RT Journal Article SR Electronic(1) A1 Raulston, Jane E. A1 Montie, Thomas C.YR 1989 T1 Early Cell Envelope Alterations by Tobramycin Associated with its Lethal Action on Pseudomonas aeruginosa JF Microbiology, VO 135 IS 11 SP 3023 OP 3034 DO https://doi.org/10.1099/00221287-135-11-3023 PB Microbiology Society, SN 1465-2080, AB The immediate activities of the aminoglycoside antibiotic tobramycin were investigated in Pseudomonas aeruginosa PAO1. The lethal action of a low concentration of tobramycin (8 μgml−1) occurred rapidly (1–3 min) and was associated with leakage of certain cellular components into the supernatant. The presence of magnesium at the time of initial exposure protected cells by preventing uptake of tobramycin; however, magnesium addition following a brief exposure did not restore viability. Analyses of supernatant material revealed a rapid 2-fold increase in protein released following tobramycin treatment. A prominent 29 kDa protein, observed by SDS-PAGE in the released material was identified as the periplasmic β-lactamase. Brief exposure to tobramycin did not result in major morphological damage or cell lysis as observed by transmission electron microscopy, and release of LPS was not a primary event. Although activity at the ribosomal level was observed by 2–3 min, leakage was detected after only 1 min. These data indicate that leakage of cellular components, particularly β-lactamase, occurs simultaneously, if not prior to inhibition of protein synthesis by tobramycin., UL https://www.microbiologyresearch.org/content/journal/micro/10.1099/00221287-135-11-3023