Spiroplasma kunkelii sp. nov.: Characterization of the Etiological Agent of Corn Stunt Disease

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Abstract
Nine strains of spiroplasma subgroup 1-3, which comprise the etiological agent of corn stunt disease, were similar in their serological properties. Strain E275T(T = type strain) was studied by using criteria proposed by the International Committee on Systematic Bacteriology Subcommittee on Taxonomy of Mollicutes for descriptions of new mollicute species. This strain was shown to belong to the class Mollicutes by the ultrastructure of its limiting membrane, its procaryotic organization, its colonial morphology, and its filtration behavior and to the family Spiroplasmataceae by its helical morphology and motility. Although some serological cross-reactions with other group I spiroplasma strains was observed, strain E275Tcould be readily distinguished from representatives of other group I subgroups. Subgroup 1-3 spiroplasmas and other group I strains also differed in their one- and two-dimensional polyacrylamide gel protein patterns, plant and insect host ranges, and pathogenicities. Growth in MIA or MID medium occurred at 20 to 30°C. Cholesterol was required for growth. Glucose was fermented, and arginine was catabolized. Subgroup 1-3 strains, including strain E275T, reacted with considerable homogeneity in deformation tests and were completely separable from strains belonging to subgroup I-1 (Spiroplasma citri) and subgroup I-2 (Spiroplasma melliferum). Strain E275Twas also serologically distinct from subgroups I-4 through I-8, Spiroplasma floricola (group III), Spiroplasma apis (group IV), Spiroplasma mirum (group V), and representative strains of spiroplasma groups II and VI through XI. The deoxyribonucleic acid of strain E275Thybridized with the deoxyribonucleic acid of S. citri at significant levels (33 to 68%, depending on the technique used). These results demonstrate that strain E275Tand similar strains meet the criteria proposed by the International Committee on Systematic Bacteriology Subcommittee for elevation of spiroplasma subgroups to species. We propose that such strains be named Spiroplasma kunkelii. Strain E275Thas been deposited in the American Type Culture Collection as strain ATCC 29320T.