Download Fungi

5. FUNGI
5.1. Introduction
Known from 17th cent., mycology 1729
Eukaryotic, filamentous or holocarpic
Fungal nuclei are haploid, except zygote
Hyphae with or within cross walls (septa)
Hyphae  2 – 10 m, length from m to
tenths m (miles)
Networks of hyphae = mycelium
Cell wall often with chitin (cellulose)
Mono-, di- and poly-karyotic structure
Heterokaryotic and homokaryotic cells
Achlorophyllous, chemoorganotrophic
Heterotrophic (saprophytic, parasitic)
rich in hydrolytic enzymes
Usually aerobic; yeasts facultatively
anaerobic; anaerobic – fungi in rumen of
cattle
Nutritional Adaptations of Fungi
Some features similar as bacteria –
chemoheterotrophs, nutrients absorption
Diferences:
 Good growth in acidic environment (pH
< 5)
 Aerobic organisms (yeasts facultatively
anaerobic)
 Resistant to osmotic pressure (high salt
and sugar concentrations)
 Growth at low moisture content
 Growth at low nitrogen content
 Metabolism of complex carbohydrates
(lignin)
5.2. Reproduction
 Vegetative: parents cells divide into 2
daughter cells, fragments of mycelia,
budding (yeasts)
 Asexual spores – conidia (Penicillium,
Aspergillus), chlamydospores,
arthrospores, sporangiospores (Mucor)
 Sexual reproduction:
(1)“parasexual processes” = fusion of two
genetically different nuclei;
(2) formation of sexual spores in gametangia
(antheridium, oogonium), no meiosis;
(3) fusion of nuclei often prolongated – cells
(mycelia) are dikaryotic
(4) sexual spores: ascospores (Ascomycota),
basidiospores (Basidiomycota)
5.3. Major division
Several changes in last decades, some former
fungi transferred to another kingdoms
The fungi kingdom (Mycota, Fungi)
embrasses: molds, mildews, rusts, smuts,
yeasts, mushrooms, puffballs)
PROTISTA
Plasmodiophora brassicae
Spongospora subterranea (Powdery
Scab of potatoes)
Slime molds
CHROMISTA Phyllum
 Oomycota
Phytophthora (potato, tomato)
Plasmophara (wine yard)
Pseudoperenospora (cucumber)
Pythium (both parasite and
biocontrol)
FUNGI
 Chytridiomycota
Synchytrium endobioticum (Black Scub –
potatoes)
 Glomeromycota
Endomycorrhizae in plants (vesicularasburcular)
 Zygomycota (=sugar fungi, =conjugation f.)
Sexual reproduction = mycelia fusion and
zygospore formation
Asexual r. = sporangiospores (sporangium)
Saprophytic
Mycelia lack septa – multinucleate mycelia
Genera: Rhizopus, Mucor – soil, fruit, food
spoilage, decomposition of pectin
 Ascomycota (=sac fungi)
Sexual reproduction by 8 ascospores in
ascus developed from dikaryotic
mycelium (the form of asci is important
for identification)
Asexual r. by chlamydo- or conidio-spores
Genera:
Taphrina (yeast - plant parasites),
Saccharomyces (ethanol fermentation,
vitamins production, bakery yeasts)
Claviceps (parasite on rye)
Candida (yeast used in feed mixtures)
o Deuteromycotina (Fungi imperfecti)
“Artificial group” - approx. 15000 species
Conidial stages of Ascomycetes (and
Basidiomycetes)
Sexual reproduction has not been primarily
observed
Genera: Alternaria, Aspergillus, Fusarium,
Geotrichum, Penicillium, Trichoderma
Several species are very important in
environment (esp. soil) – organic matter
decomposition
Often use as industrial microorganisms:
Aspergillus – enzymes, citric acid
Penicillium – antibiotic, cheese, salami
Trichoderma – enzymes
Some of them are food and feed spoilage
organisms with mycotoxin production:
Aspergillus – aflatoxin
Fusarium – zearalenon
 Basidiomycota
The most complex fungi, complicated life
cycle
Sexual reproduction by basidiospores on
basidia: + and – monokaryotic mycelia
developed from basidiospores fuse to form
dikaryotic mycelium; later basidia are
formed, where after nucleus fusion 4
haploid basidiospores are formed
on basidia
Asexual reproduction by fragmentation of
hyphae or by conidia
Both “moulds” and poisonous or edible
“mushrooms” are typical for this division
Genera: Amanita, Coprinus, Agaricus,
Boletus