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PubMedDate not supplied

Plasmid DNA satellite bands seen in lysates of Streptococcus mutans that form insoluble extracellular polysaccharides.

A satellite band of plasmid DNA was seen in cell lysates prepared from two strains of S mutans using buoyant-density equilibrium centrifugation. Mutants, defective in their ability to synthesize insoluble extracellular polysaccharides, showed no detectable satellite DNA band when prepared by the same procedure. These mutants were induced by treatment with EB, acridine orange, or SDS, which are known to be effective agents for the elimination of extrachromosomal genetic inheritance. The derived mutants produced more soluble polysaccharides from sucrose than their parent strains. The decreased ability to synthesize insoluble polysaccharides was related to both glucan and fructan formation. These findings suggest that the plasmid DNA of the S mutans strains genetically controls formation or activity of the enzymes responsible for synthesis of extracellular insoluble glucan or fructan.

Bacteriolysis↗
PubMed1975

Cytoplasmic inheritance in Saccharomyces cerevisiae: comparison of first zygotic budsite to mitochondrial inheritance patterns.

Zygotic first budsite in Saccharomyces cerevisiae was studied in relation to defined mitochondrial inheritance systems: both petite and drug resistance. It was hypothesized that a highly asymmetric inheritance pattern would be correlated to a high frequency of first budsites on the petite or drug resistant end of the zygote (i.e., that portion of the zygote which was originally the drug resistant or petite haploid before zygote formation). The data collected did not support the hypothesis. For drug resistance, the budsite pattern is identical for a highly biased and a moderately biased inheritance pattern. In a grande by grande cross there is a high probability of the first bud appearing on the conjugation bridge, with lower but equal probabilities of the first bud appearing on one end or the other of the zygote. A grande by petite cross changes this pattern to a high probability of the first bud appearing on the grade end of the zygote, with a lesser probability of the first bud appearing on the conjugation bridge and virtually no budding of the petite end. This phenomenon is independent of degree of neutrality or suppressiveness of the petite strain used, however. The difference between a grande and a grande by petite pattern may be due to the relative functional ability of the mitochondria in each end of the zygote. Tests using antimitochondrial drugs suggest that selection of first budsite on a zygote is a complex phenomenon, not simply dependent upon mitochondrial phenotype. In conclusion, selection of the first zygotic budsite appears to be independent of mitochondrial inheritance patterns.

Cell Division↗
PubMed1987

Extrachromosomal genetics in the yeast Kluyveromyces lactis. Isolation and characterization of antimycin-resistant mutants.

Antimycin-resistant (AR) mutants of the yeast Kluyveromyces lactis, obtained either spontaneously or after manganese treatment, were isolated and genetically characterized. Most of the mutants obtained after manganese mutagenesis and two spontaneous mutants, tolerated high antimycin concentrations (more than 10 micrograms/ml) and were extrachromosomal. One mutant which grew only in low antimycin (1 microgram/ml) showed a Mendelian type of inheritance. The extrachromosomal mutants could be assigned to at least two genetic loci (ARI and ARII). Mutants representative of these two groups showed increased resistance to the antibiotic when the respiration of whole cells or mitochondria was studied. Extrachromosomal mutants of Saccharomyces cerevisiae resistant to antimycin were also induced with manganese, isolated and characterized. Comparative studies of the antimycin-resistant mutants of K. lactis and S. cerevisiae permitted the following observations: a) K. lactis is more resistant to antimycin, funiculosin, mucidin and diuron than S. cerevisiae, as are the AR mutants; b) K. lactis shows correlated sensitivity to funiculosin differing in this aspect from S. cerevisiae; c) the antimycin-resistant mutants of K. lactis belonging to group II (ARII) were also resistant to diuron, tolerating concentrations of more than 200 micrograms/ml; d) all extrachromosomal antimycin-resistant-mutants of S. cerevisiae and some of the AR mutants of K. lactis were more sensitive to mucidin than the wild type.

Alkenes↗
PubMed1974

Chromosomal and nonchromosomal mutations affecting the "killer character" of Saccharomyces cerevisiae.

The "killer character" of Saccharomyces cerevisiae is a nonchromosomal genetic element which imparts to cells carrying it (a) the ability to kill cells which lack it, by secreting the soluble macromolecular killer substance and (b) the ability to resist the killing effects of the killer substance.-Mutants have been isolated from S. cerevisiae carrying the "killer character". Mutants were found in two nuclear genes (mak1 and mak2) involved in maintenance of the genetic element of the killer character. Mutants in three other nuclear genes could maintain the cytoplasmic genetic element normally; two of these were able to express resistance to killing, but not the ability to kill (kex1 and kex2), while the third could express the killing function, but was sensitive to killing and is thus a "suicide" strain (rex1). These five nuclear genes were all distinct.-Several mutants were detected which showed non-mendelian segregation indicating mutation of the "cytoplasmic" genetic element. Some such mutants had normal resistance to killing but were either unable to kill at all or showed marked reduction in the ability to kill. Others had lost both killing ability and resistance. None were suppressive.-Two nonkilling mutants, both of which showed cytoplasmic inheritance, were mated. A large, but variable, proportion of diploid colonies, plated after several generations of growth, showed normal killing which has then stably inherited on further subcloning.

Cell Nucleus↗
PubMed1989

Definition and properties of disequilibria within nuclear-mitochondrial-chloroplast and other nuclear-dicytoplasmic systems.

We define and determine the interrelationships among five sets of disequilibrium parameters that measure two- and three-locus nonrandom associations in nuclear-dicytoplasmic systems. These assume a diploid nuclear locus and two haploid cytoplasmic loci, with special reference to nuclear-mitochondrial-chloroplast systems. Three sets of two-locus disequilibria measure the association between haplotypes at the two cytoplasmic loci (DMC) and associations between each cytoplasmic locus and nuclear alleles or genotypes (DM, D1M, D2M, D3M; DC, D1C, D2C, D3C). In addition, we present two classes of higher-order disequilibria that measure nonrandom allelic or genotypic associations involving all three loci. The first class quantifies associations between the nuclear locus and the two cytoplasmic loci taken jointly (DA/MC, DAA/MC, DAa/MC, Daa/MC, etc.), whereas the second measures only those associations remaining after all two-locus associations have been taken into account (DA/M/C, DAA/M/C, DAa/M/C, Daa/M/C). Based on combinations of these five sets of measures, we suggest a variety of parameterizations of three-locus, nuclear-dicytoplasmic systems. The dynamics of these disequilibria are then investigated under models of random and mixed mating, either with both cytoplasmic genomes inherited through the same parent or through opposite parents. Except for associations between the cytoplasmic haplotypes, which are constant when the two cytoplasmic genomes are inherited through the same parent, all disequilibria ultimately decay to zero. These randomizations do not necessarily occur monotonically, however, and in some cases are preceded by an initial increase in magnitude or sign change. For both inheritance patterns, the asymptotic decay rates are steadily retarded by increasing levels of self-fertilization. This behavior contrasts with that in the extreme case of complete selfing, for which only the heterozygote disequilibria always decay to zero. For all models considered, the dynamics of the two-locus cytonuclear subsystems are solely a function of the mating system, whereas the dynamical behavior and sign patterns of the cytoplasmic and three-locus disequilibria also depend strongly on the mode of cytoplasmic inheritance.

Cell Nucleus↗