lecture 3 the main groups of fungi kingdom chromista i) slime moulds (not fungi) ii) true fungi...

Lecture 3

The Main Groups of Fungi

Lecture 3

The Main Groups of Fungi

• Kingdom Chromista i) Slime moulds (not fungi)

ii) True Fungi (Oomycetes)

Bio 318b

One scheme for classifying Chromista. This one leaves out the slime moulds placing them in the Protista.

Diatoms

Yellow-green algae

Bicoecids and Slime nets

Coccolithophorids - algae

Kelps (brown algae)

Golden algae

ChromistaChromista1. 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

SLIME MOULDSSLIME MOULDSWEB RESOURCES.• MyxoWeb

– http://www.wvonline.com/myxo/

• Fun Facts about Fungi.– http://www.herb.lsa.umich.edu/kidpage/factindx1.htm

• U. of California Museum of Paleontology.– http://www.ucmp.berkeley.edu/protista/slimemolds.html

• Movie http://www.cellsalive.com/dictyo.htm

SLIME MOULDSSLIME 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)

Chromistan Fungi

Myxostelidae.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

SLIME MOULDS .Fuligo sp. (top) and Stemonites sp. (bottom)

Photos.- courtesy of Dr. G. Thorn

Physarum polycephalum

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

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

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.

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.

Physarum polycephalum

Dictyostelidae.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.

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.

Plasmodiophoridaobligate parasites

Chromistan Fungi

Examples

Club root - cabbage

Powdery scab - potato

SLIME MOULDSSLIME MOULDS

Phylum MyxostelidaPhylum DictyostelidaPhylum LabyrinthulidaPhylum Plasmodiophorida

Plasmodiophora brassicaeClub root of cabbage familyThick 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

Roots of the infected plant swell greatly. Results in less growth of shoots -so reduction in yield.

Club root of cabbage Plasmodiophora brassicae

True Fungi - ChromistaTrue Fungi - Chromista• Phylum Hyphochytriomycota

• 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)

True FungiTrue Fungi• Phylum Hyphochytriomycota

– mostly live in water or soil– single cell or hyphae, sometimes develop rhizoids– no known sexual stages

Chromistan Fungi

True Fungi in ChromistaTrue 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.

http://www.ucmp.berkeley.edu/chromista/chromistasy.html

• 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)

oogonium with several eggs

antheridium oogonium

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.

White rust of crucifers

Albugo candida

downy mildew of grape Plasmopara viticola

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

Blue mould of tobacco

Peronospora tabacina

a branched aerial sporangiophore of Peronospora tabacina.

Oomycetes - late blight of potato - Phytophthora infestansOomycetes - late blight of

potato - Phytophthora infestans• Created havoc in Europe 1845-47 - 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.

See http://vassun.vassar.edu/~sttaylor/FAMINE/

late blight of potato Phytophthora infestans

Follow-up to lectureFollow-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.http://botit.botany.wisc.edu/toms_fungi/

Follow-up to lectureFollow-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.