[Opportunistic pathogen Candida glabrata and the mechanisms of its resistance to antifungal drugs]

Treatment of not only bacterial but also fungal infections is currently a growing concern. A major reason is the acquisition of multidrug resistance in both prokaryotic and human cells. The multidrug resistance phenotype is a cellular response to the presence of cytotoxic substances in the environment. The basic mechanism of multidrug resistance is overexpression of the membrane proteins involved in the extrusion of toxic substances outside the cell. The resistance mechanism based on the efflux of inhibitors as a result of the overproduction of transport proteins was also observed in some plant and animal pathogens and human tumour cells. The phenomenon of multidrug resistance associated with an excessive and long-term use of antifungals, in particular of azole derivatives, was also confirmed in the yeast Candida glabrata which is becoming a growing concern for health care professionals. Reduced susceptibility to azole derivatives in particular, a high potential for adapting to stressors, and multiple mechanisms of resistance to structurally and functionally unrelated antifungal drugs make the species C. glabrata a potential threat to hospital patients.

Molecular and phenotypic analysis of mutations causing anionic phospholipid deficiency in closely related yeast species

The pel1 mutation in Saccharomyces cerevisiae and the Cgpgs1Delta mutation in Candida glabrata result in deficiency of mitochondrial phosphatidylglycerolphosphate synthase and lack of two anionic phospholipids, phosphatidylglycerol and cardiolipin. DNA sequence analysis of the PCR-amplified pel1 mutant allele revealed that the pel1 mutation resulted from a single amino-acid substitution (Glu(463)Lys) in the C-terminal part of encoded enzyme. The CgPGS1 gene cloned in a centromeric pFL38 vector functionally complemented the pel1 mutation in S. cerevisiae. Likewise, the ScPGS1 gene cloned in pCgACU5 plasmid fully complemented the Cgpgs1Delta mutation in C. glabrata. This mutation increased the cell surface hydrophobicity and decreased biofilm formation. These results support a close evolutionary relatedness of S. cerevisiae and C. glabrata and point to the relationship between expression of virulence factors and anionic phospholipid deficiency in pathogenic C. glabrata.

Biology of the pathogenic yeast Candida glabrata

The yeasts, being favorite eukaryotic microorganisms used in food industry and biotechnologies for production of biomass and various substances, are also used as model organisms in genetic manipulation, molecular and biological research. In this respect, Saccharomyces cerevisiae is the best-known species but current situation in medicine and industry requires the use of other species. Here we summarize the basic taxonomic, morphological, physiological, genetic, etc. information about the pathogenic yeast Candida glabrata that is evolutionarily very closely related to baker's yeast.

Synthetic lethal interaction between the pel1 and op1 mutations in Saccharomyces cerevisiae

The Saccharomyces cerevisiae mutant strain containing the op1 mutation affecting the function of a mitochondrial ATP/ADP translocator has been crossed to the pel1 and crd1 mutants deficient in the biosynthesis of mitochondrial phosphatidylglycerol (PG) and cardiolipin (CL). Using tetrad analysis of diploids issued from corresponding crosses a synthetic lethal interaction has been observed between the op1 and pel1 mutations resulting in the lack of growth of a corresponding double mutant on minimal medium containing glucose. The op1 pel1 double mutant also displayed a decreased susceptibility to fluconazole and a compromised growth even in complex medium containing glucose. The viability of mutant cells was strongly reduced, corresponding to <30 % and 10 % of colony-forming units observed after growth in complex and minimal medium, respectively. A lower viability of the double mutant in minimal medium was accompanied by an increased formation of mitochondrial petite mutants (as determined by mtDNA rescue into diploid cells). The results indicate that in the simultaneous absence of mitochondrial anionic phospholipids (PG plus CL) and ATP/ADP exchange across the inner mitochondrial membrane the yeast mitochondrial functions are severely limited, leading to a strongly compromised cell multiplication. Since under similar conditions the op1 crd1 double mutant was able to grow on minimal medium this deleterious effect of anionic phospholipid deficiency could be at least partially substituted by PG accumulated in the cardiolipin deficient delta crd1 mutant cells.

