Ascomycota (continued)

MIKROSKOPIK

YEAST, RAGI, KHAMIR… DLL

KULIAH 7

PEMBAGIAN ASCOMYCOTA

Class 1: Laboulbeniomycetesparasitic attachments to arthropods.

Class 2: Protoascomyceteslack of ascogenous hyphae and ascomata.

Class 3: Euascomycetesmost of the fungi which form ascomata. The orders are separated on the structure of the ascus and the manner of ascus opening.

From Spatafora et al. 2006. A five-gene phylogeny of Pezizomycotina. Mycologia 98: 1018-1028

Filamentous ascomycetes

Sacccharomycetales

Archiascomycetes

Basidiomycetes

Characterized by DNA sequence analysis

Ascocarps; ascogenous hyphae; specialized ascus tip; conidia; Woronin bodies

Absence of ascogenous hyphae and ascocarps; most asci without specialized tips

Classification from Alexopoulos et al. 1996

RAGI

Ascomycetous yeastsCharacterized by absence of ascogenous hyphae and ascocarpsAsci mostly prototunicateOccur in slime fluxes, nectar, fresh or decaying fruit—able to grow in high osmotic conditions (high sugar content)Others occur in soil, dung, water, digestive tracts of animalsMany species are symbiotic with insects

Schizosaccharomyces

Saccharaomyces

Somatic structures

Yeast A single-celled fungus

that reproduces by budding (or fission)

Pseudomycelium Series of cells

adhering after budding

Budding

Bipolar Multilateral

Asexual reproduction

ConidiaArthrospores

plasmogamy

copulation

karyogamy

budding

2n somatic cells

meiosis

Mature ascus

1n somatic cells

Identification

Microscopic appearance Unicellular or budding Size & shape of yeast cells Multilateral or bipolar budding Form, structure and mode of ascus formation Ascospore shape

Identification

Physiological tests—91 different tests Ferment different sugars Assimilation tests (carbon and nitrogen

source) Vitamin requirements Growth at 37C Growth in cyclohexamide Hydrolyse urea Form acid

Importance

BrewingBakingFood productionIndustrial applicationsModel systems (S. cerevisiae)ProbioticsAnimal pathogens

MICROSCOPIC (NON-YEAST)

From Hanlin, 1998. Illustrated Genera of Ascomycetes Vol II

Ascospore by D. Geiser

•Aspergillus anamorph•Cleistothecia yellow to orange-red•Wall composed of single layer of flattened cells• Ascospores flattened, usually with equatorial groove.

Eurotium

Aspergillus anamorphCleistothecial wall surrounded by hülle cellsAscospores small, colored, lens-shaped with flange

From Hanlin, 1998. Illustrated Genera of Ascomycetes Vol II

Emericella

Emericella

Hülle cells, D. Geiser

Anamorphs--Aspergillus

SEM by Charles Mims

Penicillium anamorphCleisothecia hard, white becoming colored (yellow, orange, brown)Ascospores small, hyaline or yellowish, lens-shaped

From Hanlin, 1998. Illustrated Genera of Ascomycetes Vol II

Eupenicillium

Image by David Geiser

Anamorphs--Penicillium

phialides

Branches (metulae)

From Hanlin, 1998. Illustrated Genera of Ascomycetes Vol II

TalaromycesPaecilomyces or Penicillium anamorphCleistothecium whitish to bright yellowWall composed of interwoven hyphaeAscospores ellipsoidal, with spiny walls

Anamorphs--Paecilomyces

Divergent phialides with swollen base and long, tapering neck

Colonies may be pink, purple, yellow, brown or white, but never green as in Penicillium spp.

The good and the bad

Penicillium spp.—antibiotic productionPenicillium roqueforti—blue cheesePenicillium spp.—blue and green molds on bread, cheese, fruits, vegetablesAspergillus flavus—aflatoxins (moldy peanuts)A. flavus/A. niger--aspergillosis

PenicillinPenicillium notatum growing in Alexander Fleming’s Petri dish of Staphylococcus in 1928 led to the discovery of penicillinHoward Florey & Ernest Chain (1939) began work on purification and trials1941—work moved to US (NRRL in Peoria, IL) to escape bombing in London (WWII)

Fermentation vessels and corn steep liquor Mary Hunt (“Moldy Mary”) brought in P. chyrogenum

on a melon1945—Fleming, Florey & Chain received Noble Prize

Penicillium notatum

Penicillin prevents cross-linking of small peptide chains in peptidoglycan, the main wall polymer in bacteria. Newly formed cells are abnormal in shape and susceptible to osmotic lysis.

Fungal taxon/group Est. # species # known metabolites

Aspergillus, Eurotium, Emericella 200 525

Penicillium, Talaromyces, Eupenicillium 200 380

Trichoderma, Hypocrea 20 54

Cephalosporium-like hyphomycetes 140 116

Mucor, Rhizopus, Phycomyces 70 26

Oomycetes, Chytridiomycota 450 3

Yeasts 600 50

Basidiomycetes 30,000 300

POWDERY MILDEW

Biotrophs of vascular plants Biotroph: an obligate parasite growing on another

living organism21 genera, 437 species infecting > 40,000 species of plants (mostly dicots)Most species are host specific, a few are omnivorous, infecting hundreds of host species

Powdery Mildew Symptoms

Photo by Claudia Nitschwitz

CharacteristicsMycelium is mostly superficial

Anchored to host epidermis by appressoriaNutrients obtained via haustoria

Haustoria are intracellular structuresOverwinter as mycelium in infected buds or as ascomataAsexual reproduction via conidiaSexual reproduction via ascospores formed in cleistothecia

Asexual reproduction

Erect, hyaline conidiophores are usually formed on superficial mycelium;One-celled, hyaline thin-walled conidia are produced holoblastically in basipetal chainsOne colony can produce > 30,000 conidia

Conidia

Wind-dispersedGermination can occur at low relative humidityGermination involves germ tube, appressorium and penetration peg formationApex of penetration peg enlarges to form haustorium

From APSnet.org

Plant cell wallPlasma membrane

Host cytoplasm

Plasma membrane

haustorium

appressorium

Penetration peg

fungus

Microsphaera alni anamorph on Vaccinium

Sexual reproduction

Cleistothecia formed on superficial mycelium in late summer/early fallAsci Formed in basal layer Globose to pyriform Discharge of spore by rupture of ascus tip

Asci/Ascospores

One to numerous asci/cleistotheciumAscospores hyaline, one-celled, ovoid1-8 ascospores/ascusNumber of asci/cleistothecium is important character in identification

From APSnet.org

Identification

Anamorph typeNumber of asci/ascocarpCleistothecial appendages Mycelioid Rigid

Spear-like with inflated baseWith curled tipsWith dichotomously branched tips

Microsphaera alni cleistothecia

Sawadaea bicornis cleistothecia

Sawadaea bicornis cleistothecial appendages

Mycelioid AppendagesSeveral asci/ascocarp:

Eryisiphe (100 spp)Oidium anamorph

One ascus/ascocarp: Sphaerotheca (50 spp.)

Appendages with curled tipsOidium anamorph

Dichotomously branched appendage tips

One ascus/ascocarp: Podosphaera (12 spp.)

Oidium anamorph

Several asci/ascocarp:

Sawadaea (6 spp.)Oidium anamorph

Spear-like appendages--Phyllactinia

Ovulariopsis and Streptopodium anamorphs

Appendages with curled tips

Uncinula (81 spp) Oidium anamorph Several asci/ascocarp