School of Sciences, Lautoka Campus BIO509 Botany Lecture 8: Other members of Kingdom Protista

Phylum Myxomycota Phylum Dictyosteliomycota Phylum Oomycota

Learning outcomes Know the characteristics that Phylum Myxomycota, Phylum Dictyosteliomycota, Phylum Oomycota share with other protists. Understand why slime molds and water molds are not considered true fungi. Know the human and ecological relevance.

Phylum Myxomycota, Phylum Dictyosteliomycota Slime molds They are a puzzle to biologist because they are distinctly animal-like much of their lives but fungus-like when they reproduce. Resemble fungi in appearance and lifestyle. Cellular organization, reproduction and life cycles are more like amoeboid. Slime mold on mulch Slime mold on mulch a day later

Totally without chlorophyll Incapable of producing their own food Present everywhere – especially in airborne dust Essentially fungus-like organisms that use spores to reproduce They feed on microorganisms that live in any type of dead plant material.

Their common name refers to part of some of these organism's lifecycles where they can appear gelatinous (hence the name slime). Two types Plasmodial slime molds (Phylum Myxomycota) Cellular slime molds (Phylum Dictyosteliomycota)

Plasmodial slime molds Most species are brightly pigmented species. Single mass of cytoplasm divided many membranes containing many nuclei. Feeding stage of the life cycle is plasmodium. Feeds by phagocytosis. Unfavorable habitat conditions ceases growth differentiates into sexually reproducing stage. Reproduce by sexual reproduction.

Lifecycle of a plasmodial slime mold

Cellular slime molds Common inhabitants of litter rich soil. Usually exist as myxamoebas. Consists of individual cells ameoba like cells that feed and function individually. Feed on bacteria by phagocytosis. Forms pseuodoplasmodium when they stop feeding and clump together. Pseudoplasmodium resembles a garden snail and becomes stationary before it reproduces.

Lifecycle of a cellular slime mold

Human and ecological relevance of slime molds Contribute to ecological balance of ecosystems by breaking down organic particles to simple forms. Reduce bacterial population within their habitat. They sometimes attack cabbages and potatoes A species of slime molds cause diseases in watercress. Have little economic significance

Phylum Oomycota – water molds Large group of Oomycota are aquatic, some are terrestrial. Spherical cells to branching, threadlike. Range from unicellular, highly branched, coenocytic and filamentous forms. Have motile biflagellate cells at various life stages. Saprophytic living on remains of dead plants and animals. Have asexual and sexual reproduction. Water is needed for reproduction.

Human and ecological relevance Two particular members of this Division cause serious diseases in higher plants: Downy mildew of grapes – they kill the leaves and even the whole vines Late blight of potato – the hyphae grow into the potato and destroy them

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