The nutritional behaviour of a 'Sterile Red Fungus' (SRF) was studied with a view to the development of efficient field delivery systems for its use in plant growth promotion and disease protection. The vegetative cells of the fungus are binucleate with occasional presence of trinucleate terminal cells. Responses to 28 biochemical tests and 19 different carbon sources were determined to detect the enzymatic activities and preferred carbon source utilization for growth. Pectic enzyme patterns and manganese oxidation/reduction abilities of the SRF were also investigated. The SRF was found to have a wide range of enzymatic activity. It produced cellulase, esterase, ligninase, peroxidase, acid phosphatase, phenoloxidase and pectinase and required thiamine (0.6 mu g l(-1)) for growth. With the exception of chitin, lactose, dulcitol and L-arabinose it utilized all the carbon sources tested. It oxidized and reduced manganese and its isoenzyme pattern is characterized by distinct bands of esterase and polygalacturonase.