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Anaerobic degradation of cyclohexane by sulfate-reducing bacteria from hydrocarbon-contaminated marine sediments.

Jaekel U, Zedelius J, Wilkes H, Musat F - Front Microbiol (2015)

Bottom Line: Quantitative growth experiments showed that cyclohexane degradation was coupled with the stoichiometric reduction of sulfate to sulfide.Substrate response tests corroborated with hybridization with a sequence-specific oligonucleotide probe suggested that the dominant phylotype apparently was able to degrade other cyclic and n-alkanes, including the gaseous alkane n-butane.Other metabolites detected were 3-cyclohexylpropionate and cyclohexanecarboxylate providing evidence that the overall degradation pathway of cyclohexane under anoxic conditions is analogous to that of n-alkanes.

View Article: PubMed Central - PubMed

Affiliation: Department of Microbiology, Max Planck Institute for Marine Microbiology Bremen, Germany.

ABSTRACT
The fate of cyclohexane, often used as a model compound for the biodegradation of cyclic alkanes due to its abundance in crude oils, in anoxic marine sediments has been poorly investigated. In the present study, we obtained an enrichment culture of cyclohexane-degrading sulfate-reducing bacteria from hydrocarbon-contaminated intertidal marine sediments. Microscopic analyses showed an apparent dominance by oval cells of 1.5 × 0.8 μm. Analysis of a 16S rRNA gene library, followed by whole-cell hybridization with group- and sequence-specific oligonucleotide probes showed that these cells belonged to a single phylotype, and were accounting for more than 80% of the total cell number. The dominant phylotype, affiliated with the Desulfosarcina-Desulfococcus cluster of the Deltaproteobacteria, is proposed to be responsible for the degradation of cyclohexane. Quantitative growth experiments showed that cyclohexane degradation was coupled with the stoichiometric reduction of sulfate to sulfide. Substrate response tests corroborated with hybridization with a sequence-specific oligonucleotide probe suggested that the dominant phylotype apparently was able to degrade other cyclic and n-alkanes, including the gaseous alkane n-butane. Based on GC-MS analyses of culture extracts cyclohexylsuccinate was identified as a metabolite, indicating an activation of cyclohexane by addition to fumarate. Other metabolites detected were 3-cyclohexylpropionate and cyclohexanecarboxylate providing evidence that the overall degradation pathway of cyclohexane under anoxic conditions is analogous to that of n-alkanes.

No MeSH data available.


Whole-cell hybridization (CARD-FISH) with the group-specific probe DSS658 (A) and with the sequence-specific probe Cyhx28-EdB_152 (B), showing the dominance of the phylotype Cyhx28-EdB-clone63. The images show an overlay of probe (red) and DAPI (blue) signals. Scale bars = 5 μm.
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Figure 3: Whole-cell hybridization (CARD-FISH) with the group-specific probe DSS658 (A) and with the sequence-specific probe Cyhx28-EdB_152 (B), showing the dominance of the phylotype Cyhx28-EdB-clone63. The images show an overlay of probe (red) and DAPI (blue) signals. Scale bars = 5 μm.

Mentions: The abundance of the phylotype represented by Cyhx28-EdB-clone63 in the enrichment culture was further quantified by whole-cell hybridization. Hybridizations with the group-specific oligonucleotide probe DSS658, targeting most of the bacteria afiliated with the Desulfosarcina-Desulfococcus cluster, including Cyhx28-EdB-clone63, showed that this phylogenetic group accounted for 84.3% of the total cell number determined by DAPI staining (Figure 3). Further hybridizations with the sequence-specific oligonucleotide probe Cyhx28-EdB_152 showed that the phylotype Cyhx28-EdB-clone63 accounted for 80.2% of the total cell number (Figure 3). High abundance of single phylotypes has been found in other anaerobic, hydrocarbon-degrading enrichment cultures, for example with benzene under sulfate-reducing conditions (Musat and Widdel, 2008), or with alkylbenzenes and n-alkanes under denitrifying conditions (Rabus et al., 1999). In addition, highly abundant phylotypes in enrichment cultures of sulfate-reducing bacteria degrading gaseous alkanes have been shown to be directly involved in hydrocarbon degradation by incubations with 13C-labeled substrates followed by nanoSIMS analyses (Jaekel et al., 2013). Considering the high abundance of the phylotype Cyhx28-EdB-clone63, we propose that it plays a very important role in the biodegradation of cyclohexane.


