Effect of temperature on the growth of five obligately psychrophilic bacteria and behavior of Curtobacterium psychrophilum strain 27-O-b at elevated temperatures were studied. Most of obligate psychrophiles showed lower growth activities than a facultative psychrophile at lower temperature. Arrhenius plots of the growth of most of obligate psychrophiles were linear from a temperature little below their optimum growth temperature to 0°. However, there was a deviation in Arrhenius plots of Cytophaga antarctica strain 16-O-d and a facultative psychrophile, Pseudomonas fluorescens strain 76-O-a. Therefore, it seems unreasonable to characterize psychrophiles only from the points of growth activities at lower temperature and/or a pattern of the Arrhenius plot. When C. psychrophilum was transferred to elevated temperatures after preincubation at the optimum growth temperature of 9°, it exhibited faster growth for the first few hours than at 9°, and then the growth ceased.
Some physiological changes during the growth of a psychrophile, Curtobacteriumpsychrophilum, at supermaximum growth temperatures were studied. Leakage of intracellular materials and cell lysis at 20° were two to three times greater than those at 9°, which is the optimum growth temperature of this bacterium. Decrease of viability at 20° was ten thousand to hundred thousand times of that at 9°. Thermogram at 20° showed one-directioned decrease. Oxygen-uptake was maximum at 15° and completely lost at 40°. Total amount of ATP began to decrease from 3hr later at 20°, while the bacterium grew more rapidly than at 9°. Incorporation of 3H-methionine stopped simultaneously with cessation of growth, and incorporation of 14C-uracil and 3H-thymidine ceased. On the basis of these facts, this bacterium is considered to be heat labile in multiple points, though protein synthesis seems to be primarily inhibited at 20°.
Deoxyribonucleic acids of four species of Neurospora, N. crassa 74A, N. intermedia 10B-A, N. sitophila 56.1a, and N. tetrasperma 85A, have been compared with respect to their GC composition and nucleotide sequence homology. Three components of DNA's have been revealed for all the species studied. Thermal elution profiles of hybrid duplexes are found to be biphasic. A phylogenetic tree based on differences in percentage hybridization has been constructed.
Effect of alteration of cell envelope on the inducibility of λ phage development was studied using various bacterial preparations of the lysogens. Plasmolysis or osmotic shock did not particularly affect spontaneous induction as well as UV inducibility of λ. The λ phage inducibility was, however, significantly reduced by conversion of the lysogens into spheroplasts with lysozyme, glycine, or penicillin. Spontaneous and artificial inductions (by UV or MC) were both affected in these spheroplasts. Thermal induction of λcIts was also reduced considerably, suggesting that somesteps following repressor inactivation were impaired in spheroplasts. On the other hand, spheroplasts of λ lysogens retained the ability to exclude T4rII, even after UV irradiation. Cross induction was not detected in mixed culture of intact F- lysogenic cells and nonlysogenic Hfr spheroplasts. Based on these results, possible relationship between integrity of cell envelope and inducibility of λ phage development was discussed.