Anaerobic Hydrocarbon Metabolism
The mechanisms and genetics of aerobic hydrocarbon biodegradation have been explored for more than seven decades, but less is known about the comparable activities and processes in anaerobic bacteria, which are difficult to isolate and characterize. Studying the fundamental mechanisms and genetics of anaerobic hydrocarbon metabolism will substantially improve our understanding of the fate and transport of hydrocarbons in the environment and provide insight regarding the novel biochemical reactions governing these processes.
To date, there are two known mechanisms of anaerobic alkane biotransformation: addition to fumarate (Figure 1) and a putative carboxylation pathway (Figure 2). Sulfate-reducing strains Desulfatibacillum alkenivorans AK-01 and Desulfococcus oleovorans Hxd3 serve as model organisms for these two mechanisms, respectively.
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Figure 1. Proposed pathway of anaerobic hexadecane metabolism in Hxd3 and a nitrate-reducing consortium. The pathway is shown for the consortium incubated with H34-hexadecane and NaH13CO3. (*) designates the 13C-labeled carbon derived from NaH13CO3. Brackets designate metabolites that were not observed (Callaghan et al., 2009). |
In collaboration with Dr. Amy Callaghan and we have been sequencing the genomes of anaerobic, alkane-degrading strains Desulfococcus oleovorans Hxd3 (Figure 1) and Desulfatibacillum alkenivorans AK-01.
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Figure 2. Genome of Desulfococcus oleovorans Hxd3. Innermost ring: G+C skew; Second ring: G+C content; Third ring: Reverse CDS with COG designations; Fourth ring: Reverse strand; Fifth ring: Forward strand; Outermost ring: Forward CDS with COG designations. |
The goal of our NSF funded research is to further elucidate these pathways in strains AK-01 and Hxd3 as well as discover new pathways in other organisms and systems. Several projects are underway to elucidate the activation mechanisms in enrichment cultures utilizing short and medium-chain alkanes, PAHs and paraffins. These projects are in collaboration with other researchers in the Dept. of Botany/Microbiology, the University of Calgary, and University of Oldenberg.
References:
Callaghan, A.V., B.E.L. Morris, I.A.C. Pereira, M.J. McInerney, R.N. Austin, J. T. Groves, J.J. Kukor, J.M. Suflita, L.Y. Young , G.J. Zylstra, and B. Wawrik. The Genome Sequence of Desulfatibacillum alkenivorans AK-01: A Blueprint for Anaerobic Alkane Oxidation. In Press. Environmental Microbiology. 2011 (6).
Callaghan, A.V., I.A. Davidova, K. Savage-Ashlock, V.A. Parisi, L.M. Gieg, J.M. Suflita J.J. Kukor, and B. Wawrik. 2010. Diversity of Benzyl- and Alkylsuccinate Synthase Genes in Hydrocarbon-Impacted Environments and Enrichment Cultures. Environmental Science and Technology 44 (19), pp 7287–7294.
Callaghan, A. V., B. Wawrik, S. M. Ni Chadhain, L. Y. Young, and G. J. Zylstra. 2008. Anaerobic alkane-degrading strain AK-01 contains two alkylsuccinate synthase genes. Biochemical and Biophysical Research Communications 366:142-8.