INCORPORATION OF C14INTO BACTERIAL PEPTIDES

Abstract

Alcoholic extracts of log-phase cells of Pseudomonas hydrophila grown on glucose as the sole carbon source were concentrated, extracted with ether, and dialyzed. After fractionation of the permeates by high voltage paper electrophoresis, five to seven ninhydrin-positive acidic, one neutral, and several basic bands appeared. As many as seven ninhydrin-positive basic bands have been found in some preparations, although they have been absent in others. Photometric analyses on eluates before and after acid hydrolysis indicated the presence of acidic, neutral, and basic peptides. Amino acid compositions of 28 of these peptides, separated by a combination of high voltage paper electrophoresis and paper chromatography, included all of the amino acids commonly found in proteins. Elution of acidic, neutral, and basic amino acid and peptide fractions from C14-labelled cells was followed by measurement of total and specific radioactivities in carboxyl-C before and after acid hydrolysis. Total radioactivity was highest in proteins even 1 minute after addition of the isotope to a log-phase culture. Specific radioactivities, plotted against time, gave parallel hyperbolic curves with peptides below the curve for amino acids and with proteins still lower and almost linear. The evidence suggests rapid synthesis of peptides from amino acids.