Lecture 24 slime molds

1. Plasmodial Slime Plasmodial Slime
MoldsMolds

2. http://www.ucmp.berkeley.edu/chromista/chromistasy.html
Ribosomal RNA phylogenies place slime molds as unrelated, early
branching eurkaryote lineages

3. Actin, elongation factor, and β-tubulin phylogenies place the plasmodial and
cellular slime molds as a monophyletic group close to Animal + FungI
Baldauf and Doolittle, 1997. PNAS 94
(22): 12007-12012

4. ClassificationClassification
Mycetozoa = cellular, plasmodial slime Mycetozoa = cellular, plasmodial slime
molds plus protostelidsmolds plus protostelids
Cellular slime molds and protostelids now Cellular slime molds and protostelids now
placed in phylum Myxomycotaplaced in phylum Myxomycota
Names imply a fungal-like affinityNames imply a fungal-like affinity

5. MyxomycotaMyxomycota
Myxomycetes--5 orders, 13 families, 62 Myxomycetes--5 orders, 13 families, 62
genera, 800 speciesgenera, 800 species
Characterized by Characterized by plasmodiumplasmodium

Engulfs bacteria, fungal spores, small pieces Engulfs bacteria, fungal spores, small pieces
of organic matterof organic matter

6. PhysarumPhysarum life cycle life cycle
macrocyst
karyogamy
meiosis
microcyst
Synchronous mitotic divisions

7. Stages in Life CycleStages in Life Cycle
Spores (2nSpores (2nn)n)

4-20 4-20 µmµm, pigmented , pigmented
ornamented; meiosis ornamented; meiosis
in spore = 4 nuclei; 3 in spore = 4 nuclei; 3
degeneratedegenerate

8. Stages in Life CycleStages in Life Cycle
Myxamoebae (n)Myxamoebae (n)

feed, divide, convert to feed, divide, convert to
swarm cells, function swarm cells, function
as gametes; form as gametes; form
microcysts under microcysts under
adverse conditionsadverse conditions
www.uoguelph.ca/~gbarron/ MISCE2002/myxamo2.jpg

9. Stages in Life CycleStages in Life Cycle
Swarm cells (n)Swarm cells (n)

1-4 anterior whiplash 1-4 anterior whiplash
flagella, amoeboid flagella, amoeboid
posterior; feed posterior; feed
(absorption and (absorption and
engulfment), function engulfment), function
as gametesas gametes

can’t undergo cell can’t undergo cell
divisiondivision
http://www.botany.hawaii.edu/faculty/wong/Bot201/Myxomycota/S
warm_Cells2.jpg

10. Stages in Life CycleStages in Life Cycle
Zygote (2n)Zygote (2n)

Formed by fusion of myxamoebae or swarm Formed by fusion of myxamoebae or swarm
cells; enlarges through synchronous nuclear cells; enlarges through synchronous nuclear
divisiondivision
Plasmodium (2n)Plasmodium (2n)

Multinucleate, wall-less protoplasmMultinucleate, wall-less protoplasm
Photo by Stephen Sharnoff
http://www.plant.uga.edu/mycology-
herbarium/myxogal/Physros3.jpg

11. Stages in Life CycleStages in Life Cycle
Sporophore (2n)Sporophore (2n)

Entire plasmodium is Entire plasmodium is
converted into converted into
sporophore(s)sporophore(s)
Sclerotium or Sclerotium or
macrocyst (2n)macrocyst (2n)

Resistant stage Resistant stage
formed by plasmodiumformed by plasmodium

12. Types of plasmodiaTypes of plasmodia
PhaneroplasmodiumPhaneroplasmodium

Conspicuous, often colored, with protoplasm Conspicuous, often colored, with protoplasm
forming veins with reversible streamingforming veins with reversible streaming
AphanoplasmodiumAphanoplasmodium

With a network of fine, transparent threads With a network of fine, transparent threads
and homogenous protoplasmand homogenous protoplasm
ProtoplasmodiumProtoplasmodium

Microscopic, with homogenous protoplasm, Microscopic, with homogenous protoplasm,
giving rise to one sporophore giving rise to one sporophore

