Phenotypic modifications in amino acid profiles of cell residues of Candida utilis and Enterobacter aerogenes.

Glucose-limited chemostat cultures of Candida utilis were cultivated at various pH levels (3.0-7.5), temperatures (15-37.5 degrees C), dilution rates (0.006-0.42 hr-1), and with one of two nitrogen sources (NH+4 or NO-3). Enterobacter aerogenes was also cultivated in the chemostat under nitrogen and phosphorus limitations. The amino acid profile of total cell protein is expressed as the content of each amino acid relative to the sum of all amino acids recovered ater acid hydrolysis. Cell residues obtained after hot trichloracetic acid extraction display small variations in amino acid profile. Some of these variations correlate with the growth rate at satisfactory levels of statistical significance. In C. utilis, the correlations cover increased levels of lysine, arginine, and leucine and decreased levels of serine and glutamic acid with increased "reduced dilution rate" (D/Dc). In E. aerogenes, increased levels of lysine and arginine and a decreased level of glutamic acid correlate with increased dilution rate. The directions of most of these correlations and the extents of those pertaining to lysine and arginine are consistent with the change predicted to occur simultaneously in the relative level of the ribosomal protein group.