Anaerobic degradation of cyclohexane by sulfate-reducing bacteria from hydrocarbon-contaminated marine sediments.

Jaekel U, Zedelius J, Wilkes H, Musat F - Front Microbiol (2015)

Whole-cell hybridization (CARD-FISH) with the group-specific probe DSS658 (A) and with the sequence-specific probe Cyhx28-EdB_152 (B), showing the dominance of the phylotype Cyhx28-EdB-clone63. The images show an overlay of probe (red) and DAPI (blue) signals. Scale bars = 5 μm.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4352924&req=5

Figure 3: Whole-cell hybridization (CARD-FISH) with the group-specific probe DSS658 (A) and with the sequence-specific probe Cyhx28-EdB_152 (B), showing the dominance of the phylotype Cyhx28-EdB-clone63. The images show an overlay of probe (red) and DAPI (blue) signals. Scale bars = 5 μm.
Mentions: The abundance of the phylotype represented by Cyhx28-EdB-clone63 in the enrichment culture was further quantified by whole-cell hybridization. Hybridizations with the group-specific oligonucleotide probe DSS658, targeting most of the bacteria afiliated with the Desulfosarcina-Desulfococcus cluster, including Cyhx28-EdB-clone63, showed that this phylogenetic group accounted for 84.3% of the total cell number determined by DAPI staining (Figure 3). Further hybridizations with the sequence-specific oligonucleotide probe Cyhx28-EdB_152 showed that the phylotype Cyhx28-EdB-clone63 accounted for 80.2% of the total cell number (Figure 3). High abundance of single phylotypes has been found in other anaerobic, hydrocarbon-degrading enrichment cultures, for example with benzene under sulfate-reducing conditions (Musat and Widdel, 2008), or with alkylbenzenes and n-alkanes under denitrifying conditions (Rabus et al., 1999). In addition, highly abundant phylotypes in enrichment cultures of sulfate-reducing bacteria degrading gaseous alkanes have been shown to be directly involved in hydrocarbon degradation by incubations with 13C-labeled substrates followed by nanoSIMS analyses (Jaekel et al., 2013). Considering the high abundance of the phylotype Cyhx28-EdB-clone63, we propose that it plays a very important role in the biodegradation of cyclohexane.

Bottom Line: Quantitative growth experiments showed that cyclohexane degradation was coupled with the stoichiometric reduction of sulfate to sulfide.Substrate response tests corroborated with hybridization with a sequence-specific oligonucleotide probe suggested that the dominant phylotype apparently was able to degrade other cyclic and n-alkanes, including the gaseous alkane n-butane.Other metabolites detected were 3-cyclohexylpropionate and cyclohexanecarboxylate providing evidence that the overall degradation pathway of cyclohexane under anoxic conditions is analogous to that of n-alkanes.

View Article: PubMed Central - PubMed

Affiliation: Department of Microbiology, Max Planck Institute for Marine Microbiology Bremen, Germany.

ABSTRACT
The fate of cyclohexane, often used as a model compound for the biodegradation of cyclic alkanes due to its abundance in crude oils, in anoxic marine sediments has been poorly investigated. In the present study, we obtained an enrichment culture of cyclohexane-degrading sulfate-reducing bacteria from hydrocarbon-contaminated intertidal marine sediments. Microscopic analyses showed an apparent dominance by oval cells of 1.5 × 0.8 μm. Analysis of a 16S rRNA gene library, followed by whole-cell hybridization with group- and sequence-specific oligonucleotide probes showed that these cells belonged to a single phylotype, and were accounting for more than 80% of the total cell number. The dominant phylotype, affiliated with the Desulfosarcina-Desulfococcus cluster of the Deltaproteobacteria, is proposed to be responsible for the degradation of cyclohexane. Quantitative growth experiments showed that cyclohexane degradation was coupled with the stoichiometric reduction of sulfate to sulfide. Substrate response tests corroborated with hybridization with a sequence-specific oligonucleotide probe suggested that the dominant phylotype apparently was able to degrade other cyclic and n-alkanes, including the gaseous alkane n-butane. Based on GC-MS analyses of culture extracts cyclohexylsuccinate was identified as a metabolite, indicating an activation of cyclohexane by addition to fumarate. Other metabolites detected were 3-cyclohexylpropionate and cyclohexanecarboxylate providing evidence that the overall degradation pathway of cyclohexane under anoxic conditions is analogous to that of n-alkanes.

No MeSH data available.