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Lecture 3 The Main Groups of Fungi

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1 Lecture 3 The Main Groups of Fungi
Bio 318b Lecture 3 The Main Groups of Fungi Kingdom Chromista i) Slime moulds (not fungi) ii) True Fungi (Oomycetes)

2 One scheme for classifying Chromista
One scheme for classifying Chromista. This one leaves out the slime moulds placing them in the Protista. Golden algae Diatoms Bicoecids and Slime nets Yellow-green algae Kelps (brown algae) Coccolithophorids - algae

3 Chromista 1. Slime moulds - not really fungi
no hyphae amoeboid phases often coenocytic - no cell walls to plasmodial stages 2. Those considered as fungi with motile stages have hyphae with walls of cellulose or other non-chitin material. (The Eumycota have chitin in the walls) have motile cells bearing flagellae hyphae are diploid

4 Some slime moulds

5 SLIME MOULDS WEB RESOURCES. MyxoWeb Fun Facts about Fungi.
Fun Facts about Fungi. U. of California Museum of Paleontology. Movie

6 SLIME MOULDS Phylum Myxostelida Phylum Dictyostelida
Chromistan Fungi SLIME MOULDS Phylum Myxostelida e.g. Stemonitis (Fig 2.1) and Physarum Phylum Dictyostelida e. g. Dictyostelium (Fig 2.2) Phylum Labyrinthulida Phylum Plasmodiophorida e.g. Plasmodiophora (Fig 2.4)

7 Myxostelida e.g. Stemonitis
Can see amoeboid, diploid plasmodia of these organisms in soil, ingesting bacteria etc. Form a slimy mass Some species form stalked sporangia in which meiosis occurs, giving amoeboid or biflagellate haploid spores Fuse in pairs to re-establish diploid plasmodia

8 SLIME MOULDS .Fuligo sp. (top) and Stemonites sp. (bottom)
Photos.- courtesy of Dr. G. Thorn SLIME MOULDS .Fuligo sp. (top) and Stemonites sp. (bottom)

9 Physarum polycephalum
The yellow blob is a huge single cell with millions of nuclei. Its top speed is 1 mm per hour.

10 Physarum polycephalum
Slime molds cause very little damage. The plasmodium ingests bacteria, fungal spores, and maybe other smaller protozoa.

11 Physarum polycephalum
The millions of nuclei in a single plasmodium all divide at the same time. This makes slime molds ideal tools for scientists studying mitosis.

12 Physarum polycephalum
If the plasmodium begins to dry out too quickly or is starved, it forms a survival structure called a sclerotium The plasmodium can also produce a stalked reproductive structure containing the spores.

13 Dictyostelida e.g. Dictyostelium
Separate amoeba attract together ( due to cAMP which they release) - form large pseudoplasmodial ‘slug’ (an aggregation of many amoebae rather than a true plasmodium). This then elongates vertically and releases new amoebae.

14 How do the amoebae find each other to aggregate ?
Not done by "leader" amoebae. Instead each amoeba pumps out a chemical that leaves an invisible trail. Other amoebae cross the trail, follow it and strengthen it More amoebae are attracted by the stronger concentration till eventually all of the amoebae gather themselves into a pseudoplasmodium. What’s the connection between slime moulds and video games ? - Mathematical equations written to explain slime mold aggregation changed slightly and used in the programming of action figures in video games. Equations have also used in program StarLogo which mimics the activities of groups such as ant colonies and flocks of birds, whose orderly patterns of activity also occur without the direction of a leader.

15 Plasmodiophorida obligate parasites
Chromistan Fungi SLIME MOULDS Plasmodiophorida obligate parasites Phylum Myxostelida Phylum Dictyostelida Phylum Labyrinthulida Phylum Plasmodiophorida Examples Club root - cabbage Powdery scab - potato

16 Plasmodiophora brassicae
Club root of cabbage family Thick walled resting spores release zoospores - find new host by chemotaxis - encyst - inject protoplast into root hair. These form plasmodia inside root hair - release zoospores - infect root cortical cells - form large secondary plasmodia - meiosis - resting spores

17 Club root of cabbage Plasmodiophora brassicae
Roots of the infected plant swell greatly. Results in less growth of shoots -so reduction in yield.

18 True Fungi - Chromista Phylum Hyphochytriomycota Phylum Oomycota
single anterior tinsel flagellum (B) Phylum Oomycota Two flagellae 1 whiplash, 1 tinsel (D) mastigonemes Note - one phylum in the Eumycota, the Chytridiomycota also has flagellae - just a single posterior whiplash one. (A)

19 True Fungi Phylum Hyphochytriomycota Chromistan Fungi
mostly live in water or soil single cell or hyphae, sometimes develop rhizoids no known sexual stages

20 True Fungi in Chromista
Phylum Oomycota many live in water or soil some important pathogens have diploid hyphae (most other fungi have haploid hyphae) oogamous reproduction - separate antheridia and oogonia (fig 2.9). cellulose cell walls, (other fungi have chitin) WEB Resource.

21 Phylum Oomycota many important pathogenic species - often spread by aerial spores Saprolegnia - water mould on fish (fig2.10) Plasmopara - downy mildew of grape (fig 2.12) Peronospora - blue mould of tobacco, Phytophthora - late blight of potatoes Pythium - damping off disease (fig 2.11) Albugo - white rust of crucifers (cabbages etc)

22 oogonium with several eggs
Hyphae are diploid - meiosis occurs in the antheridia and oogonia to produce haploid nuclei. Fusion of antheridium nuclei with oospores in oogonium restores diploid state. oogonium with several eggs antheridium oogonium

23 White rust of crucifers
Albugo candida

24 downy mildew of grape Plasmopara viticola

25 Plasmopara viticola, the downy mildew of grapes.
A native of North America, in the late 1870s it was accidentally introduced to Europe at a time when the French wine industry was concerned over a massive aphid infestation. They brought resistant vine strains over from America to graft their roots onto their own grapes. However, these American stocks also brought the downy mildew which almost wiped out the entire French wine industry. The industry was saved by the serendipitous discovery of Bordeaux mixture, a mixture of lime and copper sulfate, This discovery is also important for being the first known fungicide, and in fact the first chemical used to control a plant disease

26 Blue mould of tobacco Peronospora tabacina

27 a branched aerial sporangiophore of Peronospora tabacina.

28 Oomycetes - late blight of potato - Phytophthora infestans
Created havoc in Europe e.g wiped out Irish potato crop - sole food of many poor people. Caused more than 1 million deaths - 3 million to emigrate - America. Heterothallic sp. But until 1976 only 1 mating-type in anywhere except Mexico - its origin - so was asexual. Since then, other mating-type has arrived and sexual reproduction has started - so disease becoming a problem again.

29 See

30 late blight of potato Phytophthora infestans


32 Follow-up to lecture read Chaps. 2 and 3 text/Web/CDROM
review today’s lecture slides on Bio318b Web page check out some Web pages - e.g Tom Volk’s Fungi.

33 Follow-up to lecture know main groups of Chromistan fungi and how to distinguish. Important economic species key life cycles - Plasmodiophora, Saprolegnia, Pythium, Plasmopara. review terms - saprobic/parasitic; chitin/cellulose; chemotaxis. rhizoid, anisogamy, antheridia, oogonia, oospore, sporangium, plasmodium, whiplash, tinsel, eucarpic, holocarpic.

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