FIG 5.

Flowchart and historical information for the derivation of M. xanthus laboratory strains. The first isolation and description of the species M. xanthus were reported by Beebe in 1941 (44). Although the origin of currently used M. xanthus laboratory strains is murky, Wu and colleagues (45) indicated that the Beebe strain was transferred to UC Berkeley, where it was maintained in Roger Stanier's strain collection. Both FB and DZ2 were obtained from the Berkeley collection (20, 21, 46). The claim by Wu et al. is supported by the fact that ATCC strains 19368 and 25232 are cross-listed in the ATCC database. The Beebe isolate was indeed deposited in ATCC as strain 19368. However, in the early 1960s, ATCC personnel were no longer able to revive this strain (denoted by an asterisk) (ATCC technical support staff, personal communication). The ATCC consequently requested that Marty Dworkin (University of Minnesota) deposit his M. xanthus FB strain (ATCC 25232), with the understanding that it was the same strain as 19368; hence the strains were cross-listed. It should be further noted that FB was not maintained as a pure culture; it was a mixture of related strains that had evolved from a common ancestor during prolonged laboratory propagation (47). Additional strain details can be found in Table 1, the text, and the supplemental material. Dashed arrows/lines, presumed relationships; solid arrows, known relationships; two arrows, multiple steps; sci, single-colony isolate.