A benzene-degrading nitrate-reducing microbial consortium displays aerobic and anaerobic benzene degradation pathways

Abstract

In this study, we report transcription of genes involved in aerobic and anaerobic benzene degradation pathways in a benzene-degrading denitrifying continuous culture. Transcripts associated with the family Peptococcaceae dominated all samples (21–36% relative abundance) indicating their key role in the community. We found a highly transcribed gene cluster encoding a presumed anaerobic benzene carboxylase (AbcA and AbcD) and a benzoate-coenzyme A ligase (BzlA). Predicted gene products showed >96% amino acid identity and similar gene order to the corresponding benzene degradation gene cluster described previously, providing further evidence for anaerobic benzene activation via carboxylation. For subsequent benzoyl-CoA dearomatization, bam-like genes analogous to the ones found in other strict anaerobes were transcribed, whereas gene transcripts involved in downstream benzoyl-CoA degradation were mostly analogous to the ones described in facultative anaerobes. The concurrent transcription of genes encoding enzymes involved in oxygenase-mediated aerobic benzene degradation suggested oxygen presence in the culture, possibly formed via a recently identified nitric oxide dismutase (Nod). Although we were unable to detect transcription of Nod-encoding genes, addition of nitrite and formate to the continuous culture showed indication for oxygen production. Such an oxygen production would enable aerobic microbes to thrive in oxygen-depleted and nitrate-containing subsurface environments contaminated with hydrocarbons.

Biodiversity and niche partitioning in an anaerobic benzene degrading culture

“…It has been hypothesized that these types of microbial community may hold many types of interaction between key players in benzene degradation and other members of the community [14]. A recent study on the same bioreactor revealed high levels of transcripts for an anaerobic benzene carboxylase and a benzoate-coenzyme A ligase produced by Peptococcaceae [12]. This finding was in line with other research on benzene degradation where this species was a key player in anaerobic benzene degradation [15,16].…”

“…This microbial community was inoculated from soil samples of a benzene-contaminated industrial site and has been maintained already for 15 years [8], which is enough time to purge a putative initial diversity by mechanisms like competitive exclusion and random fluctuations [9,10,11]. Nevertheless, the culture is currently remarkably rich in species [12,13]. Spatial and temporal heterogeneity as well as the variety of interactions between organisms are then created and maintained by the community itself, aided by mechanisms like wall adherence and patch formation.…”

Microbial and Phenyl Acid Dynamics during the Start-up Phase of Anaerobic Straw Degradation in Meso- and Thermophilic Batch Reactors

“…Bacillus spp. was primarily shown to degrade aromatic compounds aerobically [59,60]; however, as many Firmicutes and fermenters are associated with the anaerobic degradation of aromatic compounds [23], it is plausible that Bacillus spp. took part in the phenyl acid turnover, at least in thermophilic samples.…”

Carboxylation of Hydroxyaromatic Compounds with HCO3− by Enzyme Catalysis: Recent Advances Open the Perspective for Valorization of Lignin-Derived Aromatics

“…In crude cell extracts of the sulfate reducing enrichment culture N47, a naphthalene carboxylase enzyme converting naphthalene and 13 C-labelled hydrogencarbonate into A recent study reported by Atashgahi and coworkers [93] appears to confirm the results of previous studies reported by Meckenstock and coworkers [94] indicating the presence of a gene cluster encoding for proteins potentially involved in direct benzene carboxylation in Peptococcaceae family [93]. In particular, the gene cluster consists of: ubiD gene encoding for the benzene carboxylase, AbcD subunit, ppcC gene encoding for the benzene carboxylase large subunit, AbcA), and bzlA gene encoding for the benzoate-CoA ligase protein.…”