Ascomycota (continued)

MIKROSKOPIK

YEAST, RAGI, KHAMIR… DLL

KULIAH 7

PEMBAGIAN ASCOMYCOTA

Class 1: Laboulbeniomycetes

parasitic attachments to arthropods.

Class 2: Protoascomycetes

lack of ascogenous hyphae and ascomata.

Class 3: Euascomycetes

most 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

Conidia

Arthrospores

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

Brewing

Baking

Food production

Industrial applications

Model systems (S. cerevisiae)

Probiotics

Animal 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 anamorph

Cleistothecial wall surrounded by hülle cells

Ascospores 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 anamorph

Cleisothecia 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

Talaromyces

Paecilomyces 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 production

Penicillium roqueforti—blue cheese

Penicillium spp.—blue and green molds on bread, cheese, fruits, vegetables

Aspergillus flavus—aflatoxins (moldy peanuts)

A. flavus/A. niger--aspergillosis

Penicillin

Penicillium 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 organism

21 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

Characteristics

Mycelium is mostly superficial Anchored to host epidermis by appressoria

Nutrients obtained via haustoria Haustoria are intracellular structures

Overwinter 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 chains

One 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 fall

Asci Formed in basal layer Globose to pyriform Discharge of spore by rupture of ascus tip

Asci/Ascospores

One to numerous asci/cleistothecium

Ascospores hyaline, one-celled, ovoid

1-8 ascospores/ascus

Number of asci/cleistothecium is important character in identification

From APSnet.org

Identification

Anamorph type

Number of asci/ascocarp

Cleistothecial appendages Mycelioid Rigid

Spear-like with inflated base

With curled tips

With dichotomously branched tips

Microsphaera alni cleistothecia

Sawadaea bicornis cleistothecia

Sawadaea bicornis cleistothecial appendages

Mycelioid Appendages

Several 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