Physiological Studies on an Isolate of Saprolegnia ferax from the Larval Gut of the Blackfly Simulium vittatum

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Abstract
An isolate of Saprolegnia ferax was obtained from the gut of a larva of the blackfly Simulium vittatum. Growth occurred best over a broad temperature optimum of 19.degree.-26.degree. C. The isolate was aerobic and grew best at pH 5.6. In media containing glucose (5 g/l), the optimum concentration of vitamin-free casamino acids and lactalbumin hydrolysate was 4 g/l and 8 g/l, respectively. Any effect of various pH indicators on dry weight yield was not detected; pH indicators were not incorporated into final media because all indicators tested, except for bromophenol blue, were taken up by the fungus. The optimum concentration of P was 10 mM. The pattern of utilization of ninhydrinpositive substances from vitamin-free casamino acids and from lactalbumin hydrolysate, with and without added glucose, was determined. In the presence of lactalbumin hydrolysate, but without added glucose, aspartic acid, threonine, serine, glutamine and/or asparagine, alanine, isoleucine, leucine, tyrosine and phenylalanine were utilized more rapidly than when glucose was present. Ammonia was released into the medium at a greater rate in the absence of glucose. The release of the polyamine spermidine was detected during lysis when the isolate was grown on vitamin-free casamino acids. The polyamines spermine and spermidine were detected during lysis after growth on lactalbumin hydrolysate.