Cross-resistance to strobilurin fungicides in mitochondrial and nuclear mutants ofSaccharomyces cerevisiae

In yeast the resistance to kresoxim-methyl and azoxystrobin, like the resistance to strobilurin A (mucidin) is under the control of both mitochondrial cob gene and the PDR network of nuclear genes involved in multidrug resistance. The mucidin-resistant mucl (G137R) and muc2 (L275S) mutants of Saccharomyces cerevisiae containing point mutations in mtDNA were found to be cross-resistant to kresoxim-methyl and azoxystrobin. Cross-resistance to all three strobilurin fungicides was also observed in yeast transformants containing gain-of-function mutations in the nuclear PDR3 gene. On the other hand, nuclear mutants containing disrupted chromosomal copies of the PDR1 and PDR3 genes or the PDR5 gene alone were hypersensitive to kresoxim-methyl, azoxystrobin and strobilurin A. The frequencies of spontaneous mutants selected for resistance either to kresoxim-methyl, azoxystrobin or strobilurin A were similar and resulted from mutations both in mitochondrial and nuclear genes. The results indicate that resistance to strobilurin fungicides, differing in chemical structure and specific activity, can be caused by the same molecular mechanism involving changes in the structure of apocytochrome b and/or increased efflux of strobilurins from fungal cells.

[Vulvovaginal candidiasis and sensitivity of pathogens to antimycotics]

OBJECTIVE

Analysis of the prevalence and species representation of pathogenic yeasts in patients with vulvovaginal candidiasis. Determination of in vitro susceptibility of yeast isolates to clinically used antimycotic agents.

DESIGN

A retrospective clinical study of patients with positive vaginal cultures for the presence of pathogenic yeast species.

SETTING

I. gynekologicko-pôrodnícka klinika LF UK a FN, Zochova 7,811 03 Bratislava, Slovenská republika.

METHODS

Identification of yeast pathogens on the chromogenic medium CHROMagar CANDIDA and with API-CANDIDA identification system. In vitro susceptibility assays of clinical yeast isolates to antifungal agents using the plate dilution method, NCCLS method and ATB-FUNGUS test system.

RESULTS

The highest prevalence of vulvovaginal candidasis was found in women aged between 20-30 years. Candida albicans was the most commonly identified species of pathogenic yeasts (87.4%). Of the non-albicans species, C. glabrata (6.3%) was the most prevalent species. C. glabrata and C. krusei clinical isolates were found to be generally less susceptible to several antifungals in vitro as compared to C. albicans strains. A minimal number of resistant yeast isolates was observed for econazole, clotrimazole and nystatin. A relatively high number of resistant strains was observed for some other azole antifungals (miconazole, ketoconazole, itraconazole, fluconazole).

CONCLUSION

A successful treatment of vaginal mycotic infections requires the results of the microbiological analyses. They will bring evidence to a physician of the presence and fate of the pathogen, of its sensitivity to antifungals, both of which are essential for the rational and successful therapy of Candida vaginitis.

Growth of eukaryotic cells in relation to the structure of mitochondrial membranes and mitochondrial genome

Viability of petite-negative yeast, such as Kluyveromyces lactis, is dependent on functional mitochondrial genome encoding essential components of both mitochondrial protein synthesizing system and oxidative phosphorylation. We have isolated several nuclear mutants impaired in mitochondrial functions that were unable to grow on non-fermentable carbon and energy sources. They were used for the isolation and molecular characterization of the three genes encoding apocytochrome c, apocytochrome c1 and the protein involved in the biogenesis of cytochrome oxidase. All cytochrome-deficient mutants were viable and did not survive the ethidium bromide mutagenesis. Petite-positive Saccharomyces cerevisiae requires intact mitochondrial genome when its phosphatidylglycerolphosphate synthase was inactivated due to mutation in the PEL1 gene. Using PEL-lacZ fusion genes it was demonstrated that Pel1p is a mitochondrial protein (expressed in response to myo-inositol and choline). The pel1 mutant was deficient in phosphatidylglycerol (PG) and cardiolipin (CL) and its rho-/rho0 mutants grew extremely slowly on complex medium with glucose. Under the same conditions the growth rate of the crd1 rho- double mutants was similar to that of its parent crd1 mutant deficient in cardiolipin synthase and accumulating PG. The results demonstrate that the petite negativity in yeast is not dependent on an intact respiratory chain or functional oxidative phosphorylation. The presence of the negatively charged PG or CL seems to be essential for the maintenance of specific mitochondrial functions required for the normal mitotic growth of yeast cells.

