[Suppression of the conjugational transfer of derepressed R factors by the dye, metachrome yellow].

Metachrome yellow widely used for preparation of nutrient media was tested with respect to its effect on conjugation of R-transfer. The standardized kinetic system described by the authors earlier was used. It was shown that metachrome yellow had a pronounced inhibitory effect on conjugation transfer of depressive R-factors RI drd and R 64 drd. The effect was markedly pronounced even in the presence of 100 gamma/ml of metachrome yellow, the concentration which was practically not bacteriostatic as it was shown in the analysis of the microbial growth curve in the presence of 100, 200 and 400 gamma/ml of the dye. The inhibition coefficients for 100 gamma/ml of metachrome yellow in the experiments with the donor of E. coli J 53 (R1 drd) were 11.8 and 12.1 times at 1-hour cultivation and t leads to infinity respectively, while in the experiments with the donor of E. coli J53 (R 64 drd) the respective values were 9.1 and 11.1. It was found that metachrome yellow induced no elimination of R-factors at low concentrations, such as 100 and 200 gamma/ml, which was indicative of the fact that the inhibitory effect on R-transfer was not connected with elimination of R-factors. It was also shown that preliminary cultivation of the donor in the presence of 100 and 400 gamma/ml of the dye did not induce any decrease in its donor competence which did not confirm the assumption of the inhibitory effect of metachrome yellow on synthesis of sex-pilei.