本實驗主要目的係自土壤中分離鑑定台灣本土Tetrapisispora屬菌株，除進行分類及親緣關係之探討外，並篩選生產高產量抗菌物質高之菌株，進而分析菌株抗菌物質之生產條件及毒素特性。本研究自2016年七月至同年十二月間共採集125個土壤樣本，經分離及分子鑑定共計分得3種、7株Tetrapisispora屬菌株，包括Tetrapisispora iriomotensis 1株、Tetrapisispora namnaoensis 3株及Tetrapisispora nanseiensis 4株。本研究利用分離所得及本實驗室歷年所保存的Tetrapisispora屬菌株為進行分類及毒素特性分析研究。形態觀察方面，所有分離的菌株皆具典型Tetrapisispora屬菌株之菌落及細胞特徵且不產生菌絲或偽菌絲；而在分子鑑定及親緣關係探討方面，大部份種內菌株之間D1/D2分子序列差異落在0~4個核苷酸(不包含Gap在內)，惟在分析ITS序列及其親緣關係樹時發現，Tetrapisispora nanseiensis 菌株及Tetrapisispora namnaoensis菌株與模式菌株同群之菌株核苷酸差異數在0~4個核苷酸(不包含Gap)，但部份菌株之核苷酸差異數卻高達6~16個核苷酸之間(不包含Gap)。於生產抗菌物質試驗方面，本研究利用常見之8種發酵及腐敗酵母菌與共11株菌株為敏感性實驗菌株，其中Bacillus amyloliquefaciens MU3M77對所有Tetrapisispora菌株都可產生不同程度的敏感性反應，經進一步試驗結果發現Tetrapisispora namnaoensis CG1S05對此菌株可產生最大敏感性反應。後續實驗結果顯示Tetrapisispora namnaoensis CG1S05之最佳毒素生產條件為：以5%高濃度葡萄糖為其生長碳源、培養於pH 3.5的酸性環境、碳氮源濃度比為1 : 2.5於18℃培養3天。上述條件下生產之毒素經過121℃加熱15分鐘測試仍可保持其近100%抑菌活性。在pH穩定性發現此毒素在pH 3時抑菌活性最為穩定，隨著pH值上升抑菌效果遞減，pH上升至6時則完全失去抑菌效果。廣效性實驗中以細菌、黴菌及酵母菌等11株菌株為測試菌株，其結果發現發現，T. namnaoensis CG1S05所分泌的毒素對細菌效果最佳，其中，對革蘭氏陽性菌(Staphylococcus aureus BCRC 10781)的抑菌效果比革蘭氏陰性菌(Escherichia coli BCRC 14824)來的好，對酵母菌表現微弱的抑菌效果，而對黴菌則無法產生抑菌效果。在毒素機制探討方面，在佐以廣效性試驗結果，利用SEM觀察毒素作用於敏感性菌株後的細胞形態，其結果顯示敏感性菌株凋亡時其細胞胞呈現穿孔現象，推估該毒素以其細胞膜或細胞壁為主要作用目標。

The main purpose of this study is to isolate and identify Tetrapisispora species in Taiwan. In addition the taxonomy and phylogenetic analysis of Tetrapisispora spp. in Taiwan, screening the high toxin productivity strain against microorganism is one of the aims as well. Furthermore, we explored the optimal incubation parameters for toxin production and the characteristics of the toxin. There were totally 125 samples collected in Taiwan from July to December in 2016. Base on the molecular composistion of LSU D1/D2 sequences identification, seven strains representing 3 speceies of Tetrapisispora. were collected, including one strain of Tetrapisispora iriomotensis, three strains of Tetrapisispora namnaoensis and four strains of Tetrapisispora nanseiensis. The strains used in this study included isolated strains and the strains which previously preserved in our laboratory in the past years. In terms of morphology observation, the isolated strains demonstrated the typically colony and cell morphology compared with type strains of Tetrapisispora spp., no mycelium or pseudo-mycelium can be found. All strains showed 0 – 4 nucleotide difference of D1/D2 sequences from those of respective type strains, indicating the identification is legitimate. However, the ITS sequences and constructed phylogenetic trees was incoincident with the D1/D2 domain nucleotide discrepancy in identification of Tetrapisispora nanseiensis and Tetrapisispora namnaoensis The ITS sequence of strains in these two species revealed 6 - 16 nucleotides discrepancy (not including the gaps). In terms of the antimicrobial tests, 8 species, 11 strains of fungi and bactria were subjected to the candidates of sensitive strains in this study. Bacillus amyloliquefaciens MU3M77 was showed significant sensitivity to all strains of Tetrapisispora spp. The diffusion inhibitory tests supported that Tetrapisispora namnaoensis CG1S05 