Characterization of an operon encoding two c-type cytochromes, an aa(3)-type cytochrome oxidase, and rusticyanin in Thiobacillus ferrooxidans ATCC 33020

Despite the importance of Thiobacillus ferrooxidans in bioremediation and b ioleaching, little is known about the genes encoding electron transfer prot eins implicated in its energetic metabolism. This paper reports the sequenc es of the four cox genes encoding the subunits of an aa(3)-type cytochrome c oxidase, These genes are in a locus containing four other genes: cyc2, wh ich encodes-a high-molecular-weight cytochrome c; cyc1, which encodes a c(4 )-type cytochrome (c(552)); open reading frame 1, which encodes a putative periplasmic protein of unknown function; and rus, which encodes rusticyanin , The results of Northern and reverse transcription-PCR analyses indicated that these eight genes are cotranscribed, Two transcriptional start sites w ere identified for this operon, Upstream from each of the start sites was a sigma 70-type promoter recognized in Escherichia coli, While transcription in sulfur-grown T, ferrooxidans cells was detected from the two promoters, transcription in ferrous-iron-grown T. ferrooxidans cells was detected onl y from the downstream promoter. The cotranscription of seven genes encoding redox proteins suggests that all these proteins are involved in the same e lectron transfer chain; a model taking into account the biochemistry and: t he genetic data is discussed.