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