had the most highest inhibitory activity to Bacillus amyloliquefaciens MU3M77. The optimal condiction for killer toxin production is a medium of 5% glucose, 1.25% peptone and 0.75% yeast extracts, pH 3.5, 150 rpm at 18℃ for 3 days of cultivation. The toxin activity against Bacillus amyloliquefaciens MU3M77 indicating the toxin derived from strain CG1S05 is thermotoleent after incubation under high 121℃, 20 minutes, below pH 3.5 and the inhibitory activity was lost under pH 6.0. Tetrapisispora namnaoensis CG1S05 demonstrated the higtest inhibitory activity to the bacteria, especially the Gram (+) bacterium (Staphylococcus aureus BCRC 10781) compared with yeasts and molds. Studying the mechanism of the toxin against Bacillus amyloliquefaciens MU3M77, after the cells exposed to the toxin at 25, 150 rpm for 24 hours, the cells showed tiny perforation on them. The toxin is supposed to act on the cel membrane or cell well.

陳麗淑、鍾文全、鍾文鑫。2010.台灣草莓灰徽病菌(Botrytis Cinera)對Strobilurin類殺菌劑之抗藥性機制探討。農林學報。第59卷第3期。第231 - 252頁。
楊倩宜、陳琦華、李明勳。2013。後天免疫缺乏症候群與肺囊蟲肺炎。藥學雜誌。第114冊第29卷第1期。第147 - 152頁。
Ahmed A.F.S., Ilan N., Shih T.M., Sturley S.L., and Goldstein S.A.N. 1999. A Molecular Target for Viral Killer Toxin TOK1 Potassium Channels. Cell. 99: 283-291.
Bevan E.A., and Makower M. 1963. The physiological basis of the killer character in yeast. Genetics Today XI International Congress on Genetics. 1: 202–203.

Boekhout T., Fell J.W., and O’Donnell, K. 1995. Molecular systematics of some yeast-like　anamorphs belonging to the Ustilaginales , and Tilletiales. Studies in Mycology. 38: 175-183.
Bradford M. M. 1976. A Rapid , and Sensitive Method for the Quantitation of Microgram Quantities of Protein Utilizing the Principle of Protein-Dye Binding. Analytical Biochemistry. 72: 248-254
Breinig F., Tipper D.J., and Schmitt M.J. 2002. Kre1p, the plasma membrane receptor for the yeast K1 viral toxin. Cell. 108: 395-405.
Bussey H. 1972. Effects of yeast killer factor in sensitive cells. Nature New Biology. 235: 73-75.
Bussey H. 1991. K1 killer toxin, a pore-forming protein from yeast. Molecular Microbiology. 5: 2339-2343.
Buyuksirit T., and Kuleasan H. 2014. Antimicrobial Agents Produced by Yeasts. International Scholarly and Scientific Research and Innovation. 8: 1114-1117
Cailliez J.C., Se’guy N., Aliouat E.M., Polonelli L., Camus D., and Dei-Cas E. 1994. The yeast killer phenomenon: a hypothetical way to control Pneumocystis carinii pneumonia. Medicine Hypotheses. 43: 167-171.
Carpenter C.F., and Chambers H.F. 2004. Daptomycin: another novel agent for treating infections due to drug-resistant gram-positive pathogens. Clinical Infectious Diseases. 38: 994-1000.
Chen P.H., Chen R.Y., and Chou J.Y. 2018. Screening and Evaluation of Yeast Antagonists for Biological Control of Botrytis cinerea on Strawberry Fruits. Mycobiology. 46: 33-46.
Chen S.F., Lo S.F., Chang C.F., and Lee C.F. 2013. Tetrapisispora taiwanensis sp. nov. , and Tetrapisispora pingtungensis sp. nov., two ascosporogenous yeast species isolated from soil. International Journal of Systematic , and Evolutionary Microbiology. 63: 2351-2355.
