The yeasts

Foreword

NO class of microoiganisms has been more intimately associated with the progress and development of the human race than the yeasts. Since the earliest times, these microorganisms have been used to bring about changes which it would have been difficult to have accomplished by other methods. Since microscopic examinations have revealed the presence of yeast cells in bread found with Egyptian mummies, it is known that these people were familiar with yeast fermentations, although they probably did not have explanations for the changes which were observed. The Norsemen prepared an alcoholic drink from milk, as is done today by certain nomadic races, the fermentation of which was, in part, caused by yeasts. Today we find the yeasts of ever-increasing interest and importance. The food microbiologist must understand the physiology of these organisms if he is to successfully cope with them. They are assuming greater importance in medicine, especially in relation to certain deficiency diseases, constipation, and skin infections. Great industries have been established which rest entirely on the chemical changes brought about by yeasts and their enzymes; some of them would be developed with difficulty, we.re it necessary to use strictly chemical methods. The compressed yeast industry itself has reached a high state of development with its several factories located in different parts of America and distributing agencies in practically all of the cities and villages. Many industries have been greatly changed by the availability of fresh, active yeast whenever it is needed. Despite the facts that yeasts have always been of great significance to the human race and that they will probably have greater significance in the future, it remained for Guilliermond to collect the various data, which have accumulated in regard to them, into one volume. Several treatises have been prepared which deal with the yeasts in relation to fermentations, but no real definitive treatise on the yeasts, as such, has appeared which is comparable to the volume prepared by Guilliermond. The investigations of this authority make the book especially valuable. These facts made it seem advisable to translate the volume for publication in the English language in order that the data might be available to the practitioners and students who do not read

v

' 42;]?;;, vi FOREWORD

the French language. It is sincerely hoped, however, that the rendition of this book into the English language will in no way inhibit the study of the French language — that language in which Pasteur, Bernard, Magendie, Berthelot, and others have published their classic investigations.

This English edition is based on Guilliermond's " Les Levures," which was published in 1912, appearing as a volume in the section on Cryptogamic Botany of Encyclopedic Scientifique. This series is edited under the direction of Doctor Toulouse. To merely translate a volume on a subject which is being developed as rapidly as the yeasts would be entirely inadequate. Consequently with the collaboration of Professor Guilliermond, the translator has added much new material which has been published since 1912. Without the assistance of Professor Guilliermond, this could not have been done as completely. The English edition may not, then, be regarded as a mere translation of the last French edition.

The rendition of a text from a foreign language into the English language is beset with difficulties which are most clearly appreciated by those who have performed similar pieces of work. In all cases a literal translation has not been attempted; however, the opinions of the original author have been given as closely as possible. It is trusted that this English edition will make it easier for students to pursue their study of these important microorganisms and for the practitioner to more easily solve the problems with which he has to cope. I owe many thanks to my colleagues, too numerous to mention here, for expression of their advice at various times and for their interest during the progress of the work.

URBANA, ILLINOIS June, 1919

Author's Preface

SINCE the celebrated memoir by Pasteur on alcoholic fermentation, the yeasts have never ceased to assume an ever-increasing importance in agriculture and the industries. The classic investigations by Pasteur, followed by those of Hansen, have shown the profit that may result from a methodical study of the various species of yeasts, by a knowledge of the conditions necessary for their development and biochemical characteristics for application to the fermentation industries. No one may overlook the benefits which came to such industries by the use of pure cultures and selected species, and the avoidance of yeasts which caused defects in fermented products. The fermentologists have also benefited greatly by these methods. Finally, the relatively recent investigations have shown the relationship of yeasts to certain diseases in man and animals.

From a purely theoretical point of view the yeasts, on account of the facility with which they allow themselves to be cultivated in artificial media, and by the relatively large size of their cells, are especially favorable objects for experimentation upon which very important investigations of physiology, cytology and sexuality have been made. They have contributed appreciably to the progress of general physiology and biology.

It seemed useful to me to collect into one book all of the knowledge required on the morphology, physiology and taxonomy group of fungi, and to arrange it in such a manner that the data would be available for biologists, practitioners in industrial work, agriculturalists and physicians. That is what I attempted to accomplish in the little volume published in the Encyclopedic Scicntifique under the editorial supervision of Dr. Toulouse.

