Resistance to cellobiose lipids and specific features of lipid composition in yeast

The significance of the fatty acid composition and ergosterol content in cells for resistance to cellobiose lipids has been investigated in the cells of mutant Saccharomyces cerevisiae strains that are unable to produce ergosterol or sphingomyelin and in the cells of microorganisms that produce cellobiose lipids. S. cerevisiae mutants were shown to be less sensitive to cellobiose lipids from Cryptococcus humicola than the wild-type strain, and the strains that produced cellobiose lipids were virtually insensitive to this compound as well. The sensitivity of Pseudozyma fusiformata yeast to its own cellobiose lipids was reduced under conditions that favored the production of these compounds. No correlation between the content of ergosterol and sensitivity to cellobiose lipids was observed in S. cerevisiae or in the strains that produced cellobiose lipids. The ratio between the levels of saturated and unsaturated fatty acids in the cells of the mutant strains was correlated to the sensitivity of the cells to cellobiose lipids.     

Inorganic polyphosphate in mitochondria of Saccharomyces cerevisiae at phosphate limitation and phosphate excess

Isolated mitochondria of Saccharomyces cerevisiae cells grown on glucose possess acid-soluble inorganic polyphosphate (polyP). Its level strongly depends on phosphate (P(i)) concentration in the culture medium. The polyP level in mitochondria showed 11-fold decrease under 0.8 mM P(i) as compared with 19.3 mM P(i). When spheroplasts isolated from P(i)-starved cells were incubated in the P(i)-complete medium, they accumulated polyP and exhibited a phosphate overplus effect. Under phosphate overplus the polyP level in mitochondria was two times higher than in the complete medium without preliminary P(i) starvation. The average chain length of polyP in mitochondria was of <15 phosphate residues at 19.3 mM P(i) in the culture medium and increased at phosphate overplus. Deoxyglucose inhibited polyP accumulation in spheroplasts, but had no effect on polyP accumulation in mitochondria. Uncouplers (FCCP, dinitrophenol) and ionophores (monensin, nigericin) inhibited polyP accumulation in mitochondria more efficiently than in spheroplasts. Fast hydrolysis of polyP was observed after sonication of isolated mitochondria. Probably, the accumulation of polyP in mitochondria depended on the proton-motive force of their membranes.     

The development of A. N. Belozersky's ideas in polyphosphate biochemistry

This review covers some trends and approaches to the study of inorganic polyphosphates that originated from the fruitful ideas and pioneering works of A. N. Belozersky. This is, first of all, the elucidation of a close relationship between these biopolymers and nucleic acids in organisms at different evolutionary stages; second, the study of "fossil" reactions in polyphosphate metabolism that permit an understanding of their role in the evolution of phosphorus turnover and cell bioenergetics; third, the possible use of the conservative enzymes of polyphosphate metabolism, e.g., exopolyphosphatases, as molecular chronometers for obtaining additional data concerning the theory of the endosymbiotic origin of eukaryotic cells from prokaryotes.     

Cytoplasmic inorganic polyphosphate participates in the heavy metal tolerance of Cryptococcus humicola

The basidiomycetous yeast Cryptococcus humicola was shown to be tolerant to manganese, cobalt, nickel, zinc, lanthanum, and cadmium cations at a concentration of 2.5 mmol/L, which is toxic for many yeasts. The basidiomycetous yeast Cryptococcus terreus was sensitive to all these ions and did not grow at the above concentration. In the presence of heavy metal cations, С. humicola, as opposed to C. terreus, was characterized by the higher content of acid-soluble inorganic polyphosphates. In vivo 4′,6′-diamino-2-phenylindole dihydrochloride staining revealed polyphosphate accumulation in the cell wall and cytoplasmic inclusions of С. humicola in the presence of heavy metals. In C. terreus, polyphosphates in the presence of heavy metals accumulate mainly in vacuoles, which results in morphological changes in these organelles and, probably, disturbance of their function. The role of polyphosphate accumulation and cellular localization as factors of heavy metal tolerance of Cryptococcus humicola is discussed.     

Fungicidal activity of cellobiose lipids from culture broth of yeast <Emphasis Type="Italic">Cryptococcus humicola</Emphasis> and <Emphasis Type="Italic">Pseudozyma fusiformata</Emphasis>

Cellobiose lipids of yeast fungi Cryptococcus huminola and Pseudozyma fusiformata have similar fungicidal activities against different yeast, including pathogenic Cryptococcus and Candida species. Basidiomycetic yeast reveals maximum sensitivity to these preparations; e.g., cells of cryptococcus Filobasidiella neoformans almost completely die after 30-min incubation in a glycolipid solution at a concentration of 0.02 mg/ml. The same effect toward ascomycetous yeast, including pathogenic Candida species, is achieved only at five to eight times higher concentrations of glycolipids. The cellobiose lipid from P. fusiformata, which, unlike glycolipid from Cr. humicola, has hydroxycaproic acid residue as O-subtituent of cellobiose and additional 15-hydroxy group in aglycone, inhibits the growth of the studied mycelial fungi more efficiently than the cellobiose lipid from Cr. humicola.     