Use of mutated PDR3 gene as a dominant selectable marker in transformation of prototrophic yeast strains

For successful transformation of prototrophic industrial yeast strains dominant selectable markers are necessary. In the present study we show the applicability of a selection system based on the phenotype of multidrug resistance. The mutant pdr3-9 allele on centromeric or episomal vector, encoding a more efficient transcriptional activator with Y276H amino acid substitution, was used as a dominant selectable marker for selection of transformants. The pdr3-9 allele conferred resistance of transformed cells to cycloheximide, chloramphenicol, mucidin and oligomycin both in the absence and in the presence of a chromosomal copy of the PDR3 gene. Both multicopy YEp352/pdr3-9 and centromeric pFL38/pdr3-9 vectors bearing the mutant pdr3-9 allele have proved to be a valuable tool for a direct selection of transformants of industrial strains of Saccharomyces cerevisiae.

Identification and functional analysis of a Kluyveromyces lactis homologue of the SPT4 gene of Saccharomyces cerevisiae

Sequence analysis of a DNA fragment containing the KlCOX18 gene originating from chromosome II of the yeast Kluyveromyces lactis revealed the presence of an adjacent open reading frame (ORF) for a protein exhibiting 78.4% identity with the Saccharomyces cerevisiae Spt4p. Based on the identical length (102 aa) and the conservation of the zinc-finger motif found in Spt4p we named this ORF KlSPT4. When expressed in S. cerevisiae the KlSPT4 gene complemented all spt4 mutant phenotypes. It is proposed that KlSpt4p, like its S. cerevisiae counterpart is a protein involved in the establishment or maintenance of the chromatin structure that influences the expression of many yeast genes.

Phosphatidylglycerolphosphate synthase encoded by the PEL1/PGS1 gene in Saccharomyces cerevisiae is localized in mitochondria and its expression is regulated by phospholipid precursors

The PEL1/PGS1 gene of the yeast Saccharomyces cerevisiae is essential for the viability of rho-/rho degrees mutants and the normal cardiolipin content of cells. The PEL1-GFP fusion gene has been found to complement the pel1/pgs1 mutation and its fluorescent protein was localized to mitochondria similarly to the beta-galactosidase activity of a protein encoded by the PEL1-lacZ fusion gene. The expression of the PEL1-lacZ reporter gene was repressed in cells grown in the presence of inositol and choline, reduced in the ino2 and ino4 strains, but constitutive in the opi1 null-mutant strain. The results demonstrate that Pel1p, playing a vital role in cells impaired in the mitochondrial DNA, is localized in the mitochondria and expressed in response to inositol and choline.

Cloning and characterization of KlCOX18, a gene required for activity of cytochrome oxidase in Kluyveromyces lactis

We describe the isolation and initial characterization of KlCOX18, a gene that is essential for the assembly of a functional cytochrome oxidase in the yeast Kluyveromyces lactis. Cells carrying a recessive nuclear mutation in this gene are respiratory deficient and contain reduced levels of cytochromes a and a3. The KlCOX18 gene has been cloned by complementation of the respective nuclear mutation, sequenced, and disrupted. KlCOX18 is located on chromosome II and contains an open reading frame of 939 base pairs. The corresponding protein exhibits 70.4% similarity to the Cox18p of Saccharomyces cerevisiae. It contains three possible membrane-spanning domains and a putative amino-terminal mitochondrial import sequence. The strain carrying a null mutation in KlCOX18 does not grow on non-fermentable carbon sources and is deficient in both cytochrome c oxidase and respiratory activity. It is proposed that KlCox18p, like its S. cerevisiae counterpart, provides an important function at a later step of the cytochrome oxidase assembly pathway.

