Myxomycota Flashcards
Myxonycetes meaning
Dictosteliomycetes meaning
Protosetliomycetes meaning
True Slime molds
Cellular slime molds
Protoselid plasmodial slime mold
How do slime molds differ from Eumycota?
- Vegetative state is multinuclear plasmodium in plasmodial slime molds and individual amoeba in the dictyosteliomycetes
- Motile stage bears two anterior whiplash-like flagella may be present in plasmodial slime molds
- Amobea or plasmodia feed by the ingestion (phagocytosis) and Intracellular Digestion in vacuoles of bacteria
Largest group of slime molds and there habitat
Mycomycetes-true plasmodial slime molds
-moist, decaying wood and other organic substrates
-abundant in soil and may fulfill many ecological functions which are poorly understood
Movement of true plasmodium
- Margin of extending plasmodium. The protoplasm is particularly dense at the advancing stage. Further behind, protoplasm is concentrated in large veins which show rhythmic pulsation
- Fusion between compatible plasmodia. Note complete fusion of veins.
- Lethal reaction following fusion between incompatible (genetically distinct) plasmodia
Life cycle of Physarum Polycephalum
-low moisture and nutrition= plasmodium changes into dormant sclerotium
-numerous walled compartments, each containing several nuclei, each enveloped by a cell wall
-upon resumption of growth, the protoplast emerge from their spherules and fuse to reestablish the plasmodium
-when food supply is nearly exhausted, the plasmodium forms fruiting bodies or fruitifications: sporangia, aethalia, plasmodiocarps
Sporangia of myxomycetes
Simple fruiting bodies, stalked or sessile
-sporangia enclosed by a wall (peridium) within which the spores are contained
Aethelium life cycle
Entire plasmodium converts into hemispherical or cushion-shaped structure
Comprises several sporangia -> lost structural identity and surrounded by shared peridium
Plasmodiocarps
-sessile, irregular in shape, varying from ovoid to elongated and even branched or netlike
Formed by secreting a peridium around the veins or parts of the veins of a plasmodium just after it stops streaming and prepares to sporulate
Life cycle of myxomycetes
__________ spores germinate and release an Amoeboid cell the _______ or flagellate ______ cell
Wind-dispersed
Myxamoeba
Swarmer
Swarmer safe equipped with
Two anterior, whiplash flagella-> may behave as gametes, fusing by their posterior ends to form flagellates zygotes, which eventually withdraw their flagella
Where in the world can you find slime molds?
Where are they most common?
Anywhere!-all continents
Cultivated or native soils
Most abundant in upper layers of humus in well-established deciduous forests
Cellular slime molds crawl in ______ soil as _______ cells (________): feed on bacteria by_______ and reproduce by ______
Moist
Individual
Myxamoba
Phagocytosis
Cell division
During unfavourable conditions, what do myxamoeba do?
Encyst (Microcysts)
Microcysts germinate liberating myxamoebas that resume their normal feeding activities
Asexual sporulation of cellular slime molds
When the food supply is exhausted, the myxamoebas aggregate
-starving amoebae emit pulses of a hormone chemoattractant, cyclic adenosine mono phosphate (cAMP), that induce surrounding cells to move in their direction and to secrete cAMP pulse themselves
Pseudoplasmodium
Aggregate then transforms into a finger shaped structure
(Cellular slime molds)
-also called slug -c
-slug is comprised of individual amoeba cells
What does the slug stage enable
Enables cellular slime molds to migrate towards the surface of the litter stratum thus to have a better chance for spore dispersal
About ____% of the cells express genes that will ultimately cause them to transform into spores (cellular slime molds)
The remaining _____% will…..
75
25
Express genes that will finally cause their transformation into the stalk cells, that are doomed to die
Prestalk cells move where
Perspire cells move where
Forward to front of slug
Perspires stay back
Upon initiation of the fruiting body formation, the migrating slug ______
Contracts and points it’s tip upwards
Prestalk cells at the front first synthesize a central cellulose tube and differentiate into stalk cells
Perspore cells follow Prestalk cells up the stalk to mature into spores by loosing water and constructing spore coats
Altruism
Differentiation in the cellular slime molds poses an evolutionary problem. Because, the amoebae that contribute to the stalk die, they can not pass genes to next generations. That being the case, why do they aggregate when the other cells do?
Although a cell joins an aggregate that has a finite chance dying, it may do better than it would by remaining alone
Cheaters? In slime molds
Cells that move to the rear of the slug have an advantage -> cheater strains are known
Dictyostelium discoideum in cell bio research
Advantages to studying cytokinesis, motility, phagocytosis, chemotaxis, signal transduction and aspects of development such as cell sorting , pattern formation, and cell-type determination
