Isolation, purification, and characterization of a killer protein from Schwanniomyces occidentalis

The yeast Schwanniomyces occidentalis produces a killer toxin lethal to sensitive strains of Saccharomyces cerevisiae. Killer activity is lost after pepsin and papain treatment, suggesting that the toxin is a protein. We purified the killer protein and found that it was composed of two subunits with molecular masses of approximately 7.4 and 4.9 kDa, respectively, but was not detectable with periodic acid-Schiff staining. A BLAST search revealed that residues 3 to 14 of the 4.9-kDa subunit had 75% identity and 83% similarity with killer toxin K2 from S. cerevisiae at positions 271 to 283. Maximum killer activity was between pH 4.2 and 4.8. The protein was stable between pH 2.0 and 5.0 and inactivated at temperatures above 40 degrees C. The killer protein was chromosomally encoded. Mannan, but not beta-glucan or laminarin, prevented sensitive yeast cells from being killed by the killer protein, suggesting that mannan may bind to the killer protein. Identification and characterization of a killer strain of S. occidentalis may help reduce the risk of contamination by undesirable yeast strains during commercial fermentations.

Managing genetic material to protect intellectual property rights

One of the most important policy instruments for the promotion of further biotechnology development is intellectual property right (IPR) protection. However, one cannot improve upon a biotechnological invention without physical access to the germplasm, making exchanges of genetic material necessary. A formal transfer agreement, which addresses the key issues of ownership, access, use, and equitable benefit-sharing, is a powerful legal instrument for intellectual property. Other restrictions are generally imposed as a result of national and international safety regulations. Forming strategic alliances, such as joint ventures, collaborative research agreements, joint research and development agreements, and manufacturing and distribution alliances to exploit the economic value of genetic material, provides scientists with the mechanisms they need to bring their research material and products to the marketplace.

Molecular characterization and identification of Saprolegnia by restriction analysis of genes coding for ribosomal RNA

Restriction fragment length polymorphisms (RFLPs) in two regions of the ribosomal DNA (rDNA) repeat unit were examined in 33 strains representing 18 species of Saprolegnia. The Polymerase Chain Reaction (PCR) was used to separately amplify the 18S rDNA and the region spanning the two internal transcribed spacers (ITS) and the 5.8S ribosomal RNA gene. Amplified products were subjected to a battery of restriction endonucleases to generate various fingerprints. The internal transcribed spacer region exhibited more variability than the 18S rDNA and yielded distinctive profiles for most of the species examined. Most of the species showing 100% similarity for the 18S rDNA could be distinguished by 5.8S + ITS restriction polymorphisms except for S. hypogyna, S. delica, S. lapponica, and S. mixta. The rDNA data indicate that S. lapponica and S. lapponica and S. mixta are conspecific with S. ferax, whereas there is no support for the proposed synonymies of S. diclina with S. delica and of S. mixta with S. monoica. Results from cluster analysis of the two data sets were very consistent and tree topologies were the same, regardless of the clustering method used. A further examination of multiple strains in the S. diclina-S. parasitica complex showed that restriction profiles are conserved across different strains of S. parasitica originating from the U.K. and Japan. HhaI and BsaI restriction polymorphisms were observed in isolates from the U.S. and India. The endonuclease BstUI was diagnostic for S. parasitica, generating identical fingerprints for all stains regardless of host and geographic origin. Except for the atypical strain ATCC 36144, restriction patterns were also largely conserved in S. diclina. Correlation of the rDNA data with morphological and ultrastructural features showed that S. diclina and S. parasitica are not conspecific. Restriction polymorphisms in PCR-amplified rDNA provide a molecular basis for the classification of Saprolegnia and will be useful for the identification of strains that fail to produce antheridia and oogonia.

Analysis of ribosomal DNA restriction patterns in the genus Kluyveromyces

Riboprinting was used to determine the relationships among strains belonging to 15 species of the genus Kluyveromyces. The small subunit ribosomal RNA gene (SSU rDNA) was amplified using the Polymerase Chain Reaction (PCR) and subjected to a battery of nine restriction enzymes. Similarity coefficients between strains were calculated based on shared and unique restriction fragments. Cluster analysis revealed three major groups that generally correlated with previously reported relationships based on other molecular data. Variations in SSU rDNA restriction fragments may be used for differentiation of the Kluyveromyces strains included in this study.

