Cellular fatty acid composition of 50 strains of the genus Pseudomonas was determined by gas-liquid chromatography. Straight-chain saturated acid of C16:0 and straight-chain unsaturated acids of C16:1 and C18:1 with a double bond were commonly found in all the strains tested. The presence of hydroxy acids, cyclopropane acids, and branched-chain acids showed the characteristics for the groups and species in the genus Pseudomonas. Similarity values calculated on the basis of fatty acids exhibited a clear correlation to the taxonomic groups of this genus. Bacterial fatty acid composition was considered to be useful for the study of interrelation and for rapid identification of the bacteria. Taxonomic studies on bacteria have been mainly carried out on the basis of morphological, biochemical, and physiological characteristics. Recently, chemical constituents of bacterial cells have become of interest from the point of taxonomy, and DNA base composition, cell wall composition, and type of co-enzyme Q have been used for taxonomic criteria in some taxa. The progress of instrumental analyses has contributed to the development of chemotaxonomy, and the results involved have been useful not only for the bacterial classification, but also for rapid identification of the bacteria.
Loss and retention of mitochondrially coded drug resistance markers were studied in cytoplasmic respiration-deficient (rho-) mutants of yeast, Saccharomyces cerevisiae, induced by 4-nitroquinoline 1-oxide (4-NQO) and ethidium bromide. When the yeast cells resistant to chloramphenicol, erythromycin, and oligomycin were treated with ethidium bromide, this drug resistance was lost progressively with increasing time of treatment. In the case of 4-NQO, the retention rate of drug resistance was very high and did not change by treatment for 1, 5, and 24hr. Crossing experiments between drug-sensitive rho- mutants and resistant cells indicated that the loss of drug resistance was caused not by mutation of drug-resistance genes but by deletion of genes on mitochondrial DNA. Interpretations concerning the deletion of mitochondrial drug-resistance genes by 4-NQO and ethidium bromide are given and the difference in their actions is discussed.
A phage tail-like bacteriocin, clostocin O, from Clostridium saccharoperbutylacetonicum (ATCC 13564) was purified by two-phase fractionation and sucrose density gradient centrifugation. Clostocin O had two kinds of particle form; one is the intact form (sheathed form) and the other is an inactive form (contracted form). A part of the intact form converted into the contracted form during the purification. The s20, w of clostocin O was 95S for the intact form and 74S for the contracted form. The purified intact clostocin O was homogeneous by several criteria such as sedimentation pattern of sucrose density gradient, sedimentation velocity, and isoelectric focusing. The isoelectric point was pH 4.6. The intact clostocin O mainly consisted of protein, but contained some (2-3%) RNA. Its amino acid composition was also determined with an amino acid analyzer.
Whole cells and cell wall of Penicillium citrinum giant cells induced by tunicamycin and normal mycelia were examined in detail by scanning electron microscopy. Cell wall of giant cells was thicker (500-1, 000μm) than those of normal mycelia (about 200μm). Process of morphological change of giant cells to hyphae in the absence of tunicamycin and regeneration of protoplasts in the presence or absence of tunicamycin were also followed microscopically.
When exponentially growing cells of Bacillus subtilis are exposed to sublethal concentration (0.1μg/ml) of rifampicin, they show an immediate decrease in the rate of RNA synthesis in vivo, followed by a latent period for 60min, and then a rapid recovery to the original level in 150 min. Cell growth and the viable cell count remained stationary for 90min and then began to increase at a much slower rate. RNA polymerase activity, extracted and assayed in vitro, followed the same pattern as RNA synthesis in vivo. The rifampicin-resistant fraction of the RNA-synthesizing activity, and the amount of βγ subunit, a component of RNA polymerase (RPase) L2, increased with time after incubation in the presence of rifampicin. These results suggested that RPase L2, being a minor rifampicin-resistant fraction of RNA polymerases in normal state, increased several times in rifampicin-treated cultures, so as to make the cells phenotypically resistant to rifampicin.