The 20 Leptospira species are divided into 14 infectious and six noninfectous species. (Actually, there are now 22 species known but only 20 when this study was launched.) The infectious species are divided further into nine pathogenic and five "intermediate" species based on their genetic relatedness.
The Venn diagram below shows the number of genes that are shared among and within the three categories of Leptospira and Leptonema illini, a closely-related spirochete. Looking at the relevant intersection (overlap) in the diagram, there are 255 genes that are carried by infectious Leptospira but not by saprophytic Leptospira. (The other two figures in the overlap are the number of shared genes tabulated using looser criteria. In these cases there are 302 genes found in all but one infectious Leptospira and 369 genes when those found in the majority of infectious species are counted.) Similarly, there are 109 genes unique to the pathogenic species (or 161 or 416, if you want to use less stringent criteria). The small circles at the periphery show the number of genes unique to each species. So for example, L. interrogans, the species favored for study in molecular biology labs, has 672 genes that are not found in any other Leptospira species.
|Figure 2A from Fouts et al., 2016. Source.|
Fouts DE, Matthias MA, Adhikarla H, Adler B, Amorim-Santos L, Berg DE, Bulach D, Buschiazzo A, Chang YF, Galloway RL, Haake DA, Haft DH, Hartskeerl R, Ko AI, Levett PN, Matsunaga J, Mechaly AE, Monk JM, Nascimento AL, Nelson KE, Palsson B, Peacock SJ, Picardeau M, Ricaldi JN, Thaipandungpanit J, Wunder EA Jr, Yang XF, Zhang JJ, & Vinetz JM (2016). What makes a bacterial species pathogenic?: Comparative genomic analysis of the genus Leptospira. PLoS Neglected Tropical Diseases, 10 (2) PMID: 26890609