Identification of the electron transfer flavoprotein as an upregulated enzyme in the benzoate utilization of desulfotignum balticum

Abstract

Desulfotignum balticum utilizes benzoate coupled to sulfate reduction. Two-dimensional polyacrylamide gel electrophoresis (2D-PAGE) analysis was conducted to detect proteins that increased more after growth on benzoate than on butyrate. A comparison of proteins on 2D gels showed that at least six proteins were expressed. The N-terminal sequences of three proteins exhibited significant identities with the α and β subunits of electron transfer flavoprotein (ETF) from anaerobic aromatic-degraders. By sequence analysis of the fosmid clone insert (37, 590 bp) containing the genes encoding the ETF subunits, we identified three genes, whose deduced amino acid sequences showed 58%, 74%, and 62% identity with those of Gmet 2267 (Fe-S oxidoreductase), Gmet 2266 (ETF β subunit), and Gmet-2265 (ETF α subunit) respectively, which exist within the 300-kb genomic island of aromatic-degradation genes from Geobacter metallireducens GS-15. The genes encoding ETF subunits found in this study were upregulated in benzoate utilization.