Role for outer membrane cytochromes OmcA and OmcB of Shewanella putrefaciens MR-1 in reduction of manganese dioxide. Appl Environ Microbiol 2001 Jan;67(1):260-9
Date
01/03/2001Pubmed ID
11133454Pubmed Central ID
PMC92560DOI
10.1128/AEM.67.1.260-269.2001Scopus ID
2-s2.0-0035166832 (requires institutional sign-in at Scopus site) 218 CitationsAbstract
Shewanella putrefaciens MR-1 can use a wide variety of terminal electron acceptors for anaerobic respiration, including certain insoluble manganese and iron oxides. To examine whether the outer membrane (OM) cytochromes of MR-1 play a role in Mn(IV) and Fe(III) reduction, mutants lacking the OM cytochrome OmcA or OmcB were isolated by gene replacement. Southern blotting and PCR confirmed replacement of the omcA and omcB genes, respectively, and reverse transcription-PCR analysis demonstrated loss of the respective mRNAs, whereas mRNAs for upstream and downstream genes were retained. The omcA mutant (OMCA1) resembled MR-1 in its growth on trimethylamine N-oxide (TMAO), dimethyl sulfoxide, nitrate, fumarate, thiosulfate, and tetrathionate and its reduction of nitrate, nitrite, ferric citrate, FeOOH, and anthraquinone-2,6-disulfonic acid. Similarly, the omcB mutant (OMCB1) grew on fumarate, nitrate, TMAO, and thiosulfate and reduced ferric citrate and FeOOH. However, OMCA1 and OMCB1 were 45 and 75% slower than MR-1, respectively, at reducing MnO(2). OMCA1 lacked only OmcA. While OMCB1 lacked OmcB, other OM cytochromes were also missing or markedly depressed. The total cytochrome content of the OM of OMCB1 was less than 15% of that of MR-1. Western blots demonstrated that OMCB1 still synthesized OmcA, but most of it was localized in the cytoplasmic membrane and soluble fractions rather than in the OM. OMCB1 had therefore lost the ability to properly localize multiple OM cytochromes to the OM. Together, the results suggest that the OM cytochromes of MR-1 participate in the reduction of Mn(IV) but are not required for the reduction of Fe(III) or other electron acceptors.
Author List
Myers JM, Myers CRMESH terms used to index this publication - Major topics in bold
Amino Acid SequenceBacterial Outer Membrane Proteins
Bacterial Proteins
Base Sequence
Blotting, Southern
Cytochrome c Group
Electron Transport
Electrophoresis, Polyacrylamide Gel
Ferric Compounds
Gene Deletion
Manganese Compounds
Molecular Sequence Data
Oxidation-Reduction
Oxides
Polymerase Chain Reaction
Reverse Transcriptase Polymerase Chain Reaction
Sequence Analysis, DNA
Shewanella putrefaciens