Ciani M., and Fatichenti F. 2001. Killer Toxin of Kluyveromyces phaffii DBVPG 6076 as a Biopreservative Agent To Control Apiculate Wine Yeasts. Applied and Environmental Microbiology. 67: 3058-3063.
Comitini F., and Ciani M. 2009. The zymocidial activity of Tetrapisispora phaffii in the control of Hanseniaspora uvarum during the early stages of winemaking. Letters in Applied Microbiology ISSN 0266-8254. •
Comitini F., Mannazzu1 I., and Ciani M. 2009. Tetrapisispora phaffii killer toxin is a highly specific β-glucanase that disrupts the integrity of the yeast cell wall. Microbiology Cell Factories. 8: 55.
Comitini F., Pietro N., Zacchi L., Mannazzu L., and Ciani M. 2004. Kluyveromyces phaffii killer toxin active against wine spoilage yeasts: purification and characterization. Microbiology. 150: 2535-2541.
Daren W.B. 2011. The KP4 killer protein gene family. Current Genetics. 57: 51-62.
Dilip N. 2018. Antimicrobial Stewardship: From Principles to Practice, British Society for Antimicrobial Chemotherapy, Birmingham, United Kingdom. ch1. pp: 12-26.
Douglas C.M., Sturley S.L., and Bostian K.A. 1988. Role of protein processing, intracellular trafficking and endocytosis in production and immunity to yeast killer toxin. European Journal of Epidemiol. 4: 400-408.
Drlica K., and Zhao X. 1997. DNA gyrase, topoisomerase IV, and the 4-quinolones. Microbiol Molecular Biology Review. 61: 377-392, 1092-2172
Dubois M., Gilles K.A., Hamilton J.K., Rebers P.A., and Smith F. 1956. Colorimetric Method for Determination of Sugars and Related Substances. Analytical chemistry. 28: 350-356
El-Banna A.A., El-Sahn M.A., and Shehata M.G. 2011. Yeasts Producing Killer Toxins: An Overview. Alex, ander Journal Food Sciences and Technology. 8: 41-53.
Felsenstein J. 1985. Phylogenies and the Comparative Method. The American Naturalist. 125: 1-15.
Flegelová H., Chaloupka R., Novotná J.D., Gášková K., Maláč D.J., and anderová S.B. 2003. Changes in plasma membrane fluidity lower the sensitivity of S. cerevisiae to killer toxin K1. Folia Microbiologica. 48: 761-766.
Fukuhara H. 1995. Linear DNA plasmids of yeasts. FEMS microbiology letters. 131: 1-9.
Golubev W.I. 2006. Antagonistic interactions among yeasts. In Biodiversity , and Ecophysiology of Yeasts; Rosa, C.A., Peter, G., Eds.; Springer-Verlag: Berlin, Germany. pp: 197-219.
Golubev W.I., Ikeda R., Shinoda T., and Nakase T. 1997. Antifungal activity of Bullera alba (Hanna) Derx. Mycoscience. 38: 25-29.
Graeme M.W., Anne H.M., and Valerie J. 1995. Hodgson. Interactions between killer yeasts and pathogenic fungi. EMS Microbiology Letters. 127: 213-222.
Gunge N., Tamaru A., Ozawa F., and Sakaguchi K. 1981. Isolation and characterization of linear deoxyribonucleic acid plasmids from Kluyveromyces lactis and the plasmid-associated killer character. Journal of Bacteriology. 145: 382-390.
Guo F.J., Ma Y., Xu H.M., Wang X.H., and Chi Z.M. 2013. A novel killer toxin produced by the marine-derived yeast Wickerhamomyces anomalus YF07b. Antonie van Leeuwenhoek. 103: 737-746.
Henninger W., and Windisch S. 1976. Kluyveromyces blattae sp. n., eine neue vielsporige Hefe aus Blatta orientalis. Archives of Microbiology. 109: 153-156.
Hidalgo P., and Flores M. 1994. Occurrence of the killer character in yeasts associated with wine production. Food Microbiological. 11: 161-167.
Hill D.M., and Bull J.J. 1993. An Empirical Test of Bootstrapping as a Method for Assessing Confidence in Phylogenetic Analysis. Systematics Biological. 42: 182-192.
