Updated FTP location. The microbiologically influenced corrosion is one of the serious problems in petroleum tanks. It was found that the methanogenic archaea Methanococcus maripaludis OS7 isolated from the inside of petroleum tanks has the iron corrosive property. To identify the genes related to the iron corrosion, we have performed proteome analysis of iron-corrosive archaeon M. maripaludis OS7 and its corrosion-defective mutant.