Biochemical and molecular-genetic properties of a cytochrome-c-deficient mutant of Kluyveromyces lactis

We have isolated a respiration-deficient nuclear mutant of the yeast Kluyveromyces lactis that exhibited diminished levels of all cytochromes and did not grow on glycerol and other nonfermentable carbon sources. The mutant named cyc1 was transformed with a K. lactis genomic library and the DNA fragment conferring its wild-type properties was isolated and sequenced. The sequence of the isolated gene showed extensive homology with other eukaryotic cytochrome-c genes. The highest level of homology, based on the deduced amino acid sequences, was observed between the gene products of K. lactis and Hansenula anomala.

Isolation and molecular analysis of the gene for cytochrome c1 from Kluyveromyces lactis

By ethyl methanesulphonate mutagenesis of the yeast Kluyveromyces lactis we have isolated five nuclear mutants that were unable to grow on non-fermentable carbon sources. The mutations were found to belong to three complementation groups. After functional complementation of the mutation in one of these mutants we have cloned the structural gene for cytochrome c1, named KlCYT1. This gene has been assigned to chromosome VI and its nucleotide sequence exhibited 74.3% identity to the homologous gene of S. cerevisiae.

The pel1 mutant of Saccharomyces cerevisiae is deficient in cardiolipin and does not survive the disruption of the CHO1 gene encoding phosphatidylserine synthase

Cells of the pel1 mutant of Saccharomyces cerevisiae were found to contain an extremely low content of cardiolipin, a decreased level of phosphatidylcholine and an increased level of phosphatidylinositol. Disruption of the PEL1 gene in cells containing a null mutation in the CHO1 gene was lethal. Despite its putative functional homology with CHO1, the overexpression of the PEL1 gene in the cho1 null mutant did not restore the wild-type properties of the transformed cells and failed to stimulate the incorporation of L-[3-3H]serine into total lipids of the intact yeast cells.

Molecular characterization of the PEL1 gene encoding a putative phosphatidylserine synthase

In the yeast Saccharomyces cerevisiae the PEL1 gene is essential for the viability of rho-/rhoo petite mutants, and its mutation in respiring cells results in a pleiotropic phenotype. Results of complementation analysis with different subclones of chromosomal DNA and re-sequencing of the YCL4w-YCL3w segment of chromsome III demonstrate that the coding region of the PEL1 gene corresponds to 1467 bp. The size of the PEL1 transcript in Northern blot analysis was estimated to be approximately 1.5 kb. Transcription initiation in wild-type cells was found to occur at the position -9 relative to the ATG. The PEL1 gene was moderately expressed irrespective of the state of the mitochondrial genome and the nature of the carbon sources. Disruption of the PEL1 gene was not lethal and resulted in the same phenotype as observed with the pel1 mutant, i.e. the cells were not able to survive ethidium bromide mutagenesis, were thermosensitive for growth on glucose at 37 degrees C and failed to grow on minimal glycerol medium. Although the Pel1 protein exhibits significant similarity to a family of phosphatidylserine synthases, the disrupted PEL1 gene was not complemented by the multicopy plasmid-borne CHO1 gene encoding an essential yeast phosphatidylserine synthase.

The properties of the multicopy suppressor of the ogd1 mutation in yeast

The 8.1 kb chromosomal fragment partially suppressing the ogd1 mutation in Saccharomyces cerevisiae has been cloned. The molecular analysis revealed that its suppressor gene codes for a natural glutamine tRNA(CAG) and maps on chromosome XIII in the upstream region of the URA10 gene. The multicopy plasmids containing this tRNA gene also suppressed the standard trp1-1 amber mutation and conferred the sensitivity of yeast cells to paromomycin and increased temperature.

Characterization of Yersinia enterocolitica isolated from the oral cavity of swine in Slovakia

Yersinia enterocolitica was detected in 160 of 2760 examined samples that were prepared from dental cavity of 920 pigs. From the isolates 49 strains were characterized with respect to their genetic and phenotypic markers of virulence. All strains were belonging to serogroup 0:3, biovar 4. Forty-one isolates (84%) harboured the virulence plasmid detected by DNA colony hybridization. Of the other assays of virulence--autoagglutination, binding of crystal violet, pyrazinamidase activity, calcium dependence and Congo red binding--the latter two exhibited the best correlation with the detected presence of plasmid DNA.

