COMPARISON OF GENETIC MAPS FOR 2 LEPTOSPIRA-INTERROGANS SEROVARS PROVIDES EVIDENCE FOR 2 CHROMOSOMES AND INTRASPECIES HETEROGENEITY

Genetic maps were constructed for Leptospira interrogans serovars icte rohaemorrhagiae and pomona. Previously we independently constructed ph ysical maps of the genomes for these two serovars. The genomes of both serovars consist of a large replicon (4.4 to 4.6 Mb) and a small repl icon (350 kb). Genes were localized on the physical maps by using Sout hern blot analysis with specific probes. Among the probes used were ge nes encoding a variety of essential enzymes and genes usually found ne ar bacterial chromosomal replication origins. Most of the essential ge nes are on the larger replicon of each serovar. However, the smaller r eplicons of both serovars contain the asd gene. The asd gene encodes a spartate beta-semialdehyde dehydrogenase, an enzyme essential in amino acid and cell wall biosyntheses. The finding that both L. interrogans replicons contain essential genes suggests that both replicons are ch romosomes. Comparison of the genetic maps of the larger replicons of t he two serovars showed evidence of large rearrangements. These data sh ow that there is considerable intraspecies heterogeneity in L. interro gans.