Random UV-C mutagenesis of Scheffersomyces (formerly Pichia) stipitis NRRL Y-7124 to improve anaerobic growth on lignocellulosic sugars

Scheffersomyces (formerly Pichia) stipitis NRRL Y-7124 was mutagenized using UV-C irradiation to produce yeast strains for anaerobic conversion of lignocellulosic sugars to ethanol. UV-C irradiation potentially produces large numbers of random mutations broadly and uniformly over the whole genome to generate unique strains. Wild-type cultures of S. stipitis NRRL Y-7124 were subjected to UV-C (234 nm) irradiation targeted at approximately 40% cell survival. When surviving cells were selected in sufficient numbers via automated plating strategies and cultured anaerobically on xylose medium for 5 months at 28°C, five novel mutagenized S. stipitis strains were obtained. Variable number tandem repeat analysis revealed that mutations had occurred in the genome, which may have produced genes that allowed the anaerobic utilization of xylose. The mutagenized strains were capable of growing anaerobically on xylose/glucose substrate with higher ethanol production during 250- to 500-h growth than a Saccharomyces cerevisiae yeast strain that is the standard for industrial fuel ethanol production. The S. stipitis strains resulting from this intense multigene mutagenesis strategy have potential application in industrial fuel ethanol production from lignocellulosic hydrolysates.     

Penicillic Acid Production by Blue-Eye Fungi on Various Agricultural Commodities

Of 10 Penicillium species reported to cause blue-eye disease of corn, four (P. martensii, P. palitans, P. cyclopium, P. puberulum) were found capable of producing the mycotoxin penicillic acid on various agricultural commodities. Commodities with high protein contents did not support toxin synthesis. The extent of toxin production varied with the strain of mold, the commodity, and the temperature; low temperatures (1 to 10 C) favored toxin accumulation.     

Phylogenetic relationships among species of the genus Issatchenkia Kudriavzev

The phylogenetic relatedness of Issatchenkia spp. was estimated from partial rRNA sequences in two regions of the large subunit and one region of the small subunit. I. terricola was the most divergent species of the genus, differing from other members by 18% nucleotide differences in the highly variable 25S-635 region. These data indicate Issatchenkia to be the most divergent ascomycetous yeast genus presently known.     

Relationships among the generaAshbya,Eremothecium, Holleya andNematospora determined from rDNA sequence divergence

Summary Species of the generaAshbya, Eremothecium, Holleya, andNematospora were compared from extent of divergence in a 580-nucleotide region near the 5 end of the large subunit (26S) ribosomal DNA gene. The four genera are closely related and comprise a subclade of the hemiascomycetes. Because the taxa show little divergence, it is proposed that all be placed in the genusEremothecium. The family Eremotheciaceae, fam. nov., is proposed.This paper is dedicated to Professor Herman Jan Phaff in honor of his 50 years of active research which still continues.     

Scanning electron microscopy of ascospores of Debaryomyces and Saccharomyces

Ascospores from species of Debaryomyces and the Torulaspora-group of Saccharomyces were examined by scanning electron microscopy. Ornamentation on ascospores of D. hansenii varied from short to long interconnected ridges or broad based, elongated conical protuberances. A spiral ridge system was detected on the ascospores of D. marama, but wart-like protuberances occurred on those of D. cantarellii, D. castellii, D. coudertii, D. formicarius, D. phaffii, D. vanriji and D. yarrowii. Ascospores of D. halotolerans did not have protuberances and the species appears to be identical with Pichia farinosa. Wart-like protuberances also were found on ascospores of S. delbrueckii, S. microellipsodes, S. rosei, S. inconspicuus, S. fermentati, S. montanus and S. vafer, but the ascospore surface of S. pretoriensis was covered by fine ridges. Short tapered ridges covered the ascospores of S. kloeckerianus.     

Specimen Holder to Critical-Point Dry Microorganisms for Scanning Electron Microscopy

Critical-point drying of microorganisms for scanning electron microscopy can be rapidly and effectively accomplished by use of a newly described specimen holder. Up to eight different samples of spores or vegetative cells are placed between polycarbonate membrane filters in the holder and processed through solvent dehydration and critical-point drying using carbon dioxide without loss or cross contamination of microorganisms. Yeasts, molds, bacteria, and actinomycetes have been successfully processed.     

Polysaccharide from Dry Navy Beans, Phaseolus vulgaris: Its Isolation and Stimulation of Clostridium perfringens

A microbiological assay is described for determining gas produced by Clostridium perfringens (Veilon and Zuber) Holland from materials believed to be flatulent. A rationale for its use is given and analyzed. The fractionation and the results of the assay for several components of lima beans, Phaseolus lunatus L., and navy beans, P. vulgaris L., are given. In particular, a polysaccharide was isolated from dried P. vulgaris seeds. Only about one-seventh as much could be isolated from green P. lunatus seeds as from P. vulgaris seeds. The polysaccharide stimulates voluminous gas production by C. perfringens and meets all criteria of the rationale for flatulent sus pects. It has not been tested on humans; however, data from the microbiological assay correlate well with human results for green and dry lima beans and navy beans.     

Mechanism of radiosensitization by halogenated pyrimidines: effect of BrdU on cell killing and interphase chromosome breakage in radiation-sensitive cells

The effect of BrdU incorporation on cell radiosensitivity as well as on the induction of chromosome damage by radiation was studied in plateau-phase xrs-5 cells using the premature chromosome condensation (PCC) method. It is well known that xrs-5 cells are sensitive to ionizing radiation and defective in the repair of radiation-induced DNA double-strand breaks, chromosome damage, and potentially lethal damage (PLD). Compared to repair-proficient CHO 10B cells, a reduction was observed in the overall BrdU-mediated radiosensitization in plateau-phase xrs-5 cells for the same degree of thymidine replacement. This finding is interpreted with a model for BrdU-induced radiosensitization advanced previously, in which two distinct components act to produce the overall radiosensitization observed. One component involves processes associated with the increase in initial damage (DNA and chromosome) production per unit absorbed dose and causes an increase in the slope of the survival curve, while the second component involves enhanced fixation of radiation-induced damage (PLD) and causes a reduction in the width of the shoulder of the survival curve. It is suggested that in plateau-phase xrs-5 cells, the deficiency in the repair of radiation-induced damage compromises BrdU-mediated radiosensitization by leaving active only the radiosensitization component that is associated with an increase in damage induction. Enhancement of cell killing by BrdU in plateau-phase xrs-5 cells resulted in a decrease in D0, the relative value of which was similar to the relative increase in the production of chromosome damage as measured by the PCC method. The relative values for the change in D0 and the production of chromosome aberrations were similar in plateau-phase CHO 10B and xrs-5 cells, suggesting that the physicochemical and/or biochemical processes associated with this phenomenon are the same in the two cell lines. Radiosensitization of a magnitude similar to that observed in exponentially growing CHO 10B cells was induced by BrdU in exponentially growing xrs-5 cells. This effect is attributed to a partial expression of the repair gene (transiently during S phase in all cells, or throughout the cycle in a fraction of cells) that permits some repair of radiation-induced damage and which is compromised by BrdU.