Despite the importance of the Hms and Ybt system for flea-borne transmission and for disease in bubonic plague models, respectively, the pgm locus is subject to complete or partial loss at relatively high frequency by genomic rearrangements; and Pgm– Ybt– and Pgm–Ybt+ strains from natural plague foci have been described [5], [12]. Here, VCAN is linked to plague.