Physiological studies with the fungus Saprolegnia megasperma isolated from the freshwater nematode Neomesomermis flumenalis

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Abstract
The aquatic phycomycete Saprolegnia megasperma Coker is recorded for the first time from the freshwater nematode Neomesomermis flumenalis (Welch) Nickle. The optimum temperature for growth of the fungus is between 13 and 19 °C, and the optimum pH is between 5.2 and 5.7. The pH indicators tested were non-toxic to this isolate. The optimum concentration of phosphate was 15 mM. The optimum concentration of lactalbumin hydrolyzate under the conditions used was 4 g/litre. Glucose utilization occurred readily; 40% of the original level was utilized by day 3, and by day 4 the glucose level had dropped to 9.6% of the day 0 level. All of the detectable glucose in the medium had been utilized by day 5 under the test conditions. The utilization of ninhydrin-positive substances from media that contained lactalbumin hydrolyzate with and without glucose was determined. Under both conditions the following substances were taken up from the medium: glycerophosphoethanolamine, L-methionine sulfoxide, L-aspartic acid, L-threonine, L-serine, L-proline, L-glutamic acid, glycine, L-alanine, DL-cystathionine, L-methionine, L-isoleucine, L-leucine, L-tyrosine, L-phenylalanine, L-lysine, L-histidine, L-tryptophan, L-arginine, and L-valine. Ammonia and urea were produced in both media by the isolate. The polyamines, putrescine, cadaverine, spermidine, and spermine, were not detected as being released during autolysis.