Biochemical and physiological changes during spore germination and swarm cell morphogenesis in the acellular slime mold Fuligo septica

Abstract

Spores of the acellular slime mold Fuligo septica germinated and developed into motile, flagellated swarm cells using only endogenous carbon and energy sources. We observed no increase in the amount of any cell component during this time, whereas we did note a decrease in the amount of several substances. Glucose and glycogen were important reserves which were apparently catabolized via glycolysis and the tricarboxylic acid cycle. The synthesis of large amounts of ATP via a respiratory chain with oxygen as the terminal electron acceptor was essential for development. Another potential carbon and energy source was lipid which also decreased in amount during development, although the metabolism of glycerol could not be demonstrated. RNA synthesis was unnecessary for any of the morphological changes and did not occur at any time under these conditions. Protein synthesis was not essential for any step of morphogenesis but did occur. This synthesis did not result in the net accretion of protein nor in any change in the protein composition discernable by sodium dodecyl sulfate – polyacrylamide gel electrophoresis. Intracellular cyclic AMP levels increased fourfold coincident with the start of rapid glycogen depletion.