The addition of low concentrations of streptomycin (5–10μg/ml of medium) to Serratia marcescens caused significant alterations in the lipid composition of this organism, but neither growth nor pigmentation was affected. The acetone-soluble cyclic depsipeptides, which comprise on average 15% of the total lipid, were decreased almost to zero and the total lipid phosphorus was more than doubled in the presence of streptomycin. Most of the phospholipid increase was due to an increase in phosphatidylethanolamine. Cyclic depsipeptides were not leached from the cell in the presence of streptomycin, indicating a definite inhibition of the biosynthetic pathway. The effect of streptomycin on the reported peptidolipids of Rhodopseudomonas spheroides, Halobacterium halobium, Nocardia asteroides and Pseudomonas tabaci was investigated. In the case of the only strictly comparable cellular cyclic depsipeptide (that of N. asteroides) the biosynthesis was strongly inhibited by streptomycin, but cell weight was maintained or even slightly increased. A possible mode and site of action of low concentrations of streptomycin on bacterial lipids is discussed.
Biosynthetic pathway of .BETA.-methylnorleucine, an antimetabolite produced by Serratia marcescens.
