Black C M, Paliescheskey M, Beaman B L, Donovan R M, Goldstein E
J Infect Dis. 1986 Dec;154(6):952-8. doi: 10.1093/infdis/154.6.952.
Most strains of Nocardia asteroides are susceptible to the detrimental effects of pH 5 when grown in buffered brain-heart infusion broth. Preventing phagosomal acidification may be a mechanism by which this organism survives the microbicidal activity of macrophages. Fluorescein isothiocyanate was conjugated to the surface of Nocardia and Saccharomyces to form pH-sensitive fluorescent probes. The fluorescent emission, and thus the pH, of this probe was quantitated within individual phagosomes by using a computerized cytospectrophotometer. When either live or dead cells of virulent N. asteroides strain GUH-2 were ingested, the phagosomal pH remained above pH 7 for 2 hr. A nonpathogenic soil isolate, N. asteroides strain 19247, only partially blocked acidification. In contrast, when Saccharomyces was used as a control for normal response, the pH decreased to approximately pH 5. Therefore, virulent N. asteroides blocks phagosomal acidification. Because killed Nocardia act in the same manner, this inhibition of acidification appears to be associated with cellular components. This capacity to prevent phagosomal acidification may be prerequisite to the survival of intracellular pathogens.
当在缓冲的脑心浸液肉汤中培养时，大多数星形诺卡菌菌株对pH 5的有害影响敏感。防止吞噬体酸化可能是该生物体在巨噬细胞的杀菌活性中存活的一种机制。异硫氰酸荧光素与诺卡菌和酿酒酵母的表面结合，形成对pH敏感的荧光探针。通过使用计算机化细胞分光光度计，在单个吞噬体内对该探针的荧光发射以及pH进行定量。当摄入强毒星形诺卡菌菌株GUH-2的活细胞或死细胞时，吞噬体pH在2小时内保持在pH 7以上。一种非致病性土壤分离株，星形诺卡菌菌株19247，仅部分阻断酸化。相比之下，当使用酿酒酵母作为正常反应的对照时，pH降至约pH 5。因此，强毒星形诺卡菌阻断吞噬体酸化。由于杀死的诺卡菌以相同方式起作用，这种酸化抑制似乎与细胞成分有关。这种防止吞噬体酸化的能力可能是细胞内病原体存活的先决条件。