Professor Tanner, of the University of Illinois, undertook the translation of this book into the English language in order to render it more accessible to American students and American investigators. This is indeed a great honor to me, one which I did not dream of when I prepared this modest work a few years ago. I am very happy to have this indication of friendship between scientific America and France, a friendship which I hope may become stronger and stronger. One sufficiently understands the significance of a scientific alliance of

vii viii PREFACE

two nations which by their individual characteristics supplement each other. France claims such great teachers as Lamarck, Claude Bernard, and Pasteur, true pioneers in the field of biology. By her spirit perhaps, too traditionalistic and suppressed by old administrative machinery, she has not always understood fully the real utility of her universities and given to her scientists the necessary means for carrying on their work. On the other hand, America, with no such rich heritage from the past, has built up modern laboratories with a new spirit and equipped them with the necessary resources. She probably possesses the greatest universities in the world. She lays claim to able investigators and, thanks to her marvelous scientific organization and to her numerous investigators, is sure to gain very rapidly a foremost place in the scientific world. If the American savants have the desire to profit by the discoveries of the French, their elders, France has much to gain by imitating America in her practical ideas, her spirit of organization, her methods of work, and her tremendous activity.

The book which Professor Tanner has undertaken to present to the public cannot be regarded as a simple translation of my work; it is a new edition resulting from intimate collaboration of translator and author. Microbiology is progressing so rapidly that the French edition, now six years old, is no longer abreast with recent acquisitions of the science. It was found necessary to make numerous editions and to modify certain chapters in which Professor Tanner and myself have shared the labor. Professor Tanner, known by his work on the biochemistry of bacteria, has undertaken the revision of the Chapter on Physiology of the Yeasts which was no small task, for since the discovery of zymase by Buchner, the biochemical investigations on yeasts have followed each other without interruption and have become increasingly valuable. As for myself, I have borne the task of revising the Chapters on Morphology, Phylogeny and Description of Species, subjects with which I am more familiar. Professor Tanner had, then, a preponderant part in the translation of this new edition and the book has certainly gained much by the collaboration of a physiologist so well qualified.

ALEXANDRE GUILLIERMOND

LYON, September 8, 1919

Contents

PAGE

FOREWORD v

AUTHOR'S PREFACE vii

INTRODUCTION 1

History of the Study of Yeasts. . . '. 3

Chapter I Morphology And Development Op The Yeasts

1. General Characters of Yeasts; the Different Phases in Their Development. 5

2. Forms of Yeast Cells 6

3. Mycelial Formations 8

4. Cell Division 9

a. Budding 9

b. Transverse Division 10

5. Durable Cells 12

6. Sporulation 13 a. Copulation Preceding the Formation of the Asc 15

b. Copulation of Ascospores or Parthenogamy 23

c. Retrogradation of Copulation — Parthenogenesis 25 a. Direct Germination of Ascospores in Asc 35

Chapter II Cytology Of Yeast

1. General Considerations; Historical 37

2. The Nucleus 38

3. The Cytoplasm and Its Different Constituents 39

a. Metachromatic Corpuscles « 39

b. Glycogen 43

c. Basophile Granules 44

d. Fats 44

4. The Membrane 45

5. Changes in the Cell during Fermentation 46

6. Cytological Phenomena during Vegetative Multiplication 47

7. Cytological Phenomena of Sporulation 48

ix x CONTENTS

PAGE

Chapter III Physiology, Nutrition, Respiration, And Alcoholic Fermentation

1. Chemical Composition of Yeasts 53

2. General Considerations of the Enzymes in Yeasts 58

3. Proteolytic Enzymes in Yeasts 59

a. Proteases 59

b. Nucleases or Enzymes of Nucleo-Proteins 60

4. Lipase 61 a. Polysaccharides 62

b. Trisaccharides 63

c. Disaccharides 63

d. Glucosides : 65

6. Oxidizing and Reducing Enzymes 66

7. Toxins 67

8. Nutrition of Yeasts 68

a. Mineral Elements 68

b. Nitrogenous Substances 69 ,

c. Hydrocarbon Compounds 75

9. Respiration 80

10. General Characteristics of Alcoholic Fermentation 81

a. Conditions Necessary for Its Production 82

b. General Occurrence of Alcoholic Fermentation 84

c. Comparison of Intramolecular Respiration with Alcoholic Fermen-

tation 84

d. Differences in the Fermenting Function in Different Yeasts 85

11. Fermentable Sugars 86

12. Formula of Alcoholic Fermentation and Secondary Products 88

13. Characteristics and Properties of Buchner's Zymase 89

14. Mode of Action of Zymase 94

15. General Theories of Alcoholic Fermentation 99

a. Pasteur's Theory 99

b. Wortmann and Delbriick's 100

c. Theory which Makes Fermentation a Phase of Respiration 101

16. Autophagy or Autolysis of Yeasts 104

CHAPTER IV PHYSIOLOGY (continued)

