Fatty Acid Composition of L-Forms of Streptococcus faecalis Cultured at Different Osmolalities

Abstract

The fatty acid composition of the membranes of three different penicillin-produced L-forms of Streptococcus faecalis was determined: (i) a stable (nonreverting) L-form (T 53 ) cultured in brain heart infusion (BHI) with 0.5 M sucrose; (ii) a stable L-form (T 531 ) cultured in BHI without sucrose; and (iii) an unstable L-form (T 9 ) cultured in BHI with 0.5 M sucrose and 1,000 U of penicillin per ml. L-forms were obtained by centrifugation and lysed by washing in 1 mM tris(hydroxymethyl)aminomethane-hydrochloride buffer. The parent S. faecalis was also cultured in BHI and BHI containing 0.5 M sucrose, and washed with buffer. The fatty acid composition of L-forms of S. faecalis cultured in BHI without sucrose (370 mosmol) had higher C 18:1 and lower C 18 than L-forms cultured in the same media with added 0.5 M sucrose (950 mosmol) in both exponential and stationary cultures. In the stationary phase of growth, C 19 was reduced in the L-forms cultured without sucrose. Similar changes were seen in the parent S. faecalis cultured in the two types of media. These changes in membrane fatty acids may relate to osmo-regulation of the L-forms.