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Published: July 27, 2016
Posted: November 10, 2016

Mercury Methylation Genes involved in Additional Microbial Metabolic Pathways

The work supports the hypothesis that the function of HgcA and HgcB is linked to one-carbon metabolism of the acetyl-CoA pathway.

The Science
Comparative proteomics of the global response of Geobacter sulfurreducens PCA following the deletion of mercury methylation genes demonstrates that these genes are involved in other cellular metabolic pathways.

The Impact
This study is the first to compare differences in the proteomes of several strains of G. sulfurreducens PCA, demonstrating that the deletion of the genes for mercury methylation leads to impacts on other key metabolic processes in these strains. This work supports the hypothesis that the function of HgcA and HgcB is linked to one-carbon (C1) metabolism through the folate branch of the acetyl-CoA pathway by providing methyl groups required for mercury methylation.

Summary
In this study, shotgun proteomics was used to compare global proteome profiles between wild-type G. sulfurreducens PCA and two mutant strains in which DhgcAB is deficient in two genes known to be essential for the biosynthesis of methylmercury toxin, and DomcBESTZ is deficient in five outer membrane c-type cytochromes and thus impaired in its ability for dissimilatory metal ion reduction. The team delineated the global response of G. sulfurreducens PCA in both mutants and identified cellular networks and metabolic pathways that were affected by the loss of these genes. Deletion of hgcAB increased the relative abundances of proteins implicated in extracellular electron transfer, including most of the c-type cytochromes, PilA-C and OmpB, whereas deletion of omcBESTZ significantly increased relative abundances of various methyltransferases, suggesting that a loss of dissimilatory reduction capacity results in elevated activity among C1 metabolic pathways. These results support the hypothesis that the function of HgcA and HgcB is linked to C1 metabolism through the folate branch of the acetyl-CoA pathway by providing methyl groups required for mercury methylation.

Contact (BER PM)
Paul Bayer
DOE Office of Biological and Environmental Research
Paul.Bayer@science.doe.gov (301-903-5324)

(PI Contact)
Baohua Gu
Oak Ridge National Laboratory
gub1@ornl.gov (865-574-7286)

Funding
This research was funded by the Office of Biological and Environmental Research within the U.S. Department of Energy’s Office of Science, as part of the Mercury Science Focus Area project at Oak Ridge National Laboratory.

Publication
Qian, C., A. Johs, H. Chen, B. F. Mann, X. Lu, P.E. Abraham, R. L. Hettich, and B. Gu. 2016. “Global Proteome Response to Deletion of Genes Related to Mercury Methylation and Dissimilatory Metal Reduction Reveals Changes in Respiratory Metabolism in Geobacter sulfurreducens PCA,” Journal of Proteome Research 15(10), 3340-49. DOI: 10.1021/acs.jproteome.6b00263. (Reference link)

Topic Areas:

  • Research Area: Subsurface Biogeochemical Research
  • Research Area: Genomic Analysis and DNA Sequencing
  • Research Area: Microbes and Communities
  • Mission Science: Environmental Cleanup

Division: SC-23.1 Climate and Environmental Sciences Division, BER


 

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