Deoxyribonucleic Acid Homologies Among Organisms in the Genus Gluconobacter

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Abstract
The taxonomy of the genus Gluconobacter has undergone many changes during the past 40 years. Based on phenotypic properties, this genus has changed from numerous species to one species containing five subspecies and then to a single species, Gluconobacter oxydans, with no subspecies. The present study was designed to test the validity of this latter view. Nucleotide sequence similarites were determined for 54 strains of Gluconobacter by using an S1 nuclease procedure. Three distinct deoxyribonucleic acid homology groups were obtained. The average level of relatedness among these groups was 16%. Homology group 1 contained 32 strains and included the type strain of G. oxydans and the type strains of all previously recognized subspecies. Homology group II contained 12 strains that had an intragroup homology level of 44 to 87% (average, 65%) with reference strain IFO 3264. Homology group III contained six strains with an average intragroup homology level of 86% with reference strain IFO 3276a. Reference strains IFO 3264 and IFO 3276 were previously recognized as G. oxydans. The remaining four strains of Gluconobacter had from 0 to 23% homology with reference strains used to delineate the three homology groups. Although these data show that the genus Gluconobacter is composed of at least three species, they also support elimination of the previously designated subspecies. Three isolates implicated in pink disease of pineapples were shown either not to be gluconobacters or to be mixed with gluconobacters. The occurrence of colony variants within many of the Gluconobacter strains is described, and the significance of this observation is discussed.