SPIROPLASMA MONTANENSE SP-NOV, FROM HYBOMITRA HORSEFLIES AT NORTHERN LATITUDES IN NORTH-AMERICA

Spiroplasma strain HYOS-1(T) was isolated from a tabanid fly, Hybomitr a opaca. The organism was serologically distinct from other spiroplasm a species, groups, and subgroups and was recently designated the repre sentative of spiroplasma group XXXI. The cells of strain RYOS-1(T), as determined by light microscopy, were long motile helices, Electron mi croscopic examination revealed wall-less cells delimited by a single m embrane, The cells passed through 450- and 300-nm filter pores with a 10-fold reduction in titer, but failed to pass through 100-nm pores, S train HYOS-1(T) grew very well in most conventional medium formulation s for spiroplasmas or other mollicutes. The organism grew at temperatu res ranging from 5 to 41 degrees C, and the optimum temperature was 32 degrees C, The doubling time at the optimum temperature was 0.7 h, on e of the shortest values obtained for members of the genus Spiroplasma , The strain catabolized glucose and hydrolyzed arginine but not urea, Growth of the organism was stimulated by cholesterol and serum, but t he strain was nevertheless able to grow in the absence of sterols or s erum. The guanine-plus-cytosine content of the DNA was about 28 +/- 1 mol%, and the genome size was 1,225 kbp, On the basis of the experimen tal results reported here and previously reported data, group XXXI str ain HYOS-1 (= ATCC 51745) is designated the type strain of a new speci es, Spiroplasma montanense.