1. The 30S ribosomal subunit of the extreme halophile Halobacterium cutirubrum is unstable and loses 75% of its ribosomal protein when the 70S ribosome is dissociated into the two subunits. A stable 30S subunit is obtained if the dissociation of the 70S particle is carried out in the presence of the soluble fraction. 2. A fractionation procedure was developed for the selective removal of groups of proteins from the 30S and 50S subunits. When the ribosomes, which are stable in 4m-K(+) and 0.1m-Mg(2+), were extracted with low-ionic-strength buffer 75-80% of the 30S proteins and 60-65% of the 50S proteins as well as the 5S rRNA were released. The proteins in this fraction are the most acidic of the H. cutirubrum ribosomal proteins. Further extraction with Li(+)-EDTA releases additional protein, leaving a core particle containing either 16S rRNA or 23S rRNA and about 5% of the total ribosomal protein. The amino acid composition, mobility on polyacrylamide gels at pH4.5 and 8.7, and the molecular-weight distribution of the various protein fractions were determined. 3. The s values of the rRNA are 5S, 16S and 23S. The C+G contents of the 16S and 23S rRNA were 56.1 and 58.8% respectively and these are higher than C+G contents of the corresponding Escherichia coli rRNA (53.8 and 54.1%).

A bacteriocin produced spontaneously by a nontoxigenic strain of Clostridium botulinum, type E, PM-15, has been isolated and designated boticin P. It was purified by ammonium sulfate precipitation, gel filtration on Sephadex G-100, sucrose density gradient centrifugation, and cesium chloride equilibrium density gradient centrifugation. Boticin P is composed mainly of proteins (98.8%) with a trace amount of carbohydrates (0.4%), and has an apparent molecular weight in excess of 4 × 106 daltons as estimated by gel filtration on Sepharose 2B. Electron microscopic examination of boticin P reveals a phage tail-like structure of 100 nm in length.Boticin P exerted a static effect on vegetative growth and spore outgrowth but not on the initial events of germination. The boticin was active on 10/12 toxigenic and 3/6 nontoxigenic type E and 2/2 nonproteolytic type B strains of C. botulinum. The activity spectrum on 27 strains supports the proposal that type E and the nonproteolytic type B strains belong to the same taxosubspecies.

After addition of mitomycin C to Pseudomonas aeruginosa strain MAC-264 cells, DNA synthesis stops but resumes again after 45 min. This resumption in DNA synthesis is due to the induction of a temperate phage. Early after induction, both RNA and protein syntheses continue but later on little or no net synthesis of these macromolecules occurs. Cell lysis occurs at 90 to 105 min after addition of mitomycin C. Analysis of the lysates indicates that a DNA phage with an icosahedral head about 55 mμ in diameter with a short wedge-shaped tail is produced. This phage [Formula: see text] has a buoyant density of 1.468 g/ml in CsCl. The guanine + cytosine content of the phage DNA determined by its buoyant density in CsCl is 46% compared to 68% for the host DNA.Some phage tail-like structures which have a buoyant density of 1.305 g/ml in CsCl are also induced at the same time.

Rifampicin causes an initial rapid breakdown of about 30% of the pulse-labeled RNA in both photosynthetic and heterotrophic Rhodospirillum rubrum. An additional degradation of RNA has been observed in the heterotrophic, but not in the photosynthetic cells at a later stage of rifampicin treatment. This secondary RNA degradation is probably caused by breakdown of ribosomal RNA, especially of the 23S species, as shown by polyacrylamide gel electrophoresis analyses. No qualitative difference between the pulse-labeled RNA species in photosynthetic and heterotrophic cells can be detected by the DNA-RNA hybridization competition technique.

An asporogenous mutant of Bacillus subtilis Sp − H12-3, which is considered to have a block at stage 0, showed general growth characteristics similar to those of sporulating cultures. However, a sudden increase in the total amount of acid-soluble nucleotides observed at t 2 in sporulating bacteria was completely absent in this mutant. In sporulating cells, a marked increase in two nucleotides which were identified to be uridine diphosphate (UDP)-galactose and UDP- N -acetylglucosamine was noted, whereas UDP-glucose appeared to be accumulated in the mutant cells at t 2 . No unusual nucleotides were found in the strains of B. subtilis examined. The possible role of these UDP derivatives in early stages of sporulation in B. subtilis is discussed.