Energy-dependent mitochondrial mutagenicity of antibacterial ofloxacin and its recombinogenic activity in yeast

Ofloxacin, a specific inhibitor of bacterial topoisomerase II, is known to inhibit the growth of yeast cells and to induce rho- mutants in the yeast S. cerevisiae. The frequency of ofloxacin-induced petite mutants under non-growth conditions was found to be strongly diminished when the cells were depleted in intramitochondrial ATP. Under optimal conditions of mitochondrial mutagenesis the drug induced mitotic recombination and reverse mutation in diploid strains but failed to cure either killer plasmids or the 2 microns DNA of dividing cells. The sensitivity to ofloxacin of the strains deficient in the DNA strand-break repair pathway (rad52) was significantly higher then that of the wild-type strains and of the mutants deficient in excision or mutagenic DNA repair. The results are compatible with the idea that the cytotoxic and genetic activity of ofloxacin in yeast probably results from the inhibited DNA ligation function of topoisomerase II creating DNA breaks that are reparable through the recombination repair pathway.

Induction of respiration-deficient mutants in Saccharomyces cerevisiae by chelerythrine

Chelerythrine and sanguinarine, two structurally related benzo/c/phenanthridine alkaloids, prevented growth of yeast cells in medium containing either glucose or non-fermentable carbon sources. At concentrations permitting growth of the yeast Saccharomyces cerevisiae, chelerythrine, but not sanquinarine, induced cytoplasmic respiration-deficient mutants. The petite clones that were analysed exhibited suppressiveness and contained different fragments of the wild-type mitochondrial genome.

The ogd1 and kgd1 mutants lacking 2-oxoglutarate dehydrogenase activity in yeast are allelic and can be differentiated by the cloned amber suppressor

The activity of mitochondrial 2-oxoglutarate dehydrogenase in S. cerevisiae can be impaired either by the ogd1 or the kgd1 mutation. The OGD1 gene and two suppressor genes were isolated by complementation of the ogd1 mutant. The complementation of the kdg1 mutant by the OGD1 gene, an allelism test, and meiotic mapping, revealed that the ogd1 and kgd1 mutations are allelic. The two mutations were differentiated by the cloned suppressor gene which was able to partially complement ogd1, but not kgd1. The molecular analysis of the suppressor gene revealed its identity with the natural tRNA(GlnCAG) gene found in the upstream region of URA10.

Molecular cloning of the PEL1 gene of Saccharomyces cerevisiae that is essential for the viability of petite mutants

The PEL1 gene of Saccharomyces cerevisiae is essential for the cell viability of mitochondrial petite mutants, for the ability to utilize glycerol and ethanol on synthetic medium, and for cell growth at higher temperatures. By tetrad analysis the gene was assigned to chromosome III, centromere proximal of LEU2. The PEL1 gene has been isolated and cloned by the complementation of a pel1 mutation. The molecular analysis of the chromosomal insert carrying PEL1 revealed that this gene corresponds to the YCL4W open reading frame on the complete DNA sequence of chromosome III. The putative Pel1 protein is characterized by a low molecular weight of approximately 17 kDa, a low codon adaptation index, and a high leucine content.

High-level resistance to cycloheximide resulting from an interaction of the mutated pdr3 and cyh genes in yeast

In addition to pdr3-1, the S. cerevisiae nuclear pleiotropic drug resistance mutant 2D was found to contain another recessive nuclear mutation, cyh, conferring specific resistance to cycloheximide only. The cycloheximide resistance level due to either the pdr3-1 or the cyh mutation alone was low and was not altered by the ogd1 mutation which increased the physiological acidification of the culture. When pdr3-1 and cyh mutations occurred simultaneously in the haploid yeast strain their interaction was synergistic and resulted in high-level resistance to cycloheximide.

Ofloxacin induces cytoplasmic respiration-deficient mutants in yeast Saccharomyces cerevisiae

Ofloxacin, a new quinolone with potent antibacterial activity, was also found to be effective against yeast. At relatively high concentrations, and at mild alkaline pH, ofloxacin inhibited the growth of yeast cells in medium containing glucose, and prevented growth on glycerol, as carbon and energy source. The cells growing in the presence of ofloxacin exhibited abberrantly budded forms, lost their viability and many of them converted to cytoplasmic respiration-deficient mutants. Induction of mutants was also observed under non-growing conditions. The petite clones analysed exhibited suppressiveness and contained different fragments of the wild-type mitochondrial genome.

