Spiroplasma species, groups, and subgroups from North American Tabanidae.

Twenty-one triply cloned Spiroplasma strains from the USA east of the Rocky Mountains, all isolated from tabanid flies or serologically related to strains from tabanids, were compared reciprocally by spiroplasma deformation (DF) and metabolism inhibition (MI) serological tests. Many of the strains were also tested against 28 antisera representing known spiroplasma groups, subgroups and putative groups isolated from non-tabanid hosts. Relationships among strains 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 genomic data, strain BARC 1901 from Tabanus lineola from Georgia appeared to represent a previously unrecognized candidate group. Strain BARC 2649, also from T. lineola from Georgia, also appeared to represent a new group, but its morphology, arginine utilization and some one-way serological crossing patterns suggested that it may be distantly related to Group VIII spiroplasmas. Morphological, serological and genomic data were used to place tabanid spiroplasma strains into 3 informal clusters. These are (i) Groups IV (S. apis strain B31 from the bee Apis mellifera) and XXXI (S. montanense strain HYOS-1 from Hybomitra opaca); (ii) the 3 existing subgroups and a new candidate subgroup of Group VIII represented by strain BARC 1357 (from T. lineola) plus ungrouped strain BARC 2649 (from T. lineola); and (iii) 14 strains, including S. corruscae EC-1 (from the lampyrid Ellychnia corruscae) and TATS-1 (from T. trimaculatus) (Group XIV); S. litorale strains TN-1 (from T. nigrovittatus) and TAAS-2 (from T. atratus) (Group XVIII); S. gladiatoris strains TG-1 (from T. gladiator), TASS-1 (from T. sulcifrons) and BARC 4689 (from T. lineola) (Group XXIII), S. lineolae strain TALS-2 (from T. lineola) (Group XXVII), S. helicoides strain TABS-2 (from T. abactor) (Group XXXII), and S. tabanidicola strains TAUS-1 (from Tabanus sp.) and TABS-1 (from T. abactor) (Group XXXIII) and ungrouped but closely related strains BARC 1901, BARC 2264 and BARC 2555 (from T. lineola). Analysis of tabanids from other geographic regions probably will substantially increase the number of known spiroplasma groups from this insect family.