1. Habitat of Yeasts 106

2. Duration of Life of Yeasts. 107

3. Action of Physical Agents on Yeasts 108

a. Temperature 108

b. Light 109

c. Moisture 109

d. Metals and Salts 109

e. Pressure Ill

/. Antiseptics Ill

CONTENTS xi

PAGE

Physiological Conditions of Budding 112

Particular Types of Budding. Scums and Rings. Physiological Conditions for their Production 112

Parasitism of Yeasts. Pathenogenic Properties. Symbiosis 120

a. Parasitism 120

b. Pathenogenic Properties of Yeasts 122

c. Symbiosis of Yeasts — 124

Chapter V

ORIGIN OF THE YEASTS; THEIR POSITION IN CLASSIFICATIONS OF THE FUNGI AND THEIR SYSTEMATIC RELATIONSHIPS

1. Historical 131

a. Experiments on the Transformation of Molds into Yeasts 131

6. Studies in Life Cycles of Yeasts in Nature 134

c. Morphological and Cytological Studies on Yeasts 137

2. Phylogeny of the Yeasts. Their Affinities in the Group of Ascomycetes. 139

Chapter VI

METHODS OF CULTURE AND ISOLATION OF YEASTS. PROCEDURES FOR

OBSERVATION

1. Methods of Culture 147

a. Culture media 148

6. Methods for Obtaining Sporulation 150

2. Methods of Purification and Isolation of Yeasts 153

a. Physiological Methods 154

6. Dilution Methods for Separating Yeasts 154

1. Hansen's Method 155

2. Lindner's Method 157

3. Determination of the Number of Cells in a Culture and a Study of the Power

of Multiplication of Yeasts 157

4. Methods for Studying the Yeasts 15$

a. Observation on the Development in Moist Chambers 158

6. Methods for Examining the Cytology of Yeasts 158

c. Methods for Determining the Action of Yeasts Towards the Carbo-

hydrates 161

d. Determination of Efficiency of Yeasts 163

5. Preservation of Yeasts . . 164

Chapter VII Methods For The Characterization And Identification Of Yeasts

1. Character of the Vegetation in the Sediment 167

2. Shapes and Dimensions of Cells 167

3. Optimum Temperatures and Temperature Limits for Budding 167 xii CONTENTS

PAGE

4. Thermal Death Points of Species of Yeasts 168

5. Temperature Limits and Optimum Temperature for Spore Formation . . . 168

6. Sexuality, Morphological Characters of the Ascs and Ascospores, Germina-

tion of Ascospores 170

7. Temperature Conditions for Scum Formation and Ring Formation 171

8. Macroscopic Appearances of Cultures on Solid Media 173

9. Giant Colonies • 174

10. Biochemical Activities of Yeasts ' 174

11. Methods for Determination of Species Torula, Mycoderma and Patho-

genic Yeasts 176

Chapter VIII

1. Morphological Variations 178

a. Temporary Variations. Polymorphism 178

b. Permanent Variations. Polymorphism 179

2. Physiological Variations 184

Chapter IX Classification Of The Yeasts

1. Family of Saccharomycetes ' 193

a. First Group 193

b. Second Group 193

c. Third Group 194

d. Fourth Group , 195

e. Fifth Group 195

2. Family of Non-Saccharomycetes 196

CHAPTER X FAMILY OF NON-SACCHAROMYCETES First Group

GENUS I. — Sohizosaccharomyces.

