Characteristics of developing mitochondrial genetic and respiratory functions in germinating fungal spores.

Spores of the fungus Botryodiplodia theobromae began a cyanide-sensitive oxygen consumption immediately upon exposure to a liquid medium, and spore germination and respiration were not affected by ethidium bromide, D-threochloramphenicol, and acriflavin until later during germ tube emergence. These inhibitors of the mitochondrial genetic system all inhibited total cell protein synthesis to the same intermediate degree from the outset of incubation. When spores were incubated in water under non-germinating conditions, protein synthesis and oxygen uptake proceeded at initial rates almost identical to those seen in spores germinating in the presence of the three mitochondrial system inhibitors. Although the spores respired at rapid rates from the onset of incubation, no cytochrome absorption peaks could be observed in mitochondrial fractions prepared from ungerminated spores; they were readily observed in germinated spores, however. When the spores were germinated in the presence of inhibitors of the mitochondrial system, an excess of cytochrome c was observed in the near absence of cytochromes a and b. The results indicate that the ungerminated spores of this organism contain a preserved, potentially functional aerobic respiratory system which requires cycloheximide-sensitive ribosome activity to become functional when the spores are inoculated into a liquid medium.