Lecture 16. Ascomycota V

Transcription

1 Lecture 16 Ascomycota V - Lichenized fungi - Eurotiomycetes - Laboulbeniales Lutzoni et al., 2004, American Journal of Botany Lichen-forming Lichen-forming Sordariomycetes

2 Nature 21: Nuclear ribosomal DNA phylogeny Euascomycota - Reconstruction of ancestral character-states lichen-forming uncertain Hemiascomycota Archiascomycota Basidiomycota Generalities on Lichens LICHENS = a fungus + a photosymbiont (algae or cyanobacteria) : not a monophyletic group; LICHENS result from SYMBIOSIS between organisms from different Kingdoms ,000 recognized lichen species vs.a total of ~30,000 Asco species ==> lichen count for ca. > 40% of of all known Ascomycetes ==> one fifth of all known fungi! - Habitats: primary (eukaryotic) colonizers of harsh / abiotic habitats, including rocks; --- are found in the most extreme environments, e.g., sandstone deserts from hot Namibia to cold Antarctica and up to 7,000 m. high in Mt Everest slopes. Food for thoughts: Heckman et al., Science (2001) : speculate lichens as early colonizers of terrestrial habitats 1.5 byo Kendrick s textbook (2000) statement p.124: it has been suggested that if [early] life were found in another planet, it might well be lichen-like I consider it unlikely, because the existence of lichens depend on the previous existence of a fungus and an algae [on other planets] we should look for Archaebacteria

3 Generalities on Lichens The wedding partners: --- the fungus = an Ascomycota (very rarely a Basidio:e.g., Multiclavulina); more than one fungus can be associated to the same lichen colony. --- either an algae Trebouxia, in 80% of lichens: unicellular algae, which has never been found free-living, Trentepohlia (a filamentous, also free-living algae) or a filamentous cyanobacterium, often Nostoc. These three genera are the photobiont partner in > 90% of lichens Generalities on Lichens Trebouxia Nostoc Arrows show heterocysts, which are specialized cells that fix atmospheric nitrogen. (pics from Kendrick)

4 Generalities on Lichens Not necessarily lichenized (=captured by a fungus): Trentepohlia, a free living algae mostly found on lightexposedbark and rock. Generalities on Lichens Lichen thalli have five kinds of macromorphology (See Kendrick, Chapt. 7) (1) crustose -- so closely applied to the substrate that to collect them you often have to take some of the rock or bark they are growing on as well (2) foliose -- having leafy or tongue-like lobes which are not so closely applied to the substrate; (3) fruticose -- with upright or hanging, stalked, shrubby or hair-like thalli (fruticose means bushy, and has nothing to do with fruit); (4) squamulose -- the thallus is made up of small scales (5) leprose -- powdery, essentially made up of soredia-like aggregations, and lacking a cortex. Mixed macromorphology: E.g., in Cladonia the primary thallus is squamulose but there is also a secondary, upright, reproductive fruticose thallus called a podetium.

5 Generalities on Lichens fruticose Crustose / foliose 3) Asexual (vegetative) reproduction: - soredia: the upper surface of the thallus ruptures, exposing a powdery mass of propagules called soredia, which are small groups of algal cells entangled in fungal hyphae. - isidia: small, finger-like or branched structures called isidia, which grow up from the thallus, then break off. 4) Sexual reproduction: ascus ---> ascospores Generalities on Lichens 5) Lichens produce a wide array of unique secondary metabolites that have been used for systematics (chemotaxonomy); - many lichens have antibiotic properties and have been used in traditional medicine around the world. - extremely slow growth rate; best measured from old gravestones! - extreme longevity; some lichen colonies are thought to be > 4,000 year old - extreme sensibility to air pollution mostly acid rain and carbon dioxide; many cities are virtually lichen-free! Can be used for biocontrol of air-quality. See for instance:

6 Two small groups of lichens in the Sordariomycetes clade - Lichinomycetes - Arthoniomycetidae (= Arthoniomycetes) Lutzoni et al., 2004, American Journal of Botany Lichen-forming Lichen-forming Sordariomycetes

7 Sordariomycetes clade:lichinomycetes - derived from Dothideomycetidae - mostly crustose; bitunicate ascus - photobiont = generally cyanobacteria - Examples: Peltula tortuosa Anema nummularium Sordariomycetes clade: Arthoniomycetidae - photobiont = Trebouxia - mostly crustose; elongate apothecia with bitunicate ascus - Examples: Arthonia glaucomaria Roccella fusiformis %20Pilze/flechten_und_lichenicole_pilze2.htm

8 Lecanoroycetidae, Acarosporoycetidae, and Ostropomycetidae (three predominantly lichen-forming clades = Lecanoromycetes ) - includes the vast majority of lichens - sexual stage of the fungus = mostly Inoperculate Discomycetes (but also some perithecium) - many conflicts between traditional and molecular classification Visit (consider this website to be a mandatory reading) Some interesting or common Lecanoromycetes Letharia vulpina (the Wolf Moss ) - grows mostly on old or dead trees in dry, low temperature old growth coniferous forests; also on old wooden fenceposts. - known only from North America and Europe. - highly sensitive to human disturbance, especially the eradication of old growth forests It is now reportedly extinct in Finland!. - Toxic; widely used in both Native American and early European civilizations: ---- Scandinavians used to mix with meat to kill wolves, hence its common name, the Wolf Moss The Achomawi in Northern California used it to make poison arrowheads Water extracts also used as a medicine for internal problems and in stronger solution to wash external sores and wounds Also employed as a yellow dye for staining baskets and fibers.