Jablonowski D., Zink S., Mehlgarten C., Daum G., and Schaffrath R. Molecular. tRNAGlu wobble uridine methylation by Trm9 identifies Elongator's key role for zymocin‐induced cell death in yeast. Microbiology. 59: 677-688.
Kim H., Yoo S.J., and Kang H.A. 2015. Yeast synthetic biology for the production of recombinant therapeutic proteins. FEMS Yeast Research. 15:1-16.
Kitamoto H.K., Hasebe A., Ohmomo S., Suto E.G., Muraki M., and Iimura Y. 1999. Prevention of aerobic spoilage of maize silage by a genetically modified killer yeast, Kluyveromyces lactis, defective in the ability to grow on lactic acid. Applied Environment Microbiology. 65: 4697-4700.
Kitamoto H.K., Ohmomo S., and Nakahara T. 1993. Selection of killer yeasts (Kluyveromyces lactis) to prevent aerobic deterioration in silage making. Journal Dairy Science. 76: 803-811.
Klassen R., Paluszynski J.P., Wemhoff S., Pfeiffer A., Fricke J., and Friedhelm. 2008. The primary target of the killer toxin from Pichia acaciae is tRNAGln. Molecular Microbiology. 69: 681-697.
Klassen R., and Meinhardt F. 2002. Linear plasmids pWR1A and pWR1B of the yeast Wingea robertsiae are associated with a killer phenotype. Plasmid. 48: 142-148.
Klassen R., and Meinhard F. 2005. Induction of DNA damage and apoptosis in Saccharomyces cerevisiaebya yeast killer toxin. Cellular Microbiology. 7: 393-401.
Kohanski M.A., Dwyer D.J., and Collins J.J. 2010. How antibiotics kill bacteria: from targets to networks. Natural Review Microbiology. 8: 423-435.
Koltin Y., and Day P. 1976. Inheritance of killer phenotypes and double-stranded RNA in Ustilago maydis. Proceedings of the National Academy of Sciences. 73: 594-598.
Kulakovskaya T.V., Kulakovskaya E., and Golubev W. 2003. ATP leakage from yeast cells treated by extracellular glycolipids of Pseudozyma fusiformata. FEMS Yeast Research. 3: 401-404.
Kulakovskaya T.V., Shashkov A.S., Kulakovskaya E.V., and Golubev W.I. 2004. Characterization of an antifungal glycolipid secreted by the yeast Sympodiomycopsis paphiopedili. FEMS Yeast Research. 5: 247-252.
Kurtzman C.P., and Robnett C.J. 2003. Phylogenetic relationships among yeasts of the ‘Saccharomyces complex’ determined from multigene sequence analyses. FEMS Yeast Research. 3: 417-432.
Kurtzman C.P. 2003. Phylogenetic circumscription of Saccharomyces, Kluyveromyces and other members of the Saccharomycetaceae, and the proposal of the new genera Lachancea, Nakaseomyces, Naumovia, V, anderwaltozyma and Zygotorulaspora. FEMS Yeast Research. 4: 233-245.
Kurtzman C.P., Statzell-Tallman A., and Fell J.W. 2004. Tetrapisispora fleetii sp. nov., a new member of the Saccharomycetaceae. Studies in Mycology. 50: 397-400.
Liu G.L., Chi Z., Wang G.Y., Wang Z.P., Li Y., and Chi Z.M. 2013. Yeast killer toxins, molecular mechanisms of their action and their applications. Critical Reviews in Biotechnology. 35: 222-234
Magliani W., Conti S., Gerloni M., Bertolotti D., and Polonelli L. 1997. Yeast killer systems. Clinical microbiology reviews. 10: 369-400.
Marquina D., Santos A., and Peinado J.M. 2002. Biology of killer yeasts. International Microbiology. 5: 65-71.
McManus M.C. 1997. Mechanisms of bacterial resistance to antimicrobial agents. Americal Journal Health System Pharmaceutical. 54: 1420-1433.
Miyamoto M., Onozato N., Selvakumar D., Kimura T., Furuichi Y., and Komiyama T. 2013. The role of the histidine-35 residue in the cytocidal action of HM-1 killer toxin. Microbiology. 152: 2951-2958.
Morace G., Archibucci C., Sestito M., and Polonelli L. 1984. Strain differentiation of pathogenic yeast by the killer system. Mycopathologia. 84: 81-85.
