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Geomicrobiological linkages between short-chain alkane consumption and sulfate reduction rates in seep sediments.

Bose A, Rogers DR, Adams MM, Joye SB, Girguis PR - Front Microbiol (2013)

Bottom Line: Measured rates of alkane oxidation and sulfate reduction closely follow stoichiometric predictions that assume the complete oxidation of alkanes to CO2 (though other sinks for alkane carbon likely exist).Phylogenetic analyses indicate that distinct phylotypes are enriched in the ethane reactors, while phylotypes in the propane and butane reactors align with previously identified C3-C4 alkane-oxidizing sulfate-reducers.These data further constrain the potential influence of alkane oxidation on sulfate reduction rates (SRRs) in cold hydrocarbon-rich sediments, provide insight into their contribution to local carbon cycling, and illustrate the extent to which short-chain alkanes can serve as electron donors and govern microbial community composition and density.

View Article: PubMed Central - PubMed

Affiliation: Department of Organismic and Evolutionary Biology, Harvard University Cambridge, MA, USA.

ABSTRACT
Marine hydrocarbon seeps are ecosystems that are rich in methane, and, in some cases, short-chain (C2-C5) and longer alkanes. C2-C4 alkanes such as ethane, propane, and butane can be significant components of seeping fluids. Some sulfate-reducing microbes oxidize short-chain alkanes anaerobically, and may play an important role in both the competition for sulfate and the local carbon budget. To better understand the anaerobic oxidation of short-chain n-alkanes coupled with sulfate-reduction, hydrocarbon-rich sediments from the Gulf of Mexico (GoM) were amended with artificial, sulfate-replete seawater and one of four n-alkanes (C1-C4) then incubated under strict anaerobic conditions. Measured rates of alkane oxidation and sulfate reduction closely follow stoichiometric predictions that assume the complete oxidation of alkanes to CO2 (though other sinks for alkane carbon likely exist). Changes in the δ(13)C of all the alkanes in the reactors show enrichment over the course of the incubation, with the C3 and C4 incubations showing the greatest enrichment (4.4 and 4.5‰, respectively). The concurrent depletion in the δ(13)C of dissolved inorganic carbon (DIC) implies a transfer of carbon from the alkane to the DIC pool (-3.5 and -6.7‰ for C3 and C4 incubations, respectively). Microbial community analyses reveal that certain members of the class Deltaproteobacteria are selectively enriched as the incubations degrade C1-C4 alkanes. Phylogenetic analyses indicate that distinct phylotypes are enriched in the ethane reactors, while phylotypes in the propane and butane reactors align with previously identified C3-C4 alkane-oxidizing sulfate-reducers. These data further constrain the potential influence of alkane oxidation on sulfate reduction rates (SRRs) in cold hydrocarbon-rich sediments, provide insight into their contribution to local carbon cycling, and illustrate the extent to which short-chain alkanes can serve as electron donors and govern microbial community composition and density.

No MeSH data available.


Related in: MedlinePlus

Phylogenetic affiliation of 16S rRNA Deltaproteobacterial gene sequences retrieved from Gulf of Mexico batch reactor sediments. A total of 25 representative sequences from Gulf of Mexico sediments incubated in batch reactors with ethane (GOM_ETHANE), propane (GOM_PROPANE), and butane (GOM_BUTANE) are shown in bold. The phylogenetic tree was generated by maximum likelihood with FastTree Version 2.1.3. Local support values shown are based on the Shimodaira–Hasegawa (SH) test with 1000 resamples. Only values >80% are shown on the branches as black circles. The 16S rRNA sequence of Archaeoglobus profundus DSM 5631(NR_074522) was used as an outgroup. Scale = 0.1 substitutions per site.
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Figure 4: Phylogenetic affiliation of 16S rRNA Deltaproteobacterial gene sequences retrieved from Gulf of Mexico batch reactor sediments. A total of 25 representative sequences from Gulf of Mexico sediments incubated in batch reactors with ethane (GOM_ETHANE), propane (GOM_PROPANE), and butane (GOM_BUTANE) are shown in bold. The phylogenetic tree was generated by maximum likelihood with FastTree Version 2.1.3. Local support values shown are based on the Shimodaira–Hasegawa (SH) test with 1000 resamples. Only values >80% are shown on the branches as black circles. The 16S rRNA sequence of Archaeoglobus profundus DSM 5631(NR_074522) was used as an outgroup. Scale = 0.1 substitutions per site.

