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Sixteen spiroplasma isolates, recovered over a 2-year period from symptomatic periwinkle plants (Catharanthus roseus) collected in eight different locations in Syria, were compared with other established Spiroplasma species or serogroups. Serological analysis of selected representatives of the new isolates revealed sharing of some antigenic components with several spiroplasmas currently classified within subgroups of group I of the genus. Strain P40Twas selected as the type strain and examined, meeting the criteria proposed by the International Committee on Systematic Bacteriology Subcommittee on the Taxonomy of Mollicutes. The organism was shown to belong to the class Mollicutes by its morphology, ultrastructure of its limiting membrane, colony characteristics, and filtration patterns. The helicity and motility of the cells indicated its placement within the family Spiroplasmataceae. Although some serological cross-reactions could be observed with representatives of group I subgroups, strain P40Tcould be readily distinguished from other plant or insect pathogenic spiroplasmas in subgroup I-1 (Spiroplasma citri), subgroup I-2 (S. melliferum), or subgroup I-3 (S. kunkelii) and from spiroplasmas assigned to subgroups I-4 through I-7 and groups II through XI. Cholesterol was required for growth. Glucose was fermented, and arginine was hydrolyzed. The base composition (guanine plus cytosine) of the deoxyribonucleic acid of strain P40Twas found to be 26 mol%. Deoxyribonucleic acid-deoxyribonucleic acid hybridization comparisons between strain P40Tand other subgroup I representatives revealed approximately 60% relatedness to S. citri and S. kunkelii and 50% relatedness to S. melliferum. Experimental transmission of two of the new isolates (P40Tand P354) occurred through inoculation of spiroplasma broth cultures into leafhoppers (Macrosteles fascifrons), multiplication of the organism in the insects, and subsequent transmission of the organism by insect feeding on aster or periwinkle plants. The organism was also successfully recovered from broth cultures of symptomatic tissues of experimentally infected periwinkle plants, thus fulfilling Koch’s postulates. We propose that such strains be named Spiroplasma phoeniceum. Strain P40Thas been deposited in the American Type Culture Collection (= ATCC 43115T)
Saillard et al. (Wed,) studied this question.