Deoxyribonucleic Acid Base Composition and Homology Studies ofLeptospira

Abstract

Four distinct genetic groups of leptospiras were demonstrated among selected pathogenic and "biflexa" serological types. Pathogenic leptospiras could be divided into two groups on the basis of per cent guanine + cytosine (GC) in their deoxyribonucleic acid (DNA). One group had 36 1%, the other 39 4 1%. The biflexa strains had DNA of 39 + 1 % GC, but were further separated into two groups on the basis of DNA-annealing tests. Strains within groups had a high degree of specific duplex formation (75 % binding or more with reference to the homologous DNA). There was little or no genetic relatedness between strains of the four groups (less than 10% DNA homology). The thermal elution midpoint of heterologous DNA duplexes was always lower than the homologous reaction. The serological relationships among strains were not meaningful in terms of relatedness determined by specific duplex formation.

Presence of putative sphingomyelinase genes among members of the family Leptospiraceae

“…Nevertheless, L. interrogans, L. noguchii, and "L. alstoni" on the one hand and L. borgpetersenii, L. santarosai, and L. weilii on the other hand seem to be more related to each other than to the other pathogenic Leptospira species (13,19). A similar subdivision of the pathogenic leptospires into two groups on the basis of G+C content of the chromosomal DNA, 2,6diaminopurine resistance, and lipase production was previously reported by Haapala et al (7). The subdivision of pathogenic leptospires into two groups corresponds to the presence or absence of DNA fragments hybridizing with the sphA gene under stringent hybridization conditions (Table 1), since under such conditions PSGs hybridize in L. borgpetersenii, L. santarosai, and L. weilii but not in the other pathogenic Leptospira species.…”

“…The family Leptospiraceae is genetically very heterogeneous and comprises at least 12 different species (2,7,11,19). As deduced from DNA hybridizations involving the whole genome, the genetic relatedness among the different Leptospira species differs considerably.…”

Isoprenoid quinone and polar lipid composition of Leptospiraceae

“…The results of the lipid analyses provide further characters for the classification of leptospires but do not help to distinguish between individual species or between the regions of variation highlighted in DNA hybridisation experiments [8,9]. Thus, on the basis of menaquinone and polar lipid data it was impossible to differentiate L. biflexa or L. interrogans from the disputed taxon 'L.…”

“…The genus Leptospira [1] currently comprises two species, namely the saprophytic L. biflexa [2] and pathogenic L. interrogans [3] and one species [4,5]. The single strain of the latter has been proposed as the nucleus of a new genus, Leptonema in the family Leptospiraceae, largely on the basis of its distinctive morphology and high mol% G + C content (53%) when compared to other leptospires (35-41%; [5][6][7][8][9]). The systematics of all leptospires is difficult and is based largely on serology and a small number of morphological and physiological features [5].…”

“…Using these tests representatives of L. biflexa and L. interrogans can be organised into at least 55 serogroups and 135 serovars but only two phenotypic types [5]. The results of nucleic acid hybridisation studies, however, suggest that at least seven distinct species may exist within the genus [8,9].…”