Upon initial plating of the archival and modern-dayBG stocks, we noted distinct colony morphotypes for many of the strains, with some strains containing multiple variants ( Figure 2 , Table 2 ). Some of these morphotypes were consistent with those observed by Hayward et al. [6] whooriginally described the emergence of colony variants in ''B. globigii.'' As in the earlier report, individual morphotypes were stable and did not interconvert with high frequency (data not shown), suggesting that these morphotypes were the result of relatively rare chromosomal mutations, although 1013-1 occasionally threw off papillae in heavier streaks (not shown). Multiple morphotypes were noted for ATCC9372, ATCC 49822, Detrick, and 1013, while the archival 1942 isolate, the isolate obtained from Dugway Proving Ground (Dugway) and BACI051 appeared to be pure populations on LB. All strains tested positive for BGusing Real Time-PCR primers specific to the recF gene (Methods S1) [27] . The appearance of multiple colony morphotypes even within single ''strains'' strongly suggested an asyet undescribed level of genetic diversity within these samples that likely affected the expression of cell-surface components and/or sporulation. The intra-strain colony morphology variation was particularly dramatic in the in vitro passaged 1013 and ATCC9372 isolates, in which one variant of each lineage had lost the production of color on LB orSBAplates (Figure 2 ), suggesting more dramatic alterations to the genome.