Fumaric acid overproduction in yeast mutants deficient in fumarase

A nuclear mutant of Saccharomyces cerevisiae deficient in mitochondrial fumarase has been identified through the in vitro biochemical assay of enzyme activity after visual selection due to an increased acidification ability of its colonies. Cells of the fumarase-deficient mutant fermenting glucose accumulated extracellular fumaric acid. This accumulation was observed only in growing cultures and required functional mitochondrial electron transport from succinate dehydrogenase to oxygen.

The OGD1 gene, affecting 2-oxoglutarate dehydrogenase in S. cerevisiae, is closely linked to HIS5 on chromosome IX

Ogd1 mutants of Saccharomyces cerevisiae are deficient in mitochondrial 2-oxoglutarate dehydrogenase activity; they cannot grow on glycerol and produce an increased amount of organic acids during growth on glucose as substrate. Using gamma ray-induced rad52-mediated chromosome loss the ogd1 mutation can be assigned to chromosome IX. Tetrad analysis of crosses between ogd1 and other markers on chromosome IX revealed that the OGD1 gene maps on the left arm of this chromosome 1.9 cM from his5.

Intramitochondrial ATP and cell functions: yeast cells depleted of intramitochondrial ATP lose the ability to grow and multiply

Cells of the yeast Saccharomyces cerevisiae could be depleted of their intramitochondrial ATP bu culturing on glucose in the presence of antimycin A, which prevents production of ATP in mitochondria, along with bongkrekic acid, which prevents transport of ATP from the cytosol into mitochondria. Alternatively, the depletion could be achieved by culturing respiration-deficient mutants in the presence of bongkrekic acid. The depleted cells of the respiration-deficient mutant did not grow on glucose in a synthetic medium and growth for a few generations was made possible by adding peptone, yeast extract or some amino acids into the medium. The depleted cells did not differ from control cells in their content of amino acids, proteins, nucleic acids and major phospholipids and had preserved the ability to carry on protein and nucleic acid syntheses and to mate to other cells. No conspicuous cytological differences were found between the control and depleted cells. After culturing in a semi-synthetic medium in the presence of bongkrekic acid the cells of the respiration-deficient mutant exhibited almost no cytochrome c in their spectra and their azide-sensitive ATPase activity was drastically reduced. The results suggest that intramitochondrial syntheses of some low-molecular compounds as well as import and/or assembly of some cytoplasmically synthesized mitochondrial proteins into mitochondria may be impaired in cells lacking intramitochondrial ATP and this may be responsible for their inability to grow and multiply.

Spectral properties of cytochrome b-561 and cytochrome b-565 in mucidin-resistant mutants of Saccharomyces cerevisiae

The oxidation of NADH in submitochondrial particles isolated from MUC1, MUC2 and MUC3 mucidin-resistant mutants of Saccharomyces cerevisiae is specifically resistant to mucidin. Extra reduction of cytochrome b-565 induced by mucidin is demonstrated in all tested mucidin-resistant mutants. Red shift of cytochrome b-561 is induced by mucidin in two independent MUC3 mutants. In MUC1 and MUC2 mutants, the red shift is not induced by mucidin, while that promoted by antimycin A and 2-n-heptyl-4-hydroxyquinoline N-oxide are normal. It is concluded that the extra reduction of cytochrome b-565 and the red shift of cytochrome b-561 elicited by mucidin can be largely dissociated from the overall inhibition of the electron flow by distinct mucidin-resistant mutations in different exons of the split mitochondrial gene of cytochrome b.

Alpha-glucosidase synthesis in yeast cells depleted of intramitochondrial ATP

We have studied the dependence on mitochondrial ATP of expression of MAL genes specifying maltose utilization in yeast. It was found that bongkrekic acid does not prevent the maltose induced synthesis of alpha-glucosidase in derepressed cells of the wild-type and corresponding respiratory-deficient mutant of Saacharomyces cerevisiae. The results suggest that expression of nuclear genes specifying alpha-glucosidase and maltose catabolism in yeast is apparently not dependent on the proper function of mitochondrial adenine nucleotide translocase and does not even require the presence of normal levels of ATP in mitochondria.

