Microbial nitrate-dependent cyclohexane degradation coupled with anaerobic ammonium oxidation

Abstract

An anaerobic nitrate-reducing enrichment culture was established with a cyclic saturated petroleum hydrocarbon, cyclohexane, the fate of which in anoxic environments has been scarcely investigated. GC-MS showed cyclohexylsuccinate as a metabolite, in accordance with an anaerobic enzymatic activation of cyclohexane by carbon-carbon addition to fumarate. Furthermore, long-chain cyclohexyl-substituted cell fatty acids apparently derived from cyclohexane were detected. Nitrate reduction was not only associated with cyclohexane utilization but also with striking depletion of added ammonium ions. Significantly more ammonium was consumed than could be accounted for by assimilation. This indicated the occurrence of anaerobic ammonium oxidation (anammox) with nitrite from cyclohexane-dependent nitrate reduction. Indeed, nitrite depletion was stimulated upon further addition of ammonium. Analysis of 16S rRNA genes and subsequent cell hybridization with specific probes showed that approximately 75% of the bacterial cells affiliated with the Geobacteraceae and approximately 18% with Candidatus 'Brocadia anammoxidans' (member of the Planctomycetales), an anaerobic ammonium oxidizer. These results and additional quantitative growth experiments indicated that the member of the Geobacteraceae reduced nitrate with cyclohexane to nitrite and some ammonium; the latter two and ammonium added to the medium were scavenged by anammox bacteria to yield dinitrogen. A model was established to quantify the partition of each microorganism in the overall process. Such hydrocarbon oxidation by an alleged 'denitrification' ('pseudo-denitrification'), which in reality is a dissimilatory loop through anammox, can in principle also occur in other microbial systems with nitrate-dependent hydrocarbon attenuation.

Functional Gene Markers for Fumarate-Adding and Dearomatizing Key Enzymes in Anaerobic Aromatic Hydrocarbon Degradation in Terrestrial Environments

“…Fumarate addition is also known to be involved in the activation of non-aromatic compounds. These include short-and long-chain alkanes [Callaghan et al, 2008;Grundmann et al, 2008;Kniemeyer et al, 2007;Kropp et al, 2000;Rabus et al, 2001], cyclic alkanes [Musat et al, 2010;Rios-Hernandez et al, 2003] and also linear alkylbenzenesulfonate detergents [Lara-Martin et al, 2010]. A dual nomenclature is in use for alkane-activating enzymes: alkylsuccinate synthases (ASS) [Callaghan et al, 2008] and 1-methylalkylsuccinate synthases (MAS) [Grundmann et al, 2008].…”

Primers: Functional Genes for Anaerobic Hydrocarbon Degrading Microbes

“…Cyclic alkanes may also be activated by addition to fumarate [18,19]. Furthermore, cresols [2] and also linear alkylbenzene sulfonate detergents [20] have been reported to be activated via fumarate addition.…”

Prokaryotic Community Characterization in a Mesothermic and Water- Flooded Oil Reservoir in Colombia

“…Different metabolic groups including iron and sulfate reducers, fermenting bacteria, acetogens and methanogens have been recognized to be part of the microbial consortium involved in oil biodegradation processes (Matthew et al, 1998;Magot et al, 2000;Röling et al, 2003;Musat et al, 2010;Mbadinga et al, 2011;Voordouw, 2011).…”