Revised group classification of the genus Spiroplasma (class Mollicutes), with proposed new groups XII to XXIII

Fourteen spiroplasma strains, mostly isolated from insects (Coleoptera, Hemiptera, Culicidae and Tabanidae) with 1 (W115) from the flower of Prunus, were analysed according to criteria proposed by the International Committee on Systematic Bacteriology Subcommittee on the Taxonomy of Mollicutes for the description of new serogroups of the genus Spiroplasma. When tested by reciprocal metabolism inhibition, growth inhibition and deformation serological procedures, 12 of the strains were serologically unrelated to each other and to representative strains previously assigned to groups I to XI and subgroups I-1 to I-8. Examination by dark-field and electron microscopy indicated that each of the 12 strains possessed morphological features typical of spiroplasmas (helicity, motility, lack of a cell wall and absence of periplasmic fibrils). All strains were resistant to 500 U of penicillin per ml, and catabolized glucose but were unable to hydrolyze urea. The ability to hydrolyze arginine varied among strains. The guanine-plus-cytosine contents of the DNA of the 12 strains varied from 24 to 29 mol%. Two other strains (MQ-6 and Ar-1357) shared only a partial serological relationship to strain CC-1 (group XVI), suggesting that this group may consist of an assemblage of heterogenous serovars. It is proposed that the 12 representative strains be assigned new consecutive group designations XII to XXIII.