The conversion of several unusual purine bases into their corresponding ribonucleosides by an inosine-producing mutant of Bacillus subtilis was studied. 2-Chlorohypoxanthine was well ribosidated to 2-chloroinosine as easily as that of hypoxanthine to inosine. Several other unusual purine bases, such as 2-methylhypoxanthine, N2N2-dimethylguanine, 6-methoxypurine, 6-methylthiopurine, and N6-acetyladenine, were also converted into their corresponding ribonucleosides to the same extent as 2-chlorohypoxanthine. On the other hand, 2, 6-dichloropurine, isoguanine, 8-azaguanine, 8-azahypoxanthine, 6-chloropurine, and 6-mercaptopurine were scarcely ribosidated. On inosine denovo formation, the unusual bases which are well ribosidated were generally not inhibitory or only slightly inhibitory, while the bases that are scarcely ribosidated were found to be strongly, moderately, and slightly inhibitory or slightly stimulative.
The two models presented in this work display significantly different characteristics from the models based on the formation of inhibitors, both in batch and continuous cultures (1, 11). This provides for a number of systematic experiments to be performed (in batch and continuous cultures) to evaluate the relative merits of the two assumptions for the explanation of the growth curve, viz., the assumption of endogenous metabolism and that based on growth inhibitors.
Using Aspergillus oryzae conidia, timing of the syntheses of various RNA classes in the early phase of germination was investigated. The methylated albumin-coated kieselguhl column chromatography was employed for the
Phosphorus metabolism in sporulating Bacillus megaterium was examined by the fractionation of phosphorus compounds in cells. Marked changes in the amount of various phosphorus fractions prior to and during the endospore formation suggested that the intracellular reconstruction was occurring in these phases of spore formation. The contribution of intracellular phosphorus reserves, especially of polyphosphate, to the sporulation process was also suggested. Conspicuous decreases (up to onethird) in the amount of RNA and DNA during the course of liberation of free spores was observed. This was discussed in relation to the mode of free spore liberation.
Spectrophotometric studies in visible, ultraviolet and infrared regions of sporulating Bacillus megaterium were performed using intact cells, cell free extracts, hot-ethanol soluble extracts and dried cells of various growth phases. In the sporulating stage, the following characteristic changes of intracellular components were suggested: (1) the marked increase in the terminal electron transport system, (2) probable change in chelating metal ion with dipicolinic acid from the stage of sporulating cell to that of matured spore, and (3) decrease of poly-β-hydroxybutyrate prior to sporulation.