The assimilation of amino-acids by bacteria. 9. The passage of lysine across the cell wall of Streptococcus faecalis

Abstract

Two factors appear to influence lysine migration across the cell membrane: the phosphate ion and certain amino acids. Phosphate favors lysine accumulation by the streptococci during growth in a medium of high amino acid content. In washed suspensions of cells lysine accumulation is less if the external medium contains phosphate. The passage of lysine from the internal to the external environment of the cell occurs readily at 4[degree] in the presence of chloride, sulfate or pyrophosphate ions, but no outward migration takes place in the presence of phosphate. Outward migration takes place at 37[degree] whether phosphate is present or absent. The outward migration is influenced by the presence of other amino acida during the previous uptake of lysine. If cells deficient in free amino acids are incubated in lysine alone, then the lysine taken up can subsequently leave the cell if tnis is incubated in lysine-free phosphate at 37[degree]. If the uptake of lysine takes place from a medium containing casein hydrolysate, then the lysine will not leave the cell on subsequent incubation in phosphate although normal migration occurs in saline. The retaining effect of casein hydrolysate is also obtained if the initial incubation takes place in a medium containing, in addition to lysine, a mixture of either arginine and histidine or glutamate and aspartate. Uptake of lysine by deficient cells is also lessened by the presence of these amino acid mixtures. A mixture of neutral amino acids has no effect on either the uptake of lysine or its subsequent migration out of the cell.