Energetic aspects of malate and lactate fermentation by Acetobacterium malicum

The complete nucleotide sequence of two genes from Clostridium thermosulfurogenes EM1 homologous to E. coli genes encoding transport proteins was determined by the dideoxy procedure. The genes were cloned from plasmid pCT4, which contains the alpha-amylase gene from C. thermosulfurogenes EM1 as a 2.9-kbp XbaI fragment, inserted into the XbaI site of pUC18, to yield plasmid pCT401. The proteins encoded by the two identified complete ORFs are very hydrophobic and thus are probably integral membrane proteins. They show over 50% similarity to the maltose transport proteins MalF and MalG and to the glycerol-3-phosphate uptake proteins UgpA and UgpE of Escherichia coli. Since these genes are located immediately upstream of the alpha-amylase gene (amyA) of C. thermosulfurogenes EM1, the encoded proteins might be involved in transport of starch degradation products. The genes were tentatively designated amyC and amyD.