Physiological Comparison of a Newfoundland and a North Carolina Isolate of Saprolegnia australis

Abstract

Two isolates of Saprolegnia australis, one from Newfoundland (NFLD) and one from North Carolina (NC), were compared physio­ logically. The NFLD isolate had a temperature optimum of 26 C for mycelial growth , and the NC isolate grew best at 29 C. The optimum pH ranges for growth were 4.75 to 5.7 for the NFLD isolate and 5.3 to 5.7 for the NC isolate . Any effects of various pH indicators on dry­ weight yield were not detected. The optimum concentrations for phos­ phate were 10 to 15 mM for the NFLD isolate and 2.5 to 12.5 mM for the NC isolate. The optimum concentrations of vitamin-free casamino acids were 4 g/liter for the NFLD isolate and 12 g/liter for the NC isolate. In the presence of glucose, both isolates utilized L-aspartic acid, L-threonine, L-serine, L-proline, L-glutamic acid, glycine, L-alanine, L-a-amino-n-butyric acid, L-valine, L-methionine, L-isoleucine, L-leucine , L-tyrosine , L-phenylalanine , L-lysine, L-histidine and L-arginine from casamino acids. The NC isolate was unique in producing L-1-methyl ­ histidine and in utilizing L-ornithine . Both isolates produced ammonia and spermidine and utilized glucose during growth.