Characterization of leptospires according to fatty acid requirements.

SUMMARY: The fatty acid requirements of leptospires parasitic for mammals were compared to those of members of the ‘biflexa complex’ (leptospires not clearly demonstrated to be animal parasites). The parasitic leptospires grew on unsaturated fatty acids. Saturated fatty acids were not utilized unless an unsaturated fatty acid was also provided. This requirement for an unsaturated fatty acid was increased at temperatures above and below the optimal. In addition, these leptospires did not utilize fatty acids containing less than 15 to 16 carbon atoms unless a longer chain fatty acid was also present. Leptospires of the ‘biflexa complex’ had neither of these requirements. These leptospires grew on either long or short chain, saturated or unsaturated fatty acids. Utilizing these differences in fatty acid requirements, a means of differentiating these two groups of leptospires is provided. Members of the ‘biflexa complex’ but not the parasitic leptospires grew on an albumin medium containing 5 × 10-4 M-myristic acid, the 14-carbon saturated fatty acid.