Fluctuation in polyadenylate size and content in exponential- and stationary-phase cells of Saccharomyces cerevisiae.

Stationary-phase cells of Saccharomyces cerevisiae were found to have a reduced polyadenylate [poly(A)] content as compared with exponential-phase cells. A sizing procedure for poly(A) was devised to distinguish between alternative hypotheses to explain this reduction. Two major size classes of poly(A) were found. The decreased representation of the larger of the two classes accounted for the majority of the poly(A) loss. The remainder of the loss was accounted for by fewer poly(A)-containing sequences. The smaller of the two poly(A) classes was apparently not of mitochondrial origin and may be added transcriptionally.

Deoxyribonucleic acid-deficient strains of Candida albicans.

We analyzed a series of germ tube-negative variants isolated from Candida albicans 3153A for deoxyribonucleic acid content. As analyzed by flow microfluorometry, the deoxyribonucleic acid level in these variant strains was 50% of that of the parental strain and equivalent to that of haploid Saccharomyces cerevisiae. This finding was confirmed by comparison of survival rates when exposed to the mutagens ultraviolet light, ethyl methane sulfonate, and methyl methane sulfonate. The diameter of the variant cells as compared to the diameter of the parental 3153A strain showed a relationship similar to that of the diameters of haploid versus diploid S. cerevisiae. These results indicate that those strains may be representative of the imperfect stage of C. albicans.

Ploidy determination of Canadida albicans.

The dimorphic yeast Candida albicans, as a member of the fungi imperfecti, has been assumed to be in the haploid, or imperfect, state. The deoxyribonucleic acid content of this species has been measured by flow microfluorometry, a technique capable of analyzing single cells. These results were compared with flow microfluorometric deoxyribonucleic acid determinations on a series of strains of Saccharomyces cerevisiae of known ploidy (haploid, diploid, triploid, and tetraploid). These ploidy levels were readily distinguished by the flow microfluorometry procedure. By this criterion, C. albicans was found to contain a diploid amount of deoxyribonucleic acid. Ultraviolet radiation survival and chemical mutagenesis experiments support the conclusion that both clinically isolated and laboratory strains of C. albicans are diploid.

Germ tube formation from zonal rotor fractions of Candida albicans.

Homogenous cell populations of increasing cell volume may have been isolated from exponential and stationary culture of Candida albicans by centrifugation on a sucrose gradient. Observations of the yeast-mycelial transition using these populations showed the following. (i) No fraction from early logarithmic phase cells was unable to undergo morphological transition. (ii) The time of initiation of germ tube production was correlated with cell size in stationary-phase cultures. (iii) The rate of appearance of germ tubes was nearly identical in all fractions measured. (iv) Addition of N-acetyl-D-glucosamine to homogeneous cell populations decreased the time of initial appearance of germ tubes but did not affect the rate of appearance after initiation.

Nature of ribonucleic acid synthesis during early sporulation in Saccharomyces cerevisiae.

Phosphate uptake in sporulating cultures of Saccharomyces cerevisiae has been found to occur approximately 2 h after the transfer to sporulation medium. Early ribonucleic acid synthesis begins at approximately 4 h and continues to 8 h. Incorporation of phosphate into acid-extractable precursor pools parallels phosphate uptake. In triple-labeling experiments it was observed that the breakdown of vegetatively synthesized ribonucleic acid is not a significant source of precursors for ribonucleic acid synthesis during sporulation. The majority of the ribonucleic acid made in a 10-min period during sporulation does not migrate on gels with precursor or mature ribosomal ribonucleic acid.

Relationship between sporulation-specific 20S ribonucleic acid and ribosomal ribonucleic acid processing in Saccharomyces cerevisiae.

The nature and properties of the 20S ribonucleic acid which accumulates only during the sporulation of Saccharomyces cerevisiae were examined. The 20S ribonucleic acid (RNA) has a base composition considerably different from ribosomal RNA species and is virtually unmethylated. The 20S RNA did, however, exhibit approximately 70% homology with 18S RNA by RNA-deoxyribonucleic acid filter hybridization competitions. The 20S RNA showed a hybridization saturation plateau level 30 to 40% higher than 18S, consistent with measurements of the size difference in polyacrylamide gels. Pulse-chase experiments in the presence and absence of cycloheximide indicate that the 20S RNA has a presumptive relationship to the 20S ribosomal RNA precursor normally observed only in short pulse-labeling in vegetative cells.

Phylogenetic measurement in procaryotes by primary structural characterization.

Oligonucleotide cataloguing has been used to characterize a number of 5S RNA species from various Procaryotes. Such catalogs can be used to establish certain and detailed phylogenetic relationships among organisms. Confining attention at present to four Families of Procaryotes, theEnterobacteriaceae, theBacillaceae, theAchromobacteraceae, and thePseudomonadaceae, we have shown that the conventionally accepted classification of these organisms which places the first three in the orderEubacteriales, and the last in the orderPseudomonadales, is not phylogenetically valid.

Regeneration of ribosomes and ribosomal ribonucleic acid during repair of thermal injury to Staphylococcus.

Heating Staphylococcus aureus MF31 at 55 C for 15 min renders the organisms unable to reproduce on agar containing 7.5% NaCl (1). The heated organisms exhibited an extended lag period during which the organisms regained their ability to grow on the 7.5% NaCl-agar. Inhibitor and antibiotic data indicated that protein synthesis is not involved in this recovery process but nucleic acid synthesis is suggested (3). The data presented here further substantiate the noninvolvement of protein synthesis during recovery and further demonstrate the site of the thermally induced nucleic acid lesion. Methylated albumin kieselguhr column analysis showed the lesion site to be the ribosomal ribonucleic acid (rRNA). The rRNA is resynthesized during the extended lag period. Sucrose gradient analysis demonstrated that a ribosomal peak was undetectable subsequent to the thermal treatment, but this peak was regenerated during the recovery period.