Schizosaccharomyces octosporus 197

" Pombe, Lindner 199

" mellacei, Jorgensen 200

" asporus, Eykmann 202

" aphalarae calthae, Sulc 202

" Formosensis, Nakayaza 203

" Sautawensis, Nakayaza 204

" Nokkoensis, Nakayaza 204

" chermetis abietis, Sulc 205

CONTENTS xil

Second Group

GENUS II. — Zygosaccharomyces. PAGE

Zygosaccharomyces Barkeri (Barker), Saccardo-Sydow 206

" priorianus, Klocker 206

" javanicus, de Kruyff 207

" japonicus, Saito 207

" soya? (Saito), Guilliermond 209

" lactis a, Dombrowski 210

" Bailii (?) (Lindner), Guilliermond 211

manshuricus, Saito 212

mellis addi, Richter 212

" Nadsonii, Guilliermond. 213

" major, Takahashi and Yukawa 215

chevalieri, Guilliermond 216

salsus, Takahashi and Yukawa 218

Asporogenic Species of Zygosaccharomyces 219

Yeast F, Pearse and Barker. 219

Yeast G, Pearse and Barker 220

Zygosaccharomyces bisporus, Anderson 220

GENUS III. — Debaromyces, Klocker.

Debaromyces globosus, Klocker 221

" tyrocola, Konokotin 222

GENUS IV. — Nadsonia.

Nadsonia fulvescens '. 222

" elongata, Konokotin 223

GENUS V. — Schwanniomyces, Klocker.

Schwanniomyccs occidentalis 224

GENUS VI. — Torulaspora.

Torulaspora delbrucki, Lindner . 225

Yeast E and F of Rose 225

Saccharomyces lactis 7, Dombrowski. 226

Third Group GENUS VII. — Saccharomycodes, Hansen.

Saccharomyces, ludwigii, Hansen 227

" Behrensianus, Behrens 229

" comesii, Cavara 230

GENUS VIII. — Saccharomycopsis (Schionning).

Saccharomyces guttulatus (Robin), Schionning 230

GENUS IX. — Saccharomyces, Meyen.

