Premium
Methanogenic paraffin degradation proceeds via alkane addition to fumarate by ‘Smithella’ spp. mediated by a syntrophic coupling with hydrogenotrophic methanogens
Author(s) -
Wawrik Boris,
Marks Christopher R.,
Davidova Irene A.,
McInerney Michael J.,
Pruitt Shane,
Duncan Kathleen E.,
Suflita Joseph M.,
Callaghan Amy V.
Publication year - 2016
Publication title -
environmental microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.954
H-Index - 188
eISSN - 1462-2920
pISSN - 1462-2912
DOI - 10.1111/1462-2920.13374
Subject(s) - biology , alphaproteobacteria , methanomicrobiales , deltaproteobacteria , bacteria , hydrogenase , biochemistry , chloroflexi (class) , methanogenesis , proteobacteria , microbiology and biotechnology , gammaproteobacteria , archaea , 16s ribosomal rna , gene , genetics , methanosarcina
Summary Anaerobic microbial biodegradation of recalcitrant, water‐insoluble substrates, such as paraffins, presents unique metabolic challenges. To elucidate this process, a methanogenic consortium capable of mineralizing long‐chain n ‐paraffins (C 28 ‐C 50 ) was enriched from San Diego Bay sediment. Analysis of 16S rRNA genes indicated the dominance of Syntrophobacterales (43%) and Methanomicrobiales (26%). Metagenomic sequencing allowed draft genome assembly of dominant uncultivated community members belonging to the bacterial genus Smithella and the archaeal genera Methanoculleus and Methanosaeta . Five contigs encoding homologs of the catalytic subunit of alkylsuccinate synthase ( assA ) were detected. Additionally, mRNA transcripts for these genes, including a homolog binned within the ‘ Smithella’ sp. SDB genome scaffold, were detected via RT‐PCR, implying that paraffins are activated via ‘fumarate addition’. Metabolic reconstruction and comparison with genome scaffolds of uncultivated n ‐alkane degrading ‘ Smithella’ spp. are consistent with the hypothesis that syntrophically growing ‘ Smithella’ spp. may achieve reverse electron transfer by coupling the reoxidation of ETF red to a membrane‐bound FeS oxidoreductase functioning as an ETF:menaquinone oxidoreductase. Subsequent electron transfer could proceed via a periplasmic formate dehydrogenase and/or hydrogenase, allowing energetic coupling to hydrogenotrophic methanogens such as Methanoculleus . Ultimately, these data provide fundamental insight into the energy conservation mechanisms that dictate interspecies interactions salient to methanogenic alkane mineralization.