NATURE AND ROLE OF BACTERIAL CONTAMINANTS IN MASS CULTURES OF THERMOPHILIC CHLORELLA PYRENOIDOSA.

A study was made of bacterial contaminants isolated from an algal mass-culture unit. The study was performed specifically to determine the dependence of the size of bacterial population on algal density and the nature of any association of the contaminants with the algal cell. Growth of the bacterial contaminants on standard medium was also investigated. An estimate was made of the O(2) uptake of the bacterial population under normal operating conditions of the algal massculture system. Viable numbers of bacteria tended to increase with increased algal density. Bacteria were found imbedded in the surface of algal cells when the cultures of algae were characterized by subnormal rates of growth and photosynthetic gas exchange. Bacterial isolates failed to grow in standard medium alone, thus implying a dependency of bacterial growth on material(s) produced by the algae. A slight inhibitory effect on algal growth was noted in the case of two of three of the bacterial isolates. Manometric studies demonstrated that the bacterial population normally found in the algal cultures did not appreciably effect total gas exchange.