Membrane mutants: a yeast mutant with a lesion in phosphatidylserine biosynthesis

A single-gene nuclear choline-requiring mutant of Saccharomyces cerevisiae was studied. Choline as a growth supplement to synthetic media could be substituted by low concentrations of dimethylethanolamine, monomethylethanolamine or ethanolamine. DL-Serine also supported growth, but only at high concentrations: on a molar basis it was approximately one hundred times less effective than choline. When cultured in unsupplemented medium the mutant cells soon ceased to grow. The growth-arrested cells contained less than one fifth of the phosphatidylethanolamine present in wild-type cells and only traces of phosphatidylserine. The relative content of the two phospholipid species was raised by growing the mutant cells in the presence of choline of the other supplements but still remained lower than in wild-type cells. The mutant cells depleted of phosphatidylethanolamine and phosphatidylserine had greatly diminished ability to fuse with other cells in mating and their protoplasts showed increased resistance to hypotonic lysis. Respiration was not substantially affected by the deficit of the two phospholipid species in the mutant. In cell-free preparations, the affinity of the phosphatidylserine synthesizing system for serine was found to be almost two orders of magnitude lower in the mutant than in the wild-type. The impairment of phosphatidylserine synthesis accounts for growth requirement and the abnormal phospholipid composition of the mutant cells.

Localization of mucidin-resistant locus muc3 on mitochondrial DNA with respect to ubiquinol-cytochrome c reductase deficient box loci. Locus muc3 is allelic to box2

Genetic relations between mitochondrial mucidin-resistant locus muc3 and ubiquinol-cytochrome c reductase-deficient box loci have been studied by recombination and petite deletion analysis. It was found that the locus muc3 maps in the segment of mitochondrial DNA corresponding to the locus box2. The results suggest the participation of box2/muc3 locus in the sequences of the structural gene for cytochrome b.

Antimicrobial and cytolytic activity of N,N-dimethyl-l-methyldodecylamine oxide

N,N-Dimethyl-l-methyldodecylamine oxide inhibited the growth of bacteria, yeast and filamentous fungi; further it induced lysis of osmotically stabilized protoplasts of Saccharomyces cerevisiae and human erythrocytes. This effect is based evidently on a change in the organization and function of cell membranes.

The hemolytic activity of heterocyclic n-alkyl amine oxides

The N-alkyl derivatives of morpholine-, pyrrolidine-, piperidine- and perhydroasepine-N-oxides caused the rapid, temperature-dependent, hemolysis of human red blood cells. The most hemolytic were the amine oxides with alkyl groups having 14-18 carbon atoms.

Relationship between the structure of carbonylcyanide phenylhydrazones and inhibition of growth of microorganisms, stimulation of respiration of yeast cells and rat liver mitochondria

The effect of ten derivatives of carbonylcyanide phenylhydrazone on growth of bacteria, yeast and different species of filamentous fungi was investigated. In yeast and mitochondria isolated from rat liver the effect of these derivatives on the respiratory activity was also followed. The relative efficiency of the individual derivatives of carbonylcyanide phenylhydrazone was determined on the basis of the results obtained. It was shown that derivatives, in which the substituent on the benzene ring causes simultaneously an increase of acidity and lipophilicity of the derivative as compared with the non-substituted carbonylcyanide phenylhydrazone (4-trifluoromethoxy-, 3-chloro-, 4-chloro and 3,4-dichloro-derivatives) were most effective.

Antimicrobial activity of amine oxides: mode of action and structure-activity correlation

