and Latin spira 'coil')[1] is a genus of spirochaete bacteria, including a small number of pathogenic and saprophytic species.

For example: The currently accepted taxonomy is based on the List of Prokaryotic names with Standing in Nomenclature (LPSN)[10] and National Center for Biotechnology Information (NCBI).

The bacteria have a number of degrees of freedom; when ready to proliferate via binary fission, the bacterium noticeably bends in the place of the future split.

Leptospira, both pathogenic and saprophytic, can occupy diverse environments, habitats, and life cycles; these bacteria are found throughout the world, except in Antarctica.

High humidity and neutral (6.9–7.4) pH are necessary for their survival in the environment, with stagnant water reservoirs—bogs, shallow lakes, ponds, puddles, etc.—being the natural habitat for the bacteria.

Leptospira are cultivated at 30 °C in Ellinghausen-McCullough-Johnson-Harris (EMJH) medium, which can be supplemented with 0.21% rabbit serum to enhance growth of fastidious strains.

Leptospira are aerobes whose major carbon and energy source during in vitro growth is long-chain fatty acids, which are metabolized by beta-oxidation.

[30] Fatty acid molecules are bound by albumin in EMJH and are released slowly into the medium to prevent its toxic accumulation.

[39] L. borgpetersenii serovar Hardjo is usually transmitted by direct exposure to infected tissues, whereas L. interrogans is often acquired from water or soil contaminated by the urine of carrier animals harboring Leptospira in their kidneys.

The high number of defective genes and insertion sequences in L. borgpetersenii Hardjo together with the poor survival outside of the host and difference in transmission patterns compared to L. interrogans suggest that L. borgpetersenii is undergoing insertion-sequence mediated genomic decay, with ongoing loss of genes necessary for survival outside of the host animal.

[38] Genome sequence determination several strains of Leptospira lead to the development of multilocus VNTR (Variable Number of Tandem Repeats) typing and multilocus sequence typing (MLST) for species level identification of pathogenic Leptospira species.