13. SporophoresSporophores
Mass of spores formed inside peridium, spores Mass of spores formed inside peridium, spores
intermingled with:intermingled with:

CapillitiumCapillitium
•threadlike, often ornamentedthreadlike, often ornamented

ElatersElaters
•Threadlike, ornamented, not connected at endsThreadlike, ornamented, not connected at ends

PseudocapillitiumPseudocapillitium
•Threads, bristles, membrane or platelike networkThreads, bristles, membrane or platelike network
Lime may be present on peridium, stalk, Lime may be present on peridium, stalk,
columella or capillitium, or nodes of columella or capillitium, or nodes of
pseudocapillitumpseudocapillitum

14. www.botany.hawaii.edu/.../Bot201/ Myxomycota/elaters.jpg
Capillitium (top left; photo
by David Geiser)
Pseudocapillium (top right;
photo from Fifth Kingdom)
Elaters (bottom left)

15. Sporocarp—stalked or sessileSporocarp—stalked or sessile
May have columella 

16. AethaliumAethalium

Large, cushion-shaped Large, cushion-shaped
sporophore, one per sporophore, one per
plasmodiumplasmodium

17. PseudoaethaliumPseudoaethalium

Cluster of sporophores Cluster of sporophores
grouped tightly grouped tightly
togethertogether
Photo by David Geiser

18. PlasmodiocarpPlasmodiocarp

Sporophore developing Sporophore developing
along veins of along veins of
phaneroplasmodium; phaneroplasmodium;
takes on reticulate takes on reticulate
shape of veinsshape of veins

19. Photo by Stephen Sharnoff

20. Liceales-- Pale or brown spores, capillitium and lime absent, Liceales-- Pale or brown spores, capillitium and lime absent,
pseudocapillitium may be presentpseudocapillitium may be present
Dictydium
Lycogala Photo by Stephen Sharnoff

21. Trichiales--Pale spores (yellow, orange or red) and abundant, Trichiales--Pale spores (yellow, orange or red) and abundant,
conspicuous capillitium conspicuous capillitium
Trichia
Arcyria

22. Physarales--Purplish-brown spores, usually with abundant Physarales--Purplish-brown spores, usually with abundant
and conspicuous lime on or in sporophoreand conspicuous lime on or in sporophore
Badhamia
FuligoLeocarpus

23. Stemonitales--Violet-brown spores, lime absentStemonitales--Violet-brown spores, lime absent
Diachea
Lamproderma

24. Stemonitis
Photo by Stephen Sharnoff

25. Ceratiomyxales--Exosporous sporophores; probably Ceratiomyxales--Exosporous sporophores; probably
belongs in protostelids (one genus, belongs in protostelids (one genus, CeratiomyxaCeratiomyxa))
Photo by Stephen Sharnoff
Photo by David Geiser

26. ProtostelidsProtostelids
Simplest known slime moldsSimplest known slime molds
Discovered in 1970Discovered in 1970

Easily mistaken for mucoraceous fungi or Easily mistaken for mucoraceous fungi or
deuteromycetesdeuteromycetes
In dead, attached plant parts, herbivore In dead, attached plant parts, herbivore
dung or soil; feed on bacteria, yeast and dung or soil; feed on bacteria, yeast and
fungal sporesfungal spores
14 genera and 32 species14 genera and 32 species

27. Protostelid Life CycleProtostelid Life Cycle
Amoeboid cells (filose pseudopodia) Amoeboid cells (filose pseudopodia)
become one or more prespore cells that become one or more prespore cells that
rise on stalk and encyst to form one to four rise on stalk and encyst to form one to four
spores spores
Plasmodium and flagellated cells present Plasmodium and flagellated cells present
in “complex” life cyclesin “complex” life cycles
Sexual reproduction not knownSexual reproduction not known

28. http://comp.uark.edu/~fspiegel/protist.html#sporocarp%20morphology
Life cycle of simple protostelid

29. http://comp.uark.edu/~fspiegel/protist.html#sporocarp%20morphology
Life cycle of complex protostelid

30. Images courtesy of Fred Spiegal, Univ. of Arkansas