Acta microbiologica Polonica. Series A: Microbiologia generalis最新文献

E. coli strain CLI(V) produces colicin V which can exist in two chemically different forms. A heat-stable, liposaccharide-protein complex is present as a main component of the cell wash. An intracellular colicin is a heat-labile and seems to be a simple protein. Preliminary experiments have shown that colicin V inhibits simultaneously synthesis of protein, RNA and DNA. Its mode of action is similar to colicins: E1, B, K and A.

Morphological changes and synthesis of DNA, RNA and protein during conjugation of Saccharomyces cerevisiae was studied. It was found that during conjugation distinct cell expansion and increase in the dry mass of the cell takes place. DNA synthesis is inhibited during mating while synthesis of RNA and protein is not affected. Conjugation of temperature sensitive mutant defective in elongation of DNA chain was normal both in permissive and restrictive temperature. Conjugation of mutants defective in the initiation of DNA synthesis or defective in RNA and protein synthesis was inhibited in restrictive temperature. The results obtained with temperature sensitive mutants suggest that RNA and protein synthesis is necessary for mating reaction while DNA synthesis is not required.

The existence of two postulated pathways of anabolic cysteine biosynthesis in Aspergillus midulans was investigated. No activities of the postulated pathway involving S-sulfocysteine as intermediate have been detected. Investigations on cyteine and methionine requiring mutants revealed independent regulation of O-acetylserine sulfhydrylase by endogeneous cysteine and methionine pools. The reaction catalysed by O-acetylserine sulfhydrylase is postulated as the only anabolic pathway of cysteine biosynthesis in A. nidulans.

Competent cultures of Rhizobium meliloti cells and spheroplasts obtained by various methods were infected with DNA of phage 1A. The Frequency of infection among the cells and spheroplasts was 2 X 10(-8)-5 X 10(-10). The efficiency of transfection calculated from the ratio of plaque forming units to infective DNA molecule of phage 1A was 5 X 10(-8) to 10(-10). Frequency of infection and efficiency of transfection among the competent cells were by one order of magnitude higher in the case of the spheroplasts. The use of various media did not noticeably alter the efficiency of transfection.

It has been found that Mod2- mutation restores respiratory sufficient phenotype in cytochrome b less mutant MB127-20C. Mod2- gene when present in the same haploid cell with mutant gene pet25 causing deficiency in cytochromes a+a3 and b seems to be responsible for reappearance of cytochrome b in the cytochrome spectrum as well partial respiratory activity. However, the restored respiratory activity seems to be inefficient as growth on unfermentable carbon sources is still impossible. Evidences are presented that the Mod2- mutation originates from respiratory sufficient strain 18-27 in which op1 mutation has been induced.

A total of 218 Proteus strains isolated from clinical sources were tested for their susceptibility to three penicillins and two cephalosporins. The ability to beta-lactamase production was examined in 36 of these strains. Proteus mirabilis strains were generally more susceptible to cephalosporins than to penicillins, whereas indole-positive Protei were almost uniformely resistant to cephalosporins as well as to ampicillin and benzylpenicillin but susceptible to carbenicillin. Fairly good correlation was found between the amount and hydrolytic soectryn if beta-lactamase activity and the pattern of resistance to penicillins and cephalosporins in the strains examined. Some observations indicate, however, that the resistance of Proteus bacilli to this group of antibiotics is partly related to permeability barriers in bacterial cell. About 37% of Proteus strains transferred their ampicillin resistance to E. coli K12. Beta-lactamase activities mediated by R plasmids in E. coli cultures were 1.5 to 5 times higher than in respective Proteus donors.

Synthesis of cytochrome b2 together with that of other hemoproteins is induced by oxygen. It is further stimulated by L-lactate. This is true for the enyzme in mitochondrial as well as cytoplasmic cell fractions. Chloramphenicol and erythromycin do not effect cytochrome b2 biosynthesis, whereas cycloheximide prevents it in aerobicallly adapting cells. Mutants lacking cytochrome b2 activity still exhibit the activities of D-lactate dehydrogenase and D-2hydroxyacid dehydrogenase.