Muccilli S., and Restuccia C. 2015. Bioprotective Role of Yeasts. Microorganisms. 3: 588-611.
Neu H.C. 1992. The crisis in antibiotic resistance. Science. 257: 1064-1073.
Oro L., Zara S., Fancellu M.I., Budroni M., Ciani M. , and Comitini F. 2013. TpBGL2 codes for a Tetrapisispora phaffii killer toxin active against wine spoilage yeasts. FEMS Yeast Research. 14: 464-471.
Oro L., Zararino S., Fancellu F., Mannazzu I., Budroni M., Ciani M., and Comitini F. 2013. TpBGL2 codes for a Tetrapisispora phaffii killer toxin active against wine spoilage yeasts. FEMS Yeast Research. 14: 464-71.
Peng Y., Chi Z., Wang X., and Li J. β-1,3-Glucanase Inhibits Activity of the Killer Toxin Produced by the Marine-Derived Yeast Williopsis saturnus WC91-2. Marine Biotechnology. 12: 479-485.
Petri W.A.J. 2005. Antimicrobial agents: sulfonamides, trimethoprim-sulfamethoxazole, quinolones, , and agents for urinary tract infections. International Goodman and Gilman’s The Pharmacological Basis of Therapeutics, McGraw- Hill Professional, New York. ch5. pp: 1111-1126.
Pfeiffer P., and Radler F. 1982. Purification and characterization of extracellular and interacellular killer toxins of Saccharomyces cerevisiae- strain 28. Journal General Microbiology. 128: 2699-2706.
Polonelli L., Conti S., Gerloni M., Magliani W., Chezzi C. , and Morace G. 1991. Interfaces of the yeast killer phenomenon. Critical reviews in microbiology. 18: 47-87.
Provost F., Polonelli L, Conti S., Fisicaro P., Gerlon M., and Boiron P. 1995. Use of yeast killer system to identify species of the Nocardia asteroides complex. Journal Clinical Microbiol. 33: 8-10.
Radler F., Pfieffer P., and Dennert M. 1985. Killer toxins in new isolates of the yeasts Hanseniaspora uvarum and Pichia kluyveri. FEMS Microbiology Letter. 29: 269-272.
Rhaisa A., and Ramirez C. 2016. Studies of Debaryomyces hansenii killer toxin and its effect on pathogenic bloodstream C, andida isolates. pp: 38-39.
Saitou N., and Nei M. 1987. The Neighbor-joining Method: A New Method for Reconstructing Phylogenetic Trees. Molecular Biochemisry and Evolution. 4: 406-425.
Santos A, Marquina D, Leal J.A., and Peinado J.M. 2000. (1-6)-β-D-Glucan as cell wall receptor for Pichia membranifaciens killer toxin. Application Environment Microbiology. 66: 1809-1813.
Santos A., Sa´nchez A., and Marquina D. 2004. Yeasts as biological agents to control Botrytis cinerea. Microbiological Research.159: 331-338.
Santos A., and Marquina D. 2004. Killer toxin of Pichia membranifaciens , and its possible use as a biocontrol agent against grey mould disease of grapevine. Microbiology.150: 2527-2534.
Santos A., Navascues E., Bravo E., and Marquina D. 2011. Ustilago maydis killer toxin as a new tool for the biocontrol of the wine spoilage yeast Brettanomyces bruxellensis. International Journal of Food Microbiology. 145: 147-154.
Schmitt M.J. 1995. Cloning and expression of a cDNA copy of the viral K28 killer toxin gene in yeast. Molecular Generale Genetics. 246: 236-246.
Schmitt M.J., and Breinig F. 2002. The viral killer system in yeast: from molecular biology to application. FEMS Microbiology Reviews. 26: 257-276.
Schmitt M.J., and Breinig F. 2006. Yeast viral killer toxins: lethality and self-protection. Nature Reviews Microbiology. 4: 212-221.
Seguy N., Cailliez J-C., Delcourt P., Conti S., Camus D., Dei-Cas E., and Polonelli L.1997. Inhibitory Effect of Human Natural Yeast Killer Toxin-like C, andidacidal Antibodies on Pneumocystis carinii. Molecular Medicine. 3: 544-552.
Siang Y.T., Tatsumura Y., and Fleming A. (1881–1955). 2015. Discoverer of penicillin. Singapore Medicine Journal. 56: 366-367.