The fungicidal activity of an extracellular glycolipid from <Emphasis Type="Italic">Sympodiomycopsis paphiopedili</Emphasis> sugiyama <Emphasis Type="Italic">et al.</Emphasis>

The yeast Sympodiomycopsis paphiopedili (Ustilaginomycetes) produces an extracellular glycolipid, which possesses the maximum antifungal activity at a pH of the medium equal to 4.0–4.5. Among the approximately 300 tested species of yeastlike and mycelial fungi, more than 80% (including species pathogenic for plants, animals, and humans) were found to be sensitive to this glycolipid.Translated from Mikrobiologiya, Vol. 73, No. 6, 2004, pp. 841–845.Original Russian Text Copyright © 2004 by W. Golubev, T. Kulakovskaya, E. Kulakovskaya, N. Golubev.     

Accumulation of phosphate and polyphosphate by Cryptococcus humicola and Saccharomyces cerevisiae in the absence of nitrogen

The search for new phosphate-accumulating microorganisms is of interest in connection with the problem of excess phosphate in environment. The ability of some yeast species belonging to ascomycetes and basidiomycetes for phosphate (P (i) ) accumulation in nitrogen-deficient medium was studied. The ascomycetous Saccharomyces cerevisiae and Kuraishia capsulata and basidiomycetous Cryptococcus humicola, Cryptococcus curvatus, and Pseudozyma fusiformata were the best in P (i) removal. The cells of Cryptococcus humicola and S.?cerevisiae took up 40% P (i) from the media containing P (i) and glucose (5 and 30?mM, respectively), and up to 80% upon addition of 5?mM MgSO(4) (.) The cells accumulated P (i) mostly in the form of polyphosphate (PolyP). In the presence of Mg(2+) , the content of PolyP with longer average chain length increased in both yeasts; they both had numerous inclusions fluorescing in the yellow region of the spectrum, typical of DAPI-PolyP complexes. Among the yeast species tested, Cryptococcus humicola is a new promising model organisms to study phosphorus removal from the media and biomineralization in microbial cells.     

Synthesis of magneto-sensitive iron-containing nanoparticles by yeasts

Industrial production of magneto-sensitive nanoparticles, which can be used in the production of target drug delivery carriers, is a subject of interest for biotechnology and microbiology. Synthesis of these nanoparticles by microorganisms has been described only for bacterial species. At the same time, it is well known that yeasts can form various metal-containing nanoparticles used, for instance, in semiconductors, etc. This paper describes the first results of the biosynthesis of magneto-sensitive nanoparticles by yeasts. The organisms we used—Saccharomyces cerevisiae and Cryptococcus humicola—represented two different genera. Magneto-sensitive nanoparticles were synthesized at room temperature in bench-scale experiments. The study included transmission electron microscopy of the yeast cells and their energy dispersive spectrum analyses and revealed the presence of iron-containing nanoparticles. Both yeast cultures synthesized nanoparticles at high concentrations of dissolved iron. Electron microscopy showed that nanoparticles were associated mainly with the yeast cell wall. Formation of magneto-sensitive nanoparticles was studied under conditions of applied magnetic fields; a possible stimulating role of magnetic field is suggested. On the whole, the paper reports a novel approach to green biosynthesis of magneto-sensitive nanoparticles.     

Inorganic polyphosphates and phosphohydrolases inHalobacterium salinarium

Halobacterium salinarium grown in a liquid medium consumed up to 75% of phosphates originally present in the growth medium and accumulated up to 100 μmol P_i/g wet biomass by the time it entered the growth retardation phase. The content of acid-soluble oligophosphates in the biomass was maximum at the early stage of active growth and drastically decreased when cells reached the growth-retardation phase. The total content of alkali-soluble and acid-insoluble polyphosphates changed very little throughout the cultivation period (five days). The polyphosphate content ofH. salinarium cells was close to that of yeasts and eubacteria. The pyrophosphatase, polyphosphatase, and nonspecific phosphatase activities ofH. salinarium cells were several times lower than those of the majority of eubacteria. The specific activity of pyrophosphatase, the most active hydrolase ofH. salinarium, gradually increased during cultivation, reaching 540 mU/mg protein by the end of the cultivation period. Half of the total pyrophosphatase activity of this halobacterium was localized in the cytosol. The molecular weight of pyrophosphatase, evaluated by gel filtration, was 86 kDa. The effective K_m of this enzyme with respect to pyrophosphate was 115 μM.     

Synthetic Oligopeptides Mimicking γ-Core Regions of Cysteine-Rich Peptides of Solanum lycopersicum Possess Antimicrobial Activity against Human and Plant Pathogens

Plant cysteine-rich peptides (CRPs) represent a diverse group of molecules involved in different aspects of plant physiology. Antimicrobial peptides, which directly suppress the growth of pathogens, are regarded as promising templates for the development of next-generation pharmaceuticals and ecologically friendly plant disease control agents. Their oligopeptide fragments are even more promising because of their low production costs. The goal of this work was to explore the antimicrobial activity of nine short peptides derived from the γ-core-containing regions of tomato CRPs against important plant and human pathogens. We discovered antimicrobial activity in peptides derived from the defensin-like peptides, snakins, and MEG, which demonstrates the direct involvement of these CRPs in defense reactions in tomato. The CRP-derived short peptides appeared particularly active against the gram-positive bacterium Clavibacter michiganensis, which causes bacterial wilt—opening up new possibilities for their use in agriculture to control this dangerous disease. Furthermore, high inhibitory potency of short oligopeptides was demonstrated against the yeast Cryptococcus neoformans, which causes serious diseases in humans, making these peptide molecules promising candidates for the development of next-generation pharmaceuticals. Studies of the mode of action of the two most active peptides indicate fungal membrane permeabilization as a mechanism of antimicrobial action.