SPIROPLASMA SPECIES, GROUPS, AND SUBGROUPS FROM NORTH-AMERICAN TABANIDAE

Twenty-one triply cloned spiroplasma strains from the United States ea st of the Rocky Mountains, all isolated from tabanid (Diptera:Tabanida e) flies or serologically related to strains from tabanids, were compa red reciprocally by spiroplasma deformation (DF) and metabolism inhibi tion (MI) serological. tests. Many of the strains were also tested aga inst 28 antisera representing known spiroplasma groups, subgroups, and putative groups isolated from nontabanid hosts. Relationships among s trains were indicated by reciprocal cross-reactivity in both DF and MI tests. The strains were found to represent 11 recognized spiroplasma groups or subgroups. On the basis of serological, biochemical, and gen omic data, strain BARC 1901 from Tabanus lineola appeared to represent a previously unrecognized candidate group. Strain BARC 2649, also fro m T. lineola, also appeared to represent a new group, but its morpholo gy, arginine utilization, and some one-way serological crossing patter ns suggested that it may be distantly related to group VIII spiroplasm as. Morphological, serological, and genomic data were used to place ta banid spiroplasma strains into three informal clusters. These are (i) groups IV (strain B31) and XXXI (strain HYOS-1); (ii) the three existi ng subgroups and a new candidate subgroup of group Vm represented by s train BARC 1357 plus ungrouped strain BARC 2649; and (iii) 14 strains, including EC-1 and TATS-1 (group XIV); strains TN-1 and TAAS-2 (group XVIII); strains TG-1, TASS-1, and BARC 4689 (group XXIII), strains TA LS-2 (group XXVII), strain TABS-2 (group XXXII), and strains TAUS-1 an d TABS-1 (group XXXIII) and ungrouped but closely related strains BARC 1901, BARC 2264 and BARC 2555. Analysis of tabanids from other geogra phic regions probably will substantially increase the number of known spiroplasma groups from this insect family.