ) reduction in hydrogen (H 2 )-fed membrane biofilm reactors (H 2 -MBfRs) was studied in combinations with other common electron acceptors. We employed H 2 -MBfRs with two distinctly different conditions: R1, with ample electron-donor availability and acceptors SeO 4 2− and sulfate (SO 4 2− ), and R2, with electron-donor limitation and the presence of electron acceptors SeO 4 2− , nitrate (NO 3 − ), and SO 4 2− . Even though H 2 was available to reduce all input SeO 4 2− and SO 4 2− in R1, SeO 4 2− reduction was preferred over SO 4 2− reduction. In R2, co-reduction of NO 3 − and SeO 4 2− occurred, and SO 4 2− reduction was mostly suppressed. Biofilms in all MBfRs had high microbial diversity that was influenced by the "rare biosphere" (RB), phylotypes with relative abundance less than 1%. While all MBfR biofilms had abundant members, such as Dechloromonas and Methyloversatilis, the bacterial communities were significantly different between R1 and R2. For R1, abundant genera were Methyloversatilis, Melioribacter, and Propionivibrio; for R2, abundant genera were Dechloromonas, Hydrogenophaga, Cystobacter, Methyloversatilis, and Thauera. Although changes in electron-acceptor or -donor loading altered the phylogenetic structure of the microbial communities, the biofilm communities were resilient in terms of SeO 4 2− and NO 3 − reductions, because interacting members of the RB had the capacity of respiring these electron acceptors.

A network perspective on the ecology of gut microbiota and progression of type 2 diabetes: Linkages to keystone taxa in a Mexican cohort

“…Therefore, a greater density value indicates higher crosstalk among the resident microbes represented in the network nodes ( 35 ). Moreover, network density shows how quickly perturbations may spread ( 51 ). Thus, the small network density ( Figure S4A ) indicated microbial communities composed of scarcely connected groups.…”

New Representatives of the Class Ignavibacteria Inhabiting Subsurface Aquifers of Yessentuki Mineral Water Deposit

“…Despite the thermophilic lifestyle of both cultivated representatives, other members of Ignavibacteria have been detected in a variety of environments: thermal springs in Armenia [5], China [6], USA [7,8] and Russia [9], an anammox membrane bioreactor [10], microbial fuel cells [11], and an upflow anaerobic sludge blanket reactor [12]. Considering the outstanding ability of M. roseus to utilize different electron acceptors, it is interesting to note that members of Ignavibacteria are often detected in sites enriched with iron [13], nitrous [14,15] or sulfur compounds [12], and selenate [16]. In addition, more recent work has shown that the members of Ignavibacteria can play an important role in the degradation of a number of aromatic compounds, such as aniline [17], nitro-and aminophenol [18], or benzoate [19], suggesting their potential involvement in bioremediation.…”