J. Čáslavská

Production of quinomycin A inStreptomyces lasaliensis

In addition to lasalocid, an oligoether coccidiostatic compound, other compounds are synthesized byStreptomyces lasaliensis. Mutants producing either of two antibiotics, lasalocid A or quinomycin A (an antibiotic of quinoxaline character), were obtained by natural selection and by mutagenesis. Methods of isolation, purification and estimation of both compounds were established.

Turnover of murein in cellular and filamentous populations ofBacillus megaterium

Bacillus megaterium grows in the form of filaments at temperatures above 45°C. The rate of turnover of the cell wall begins to decrease gradually under these conditions. At the same time sensitivity of the filamentous forms to lysozyme decreases. Filaments outgrown at 48°C retain the decreased rate of turnover of the cell wall for a certain time after transfer to 30°C, in spite of the fact that septa are formed and filaments are converted to cells. However, a population incubated longer than 2 h at 48°C often ceases to grow and the growth is not restored even after transfer to 30°C. Three clones of the asporogenic strainBacillus megaterium KM differing somewhat in their ability to form filaments at 35°C differ mutually also in the rate of turnover of the cell wall. However, the decreased rate of the turnover cannot be unambiguously correlated with the increased tendency to form filaments.

Taxonomic studies of Streptomyces virginiae mutants overproducing virginiamycin M1.

By using both the traditionalInternational Streptomycetes Project methods and chemical approaches followed by a hierarchical cluster analysis,Streptomyces virginiae mutants A-1 and B-43 (yielding higher amounts of the M1 component of virginiamycin complex), their wild ancestor ATCC 13161, and another virginiamycin producer,S. pristinaespiralis NRRL 2958, were subjected to taxonomic studies to find kinship or differences among the strains. Of the methods used, only the test of carbon utilization, investigation of spore surface and analysis of sugar constituents of cell walls proved to be reliable enough to demonstrate the species identity ofS. virginiae strains and to distinguish them fromS. pristinaespiralis.l,l-2,6-Diaminopimelic acid was present in all strains. Analysis of fatty acids and total proteins as well as investigations of morphology and pigmentation of agar cultures led to confusing results.

Effect of prolonged cultivation in a chemostat under nitrogen limitation on the morphology and ultrastructure ofBacillus subtilis

Cells ofBacillus subtilis A32 grown in a chemostat under nitrogen limitation display morphological changes after long-term cultivation. Bacillary rods are transformed into irregular spherical forms. A general chemical analysis of the normal and of the altered cells was carried out. The spherical cells were studied by electron microscopy in ultrathin sections. Differences in the arrangement of the superficial layers and a damaged mechanism of regular division were observed. The spherical forms revert to rods after removing the limitation.

Characteristics ofStreptomyces globisporus strain 0234A forming endospores in submerged cultures

Thermosensitive submerged endospores formed byStreptomyces globisporus 0234 and its natural variant A resembled those of thermoresistant actinomycetes not only in their morphology and ultrastructure, but also in the content of dipicolinic acid. The production of endospores containing this substance is unusual inStreptomyces while other features of the strain indicate relatedness to other streptomycetes. Chemotaxonomic analysis of variant A revealed the cell wall to be of chemotype I and fatty acid content typical ofStreptomyces. Most characteristics of surface cultures of variant A coincided with those of the original strain 0234 and its endosporeless variant B. Both the strain 0234 and its variants A and B produced identical antibiotics and pesticidal compounds.

Interaction ofStreptomyces felleus with bromoxynil during growth on laboratory media

Streptomyces felleus resistant to the herbicide bromoxynil (BX) took up 95 % of the initial amount of BX from the solid or liquid medium containing 100 μg of the herbicide per mL during a 5-d incubation. 50 % of the amount taken up was degraded and 45 % deposited in the cell (90 % in the cytoplasm, 10 % in the cell wall). A prolonged incubation time did not result in any further decrease of BX concentration. The addition of KC1 (the effect of NaCl was less pronounced) increased the affinity of BX for the cell wall and slowed down both the uptake and degradation of BX. Though P-14 was capable of growing at 5- to 10 times higher concentrations of BX in comparison with sensitiveStreptomyces strains, the herbicide caused its physiological (growth rate decrease, antibacterial antibiotic production, pigmentation, dehydrogenase activities), morphological and ultrastructural changes.

Modification of the cell wall inBrevibacterium sp. M 27

Osmotically fragile cells ofBrevibacterium sp. M 27 were obtained after treatment with lysozyme and penicillin. These forms were detected by optical and electron microscopy.

Origin and morphology of atypical forms ofStreptomyces granaticolor

Nonfilamentous forms ofStreptomyces granaticolor are formed in a medium with amino acids and glucose. They form filaments again after transfer to a medium with glucose and peptone. The nonfilamentous forms do not produce granaticin. Formation of nonfilamentous forms depends on the concentration of the inoculum, on the cultivation temperature and on the presence of simple sugars. Ultrathin sections revealed atypical septation in the nonmycelial forms and non-uniform accumulation of the wall material.

Mutation affecting normal colony formation inEscherichia coli K-12

The effect of a mutation in a gene located near thepro marker and determining the normal colony formation and the cell density inEscherichia coli has been analyzed. Thencf mutation has no effect on the permeability of the cell to actinomycin D. On the other hand, a higher level of ATP and a defect in the accumulation of the reserve material in the mutant cell were detected.

Protein turnover in asporogenicBacillus megaterium KM under limited nitrogen supply

Protein turnover was found to take place in cells of the asporogenic strain ofBacillus mega, terium KM during the stationary phase brought about by exhaustion of a nitrogen source. Its rate measured by degradation of prelabelled proteins varied around 4%/h. however, the synthesis of proteins at the beginning of the stationary phase was slightly higher (7–8%/h). Protein turnover started already during growth in the medium with a limiting nitrogen concentration. Addition of low doses of ammonium chloride (2 μg NH4Cl/ml and higher) to the nongrowing population at thirty min intervals stimulated protein synthesis. This resulted both in the increased incorporation of14C-leucine into proteins and in the increased synthesis of exocellular protease. On the other hand, the intracellular degradation of proteins decreased only slightly. The number of “colony forming units” in the starving population as well as in the population which was given 2 μg NH4Cl/ml/30 min did not change during 4 h. The number of cells not exhibiting protein synthesis was negligible in both cases.