Mentions: A total of 11,725, 17,003, 12,529, 16,208, and 18,015 bacterial sequences were analyzed from sediments incubated with N2, methane, ethane, propane, and butane, respectively, and 12,944 bacterial sequences from the T0 sediment. There were shifts between the Proteobacterial communities of the alkane batch reactors in comparison to the control and T0 sediment community (Figure 3A). Among sequences allied to known sulfate-reducing Deltaproteobacteria, there was an increase from the T0 sequences (~20%) in the N2, methane, ethane, propane, and butane sequence libraries (~23, 32, 23, 33, and 55%, respectively) (Figure 3A). In turn, there was a decrease in the representation of Gammaproteobacteria in the N2, methane, ethane, propane, and butane sequence libraries (~37, 17, 30, 26, and 12%, respectively) from the T0 sequences (~53%). 16S rRNA gene phylogeny revealed that the ethane reactors harbored a putative SRP community that was distinct from the propane and butane reactors (Figure 4). These sequences comprised the majority (90–95%) of the Deltaproteobacterial community (Figure 4). In the ethane reactor community, the most closely related Deltaproteobacterial 16S rRNA gene sequences (95–99% nucleotide sequence identity) included strain BuS5 (accession no. EF077225), the enrichment culture “Butane12-GMe” (accession no. EF077226), and other SRP clones from sediments retrieved from the GoM (clone GoM_DSSGM3_28, accession no. FR872064; clone GoM_DSSGM3_19, accession no. FR872059; and clone GoM161_Bac9, accession no. AM745163) (Kniemeyer et al., 2007; Orcutt et al., 2010; Kleindienst et al., 2012). In contrast, SRP sequences in the propane and butane batch reactor communities were most closely allied to uncultured Deltaproteobacteria clones from propane- and butane-oxidizing enrichments of hydrocarbon seep sediments from the GoM (Propane12-GMe clone 230, accession no. FR823371) and Hydrate Ridge (Butane12-HR clone 302, accession no. FR823375 and Butane12-HR clone 342, accession no. FR823377) (Jaekel et al., 2013).


Geomicrobiological linkages between short-chain alkane consumption and sulfate reduction rates in seep sediments.

Bose A, Rogers DR, Adams MM, Joye SB, Girguis PR - Front Microbiol (2013)

Phylogenetic affiliation of 16S rRNA Deltaproteobacterial gene sequences retrieved from Gulf of Mexico batch reactor sediments. A total of 25 representative sequences from Gulf of Mexico sediments incubated in batch reactors with ethane (GOM_ETHANE), propane (GOM_PROPANE), and butane (GOM_BUTANE) are shown in bold. The phylogenetic tree was generated by maximum likelihood with FastTree Version 2.1.3. Local support values shown are based on the Shimodaira–Hasegawa (SH) test with 1000 resamples. Only values >80% are shown on the branches as black circles. The 16S rRNA sequence of Archaeoglobus profundus DSM 5631(NR_074522) was used as an outgroup. Scale = 0.1 substitutions per site.
© Copyright Policy - open-access
Related In: Results  -  Collection

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Show All Figures
getmorefigures.php?uid=PMC3860272&req=5

