Kadurugamuwa J L, Beveridge T J
Department of Microbiology, College of Biological Science, University of Guelph, Ontario, Canada.
J Bacteriol. 1996 May;178(10):2767-74. doi: 10.1128/jb.178.10.2767-2774.1996.
Pseudomonas aeruginosa releases membrane vesicles (MVs) filled with periplasmic components during normal growth, and the quantity of these vesicles can be increased by brief exposure to gentamicin. Natural and gentamicin-induced membrane vesicles (n-MVs and g-MVs, respectively) are subtly different from one another, but both contain several important virulence factors, including hydrolytic enzyme factors (J. L. Kadurugamuwa and T. J. Beveridge, J. Bacteriol. 177:3998-4008, 1995). Peptidoglycan hydrolases (autolysins) were detected in both MV types, especially a periplasmic 26-kDa autolysin whose expression has been related to growth phase (Z. Li, A. J. Clarke, and T. J. Beveridge, J. Bacteriol. 178:2479-2488, 1996). g-MVs possessed slightly higher autolysin activity and, at the same time, small quantities of gentamicin. Both MV types hydrolyzed isolated gram-positive and gram-negative murein sacculi and were also capable of hydrolyzing several glycyl peptides. Because the MVs were bilayered, they readily fused with the outer membrane of gram-negative bacteria. They also adhered to the cell wall of gram-positive bacteria. g-MVs were more effective in lysing other bacteria because, in addition to the autolysins, they also contained small amounts of gentamicin. The bactericidal activity was 2.5 times the MIC of gentamicin, which demonstrates the synergistic effect of the antibiotic with the autolysins. n-MVs were capable of killing cultures of P. aeruginosa with permeability resistance against gentamicin, indicating that the fusion of n-MV to the outer membrane liberated autolysins into the periplasm, where they degraded the peptidoglycan and lysed the cells. g-MVs had even greater killing power since they liberated both gentamicin and autolysins into these resistant cells. These findings may help develop a conceptually new group of antibiotics designed to be effective against hard-to-kill bacteria.
铜绿假单胞菌在正常生长过程中会释放充满周质成分的膜泡（MVs），短暂暴露于庆大霉素可增加这些膜泡的数量。天然膜泡和庆大霉素诱导的膜泡（分别为n-MVs和g-MVs）彼此略有不同，但都含有几种重要的毒力因子，包括水解酶因子（J. L. Kadurugamuwa和T. J. Beveridge，《细菌学杂志》177:3998 - 4008，1995）。在两种类型的膜泡中均检测到肽聚糖水解酶（自溶素），尤其是一种周质26-kDa自溶素，其表达与生长阶段有关（Z. Li、A. J. Clarke和T. J. Beveridge，《细菌学杂志》178:2479 - 2488，1996）。g-MVs具有略高的自溶素活性，同时含有少量庆大霉素。两种类型的膜泡都能水解分离的革兰氏阳性和革兰氏阴性菌细胞壁肽聚糖，并且还能够水解几种甘氨酰肽。由于膜泡是双层的，它们很容易与革兰氏阴性菌的外膜融合。它们也能粘附在革兰氏阳性菌的细胞壁上。g-MVs在裂解其他细菌方面更有效，因为除了自溶素外，它们还含有少量庆大霉素。杀菌活性是庆大霉素最低抑菌浓度的2.5倍，这证明了抗生素与自溶素的协同作用。n-MVs能够杀死对庆大霉素具有通透性抗性的铜绿假单胞菌培养物，这表明n-MV与外膜的融合将自溶素释放到周质中，在那里它们降解肽聚糖并裂解细胞。g-MVs具有更强的杀伤力，因为它们将庆大霉素和自溶素都释放到这些抗性细胞中。这些发现可能有助于开发一类从概念上讲全新的抗生素，旨在有效对抗难以杀灭的细菌。
