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Plasmodial Slime Molds

Plasmodial Slime Molds. Pl P 421/521. http://www.ucmp.berkeley.edu/chromista/chromistasy.html. Ribosomal RNA phylogenies place slime molds as unrelated, early branching eurkaryote lineages . Baldauf and Doolittle, 1997. PNAS 94 (22): 12007-12012.

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Plasmodial Slime Molds

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  1. Plasmodial Slime Molds Pl P 421/521

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

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

  4. Classification • Mycetozoa = cellular, plasmodial slime molds plus protostelids • Cellular slime molds and protostelids now placed in phylum Myxomycota • Names imply a fungal-like affinity

  5. Myxomycota • Myxomycetes--5 orders, 13 families, 62 genera, 800 species • Characterized by plasmodium • Engulfs bacteria, fungal spores, small pieces of organic matter

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

  7. Stages in Life Cycle • Spores (2nn) • 4-20 µm, pigmented ornamented; meiosis in spore = 4 nuclei; 3 degenerate

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

  9. Stages in Life Cycle • Swarm cells (n) • 1-4 anterior whiplash flagella, amoeboid posterior; feed (absorption and engulfment), function as gametes • can’t undergo cell division http://www.botany.hawaii.edu/faculty/wong/Bot201/Myxomycota/Swarm_Cells2.jpg

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

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

  12. Types of plasmodia • Phaneroplasmodium • Conspicuous, often colored, with protoplasm forming veins with reversible streaming • Aphanoplasmodium • With a network of fine, transparent threads and homogenous protoplasm • Protoplasmodium • Microscopic, with homogenous protoplasm, giving rise to one sporophore

  13. Sporophores • Mass of spores formed inside peridium, spores intermingled with: • Capillitium • threadlike, often ornamented • Elaters • Threadlike, ornamented, not connected at ends • Pseudocapillitium • Threads, bristles, membrane or platelike network • Lime may be present on peridium, stalk, columella or capillitium, or nodes of pseudocapillitum

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

  15. Sporocarp—stalked or sessile May have columella 

  16. Aethalium • Large, cushion-shaped sporophore, one per plasmodium

  17. Pseudoaethalium • Cluster of sporophores grouped tightly together Photo by David Geiser

  18. Plasmodiocarp • Sporophore developing along veins of phaneroplasmodium; takes on reticulate shape of veins

  19. Photo by Stephen Sharnoff

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

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

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

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

  24. Photo by Stephen Sharnoff Stemonitis

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

  26. Protostelids • Simplest known slime molds • Discovered in 1970 • Easily mistaken for mucoraceous fungi or deuteromycetes • In dead, attached plant parts, herbivore dung or soil; feed on bacteria, yeast and fungal spores • 14 genera and 32 species

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

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

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

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

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