REACTIVATION OF ULTRAVIOLET INACTIVATED ESCHERICHIA COLI BY PYRUVATE

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Abstract
Photochemical reactions produced by u.-v. irradiations, in general, can be reversible or irreversible. Exptl. evidence indicates that u._v. irradiation effects on bacteria can be reversed only within certain radiation dose ranges. In order to increase the survival capacity of the cell, the nonreversible fraction of the cell injury also should be reduced or eliminated. As long as the cell has remaining sufficient ability to metabolize and synthesize, a recovery process may take place provided that suitable metabolites are available which may be used to rebuild the damaged metabolic links, reestablish the balance of the enzyme system, or develop alternate metabolic pathways. To achieve such results, a sufficiently long incubation of irradiated cells, suspended in various metabolites at temps. suitable for metabolic activity, suggests itself. In an E.coli -strain B/r control suspension, the original log cell count (8.7) was reduced to 3.1 after u._v. irradiation. Irradiated bacteria suspended in 3.5 x 10-3 [image]_pyruvic acid soln. (in 0.1[image] phosphate buffer, pH 7) and plated after 24 hrs. of incubation at 37[degree]C. yield a plate count of 7.2 log units, indicating a 4.1 unit increase of viable cell count. Also, bacterial suspensions, rendered sterile by u._v. irradiations, exhibit large numbers of viable cells when incubated with pyruvate. E. coli - strain B exhibits similar reactivating properties.