ABSTRACT
Certain methanogens deteriorate steel surfaces through a process called microbiologically influenced corrosion (MIC). However, the mechanisms of MIC, whereby methanogens oxidize zerovalent iron (Fe0), are largely unknown. In this study, Fe0-corroding Methanococcus maripaludis strain OS7 and its derivative (strain OS7mut1) defective in Fe0-corroding activity were isolated. Genomic analysis of these strains demonstrated that the strain OS7mut1 contained a 12-kb chromosomal deletion. The deleted region, termed "MIC island", encoded the genes for the large and small subunits of a [NiFe] hydrogenase, the TatA/TatC genes necessary for the secretion of the [NiFe] hydrogenase, and a gene for the hydrogenase maturation protease. Thus, the [NiFe] hydrogenase may be secreted outside the cytoplasmic membrane, where the [NiFe] hydrogenase can make direct contact with Fe0, and oxidize it, generating hydrogen gas: Fe0 + 2 H+ â Fe2+ + H2. Comparative analysis of extracellular and intracellular proteomes of strain OS7 supported this hypothesis. The identification of the MIC genes enables the development of molecular tools to monitor epidemiology, and to perform surveillance and risk assessment of MIC-inducing M. maripaludis.
Subject(s)
Genome, Bacterial , Genomic Islands , Hydrogenase/genetics , Hydrogenase/metabolism , Iron/metabolism , Methanococcus/genetics , Methanococcus/metabolism , Anti-Bacterial Agents/pharmacology , Base Sequence , Corrosion , Gene Order , Genomic Instability , Methanococcus/drug effects , Microbial Sensitivity Tests , Models, Theoretical , Oxidation-ReductionABSTRACT
We analyzed the proteome of a crenararchaeon, Aeropyrum pernix K1, by using the following four methods: (i) two-dimensional PAGE followed by MALDI-TOF MS, (ii) one-dimensional SDS-PAGE in combination with two-dimensional LC-MS/MS, (iii) multidimensional LC-MS/MS, and (iv) two-dimensional PAGE followed by amino-terminal amino acid sequencing. These methods were found to be complementary to each other, and biases in the data obtained in one method could largely be compensated by the data obtained in the other methods. Consequently a total of 704 proteins were successfully identified, 134 of which were unique to A. pernix K1, and 19 were not described previously in the genomic annotation. We found that the original annotation of the genomic data of this archaeon was not adequate in particular with respect to proteins of 10-20 kDa in size, many of which were described as hypothetical. Furthermore the amino-terminal amino acid sequence analysis indicated that surprisingly the translation of 52% of their genes starts with TTG in contrast to ATG (28%) and GTG (20%). Thus, A. pernix K1 is the first example of an organism in which TTG is the most predominant translational initiation codon.
