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Molds and Yeasts
Classification of organismsSystems of classification: A. The “old” system
2 Kingdoms-- Plants and Animals3 Kingdoms--Plants, Animals, Fungi5 Kingdoms--Plants, Animals, Fungi,
Bacteria, Protists
Classification of organisms
B. Newer systems3 Domains--
Archaea-primitive extremophiles Bacteria-more advanced? prokaryotesEukarya-Plants, Animals, Fungi,
Protists
Classification of fungi
C. Several ways to classify fungi: a. Based on nutrition b. Based on morphology of reproductive
structures
Classification of fungi a. Modes of nutrition (DeBary 1831-1888) 1. Saprophytes-nutrition derived from dead
organic material (ex. Agaricus) 2. Parasites-nutrition derived absolutely from
living host (ex. athletes foot)3. Facultative saprophytes-can exist for a time as a saprophyte (ex. smuts)4. Facultative parasites-primarily saprophytic but may attack living organisms (ex. Aspergillus)
Classification of fungi
b. Reproductive structures- 1. Basidiomycota 2. Ascomycota
3. Zygomycota4. Chytridiomycota
Classification of fungi
Basidiomycota- form their spores on
basidia (club shaped)
Classification of fungi
Ascomycota- form their spores in asci (sac-like)
Classification of fungi
Zygomycota- form their spores at the
junction of two gametangia
Classification of fungi
Chytridiomycota- form motile cells at some stage in their life
history
Molds vs. Yeasts (Habitat)Molds – found in most environments
particularly the soil where they cause decay of plants and animals; soil and water (parasites of plants and animals (multicellular)
Yeasts – water, soil, dust, fruits and vegetables (one-celled or unicellular)
Mold – cottony or velvety growths (mass of mycelium)
- mature, spore bearing heads are generally colored
- unripe spores and mycelium are white or colorless
- grow very slowly thus not used in routine biochemical testing
Yeast – colonies are usually soft, opaque, 1 – 3 mm in size, and cream-colored
Molds vs. Yeasts (Cultural Characteristics)
Molds vs. Yeasts (Structure/Function)Mold- with hyphae (nonseptate or septate)
Yeast – with thick rigid wall surrounds the protoplasm of the mature cellGenerally larger than bacteria (1 to 5 um in
width and 5 to 30 um in length); spherical to ellipsoidal
Contains inclusions like granules of glycogen and volutin (stain reddish brown with iodine and pink on volutin in solution of neutral red)
With distinct, usually eccentric nucleus seen by special staining
Molds v s. Fungi (Mode of Nutrition)Molds – saprophytic (live on dead or decaying
organic matter (outside its body) by decomposing wastes and dead bodies of plants and animals in soil and water, then absorb and utilize the digested products for foodChemo organotrophic: obtain nutrition from non-
living organisms
Yeasts - Mainly saprophytic, decomposing a variety of dead organic material
Mold vs. Yeast (Conditions Affecting growth)Molds 1) abundant moisture
2) supply of organic matter and oxygen3) warm humid environment (accelerate growth)4) environment containing large amounts of sugar (high osmotic pressure) like surface of jellies and jams
Yeasts - mostly aerobic (oxidize glucose completely to CO2 and H2O through the citric ac cycle); some facultative aerobe converts glucose through fermentation (using yeast enzyme) into alcohol and carbon dioxide
Mold vs. Yeast (Reproduction)Molds - by germination of asexual or sexual
spores or both
Yeasts - some produce true filamentous growth by fission but mostly form buds (usually asexual through budding)
Molds vs. Yeasts (significance)Molds
1) highly destructive causing deterioration of products like wood, leather, paper, fabrics and glass lenses2) Cause diseases in cultivated plants and humans3) enzymes of certain molds act on the curd, during the ripening process of Camembert, roquefort and blue cheese4) commercial and medical uses (production of alcohol, adhesive, citrates and gluconates, and ergots)5) Gallic acid – important in dye and ink industries
Molds vs. Yeasts (significance)Yeasts
1) used in the manufacture of food 2) industrial fermentation (wine, whiskey, rum and brandy, beer, glycerin)3) lactose fermentation (fermented milk drinks)4) cause diseases such as meningitis, thrush
Examples of Molds and YeastsMolds
Penicillium camembertiP. roquefortiiClaviceps purpureaPenicillium notatum
YeastSaccharomyces cerevisiaeSaccharomyces ellipsoideusCryptococcus neoformans
Classification of organisms
rustsrusts aquatic fungiaquatic fungi mushroomsmushrooms
Kind of Asexual SporesArthrospore – spore formed by
fragmentation of the tip of the hyphaeBlastospore – produced as an outgrowth
along a septate hypha.Conidiospores – unprotected spores
formed by mitosis at the tips of the hyphaeSporangiospores – spores produced within
a sac called sporangium
PhycomycetesMost primitive: algae-like fungiHabitat: Water, soil and all sorts of decaying matterStructural Characteristics: Mass of interangled filaments
and grow as fluffy colonies (coenocytic or nonseptate mycelium)
Reproduction: Asexual and sexual1) Asexual – production of sporangiospores (both motile and non-motile); by external conidiospores (conidia)2) Sexual – formation of thick walled zygospore or oospore
Examples: Saprolegnia (water mold): infects goldfishRhizopus (bread mold); appear as white or gray fuzzy
growth on bread or other starchy foodsMucor: cottony in soil, rotting manure, fruits and other
organic matter
AscomycetesWith unicellular form like yeastsHabitat: freshwater, swampsStructural Characteristics: septated myceliumReproduction: Asexual and sexual
a) Asexual: budding (yeasts), cell division, segmentation or production of conidiosporesb) Sexual: production of ascospores
Example: Penicillium – mold that give characteristic green
or olive green color; source of penicillin antibiotic
DeuteromycetesOther Name: Fungi ImperfectiCharacteristics: with septate mycelium; most
pathogenic fungi in manReproduction
- asexual: formation of conidia and other forms of asexual spores
Examples:Aspergillus niger (most common): with sooty, black
conidia while others appear golden to yellowsh green
Aspergillus fumigatus – AspergillosisCandida, Alternaria, Coccidiodies immitis and
Blastomyces dermatitis
BasidiomycetesNone are pathogenic to man except in
mushroom poisoning and crytococcus in immunocompromised host
ReproductionSexual: production of basidiospores (sexual
spores on a base called basidium)Examples
Rusts and smuts which parasitize plants and few yeasts large fleshy fungi-like mushroom, puffballs and bracket fungi, and Cryptococccus
Pseudomycetes1) Myxomycetes (slime molds)
Free-living organisms existing as: Motile, amoeboid masses (spores) in one stage Sessile, spore-bearing, fungus-like forms in
another stage Example. Mycetozoa or fungus animals
2) Schizomycetes (fission fungi) Unicellular, chlorophyl free and reproduce by
binary fission