The respiratory system of the aquatic phycomycete Allomyces macrogynus wild-type and sexual mutants

Abstract

A series of predominantly male mutants induced with ethidium bromide were isolated from Allomyces macrogynus (Emerson) Emerson and Wilson strain Burma 3–35 (35°C) and crossed to the wild-type female. Gametangia and sporangia from ethidium bromide-induced mutants, predominantly male and female Mendelian mutants, and double mutants constructed from these Mendelian sexual mutants, were analyzed for their response to cyanide, propyl gallate, and CCCP. Reduced minus oxidized room temperature cytochrome difference spectra were made on homogenized mycelium from wild-type and sexual mutants. The ethidium bromide-induced male mutants showed a non-Mendelian segregation pattern when crossed to wild type. Mendelian and non-Mendelian mutants have lower respiratory rates than the wild type. Neither the mutants nor the wild type were sensitive to propyl gallate. Mutants and wild type have the same response to CCCP. The concentrations of the cytochromes from the mutants were generally the same as in the wild type, but the ratio of a-type cytochromes to c- and b-type cytochromes was lowered in many mutants. Both higher and lower relative amounts of cyanide insensitive respiration (compared to total respiration) were observed among the sexual mutants when the sexual mutants were compared to wild type. The relative amount of cyanide-insensitive respiration of the double mutants can be related to the relative amount of cyanide-insensitive respiration of the single mutants from which the double mutants were constructed. It is concluded that the respiratory deficiency of the sexual mutants disturbs the respiratory system in a complex manner.