Arenas G N, Staskevich A S, Aballay A, Mayorga L S
Cátedra de Microbiología, Facultad de Ciencias Médicas, Universidad Nacional de Cuyo, Casilla de Correo 56, Mendoza (5500), Argentina.
Infect Immun. 2000 Jul;68(7):4255-63. doi: 10.1128/IAI.68.7.4255-4263.2000.
Brucella abortus is a facultative intracellular bacterium capable of surviving inside professional and nonprofessional phagocytes. The microorganism remains in membrane-bound compartments that in several cell types resemble modified endoplasmic reticulum structures. To monitor the intracellular transport of B. abortus in macrophages, the kinetics of fusion of phagosomes with preformed lysosomes labeled with colloidal gold particles was observed by electron microscopy. The results indicated that phagosomes containing live B. abortus were reluctant to fuse with lysosomes. Furthermore, newly endocytosed material was not incorporated into these phagosomes. These observations indicate that the bacteria strongly affect the normal maturation process of macrophage phagosomes. However, after overnight incubation, a significant percentage of the microorganisms were found in large phagosomes containing gold particles, resembling phagolysosomes. Most of the Brucella bacteria present in phagolysosomes were not morphologically altered, suggesting that they can also resist the harsh conditions prevalent in this compartment. About 50% colocalization of B. abortus with LysoSensor, a weak base that accumulates in acidic compartments, was observed, indicating that the B. abortus bacteria do not prevent phagosome acidification. In contrast to what has been described for HeLa cells, only a minor percentage of the microorganisms were found in compartments labeled with monodansylcadaverine, a marker for autophagosomes, and with DiOC6 (3,3'-dihexyloxacarbocyanine iodide), a marker for the endoplasmic reticulum. These results indicate that B. abortus bacteria alter phagosome maturation in macrophages. However, acidification does occur in these phagosomes, and some of them can eventually mature to phagolysosomes.
流产布鲁氏菌是一种兼性胞内细菌，能够在专职和非专职吞噬细胞内存活。该微生物存在于膜结合区室中，在几种细胞类型中，这些区室类似于内质网结构的修饰形式。为了监测流产布鲁氏菌在巨噬细胞内的转运情况，通过电子显微镜观察了吞噬体与用胶体金颗粒标记的预先形成的溶酶体融合的动力学过程。结果表明，含有活流产布鲁氏菌的吞噬体不易与溶酶体融合。此外，新内吞的物质未被纳入这些吞噬体。这些观察结果表明，细菌强烈影响巨噬细胞吞噬体的正常成熟过程。然而，经过过夜孵育后，在含有金颗粒的大吞噬体中发现了相当比例的微生物，这些吞噬体类似于吞噬溶酶体。存在于吞噬溶酶体中的大多数布鲁氏菌在形态上没有改变，这表明它们也能抵抗该区室中普遍存在的恶劣条件。观察到流产布鲁氏菌与LysoSensor（一种积聚在酸性区室中的弱碱）的共定位率约为50%，这表明流产布鲁氏菌细菌不会阻止吞噬体酸化。与对HeLa细胞的描述相反，仅在少数微生物中发现它们存在于用单丹磺酰尸胺（自噬体标记物）和DiOC6（3,3'-二己基氧杂羰花青碘化物，内质网标记物）标记的区室中。这些结果表明，流产布鲁氏菌细菌改变了巨噬细胞中吞噬体的成熟过程。然而，这些吞噬体确实会发生酸化，并且其中一些最终可以成熟为吞噬溶酶体。
