Lipid Catabolism of Relapsing Fever Borreliae

Abstract

Relapsing fever borreliae require lipid compounds for growth in vitro. In this study, the major pathways of lipid catabolism in three species of tick-borne relapsing fever borreliae were investigated. Thin-layer chromatography was used to compare chloroform-methanol extracts of fresh culture media with extracts of exhausted culture media after organisms were removed by centrifugation. The chromatographic data demonstrated that lysolecithin was removed from the culture media during growth of the spirochetes, whereas lecithin, sphingomyelin, triglycerides, and cholesterol esters were not affected by growth of the organisms. Sonic extracts of the organism were tested for the presence of specific enzymes of lipid catabolism. Lysolecithinase, glycerophosphorylcholine diesterase, and acid phosphatase activities were demonstrated. Thus, these organisms can sequentially dissimilate lysolecithin to fatty acids, choline, inorganic phosphate, and glycerol. Assays for phospholipases A, C, and D, a-glycerophosphate dehydrogenase, alkaline phosphatase, and lipase were negative.

Lipid metabolism of Borrelia hermsi

“…Apparently, direct incorporation of preformed complex lipids does not account for much of the lipid found in the cells. Pickett and Kelly have reported that B. hermsi contains the enzymes for and can indeed dissimilate lysolecithin, but not other diacyl phospholipids or triacyl glycerols (6). Our data, while not contradicting this claim, suggest another explanation of their findings.…”

“…The synthesis of cholesteryl glucoside by B. hermsi also helps to explain the selective removal of cholesterol from the culture medium that Pickett and Kelly have reported (6). Cholesterol has been reported to be an essential nutrient for Treponema refringens biotype Noguchi (7) and is also required by the other biotypes of this spirochete (unpublished data).…”

“…Previous work by Kelly indicated that B. hermsi requires a pair of fatty acids for growth, one saturated and the other unsaturated, and that the organism will not grow in a lipid-free medium unless so supplemented (4,6). This suggests that B. hermsi does not have the metabolic ability to either synthesize or desaturate fatty acids.…”

Biology of Borrelia species.

“…We continue to use bovine albumin and rabbit serum in our medium (23,26). The albumin preparation alone or in combination with rabbit serum provides the required long-chain fatty acids that are incorporated unaltered into the cellular lipids (143,173,202). A borrelia does not have the ability to elongate the chain or to beta-oxidize the fatty acids that are supplied (173).…”

“…Cholesterol in the medium is also incorporated into cells (173,202). In addition, an unusual cholesterol glucoside and its acylated derivative are synthesized from cholesterol by B. hermsii (173).…”