A. First Sub-Group.

Saccharomyces cerevisiae, Hansen 231

Will's Yeasts 233

Yeast of Saaz and Frohberg 233

Saccharomyces carlsbergensis, Hansen 234

monacensis, Hansen 235

" Pastorianus, Hansen. 237

" intermedius, Hansen 238

Logus Yeast, Van Laer and Denamur 241

Saccharomyces ettipsoideus, Hansen 241 xiv CONTENTS

PAGE

Yeasts Related to Ellipsoideus 242

Johannisberg Yeast 1 243

Johannisberg Yeast II 243

Saccharomyces vini, Miintzii 243

" turbtdans, Hansen 244

" willianus, Saccardo 245

" bayanus, Saccardo 246

" ilids, Gronlund 246

" aquifolii, Gronlund 246

" piriformis, Marshall- Ward 247

" vordermannii, Went and Prinzen-Geerligs 247

sake, Yabe 247

" cartilaginosus, Lindner 248

" batatae, Saito 248

" multisporus, Jorgensen 248

" mali risleri, Kayser 249

Cider Yeasts of Pearse and Barker 249

Saccharomyces Tokyo, Nakazawa 250

" Yeddo, Nakayaza 251

Saccharomyces of Shiro-Koji, Saito . . * 251

" T and V of Ludwig Rose 252

B. Second Sub-Group.

Saccharomyces marxianus, Hansen 252

" manshuricus, Saito 253

" exiguus, Rees-Hansen 254

" Zopfii, Artari 254

" Coreanus, Saito 255

" " Forma Major, Saito 256

" Jorgensii, Lasche 256

C. Third Sub-Group.

Saccharomyces rouxii, Boutroux. 256

Yeast from Pulque, No. 2, Guilliermond 257

Saccharomyces soja, Takahashi and Yukawa 258

" Lindneri, Guilliermond 260

" paradoxus, Barschniskaia , 260

" Mangini, Guilliermond 261

" chevalieri, Guilliermond 262

" Etienne, Potron 263

D. Fourth Sub-Group.

Saccharomyces mali Duclauxi, Kayser 264

" unisporus, Jorgensen 264

E. Fifth Group.

Saccharomyces fragilis, Jorgensen 264

" flava lactis, Krueger . 265

" acidi lactici, Grotenfelt 266

" lactis a, Dombrowski 266

" lactis ft Dombrowski 266

. Yeast from Koumys, Schipin 267

Saccharomyces anamensis, Will 268

" taette, major and minor, Olsen-Sopp 268

CONTENTS xv

F. Sixth Sub-Group. PAGE

Saccharomyces conglomerates, Reess 269

Hansenii, Zopf 269

'• theobromae, Preyer 269

Yeast from Salt, Hoye 270

Saccharomyces anginae, Achalme and Troisier 270

" tumefaciens (Curtis), Basse 270

" granulatus, Vuillemin and Legrain 271

" Blanchardii (Blanchard), Guiart 271

" minor, Engel 272

uvarum, Beijerinck 272

" Lemonniere, Sartory and Laneur 273

GENUS X. — Hansenia, Lindner-Klocker.

Hansenia apiculata, Lindner 273

" valbyensis, Klocker 275

Fourth Group GENUS XI. — Pichia.

Pichia membranaefaciens, Hansen 275

// and ///, Pichii 277

" hyalospora, Lindner 277

" taurica, Siefert 278

" tamarindorum, Siefert 278

" californica, Siefert 278

" radaisii, Lutz 279

" farinosa, Lindner 279

" suavebleus, Klocker 280

" alcoholophila, Klocker 281

" polymorpha, Klocker 281

" calliphora, Klocker . . 281

" mandshuricus, Saito ". 282

Yeast from Pulque No. 1, Guilliermond 282

Pichia orientalia, Beijerinck 283

Saccharomyces mycoderma punctisporus, Melard 283

GENUS XII. — Willia, Hansen 283

Wittia anomala, Hansen 284

Biological Varieties of Willia anomola ' . . . . 284

Willia anomola 7, Steuber 285

" //, Steuber 286

" IV, Steuber 286

11 belgica, Lindner 287

" wichmanni, Zikes 287

" anomala, Saito 287

" salurnus, Klocker 288

Fifth Group

GENUS XIII. — Monospora, Metschnikoff.