The effect of N-alkyl derivatives of saturated heterocyclic amine oxides on the growth and metabolism of microorganisms has been studied. 4-Dodecylmorpholine-N-oxide inhibited the differentiation and growth of Bacillus cereus, of different species of filamentous fungi, and of the yeast Saccharomyces cerevisiae. For vegetative cells, the effect of 4-dodecylmorpholine-N-oxide was lethal. Cells of S. cerevisiae, after interaction with 4-dodecylmorpholine-N-oxide, released intracellular K(+) and were unable to oxidize or ferment glucose. The functions of isolated yeast mitochondria were also impaired. 4-Dodecylmorpholine-N-oxide at growth-inhibiting concentrations induced rapid lysis of osmotically stabilized yeast protoplasts, with the rate of lysis a function of temperature and of amine oxide concentration. A study of the relationships between structure, antimicrobial activity, and cytolytic activity was made with a group of structurally different amine oxides involving a series of homologous 4-alkylmorpholine-N-oxides, 1-alkylpiperidine-N-oxides, 1-dodecylpyrrolidine-N-oxide, 1-dodecylperhydroasepine-N-oxide, and N,N-dimethyldodecylamine oxide. Disorganization of the membrane structure after interaction of cells with the tested amine oxides was primarily responsible for the antimicrobial activity of the amine oxides. This activity was found to be dependent on the chain length of the hydrophobic alkyl group and was only moderately influenced by other substituents of the polarized N-oxide group.

Mucidin resistance in yeast. Isolation, characterization and genetic analysis of nuclear and mitochondrial mucidin-resistant mutants of Saccharomyces cerevisiae

Mutants of Saccharomyces cerevisiae resistant to the antibiotic mucidin, a specific inhibitor of electron transport between cytochrome b and c, were isolated and divided into three phenotypic groups, as follows. Class 1 mutants were cross-resistant to a variety of mitochondrial inhibitors and exhibited no resistance at the mitochondrial level. Class 2 mutants were specifically resistant to mucidin exhibiting resistance also at the level of isolated mitochondria. Biochemical studies indicated that the mucidin resistance in class 2 mutants involved a modification of mucidin binding of inhibitory sites on the mitochondrial inner membrane without a significance change in the sensitivity of mitochondrial oxygen uptake to antimycin A, 2-heptyl-4-hydroxyquinoline-N-oxide, and 2,3-dimercaptopropanol. Class 3 was represented by a mutant which showed a high degree of resistance to mucidin and was cross-resistant to a variety of mitochondrial inhibitors at the cellular level but exhibited only a resistance to mucidin at the mitochondrial level. Genetic analysis of mucidin-resistant mutants revealed the presence of both nuclear and mitochondrial genes determining mucidin resistance/sensitivity in yeast. Resistance to mucidin in class 1 mutants was due to a single-gene nuclear recessive mutation (mucPR) whereas that in class 2 mutants was caused by mutations of mitochondrial genes. Resistance in class 3 mutant was determined both by single-gene nuclear and mitochondrial mutations. In the mitochondrial mutants the mucidin resistance segregated mitotically and the resistance determinant was lost upon induction of petite mutation by ethidium bromide. Allelism tests indicated that the mucidin resistance mutations fell into two genetic loci (MUC1 and MUC2) which were apparently not closely linked in the mitochondrial genome. Recombination studies showed that the two mitochondrial mucidin loci were not allelic with other mitochondrial loci RIB1, RIB2 and OLI1. An extremely high mucidin resistance at the cellular level was shown to arise from synergistic interaction of the nuclear gene mucPR and the mitochondrial mucidin-resistance gene (MR) in a cell. The results suggest that at least two mitochondrial gene products, responsible for mucidin resistance/sensitivity in yeast, take part in the formation of the cytochrome bc1 region of the mitochondrial respiratory chain.

Genetic determination of the mitochondrial adenine nucleotide translocation system and its role in the eukaryotic cell

On integrating experimental data published previously, the following picture of the mitochondrial adenine nucleotide (AdN) translocation system is being presented: 1. The AdN translocation system serves not only to transport ATP synthesized within mitochondria into the cytosol but also to transport cytosolic ATP into the mitochondria when oxidative phosphorylation is not functioning. 2. The AdN translocator is coded for by nuclear genes and the mitochondrial protein synthesis is not involved in its formation. 3. The AdN translocation system must be preserved and functioning even in cells which could dispense with oxidative phosphorylation. It assures appropriate concentrations of intramitochondrial ATP. 4. The intramitochondrial ATP is required for normal replication of mitochondrial DNA. Tis supports the view that the mitochondrion is a self-replicating semi-autonomous organelle. 5. The appropriate concentration of ATP must be present in mitochondria to make possible cell growth or multiplication. This points to a direct or indirect role of mitochondria in the control of cell proliferation.