Loss of Acetic Acid Resistance and Ethanol Oxidizing Ability in an Acetobacter Strain

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A thermophilic strain, No. 1023, of Acetobacter aceti was isolated, by which it became possible to carry out submerged vinegar production at 35°C. The thermophilic property of the strain correlated closely with its acetic acid resistance. Strain No. 1023 lost acetic acid resistance at high frequency (more than 55% in isolated strains) and lost ethanol oxidizing ability at lower frequency (about 40%) compared to the above in the stationary growth phase in a liquid medium containing ethanol. The loss of these properties during the stationary phase was confirmed using a genetically marked strain (pro^-) of No. 1023. Such frequent loss of acetic acid resistance and ethanol oxidizing ability suggested a relationship between these properties and a plasmid. A plasmid, pTA 5001, was found in strain No. 1023, and its molecular weight was determined to be 17 × 106 daltons by electron microscopy. The plasmid, however, seemed to have no direct connection with acetic acid resistance or ethanol oxidizing ability, because the same plasmid was found in all strains which had no these properties.