Monospora cuspidatat Metschnikoff 290 xvi CONTENTS

GENUS XIV. — Nematospora, Peglion. PAGE

Nematospora coryli, Peglion 290

" Lycopersici, Schneider 291

GENUS XV. — Coccidiascus, Chatton 292

Coccidiascus Legeri, Chatton 292

Chapter XI Family Of Non-saccharomycetes Or Doubtful Yeasts

I. GENUS TORULA, Turpin.

A. Torula from Breweries or Various other Sources.

Hansen's Torula 293

Will's Torula : 295

Torula of Lindner and Meissner 299

Torula novae cralsbergiae, Gronlund 299

" brettanomyces, Clausen 299

Beijerinck's Torula 300

Torula colliculosa, Hartmann 301

Saccharomyces spec, Saito 301

" awamori, Inui 302

De Kruyff 's Torula 302

Torula of Pearse and Barker 302

Saccharomyces brassicae I, Wehmer 303

" II, Wehmer 303

Torula holmii (Holm), Jorgensen 304

" thermantitonum, Johnson 304

Torula from Vaccine Pulp, Lesieur and Mangini 304

Torula of Rose 305

Wehmer's Torula 305

Torula sp., Saito 306

Hoyes Torula 306

B. Torula from Milk.

Torula kephir, Heinze and Cohn 307

Saccharomyces tyrocola, Beijerinck 307

Freudenreich's Kephir Yeast 307

Duclaux's Torula 307

Torula lactis (Adanletz), Heinze and Cohn , 308

Kayser's Yeast 309

Torula communis, Browne 309

Lactomyces inflans caseigana, Bochicchio 310

Saccharomyces iebenis, Rist and Khoury 310

Torula kephir, Nokolajewa 311

Torula ellipsoidea, Nikolajewa 311

" amara, Harrison 311

Dombrowski's Torula 311

C. Yeasts from Fats.

Saccharomyces olei, Van Tieghem 313

Roger's Torula 313

CONTENTS xvii

PAGE

D. Colored Torula 314

Torula pulcherrima, Lindner 314

" mucilaginosa, Jorgensen 314

" dnnabarina, Jorgensen 315

Red Torula, No. 36, Janssens and Martens 315

Torvla glutinis, Pringsheim and Bilewsky 316

Cryptococcus bainieri, Sartory 318

Pseudosaccharomyces Stevensi 318

Cryptococcus verrucosus, Anderson 319

ovoideus, Anderson 320

glabratus, Anderson 320

agregatus, Anderson 321

Kramer's Red Torula 321

Saccharomyces japonicus, Yabe 322

" keiskeana, Yabe 322

Torula 'bogoriensis rubra, De Kruyff 323

" rubefaciens, Grosbusch 323

GENUS II. Pseudosaccharomyces, Klocker 323

Pseudosaccharomyces apiculatus, Klocker. 323

apiculatus parasiticus, Klocker 324

Saccharomyces macropsidis lanionis, Sulc 325

Pseudosaccharomyces austricus, Klocker 325

" Africanus, Klocker 325

" cortid, Klocker 325

" Mullen, Klocker 325

" Lindneri, Klocker 326

" Germanii, Klocker 326

Jensenii, Klocker 326

" Malaianus, Klocker. . ; 326

La/an, Klocker 326

Willii, Klocker 326

antillarum, Klocker 327

" occidentalis, Klocker '. . : 327

" . sautranzensis, Klocker 327

" indicus, Klocker 327

of Will 327

Torula nigra, Marpmann 328

Torula from "Soya" Mash, Kita 330

III. GENUS MYCODERMA, Persoon.

Mycoderma cerevisiae, Desm, Hansen 331

vini, Desm 331

Henneberg 333

cucumerina, Aderhold : . . 334

" valida, Leberle-Will 334

gallica, Leberle-Will 334

decolorans, Wull 335

Saito's Mycoderma 335

Brusendorf 's Mycoderma 336

Saccharomyces mycoderma I , Wehmer 336 xviii CONTENTS

PAGE

DuClaux's Yeast (Mycolevure) 336

Mycoderma from Pineapple, Kayser 337

" lebenis, Rist and Khoury 337

Dombrowski's Mycoderma from Milk 338

Mycoderma Chevalieri, Guilliermond 339

Mycoderma of Fischer and Brebeck 340

" monosa, Anderson 341

rugosa, Anderson 341

tannica, Asai 342

IV. GENUS MEDUSOMYCES, Lindau.

Medusomyces Gisevii, Lindau 343

CHAPTER XII Cryptococcus degenerans, Vuillemin 345

gilchristi, Vuillemin 345

tokishigei (Tokishige), Vuillemin 346

" farciminosus, Rivolta and Micellone 348

" hominis (Busse), Vuillemin 348

" linguae-pilosae, Vuillemin 349

" Lithogenes, Vuillemin 349

Granulomatogenes, Vuillemin 350

niger (Maffuci and Sirleo), Vuillemin 350

" Plimmeri, Costantin 351

" Corsellii, Corselli and Frisco 351

" De Gotti and Brazzola 351

hominis Costantini (Constantin) 352

Kleinii, Erich Cohn 352

" Anobii, Escherich 352

" Parasitaris (Trabut), Vuillemin 353

" Psoriaris, Rivolta 353

" Capillitii, Vuillemin 353

" ovalis, Vuillemin 353

Cavicola, Arthault 353

neoformans, San Felice 354

" of Clerc and Sartory 354

Blastomyces Hessleri, Rettger 354

Cryptococcus ruber, Vuillemin 355

Guilliermondia, Brauverie and Lesieur 355

Lesieuri, Beauverie and Lesieur 356

sulfureus, Beauverie and Lesieur 356

rogeri, Sartory and Demanche 356

Salmoneus, Sartory 357

Le Dantec's Yeast 357

Saccharomyces membranogenes, Steinhaus 357

Atelosaccharomyces of Hudelo, De Beurmann and Gougerot 358

CONTENTS xix

PAGE

Atelosaccharomyces of Brewer and Wood 359

Harteri (Harter), De Beurmann and Gougerot 359

Mercier's Yeast 360

Saccharomyces Conomeli and Limbati, Karel Sulc 360

CHAPTER XIII FUNGI RELATED TO THE YEASTS Endomyces albicans, Vuillemin 361

Parasaccharomyces Ashfordii, Anderson 364

Thomasii, Anderson 365

Endomyces Lindneri, Saito 366

" Hordei, Saito 366

" capsularis, Guilliermond 367

" fibuliger, Lindner 370

javanensis, Klocker 373

" Cruzi, Mello and Paes 374

Monilia Candida, Boborden 375

Monilia nigra, Browne 378

Monilia fusca, Browne 378

Geiger's Pseudomonilia 378

Pseudomonilia albomarginata, Geiger 378

rubescens, Geiger 379

" mesentericus, Geiger 379

" cartilaginosa, Geiger 379

Monilia vini, Osterwalder 379

Parendomyces pvlmonalis, Plaut 380

INDEX 417

THE YEASTS

THE YEASTS

INTRODUCTION What are Yeasts?