Starmer W.T., Ganter P.F., Aberdeen V., Lachance M.A., and Phaff H.J. 1987. The ecological role of killer yeasts in natural communities of yeasts. Canadian Journal Microbiolgy. 33: 783-796.
Steinlauf, R., Peery, T., Koltin, Y., and Bruenn, J. 1988. The Ustilago maydis virusencoded toxin—Effect of KP6 on sensitive cells and spheroplasts. Experimental mycology. 12: 264-274.
Storm, D.R., Rosenthal K.S., and Swanson P.E. 1977. Polymyxin and related peptide antibiotics. Annu Rev Biochem. 46: 723-763.
Stringer J.R., Beard C.B., Miller, R.F., and Wakefield A.E. 2002. New Name for Pneumocystis from Humans and New Perspectives on the Host-Pathogen Relationship. Emergency Infection Disease. 8: 891-896.
Sumpradit T., Limtong S., Yongmanitchai W., Kawasaki H., and Seki T. 2005. Tetrapisispora namnaonensis sp. nov., a novel ascomycetous yeast species isolated from forest soil of Nam Nao National Park, Thail, and International Journal of Systematic and Evolutionary Microbiology. 55: 1735-1738.
Suzuki C. 2004. Acidophilic structure and killing mechanism of the Pichia farinosa killer toxin SMKT. In book: Microbial Protein Toxins. pp: 189-214.
Tačić A., Nikolić V., Nikolić L., and Savić I. 2017. Advanced technologies. 6:58-71.
Tamura K., Stecher G., Peterson D., Filipski A., and Kumar S. 2013. MEGA6: Molecular Evolutionary Genetics Analysis Version 6.0. Molecular Biology Evolution. 30: 2725-2729.
Ueda-Nishimura K., and Mikata K. 1999. A new yeast genus, Tetrapisispora gen. nov. : Tetrapisispora iriornotensis sp. nov., Tetrapisispora nanseiensis sp. nov. and Tetrapisispora arboricola sp. nov., frorn the Nansei Island, and reclassification of Kluyveromyces phaffii (van der Walt) van der Walt as Tetrapisispora phaffii comb. nov.. International Journal of Systematic Bacteriology. 49: 1915-1924.
Vagnoli, P., Musmano R.A., Cresti S., Maggio T., and Croatza G. 1993. Occurrence of killer yeasts in spontaneous fermentation from the Tuscany region of Italy. Applicaton Environment Microbiology. 59: 4037-4043.
Walker G.M. 1998. Yeast physiology and biotechnology. Wiley, New York.
Welsh J., and McClell, and M. 1990. Fingerprinting genomes using PCR with arbitrary primers. Nucleic Acids Research. 18: 7213-7218.
White T.J., Bruns T., Lee S. , and Taylor J. 1990. Amplification , and direct sequencing of fungal ribosomal RNA genes. Orl, ando, Florida: Academic Press.
Wickner R.B. 1996. Double-str, anded RNA viruses of Saccharomyces cerevisiae. Microbiology Review. 60: 250-265.
Williams J.G., Kubelik A.R., Livak K.J., Rafalski J.A., and Tingey S.V. 1990. DNA polymorphisms amplified by arbitrary primers are useful as genetic markers. Nucleic Acids Research. 18: 6531-6535.
Woods D.R., and Bevan E.A. 1968. Studies on the Nature of the Killer Factor Produced by Saccharomyces cerevisiae. Journal Generale Microbiology. 51: 115-126.
Yao J. , and Moellering R.J. 2003. Antibacterial agents. In: Manual of Clinical Microbiology., ASM Press, Washington D.C. pp. 1039-1073.
Young, T.W., and Yagiu M. 1978. A comparison of the killer character in different yeast and its classification. Anotonie van Leeuwenhoek Journal Microbiology Serology. 44: 59-77.
Zalar P., Gostinčar C., de Hoog G.S., Uršič V., Sudhadham M. and Gunde-Cimerman N. 2008. Redefinition of Aureobasidium pullulans and its varieties. Studies in Mycology. 61: 21–38.
Zhu, Y.S., Kane J., Zhang X.Y., Zhang M., and Tipper D.J. 1993. Role of the Gamma Component of Pretoxin in Expression of the Yeast K1 killer Phenotype. Yeast. 9: 251-266.