9 Some interesting or common Lecanoromycetes Letharia vulpina (the Wolf Moss ) Some interesting or common Lecanoromycetes Xanthoparmelia chlorochroa - a "vagrant" lichen, not attached to any substrate and blown around by wind; - source of dye for Navajo weavers.

10 Some interesting or common Lecanoromycetes Usnea species - long use in traditional Chinese and European medicine, also by natives in the Pacific Islands and New Zealand. - contain usnic acid; recently used as antibiotic in salves and deodorants; also used in contemporary homeopathic medicine. Some interesting or common Lecanoromycetes Cladonia species Peltigera species

11 Eurotiomycetes Two clades: - Chaetothyriomycetidae Capronia, Verrucaria, Pyrenula, Dermatocarpon, Chaetothyriales - Eurotiomycetidae - ascomata = cleistothecium (sometimes lacking) - asci --- scattered within the cleistothecium (i.e. not forming an hymenium) --- thin walled, often ellipsoid, inoperculate, evanescent --- many conidial forms (anamorphs) known Major Orders: Ascosphaerales, Eurotiales and Onygenales Eurotiomycetes Ascosphaerales Genus Ascosphaera - associated with bees: --- feed on pollen and nectar(saprobic); --- some species pathogens on larvae. - ascospores become united in cysts From Alexopoulos

12 Eurotiomycetes Ascosphaerales Genus Eremascus - lacks ascomata (secondary loss?), otherwise typically ascomycota (no yeast phase known as in Archaeascomycota or Hemiascomycota) - basically, multiple, independent formation of asci from the mycelial mat, - saprophytic From Alexopoulos Eurotiales Eurotiomycetes - Many genera known as teleomorph of Penicillium and Aspergillus spp., and other phialidic anamorphs. (Note that neither Penicillium or Aspergillus are monophyletic ) - Major genera: Talaromyces, Eupenicillium, Eurotium, Emericella Talaromyces anamorphs: Penicillium, Paecilomyces... Pics from Malloch s web site Eurotium anamorphs: Aspergillus,... Eupenicillium anamorphs: Penicillium,... Myco/fiches/Eochra.htm

13 Penicillium Talaromyces From Alexopoulos Eurotiomycetes Eurotiales: Emericella Emericella nidulans A. Colony on Oatmeal agar, 14 days at 25 C. B. Macrograph of the conidial heads and ascoma. C-D. Hülle cells: C. 700x; D. 1200x. E. Conidiophore and conidia 1700x. F. Ascospores 1600x. Note the Aspergillus anamorph

14 Eurotiomycetes Onygenales - High diversity in cleistothecium types. - species with the ability to degrade keratin (a major component of skin, hairs, nails, horns, feathers etc ) are all found in this order ===> associations with animals (saprobic or pathogens); pathogenic forms generally the anamorph (sometimes yeast-like), which may have an optimal growth temperature at 37C! Some important genera of human / animals pathogens: - Ajellomyces, Coccidioides, Arthroderma Arthroderma species Conidial anamorphs Microsporum, Trichophyton - saprobic in soil, ringworm on skin Eurotiomycetes Onygenales - High diversity in cleistothecium types - Taxonomic diversity From Alexopoulos

15 Eurotiomycetes Onygenales Ajellomyces capsulatum Yeast anamorph = Histoplasma capsulatum - lung infection; in immunodepressed people the disease can spread to other body parts including bones <===> More info from cleistothecium Eurotiomycetes Onygenales Ajellomyces dermatitidis Yeast anamorph Blastomyces dermatitidis (mutinucleate, generally 2-5 nuclei) - skin disease& lesion in humans, dogs, cats etc.; widespread in Africa More info from <===> Blastomyces dermatitidis Ajellomyces dermatitidis: simple cleistothecium

16 Eurotiomycetes Onygenales An anamorph Coccidioides immitis: teleomorph not known - systemic human pathogen; also grow in soil - generally starts from lung infection; can transfer to other body parts; allergic reactions (e.g. reddening of skin) - dimorphism mycelium <==> asexual endospores (better adapted for circulation in the blood) <===> More info from Laboulbeniales / Laboulbeniomycetes - All the ca 1700 described morphospecies are invariably found attached to the exoskeleton of insects, or occasionally, millipedes and mites. - Poorly studied group; evolutionary relationships to other Ascomycota still unclear;. - apparently, don't produce anamorphs; - extreme species and site-specificity: many species are only found in one part of their insect host, for example, on a particular limb, or restricted to either males or females. Fig. on the right: Development of Stigmatomyces baerii on houseflies: An ascospore (A) becomes attached to the animal, germinates, and sends a foot into the exoskeleton to absorb nutrients. Although haustoria may penetrate as far as the epidermal cells, there is never any real invasion of host tissues. The ascospore develops a median septum, and the upper cell becomes differentiated into a male organ, with several phialide-like cells (B) that produce spermatia. The lower cell then develops an ascogonium with a trichogyne, which is fertilized by the spermatia (C). Several asci then develop from the ascogonium, and eventually deliquesce. The mature ascoma is spine-like, projecting from the exterior of the host, and can be seen with a hand-lens (D). Other genera exhibit the same basic features (Hesperomyces - E and Corethromyces - F). From Kendrick