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#slime mold

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Dictyostelium

Dictyostelium is commonly known as:

Dictyostelium is classically termed cellular slime mold to distinguish it from plasmodial slime molds forming multinucleate syncytia. Vegetative amoebae live singly ingesting soil bacteria, but upon starvation thousands chemotax and aggregate into motile grex resembling slug. Grex later culminates into stalked fruiting body releasing dormant spores. Term slime mold captures both mucoid trail during migration and mold-like aerial fruiting structure, highlighting facultative multicellularity that fascinated early developmental biologists studying cell adhesion, chemotactic signaling, proportion regulation, and altruistic cellular differentiation during survival morphogenesis and dispersal.

Ref: Gilbert, Developmental Biology, 12th ed., Chapter 22: Cellular slime molds - life cycle and facultative multicellularity.

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Fertilization in mammals-lll

Dictyostelium slug migrates to:

After aggregation Dictyostelium forms motile multicellular slug capable of phototactic and thermotactic migration before culmination. Slug displays positive phototaxis moving toward light source guided by lens effect of slug tip focusing light onto prestalk region and via opsin-like proteins modulating ammonia and cAMP chemotaxis. Migration toward bright, warm, elevated surfaces enhances spore dispersal by wind and reduces competition. Movement to dark or nutrient-rich areas would be counterproductive for dispersal. Therefore slug phototaxis to bright regions represents adaptive strategy seeking optimal site with stalk formation triggered at illuminated apex.

Ref: Fisher et al., J Cell Sci 1989: Phototactic migration of Dictyostelium slug toward light for optimal fruiting body placement.

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Fertilization in mammals-lll

High ammonia in Dictyostelium favors:

In Dictyostelium slug ammonia is metabolic waste acting as signaling molecule regulating cell fate proportion. High ammonia concentration, generated by protein catabolism, inhibits prestalk differentiation by antagonizing DIF-1 signaling and raising intracellular pH, favoring prespore gene expression including spore coat proteins and promoting slug migration rather than stalk formation. Low ammonia permits DIF-1 dependent prestalk maturation and culmination into stalk cells. In sorus ammonia drop triggers terminal differentiation. Thus elevated ammonia within slug microenvironment biases toward spore formation, extending migratory phase seeking favorable fruiting site while suppressing premature stalk specification essential for survival strategy.

Ref: Feit et al., Development 2001: Ammonia as morphogen regulating Dictyostelium spore versus stalk differentiation and slug migration.

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