PCR amplification of the 3' external transcribed and intergenic spacers of the ribosomal DNA repeat unit in three species of Saccharomyces

Two spacer regions outside the ribosomal DNA (rDNA) transcriptional unit in three species of Saccharomyces, S. cerevisiae, S. carlsbergensis and S. pastorianus, were amplified using the polymerase chain reaction. These regions were composed of the 3' external transcribed spacer (ETS) and the intergenic spacer (IGS). Primers were developed from sequence alignments and by taking the reverse complement of a previously described sequence. The region amplified spanned base position 3110 on the 26S rRNA to base position 27 on the 5S rRNA of S. cerevisiae. Nine of the twelve strains used in this study exhibited different restriction profiles, showing that the spacers are highly variable between species. The results suggest that PCR fingerprinting of the non-coding spacer regions can be used to distinguish between closely related Saccharomyces species and may have potential in DNA profiling of other yeasts.

Validation of the species concept in the genus Dekkera by restriction analysis of genes coding for rRNA

The gene coding for the small-subunit rRNA of 11 type strains belonging to the genus Dekkera and its anamorph, Brettanomyces, was amplified by using the polymerase chain reaction and subjected to digestion with a series of restriction endonucleases. Similarity coefficients were calculated from the number of shared and unique fragments, and a cluster analysis yielded four distinct groups with the following ascosporogenous states: Dekkera anomala, Dekkera bruxellensis, Dekkera custersiana, and Dekkera naardenensis. Results correlate with evidence from isoenzyme electrophoresis and DNA homology analysis. They also confirm previously reported anamorph-teleomorph connections and recently proposed synonymies within the genus.

Restriction polymorphisms in the internal transcribed spacers and 5.8S rDNA ofSaccharomyces

Polymorphisms in enzymatically amplified ribosomal DNA (rDNA) were examined in 18 strains of Saccharomyces. Restriction patterns generated from the region spanning the internal transcribed spacers (ITS) and the 5.8S rDNA produced two clusters corresponding to S. bayanus and S. cerevisiae. The type culture of S. carlsbergensis (ATCC 76529), which could not be separated from the S. cerevisiae group by small subunit (SSU) rDNA patterns, showed a ScrfI profile that was distinct from all the other strains. The type culture of S. intermedius var. turicensis (ATCC 76519) is assigned to S. bayanus on the basis of the combined results of SSU and ITS restriction analyses. S. kluyveri occurred at a separate branch of the distance tree and is unrelated to any of the strains. Results were in general agreement with reported DNA homologies and are discussed in relation to other molecular and genetic data.

Ribosomal DNA Restriction Analysis Reveals Genetic Heterogeneity in Saccharomyces cerevisiae Meyen ex Hansen

A ribosomal DNA restriction analysis of 17 strains belonging to the Saccharomyces cerevisiae complex revealed two major groups, one of which corresponded to Saccharomyces bayanus. Our results generally correlate with previously reported genetic and molecular data and support the conclusion that S. bayanus should be reinstated as a separate taxon.

Application of good laboratory practice (GLP) to culture collections of microbial and cell cultures

Although the principles and the necessity for good laboratory practice (GLP) guidelines to confirm the credibility, integrity, and quality of non-clinical laboratory studies have been known for more than a decade, culture collection activities are not subject to them. Because of recent advances in biotechnology, culture collections face increased demands not only for quality cultures but also current information. When applied in culture collections, GLP guidelines prove to be an excellent management tool as well as a cost-effective system of providing authentic and reliable microbial and cell cultures and associated data.

Factors affecting the production of eremofortin C and PR toxin in Penicillium roqueforti

Eremofortin C (EC) and PR toxin are secondary metabolites of Penicillium roqueforti. Of 17 strains from the American Type Culture Collection that were studied for their ability to produce EC and PR toxin, 13 produced these metabolites. Toxin production by strains grown in solid media (10 cereals and 8 other agricultural products) was also investigated. Production of EC and PR toxin by fungi grown on cereals was greater than production of EC and PR toxin by fungi grown on legumes; fungi grown on corn produced the greatest amount of PR toxin. Addition of corn extracts to the culture medium greatly increased the production of EC and PR toxin in a coordinated manner, with no significant change in mycelial dry weight. The fungi produced the highest levels of EC and PR toxin at 20 to 24 degrees C depending on the strain. Toxin production was higher in stationary cultures than in cultures that were gently shaken at 120 rpm. The optimum pH for production of both EC and PR toxin was around pH 4.0. With regard to spore age, toxin levels did not change significantly when we used spores obtained from fungi that were grown at 24 degrees C for 3 up to 48 days.

