The influence of carbon dioxide on the growth and sporulation of Dermatophilus dermatonomus

Abstract

In cultures of Dermatophilus dermatonomus the provision of carbon dioxide (CO₂) stimulated the germination and budding of zoospores and subsequent hyphal growth, but inhibited hyphal division and the production of zoospores. Similar effects, associated with the restriction of aeration in closed cultures, were found to be due to the accumulation of endogenous CO₂ and not to oxygen limitation. Sporulating cultures produced about 0.5 ml CO₂/ml broth medium during agitation for 18 hr at 27°C. Rapid removal of the endogenous CO₂ promoted early abundant sporulation, especially when the oxygen content of the gaseous environment was reduced to about 10%.

Observations on mycelial growth in cultures suggested that hyphae would not penetrate through the medium or grow into an atmosphere unless CO₂ was present. CO₂ in the sheep's skin thus seems likely not only to stimulate the germination of D. dermatonomus zoospores on the skin surface but to favour the subsequent hyphal invasion of the skin. Sporulation of the hyphae is probably influenced by changes in the CO₂ production of infected tissue cells, and by differences in the rate of CO₂ diffusion from different depths in the lesion.