The Role of 4-Hydroxyphenylpyruvate Dioxygenase in Enhancement of Solid-Phase Electron Transfer by Shewanella oneidensis MR-1
- Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL)
- Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
- Nova Research Inc., Alexandria, VA (United States)
- Univ. of South Carolina, Aiken, SC (United States)
- Winthrop Univ., Rock Hill, SC (United States)
ABSTRACT - While mechanistic details of dissimilatory metal reduction are far from being understood, it is postulated that the electron transfer to solid metal oxides is mediated by outer membrane associated c-type cytochromes and electron shuttling compounds. This study focuses on the production of homogensitate in Shewanella oneidensis MR-1, an intermediate of the tyrosine degradation pathway, which is a precursor of a redox cycling metabolite, pyomelanin. We determined that two enzymes involved in this pathway, 4-hydroxyphenylpyruvate dioxygenase (4HPPD) and homogentisate 1,2-dioxygenase are responsible for homogentisate production and oxidation, respectively. Inhibition of 4-HPPD activity with the specific inhibitor sulcotrione ([2-(2- chloro- 4- methane sulfonylbenzoyl)-1,3-cyclohexanedione), and deletion of melA, a gene encoding 4-HPPD, resulted in no pyomelanin production by S. oneidensis MR-1. Conversely, deletion of hmgA, which encodes the putative homogentisate 1,2-dioxygenase, resulted in pyomelanin overproduction. The efficiency and rates at which MR-1 reduces hydrous ferric oxide were directly linked to the ability of mutant strains to produce pyomelanin. Electrochemical studies with whole cells demonstrated that pyomelanin substantially increases the formal potential (E°') of S. oneidensis MR-1. Based on our findings, environmental production of pyomelanin likely contributes to an increased solid-phase metal reduction capacity in S. oneidensis MR-1.
- Research Organization:
- Pacific Northwest National Laboratory (PNNL), Richland, WA (United States)
- Sponsoring Organization:
- USDOE
- DOE Contract Number:
- AC05-76RL01830
- OSTI ID:
- 952906
- Report Number(s):
- PNNL-SA--61518; KP1501021
- Journal Information:
- FEMS Microbiology Ecology, Journal Name: FEMS Microbiology Ecology Journal Issue: 2 Vol. 68; ISSN 0168-6496; ISSN FMECEZ
- Country of Publication:
- United States
- Language:
- English
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PYOMELANIN IS PRODUCED BY SHEWANELLA ALGAE BRY AND EFFECTED BY EXOGENOUS IRON