A numerical taxonomic study of the genus Kurthia with a revised description of Kurthia zopfii and a description of Kurthia gibsonii sp. nov.

One hundred and twelve strains including fresh isolates of Kurthia from a wide variety of habitats and named reference strains of the genera Arthrobacter, Bacillus, Brevibacterium, Cellulomonas, Corynebacterium, Curtobacterium, "Flavobacterium', Kurthia, Microbacterium, Nocardia and Rhodococcus were tested for 192 morphological, cultural, biochemical, and physiological characters. Various numerical analyses were performed on the data. All reference strains and most fresh isolates of Kurthia formed a distinct group considered to represent the genus. This group was divided into two clusters: one contained the type strain of K. zopfii and was considered to represent that species; the other was considered to represent a new species for which the name K. gibsonii is proposed. The two species are distinguished from each other by nine characters. A few presumptive Kurthia isolates were separated from the main Kurthia group; their taxonomic position was not resolved. Low levels of phenetic similarity were found between Kurthia and the coryneform and nocardioform bacteria, and with most Bacillus spp. studied, suggesting little relationship with these groups. However evidence was obtained that Kurthia bears a closer relationship to some aerobic Bacillus spp. than to the coryneform bacteria.