Production of aflatoxins by strains of the Aspergillus flavus group maintained in ATCC

A total of 169 strains of the Aspergillus reference cultures in the Aspergillus flavus group maintained in the American Type Culture Collection (ATCC) were studied for their aflatoxin-producing abilities in rice, peanut and semisynthetic medium, utilizing high pressure liquid chromatography. Fifty-nine of the strains examined were positive for aflatoxin formation. No strains of the food fungi A. oryzae or A. sojae produced detectable levels of aflatoxins, while 33-85% of the strains of A. flavus and A. parasiticus were toxigenic.

Biochemical variation of Cryptococcus neoformans

Ninety-seven strains of Cryptococcus neoformans and C. bacillisporus were examined for 44 biochemical characters and the results were analyzed numerically. One phenon emerged at the 86% level of similarity when strains were clustered according to their M-similarity values. All strains grew in ten carbon sources (D-glucose, D-galactose, arbutin, maltose, sucrose, D-melezitose, D-xylose, D-mannitol, D-glucitol, and meso-inositol), and also grew at 37 degrees C and produced urease and phenoloxidase. None of them grew in melibiose, lactose, nor valine, and none reduced nitrate to nitrite. Comparison of selected biochemical characters, creatinine utilization, and serotypes of 49 aberrant strains is presented. Forty-eight of the 97 strains produced the Filobasidiella state either alone or when paired with a strain of compatible mating-type. Filobasidiella neoformans serotypes A and D were interfertile with compatible mating-types of F. bacillispora serotypes B and C. The 44 biochemical characters and 4 serotypes did not predict barriers to mating competence. The present study further substantiates that Filobasidiella neoformans and F. bacillispora are one species.

Serologic grouping and sexual compatibility of airborne Cryptococcus neoformans

Through the use of Anderson air samples, 214 isolates of Cryptococcus neoformans were cultured from the air in a vacant tower in a large complex of buildings in Oklahoma City. The tower contained hundreds of pigeons, a massive amount of droppings, nests with eggs and young, dying and dead pigeons. All isolates were serotype A-D and self-sterile for the production of basidiospores. Among these 193 were of the "alpha" mating type, producing basidiospores when paired with "alpha" mating type. No isolates of "alpha" mating type were found. The findings imply that the infectious particles of C. neoformans in nature are relatively small, nonencapsulated yeast cells and not basidiospores.

Conservation of reference strains of Fusarium in pure culture

More than 300 reference strains representing 60 species and varieties of Fusarium cultures named according to different taxonomic systems are currently maintained at the American Type Culture Collection (ATCC). They have been preserved by freeze-drying and by freezing and subsequent storage in liquid nitrogen (-196 degrees C) to insure their viability without contamination, variation, mutation, or deterioration. The materials and procedures used at the ATCC for the acquisition, accessioning, cataloguing, preservation and distribution are described. Longevity storage data for the strains available for distribution are presented and discussed.

Reproducibility of vitamin assays with mutants of Neurospora crassa maintained by freeze-drying

Three mutant strains (ATCC 9277, ATCC 9278, ATCC 9683) of Neurospora crassa requiring choline, inositol, and p-aminobenzoic acid respectively for normal growth were deposited at the ATCC by G.W. Beadle 30 years ago and were preserved at various time intervals by freeze-drying. Each preservation batch yielded cultures that, when used for biological assays, exhibited the same biochemical properties as they originally possessed. The freeze-drying technique is shown to be applicable to preserving biological properties of sporulating fungi for bioassay over prolonged periods of time.

Effect of carbon source on conidiogenesis in Fonsecaea dermatitidis, agent of chromomycosis

Hormiscium dermatitidis Kano is a well known etiological agent of cutaneous and generalized chromomycosis. However, the generic designation of this fungus has long been a much debated question. The results of the present study of the type culture ATCC 28869 indicate that the fungus is polymorphic, producing a Phialophora state in media containing glucose or maltose and a Cladosporium state in media containing galactose or melibiose. Morphologically and developmentally this chromomycotic agent is closely related to Fonsecaea pedrosoi (Brumpt) Negroni and should be classified as Fonsecaes dermatitidis (Kano) Carrion.

Preservation of living fungi pathogenic for man and animals

The paper describes the materials and procedures presently used at the American Type Culture Collection (ATCC) for the long-term preservation of living fungi pathogenic for man and animals by freeze-drying and by freezing and subsequent storage in liquid nitrogen. Longevity storage data for the strains available for distribution is presented.