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Sci Rep. 2018 Mar 14;8(1):4490. doi: 10.1038/s41598-018-22617-x.

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

Author information

1
Wageningen University & Research, Laboratory of Microbiology, Stippeneng 4, 6708 WE, Wageningen, The Netherlands. siavash.atashgahi@wur.nl.
2
Wageningen University & Research, Laboratory of Systems and Synthetic Biology, Stippeneng 4, 6708 WE, Wageningen, The Netherlands.
3
Wageningen University & Research, Laboratory of Microbiology, Stippeneng 4, 6708 WE, Wageningen, The Netherlands.
4
Deltares, Subsurface and Groundwater Systems, Daltonlaan 600, 3584 BK, Utrecht, The Netherlands.
5
Vrije Universiteit Amsterdam, Department of Molecular Cell Biology, De Boelelaan 1108, 1081 HZ, Amsterdam, The Netherlands.
6
Department of Environmental Microbiology, Helmholtz Centre for Environmental Research - UFZ, Leipzig, Germany.
7
Centre of Biological Engineering, University of Minho, Braga, Portugal.

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.

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