Chemotactic bevaviour of the infective zoospores of Dermatophilus dermatonomus

Abstract

When carbon dioxide (CO₂) concentration gradients were established experimentally in Dermatophilus dermatonomus cultures and zoospore suspensions, the zoospores showed a chemotactic response by moving towards an optimum CO₂ concentration. The characteristic negative aerotaxis of the zoospores was found to be a response to a CO₂ concentration gradient resulting from their own CO2 production and the simultaneous loss of CO₂ at the air-liquid interface.

The zoospores exhibit a negative chemotactic response to toxic electrolytes, as demonstrated by their reaction in suspensions exposed to ammonia, hydrogen chloride, and sulphur dioxide fumes. Oxygen, hydrogen, nitrogen, and defibrinated sheep blood all failed to exert any detectable chemotactic effect.

It is deduced that the response of the zoospores to CO₂ would facilitate two important steps in the life cycle of D. dermatonomus. The high CO₂ concentration, probably produced in wet mycotic dermatitis scabs by the dense populations of zoospores, would accelerate their escape to the exterior, while the respiratory efflux of CO₂ from the skin would attract the zoospores to susceptible areas on the skin surface.