Figure 4: Phylogenetic affiliation of 16S rRNA Deltaproteobacterial gene sequences retrieved from Gulf of Mexico batch reactor sediments. A total of 25 representative sequences from Gulf of Mexico sediments incubated in batch reactors with ethane (GOM_ETHANE), propane (GOM_PROPANE), and butane (GOM_BUTANE) are shown in bold. The phylogenetic tree was generated by maximum likelihood with FastTree Version 2.1.3. Local support values shown are based on the Shimodaira–Hasegawa (SH) test with 1000 resamples. Only values >80% are shown on the branches as black circles. The 16S rRNA sequence of Archaeoglobus profundus DSM 5631(NR_074522) was used as an outgroup. Scale = 0.1 substitutions per site.
Mentions: A total of 11,725, 17,003, 12,529, 16,208, and 18,015 bacterial sequences were analyzed from sediments incubated with N2, methane, ethane, propane, and butane, respectively, and 12,944 bacterial sequences from the T0 sediment. There were shifts between the Proteobacterial communities of the alkane batch reactors in comparison to the control and T0 sediment community (Figure 3A). Among sequences allied to known sulfate-reducing Deltaproteobacteria, there was an increase from the T0 sequences (~20%) in the N2, methane, ethane, propane, and butane sequence libraries (~23, 32, 23, 33, and 55%, respectively) (Figure 3A). In turn, there was a decrease in the representation of Gammaproteobacteria in the N2, methane, ethane, propane, and butane sequence libraries (~37, 17, 30, 26, and 12%, respectively) from the T0 sequences (~53%). 16S rRNA gene phylogeny revealed that the ethane reactors harbored a putative SRP community that was distinct from the propane and butane reactors (Figure 4). These sequences comprised the majority (90–95%) of the Deltaproteobacterial community (Figure 4). In the ethane reactor community, the most closely related Deltaproteobacterial 16S rRNA gene sequences (95–99% nucleotide sequence identity) included strain BuS5 (accession no. EF077225), the enrichment culture “Butane12-GMe” (accession no. EF077226), and other SRP clones from sediments retrieved from the GoM (clone GoM_DSSGM3_28, accession no. FR872064; clone GoM_DSSGM3_19, accession no. FR872059; and clone GoM161_Bac9, accession no. AM745163) (Kniemeyer et al., 2007; Orcutt et al., 2010; Kleindienst et al., 2012). In contrast, SRP sequences in the propane and butane batch reactor communities were most closely allied to uncultured Deltaproteobacteria clones from propane- and butane-oxidizing enrichments of hydrocarbon seep sediments from the GoM (Propane12-GMe clone 230, accession no. FR823371) and Hydrate Ridge (Butane12-HR clone 302, accession no. FR823375 and Butane12-HR clone 342, accession no. FR823377) (Jaekel et al., 2013).

Bottom Line: Measured rates of alkane oxidation and sulfate reduction closely follow stoichiometric predictions that assume the complete oxidation of alkanes to CO2 (though other sinks for alkane carbon likely exist).Phylogenetic analyses indicate that distinct phylotypes are enriched in the ethane reactors, while phylotypes in the propane and butane reactors align with previously identified C3-C4 alkane-oxidizing sulfate-reducers.These data further constrain the potential influence of alkane oxidation on sulfate reduction rates (SRRs) in cold hydrocarbon-rich sediments, provide insight into their contribution to local carbon cycling, and illustrate the extent to which short-chain alkanes can serve as electron donors and govern microbial community composition and density.

View Article: PubMed Central - PubMed

Affiliation: Department of Organismic and Evolutionary Biology, Harvard University Cambridge, MA, USA.

ABSTRACT
Marine hydrocarbon seeps are ecosystems that are rich in methane, and, in some cases, short-chain (C2-C5) and longer alkanes. C2-C4 alkanes such as ethane, propane, and butane can be significant components of seeping fluids. Some sulfate-reducing microbes oxidize short-chain alkanes anaerobically, and may play an important role in both the competition for sulfate and the local carbon budget. To better understand the anaerobic oxidation of short-chain n-alkanes coupled with sulfate-reduction, hydrocarbon-rich sediments from the Gulf of Mexico (GoM) were amended with artificial, sulfate-replete seawater and one of four n-alkanes (C1-C4) then incubated under strict anaerobic conditions. Measured rates of alkane oxidation and sulfate reduction closely follow stoichiometric predictions that assume the complete oxidation of alkanes to CO2 (though other sinks for alkane carbon likely exist). Changes in the δ(13)C of all the alkanes in the reactors show enrichment over the course of the incubation, with the C3 and C4 incubations showing the greatest enrichment (4.4 and 4.5‰, respectively). The concurrent depletion in the δ(13)C of dissolved inorganic carbon (DIC) implies a transfer of carbon from the alkane to the DIC pool (-3.5 and -6.7‰ for C3 and C4 incubations, respectively). Microbial community analyses reveal that certain members of the class Deltaproteobacteria are selectively enriched as the incubations degrade C1-C4 alkanes. Phylogenetic analyses indicate that distinct phylotypes are enriched in the ethane reactors, while phylotypes in the propane and butane reactors align with previously identified C3-C4 alkane-oxidizing sulfate-reducers. These data further constrain the potential influence of alkane oxidation on sulfate reduction rates (SRRs) in cold hydrocarbon-rich sediments, provide insight into their contribution to local carbon cycling, and illustrate the extent to which short-chain alkanes can serve as electron donors and govern microbial community composition and density.

No MeSH data available.


Related in: MedlinePlus