The Assimilation of Amino-acids by Bacteria: 4. The Action of Triphenylmethane Dyes on Glutamic Acid Assimilation

Abstract

SUMMARY:The level of glutamic acid concentration measured inside the streptococcal cell during assimilation represents a balance between the rate a t which the amino-acid is withdrawn from the external medium and the rate a t which it is metabolized within the cell.Treatment of the cells, prior to or during assimilation, with dyes of the triphenylmethane series results in raising the level of free glutamic acid attained within the cell. Evidence is presented that the triphenylmethane dyes prevent the metabolism of glutamic acid within the cell. The activity of the triphenylmethane molecule as an antibacterial agent and in raising the level of glutamic acid assimilation is increased by alkyl substitution and can be correlated with the lipid solubility of the dye.Dyes of the triphenylmethane series have long been known as effective antibacterial agents. Kligler (1918) showed that the quinonoid structure of the dye molecule is important for antimicrobial activity and that the effectiveness of the dyes is increased by substitution of alkyl radicles in the amino-groups of triamino-and diamino-triphenylmethanes. He showed that bacteria differ widely in their sensitivity to these dyestuffs and that, in general, Gram-positive organisms are more sensitive than Gram-negative species. The dyes fell into the following order of increasing effectiveness : fuchsin (1 CH,), methyl violet ( 5 CH,), crystal violet (6 CH,), malachite green (4CH,), brilliant green (4C2H5).

The Assimilation of Glutamic Acid by Yeast

“…The concentration of free amino-acids found inside the cell represents a balance between the rate at which they are utilized and the rate at which they are synthesized or taken up from the external medium (Gale & Mitchell, 1947). Consequently the appearance of free amino-acids inside a cell must mean that the amino-acids are either synthesized or taken from the medium at a rate greater than that at which they can be metabolized within the cell.…”

The Assimilation of Amino-acids by Bacteria: 5. The Action of Penicillin in Preventing the Assimilation of Glutamic Acid by Staphylococcus aureus

“…2 there is definitely an increase in turbidity a€ter the point a t which the internal concentration of glutamic acid begins to fall instead of to rise, and the internal concentration does not reach a new steady level until growth {as measured by turbidity increase) ceases. The glutamic acid which accumulates inside the cell acts as a reservoir of amino-acid for protein synthesis (Gale, 1947b) and for other metabolic purposes (Gale & Mitchell, 1947), and it may be that growth will continue as long as there is more than a certain limiting concentration within the cell. In that case the sequence of events would be: (i) penicillin prevents the passage of glutamic acid into the cell; (ii) the synthesis of protein, etc., proceeds a t the expense of the accumulated glutamic acid (and other aminoacids) within the cell and consequently the concentration falls; (iii) the internal concentration falls to the lowest level permitting synthesis of protein and growth ceases.…”

“…In the previous paper (Gale & Mitchell, 1947) it was shown that some metabolism of glutamic acid took place after it had passed into the internal environment of the cell. This metabolism could be demonstrated since, if the amount of glutamic acid which accuniulated inside the cell during assimilation was compared with the amount which was removed from the external environment, there was on balance a ' disappearance ' of the amino-acid.…”

“…The maintenance of a concentration of glutamic acid within the internal environment higher than that in the external medium is dependent upon an intact cell wall (Gale & Taylor, 1947). After glutamic acid has passed through the cell wall, a portion of it undergoes metabolic change, and the level of glutamic acid concentration measured inside the cell represents the balance between the rate of entry of that amino-acid into the cell and the rate of its metabolism within the cell (Gale & Mitchell, 1947).Since the ability to concentrate amino-acids within the internal environment is a property of Gram-positive organisms, the effect on this property of various chemotherapeutic agents has now been tested. A preliminary note on the effect of penicillin in preventing the assirnilation of glutamic acid by Staphylococcus aureus has been published (Gale & Taylor, 1946).…”

“…The maintenance of a concentration of glutamic acid within the internal environment higher than that in the external medium is dependent upon an intact cell wall (Gale & Taylor, 1947). After glutamic acid has passed through the cell wall, a portion of it undergoes metabolic change, and the level of glutamic acid concentration measured inside the cell represents the balance between the rate of entry of that amino-acid into the cell and the rate of its metabolism within the cell (Gale & Mitchell, 1947).…”