EFFECTS OF ANTIBIOTICS ON PROTEIN AND RIBONUCLEIC ACID SYNTHESIS IN RELATION TO CONTROL OF BACTERIAL GROWTH IN EXCISED TISSUES

Penicillin in the range 15-1000 mg/l. is generally without effect on incorporation of 14C-leucine into protein or of 14C-adenine into ribonucleic acid by excised pea and cucumber segments. After 16 hr. pretreatment in 1000 mg/l. penicillin, leucine incorporation is depressed somewhat. Incubation in sterile buffer supplemented with penicillin gives considerable control of bacterial growth within the tissues. Streptomycin strongly inhibits protein synthesis, producing 50-75% inhibition at 50 mg/l. Adenine incorporation is affected to a lesser extent. Evidence based on the differential effects of penicillin and of cycloheximide on leucine incorporation and on bacterial growth indicates that even high levels of bacterial contamination, obtained in tissues incubated without penicillin, do not contribute significantly to the measured rates of incorporation.