Search

A cadmium-sensitive mutant strain was isolated from a Cd2+-tolerant bacterium, Pseudomonas aeruginosa G-1 strain by mutagenesis with N-methyl-N′-nitro-N-mtrosoguanidine. The Cd2+-sensitive mutant strain was about 8-times as sensitive to Cd2+ and 2-times as sensitive to Hg2+, Cr2+ and achromycin, and not sensitive to Cu2+, as the parent strain.Vacuole-like substances were observed in the parent strain by transmission electron microscope in the presence of Cd2+, but not in the absence of Cd2+. The mutant strain took up 3.3-times the amount of Cd2+ into cells when compared with the parent strain. Disc electrophoretic patterns showed a characteristic protein band in the parent strain at the stationary phase, but the corresponding protein band was present in the mutant strain at the late exponential phase.

Mercuric ion-resistant mechanism in Pseudomonas K-62 was investigated by isolating a mercuric ion-sensitive mutant strain (H-2 strain) from a resistant wild-type strain (P strain) and comparing the physiological properties of these two strains. Growth curves obtained in mercuric ion-containing medium suggested that P strain constitutively has a resistant mechanism. The capacity of P and H-2 strains to decrease the concentration of mercuric ions in the medium was found to be almost equal; thus, the presence of a resistant mechanism was expected other than MMR-enzyme, which is an inducible system. From the characteristic property of the inhibitory effect of mercuric ions on respiration of the two strains, a resistant mechanism, a permeability barrier mechanism, was proposed. The barrier mechanism in P strain traps mercuric ions with high selectivity to prevent the penetration of ions to the intracellular space where the functional units are located. Finally, the resistance mechanism to mercuric ions in the ...

Sporulation marker enzymes, d-glucose dehydrogenase and l-alanine dehydrogenase were synthesized derepressively by vegetative cells of a Bacillus species mutant which was isolated as an improved d-ribose producer. It was also elucidated by electron microscopy that no morphological change concerning sporulation took place during the course of the enzyme syntheses in the mutant strain. The presence of Mn2+ and Ca2+ in the medium was necessary for the morphological development of sporulation even in the mutant strain. The mechanism of derepressed enzyme syntheses is discussed in relation to regulation of sporulation.

The cultural conditions for the production of bactobolin, an antitumor antibiotic produced by Pseudomonas yoshitomiensis, were studied using a mutant strain, C-17-20. The following cultural conditions were found to be suitable: 2.0% mannitol, 0.25% dried yeast, 0.5% (NH4)2SO4, 0.4% KCl, 0.02% K2HPO4 and 0.8% CaCO3; temperature, 25°C. The highest bactobolin production under the conditions was 189 μg/ml, although the wild strain, Y-12278, produced only 4 μg/ml in the basal conditions.