Oligopeptide Uptake by Bacteroides ruminicola

Abstract

Bacteroides ruminicola did not take up 14 C from exogenous 14 C-labeled l -proline or 14 C-labeled l -glutamic acid and took up very little 14 C from exogenous 14 C-labeled l -valine. Growing cultures of B. ruminicola rapidly took up 14 C from 14 C-proline-labeled peptides of molecular weights up to 2,000 and incorporated it into trichloroacetic acid-insoluble cell material. Uptake and incorporation did not occur at 0 C and were reduced or eliminated in glucose-starved cells, depending upon the length of time the cells were starved. The initial rate of uptake of peptides seemed to exhibit saturation kinetics, but it was impossible to establish this conclusively. The initial uptake of 14 C from peptides was not affected by chloramphenicol but the incorporation of it into trichloroacetic acid-insoluble cell material was virtually eliminated. Only moderate amounts of trichloroacetic acid-extractable, labeled material were present in cells during peptide uptake, whether or not chloramphenicol was present. 14 C-proline was rapidly released from labeled peptides during uptake, whether or not chloramphenicol was present. The amount of 14 C fixed into trichloroacetic acid-insoluble cell material was directly related to the size of peptides originally supplied in the medium. It is concluded that B. ruminicola possesses a general system for the uptake of peptides, that peptides are rapidly hydrolyzed during or after uptake, and that oligopeptides function only to supply amino acids in a form available to the organism.