Spiroplasma litorale sp. nov., from tabanid flies (Tabanidae: Diptera) in the southeastern United States

Spiroplasma strain TN-1T (T = type strain), a strain serologically distinct from other spiroplasma species, groups and subgroups, was isolated from the gut of a horsefly (Tabanus nigrovittatus) from a barrier island off the coast of North Carolina, USA. Related strains were isolated from T. atratus, T. americanus, T. gladiator, T. lineola, T. sulcifrons and T. zythicolor, from coastal Georgia. Cells of strain TN-1T in culture were helical and motile with an average of 5-10 helical turns per cell. Electron microscopy determined that the cells of strain TN-1T were surrounded by a single cytoplasmic membrane, and there was no evidence of a cell wall. The spiroplasma grew well in M1D and SP-4 liquid media. Serum fraction (1%) medium and conventional horse serum medium also supported growth of strain TN-1T. Fried-egg colonies were not produced; instead, the strain produced small diffuse colonies that were surrounded by satellite growth. The optimum temperature for growth was 32°C, but multiplication was observed at temperatures from 10 to 41°C. The doubling time at the optimum temperature (32°C) was 1.6 h. No growth was observed at 5 or 43°C. Spiroplasma strain TN-1T passed through 220-nm filter pores but failed to pass through 100-nm filter pores. Strain TN-1T catabolized glucose but hydrolysed neither arginine nor urea. The guanine-plus-cytosine content of the DNA was about 25±1 mol%, and the genome size was 1370 kbp. Based on results from this study and previously published data, strain TN-1T ( = ATCC 43211) (group XVIII) is designated the type strain of a new spiroplasma species, S. litorale sp. nov.