"|" TNDER the name of yeasts have been generally grouped all micro- « organisms which, when placed in sugar solutions, decompose V*^ them into alcohol and carbon dioxide — cause alcoholic fermentation. Knowledge with regard to the chemical properties of the yeasts has, to a great extent, preceded that with regard to their nature. The old word yeasts (Fr. levure = Latin lever) which emphasized their chemical properties dates from an epoch when no attention was given to their biological significance or nature. But today the name yeast has taken on a restricted meaning among botanists. In the botanical sense, yeasts are unicellular fungi of biochemical interest, spherical or oval in shape, and which multiply by budding. A yeast, then, is a fungus with special morphology. Be that as it may, the term is not applied to an indefinite group of fungi but to a natural one. Many fungi, more or less developed, living normally with a mycelium are able to reproduce by budding of their filaments, to form cells which have the shapes of yeasts. These multiply in their turn by budding and retain the form of yeasts for many generations. (Fig. 1.) The basidiospores of certain Basidiomycetes (Calcera viscosa) and ascospores of certain Ascomycetes (Sphaerulina intermixta Taphria) give rise to yeasts and it is only after living for a certain time in this form that the yeast cells elongate filaments and produce a mycelium. Among the Ustilaginaks, the sporidia, which spring from the promycelium, exist also in the shape of yeasts; it is this state in which they develop, and which they constantly retain when cultivated in artificial media. The Mucors, when placed in sugar solutions, are able to dissociate their filaments into round bodies, or buds, in a similar manner as the yeasts. Dematium pullulans (Fig. 1), a mold with a well-differentiated mycelium, produces in a regular fashion, by budding of its filaments, numerous yeast conidia; when these are cultivated under certain conditions, they are transformed with difficulty into mycelium. Vegetation with forms like yeasts is, then, rather widespread among the fungi.

Aside from these fungi, in which yeast forms are merely stages of development, there are others which live constantly in the forms of

INTRODUCTION yeasts. These do not present a true mycelium at any time. They reproduce at times by elongation of their cells, which adhere together, forming structures resembling mycelium; but these never offer the complexity of a typical mycelium. In the category of yeasts belong the alcoholic ferments and all of the fungi more generally known under the name of yeasts.

These yeasts, which are often designated as " true yeasts " in contradistinction to " yeast-like fungi " derived from more highly

developed fungi, are not distinguishable in any manner from the latter. The general form and the internal characteristics of the cells are the same in both cases. Physiologically, certain true yeasts differ only from yeast forms of molds by their resistance to anaerobic conditions and exceptional activity of the fermenting function, but very many yeast-like structures, derived from fungi more highly developed, are equally capable of producing alcoholic fermentation, and only differ, from this point of view, from true j^easts by a decreased activity of fermentation. On the

F^l.-Dematiumpullulans. °ther hand> a certaif1 nUmbu6r °f tme

1 to 4, Mycelium Forming Yeasts; 5, yeafits ar6 totally deprived of the ferment-

*>-ocess of ing function. It is understood then, how the early investigators were much confused when it became necessary to characterize the yeasts.

In the meantime, an essential difference which did not escape investigators existed between the yeast-like fungi and the yeasts properly so-called. Indeed, most of the true yeasts are distinguished closely from " yeast-forms " by their aptitude to produce resistant endospores at certain stages in their life cycles (unfavorable conditions), in the interior of their cells; the cells are then transformed into sporangia. De Bary, Rees, and Hansen first compared these sporangia to ascs of Ascomycetes, considering the true yeasts as autonomous fungi which live only in the form of yeasts and are incapable of developing a mycelium.

