SUPPRESSION OF AN ETHANOL-SENSITIVE MUTATION OF ACETOBACTER-PASTEURIANUS BY OVEREXPRESSION OF THE HIS1 GENE ENCODING HISTIDINOL PHOSPHATE AMINOTRANSFERASE

An ethanol-sensitive mutant strain of Acetobacter pasteurianus was isolated by chemical mutagenesis with N-methyl-N'-nitro-N-nitrosoguanidine. The his1 gene of A. pasteurianus, which codes for histidinol phosphate aminotransferase (HPAT), was cloned on a multicopy plasmid pMV24 because of its ability to complement the ethanol-sensitive mutation. The mutant was found still to possess almost the same HPAT activity as the parental strain, which was increased to five times that of the basal activity by the introduction of a multicopy plasmid containing the his1 gene into the mutant. It was thus concluded that an increase in the HPAT activity led to the suppression of the ethanol-sensitive mutation.