Amino acid uptake systems in Bacteroides ruminicola

Abstract

Uptake of amino acids by B. ruminicola was observed in cells grown in a complete defined medium containing ammonia as the N source. A high rate of uptake occurred only in fresh medium, as an inhibitory substance, possibly acetate, apparently accumulated during growth. All amino acids except proline were taken up and incorporated into cold trichloroacetic acid precipitable material. Different patterns of incorporation and different responses to 2,4-dinitrophenol and potassium ferricyanide indicated that multiple uptake systems were involved. Kinetic inhibition patterns suggested 6 distinct systems were present for amino acid uptake, with specificities related to the chemical structures of the amino acids. Thus, the failure of free amino acids to act as sole N sources for growth of B. ruminicola is not due to the absence of transport systems for these compounds.