This conception is definitely admitted today, as we shall see when the origin and systematic relationships of the yeasts are taken up. The autonomy of the yeasts and their incorporation as a group of Ascomycetes have been demonstrated only since Hansen observed their life cycles in nature and since certain investigators have given evidence in the origin of the asc of certain yeasts, of the presence of

Myc

Yeast-Like Bodies m Budding (after Loew).

INTRODUCTION 3

a sexuality quite comparable to that which is observed in the lower Ascomycetes. The yeasts make up a family of the Ascomycetes known as Saccharomycetes.

True yeasts never produce endo- or ascospores. Do they represent forms derived from more highly developed fungi and made constant by a long adaptation to this condition? Or, are they true Saccharomycetes having lost, by a series of unknown circumstances, their aptitude of forming spores? We shall see that a definite loss of this characteristic has often been proved among the Saccharomycetes during certain special conditions. Be that as it may, the origin of the yeasts is entirely ignored; the Saccharomycetes are then separated and regarded as yeasts of uncertain origin. In this book, we shall examine extendedly only the true yeasts; first, yeasts with ascospores, or Saccharomycetes; secondly, those cells which exhibit all the characteristics of Saccharomycetes with the exception of ascospore formation and which, from the above, one might call pseudo-yeasts. All of those yeast-like structures of other fungi will be neglected. True yeasts are very abundant in nature; over five hundred are known. The limits of our study must be rather wide.

History of the Study of Yeasts

The study of yeasts is intimately associated with that of fermentation. The idea that alcoholic fermentations are caused by living organisms originated with Linne. In 1680 Leewenhoek first described the yeasts. He described them as globular bodies, oval or spherical in shape. In 1799 Fabroni compared yeasts to albuminoids. About 1825, and for some time after this, Mitscherlick, Cagnard-Latour, Schwann, and Kiitzing demonstrated that beer and wine yeasts were composed of cells which multiplied by budding. In 1839 Schwann observed, for the first time, endospores in yeasts. He proved that they might be freed by a rupturing of the cell wall.

But the nature of yeasts has been definitely known since the period in which Pasteur commenced his investigations on fermentation. Up to this time, it was known that beer yeast multiplied when introduced into saccharine wort; it was believed that it was formed spontaneously and that, in the yeast, was an occult force which produced the fermentation; that was all there was to it. With Pasteur, definite knowledge with regard to yeasts commenced. It was in 1859 that he established, by his memorable experiments which cannot be reproduced here on account of the lack of space, that fermentation is correlative with the life of yeasts. Some years later, he demonstrated the impossibility of spontaneous generation

4 INTRODUCTION

and introduced the methods of pure culture which permitted a morphological study of yeasts.

After this, the yeasts were subjected to many investigations. In the meantime, the methods of culture were not quickly taken up, and their perfection was rather slow. It was also difficult for the earlier investigators to distinguish between yeasts and other microorganisms which developed at the same temperature. The early work on yeasts conflicted with the erroneous conceptions of the pleomorphists who maintained that the microorganisms could be reduced to a small number of species capable of exhibiting different shapes dependent upon the conditions. About 1871, Bechamp reported that the acetic acid bacteria could change into yeasts. In 1872, Trecul thought that he had obtained the transformation of the spores of Penicillium glaucum into yeasts. In 187£, Robin stated that many of the yeasts (Torula cerevisiae, Mycoderma cerevisiae) are, with Penicillium glaucum, only forms of the same fungus. A little later, however, very careful investigations were reported. Between 1868 and 1870, Rees observed endospores in many species of yeasts, and gave the first accurate description of these organs. This was followed by the work of Engel, Seynes, Brefeld, and de Bary. The last of these, in his " Morphology and Biology of the Fungi," classed the yeasts among the Ascomycetes.

The introduction and perfection of pure cultures permitted the exact morphological studies of the yeasts. This was the work of Hansen, who is the true founder of this study, and whose name marks a second step in the history of the yeasts. Through his careful investigations for a period of 30 years, this mycologist perfected methods which were introduced by Pasteur for culturing and isolating the yeasts. He succeeded in inoculating cultures with a single cell and separating one species from another. By careful studies on the morphological and physiological properties of yeasts, Hansen found the characteristics which allowed the differentiation of one species from another. He has thus been able to characterize a large number of species the majority of which are known. Hansen is responsible for our knowledge of the life cycle and the systematic relationships of the yeasts. In recent years, he has proposed a classification which has been universally accepted.