Utilization of calcium phosphates for microbial growth at alkaline pH

A strain of aerobic yeast isolated from marine environment, and a number of spore-forming bacteria isolated from soil and from sewage, were grown on defined media at pH 8 containing various calcium phosphates as sole sources of phosphorus. Direct measurements confirm that, at this pH, the concentrations of inorganic phosphate in solution, released through the dissociation of the calcium phosphates, are more than adequate for the microbial phosphate uptake systems to function efficiently. This conclusion is supported by the observation that growth is even more rapid when the calcium phosphates were enclosed in dialysis bags and thus not in direct contact with the micro-organisms.