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.

Thermosensitive submerged endospores formed by Streptomyces 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 in Streptomyces 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 of Streptomyces. Most characteristics of surface cultures of variant A coincided with those of the original strain 0234 and its endosporeless variant B. Both the strain 023.4 and its variants A and B produced identical antibiotics and pesticidal compounds.

By using both the traditional International 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 of S. virginiae strains and to distinguish them from S. 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.

An asporogenous spontaneous mutant of Streptomyces aureofaciens named ASR1 was selected on streptomycin gradient plates. The mutant is very stable and differs in ultrastructure and morphology, it is prototrophic but it lost the ability to grow well on soybean extract medium and produces one-tenth tetracyclines of the parent. The ASR1 mutant has a 3-4-fold increased resistance to streptomycin and is cross-resistant to other aminoglycosides. Comparison of the protein profiles from both strains on SDS gels revealed a very low expression of a 29.5 kDa protein in the ASR1 mutant which is overexpressed in both vegetative cells and spores of the parental strain.

Conditions for microcycle sporogenesis in two streptomycete strains without shifting the culture were found. The sporulation in Streptomyces granaticolor took place after 24 h of cultivation. The dry mass was increasing till 32 h probably due to production of a hydrophobic substance resembling fibrous sheath of aerial hyphae and spores. Ultrathin section of microcycle spores are presented.

In addition to lasalocid, an oligoether coccidiostatic compound, other compounds are synthesized by Streptomyces 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.

A thy- tetracycline-resistant mutant of Streptomyces granaticolor was prepared by mutagenesis of the parental strain ETH 7437. The mutant exhibits a different morphology and an overproduction of granaticins. The ability to form an aerial mycelium and spores has been lost. The mutant cells have a round or an atypical shape and a thick cell wall, the membraneous system is enlarged by numerous mesosomes. Division septa are formed rarely. The mutant is more sensitive to both low and high temperature than the parental strain. The altered features are stably maintained for many generations. Ribosomal proteins of the mutant do not differ substantially from those of the original strain indicating that the mutant phenotype is not due to an alteration at the translational level.

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.

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

Nalidixic acid was used for describing more accurately the terminal replication region of theMycobacterium phlei chromosome. Cell division in synchronized cultures was not sensitive to this acid any more between 185–190 min,i.e. about 10 min after replication of theser gene the last of 24 genes of the replication map described so far. The replication of the chromosome was controlled by determining the position of thebac gene. Microscopic studies in phase contrast of the cells that were subjected for long time periods to nalidixic acid treatment at a bactericidal concentration showed elongated cells. The electron-microscopic observation showed that a portion of the population influenced by nalidixic acid lyzes, whereas other cells remain intact and resemble control cells.

Nonfilamentous forms of Streptomyces 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.

It was found that the externally added histone changes remarkably both the surface and the internal ultrastructure of cells ofEscherichia coli. The interaction of histone with surface structures results in thickening of the inner layer of the cell wall. Cytoplasm becomes condensed, contains extensive electrontransparent zones and neither ribosomes nor the nuclear structure are differentiated. The addition of histone to germinating spores ofBacillus cereus decelerates germination and postgerminative development of this organism and changes ultrastructure of the external surface of the exosporium. The addition of Mg2+ ions reverting the effect of histone results in a renewal of the original ultrastruoture of the exosporium.

Anomalous forms ofBacillus subtilis A 32 produced by prolonged cultivation in a chemostat under nitrogen limitation are described. A change in the cultivation conditions brings about a transformation of these forms to bacillar rods. The transformation is gradual and lasts for several generations.