Modification of cell membrane lipids in Micrococcus lysodeikticus induced by pantoyl lactone.

Growth of Microccoccus lysodeikticus in the presence of pantoyl lactone brings about both qualitative and quantitative changes in cell membrane lipids. Significant amounts of the two major phospholipids (phosphatidylglycerol and diphosphatidylglycerol) are converted to lyso forms; the largest conversion occurs in the phosphatidylglycerol. In addition, amounts of several phospholipid fatty acids are changed. Physical alteration of the call membrane can be demonstrated using differential scanning calorimetry. Although growth and transport are significantly inhibited when pantoyl lactone is present, cells possessing altered call membrane phospholipds and phospholipid fatty acids, brought about by growth in the presence of pantoyl lactone, transport D-alanine, L-glutamic and L-aspartic acid normally when washed free of the pantoyl lactone.

Cell membrane phospholipids and their constitutent fatty acids in dividing and nondividing cells of Micrococcus lysodeikticus.

Changes occurring in the cell membrane of nondividing cells of Micrococcus lysodeikticus disIIp+ grown in the presence of the mucopeptide synthesis inhibitor D-cycloserine include (a) an increae in the relative amount of diphosphatidylglycerol with a concomitant decrease in the relative content of phosphatidylglycerol, (b) a small increase in the relative palmitic acid content of phosphatidylinositol, and (c) leakage of membrane components into the growth medium. Growth of the organism in the presence of both D-cycloserine and D-alanine (which prevents the effects of D-cycloserine on cell division and mucopeptide synthesis) prevents the above changes in the cell membrane, demonstrating that secondary damage to the cell membrane can occur as a rsult of inhibition in mucopeptide synthesis. Growth of the organism in the presence of D-cycloserine and pantoyl lactone prevents the leakage of membrne components and cell division inhibition. Possible relationships of these changes to cell division are discussed.

Noninvolvement of beauvericin in the entomopathogenicity of Beauveria bassiana.

Development of a microbiological autobiographic assay procedure permitted a detailed investigation of the possible role of beauvericin (a toxic ionophoric antibiotic produced by Beauveria bassiana) in the entomopathogenicity of B. bassiana against corn earworm (Heliothis zea) larvae. Analysis of spent media of B. bassiana and the hemolymph of infected and moribund larvae revealed that beauvericin was not present in a soluble form during the time that most (about 90%) larvae died of fungal infection (4 days). Intrahemocoelic injections of up to 6 micrograms of synthetic beauvericin failed to induce any deleterious effects. In addition, although methanol-soluble ionophores, such as valinomycin and bassianolide, were toxic to corn earworm larvae, no methanol-soluble toxin could be detected in the hemolymph of moribund larvae.

Requirement for pantothenate for filament formation by Erwinia carotovora.

Pantothenate is required for the formation of filaments by Erwinia carotovora. This has been demonstrated for the following division-inhibiting agents: D-serine, D-cycloserine, penicillin, vancomycin, fluoride ion, and ultraviolet light. D-Serine inhibits pantothenate synthesis in an ammonia-glucose or an ammonia-pyruvate medium; therefore, it is necessary to add pantothenate to obtain filament formation in these media, using D-serine as the division-inhibiting agent. Under conditions in which pantothenate synthesis is not inhibited by the agent producing filaments, the need for it for filamentation was shown by the use of salicylate, an inhibitor of endogenous pantothenate synthesis. Evidence is presented that the production of filaments is a specific response to pantothenate, rather than a nonspecific growth stimulation.

Cell division in Erwinia: inhibition of nuclear body division in filaments grown in penicillin or mitomycin C.

Low concentrations of penicillin or mitomycin C in cultures of Erwinia sp. inhibit cell division. Electron-microscopic analysis of serial sections of these nondividing cells reveals that division of the nuclear body is also inhibited.