Transcript 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)
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
Coccolithophorids algae
Kelps (brown
algae)
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
SLIME MOULDS
WEB 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
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)
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
Photos.- courtesy of
Dr. G. Thorn
SLIME MOULDS .Fuligo sp. (top) and Stemonites sp. (bottom)
Physarum polycephalum
The yellow blob is a
huge single cell
with millions of
nuclei. Its top speed
is 1 mm per hour.
Physarum polycephalum
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.
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.
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.
Chromistan Fungi
SLIME MOULDS
Plasmodiophorida
obligate parasites
Phylum Myxostelida
Phylum Dictyostelida
Phylum Labyrinthulida
Phylum Plasmodiophorida
Examples
Club root - cabbage
Powdery scab - potato
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
Club root of cabbage
Plasmodiophora brassicae
Roots of the infected plant swell greatly. Results in less
growth of shoots -so reduction in yield.
True Fungi - Chromista
• Phylum Hyphochytriomycota
• single anterior tinsel flagellum (B)
• Phylum Oomycota
• Two flagellae
• 1 whiplash, 1 tinsel (D)
Note - one phylum in the
Eumycota, the
Chytridiomycota also has
flagellae - just a single
posterior whiplash one. (A)
mastigonemes
Chromistan Fungi
True Fungi
• Phylum Hyphochytriomycota
– mostly live in water or soil
– single cell or hyphae, sometimes develop rhizoids
– no known sexual stages
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.
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)
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.
antheridium oogonium
oogonium
with several
eggs
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 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 matingtype 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 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 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.