Frases Susana, Chaskes Stuart, Dadachova Ekaterina, Casadevall Arturo
Department of Microbiology and Immunology, Albert Einstein College of Medicine, Bronx, NY 10461, USA.
Appl Environ Microbiol. 2006 Feb;72(2):1542-50. doi: 10.1128/AEM.72.2.1542-1550.2006.
While studying the interaction of Cryptococcus neoformans with Dictyostelium discoideum, we noticed that yeast colonies in agar with a feeder lawn of Klebsiella aerogenes were brown. This finding was intriguing because C. neoformans colonies are not pigmented unless they are provided with precursors for melanization. Strains of all C. neoformans serotypes produced brown pigment in response to K. aerogenes at 22, 30, and 37 degrees C. Pigment production required fungal laccase and was suppressed by high concentrations of glucose. Treatment of brown cells with guanidinium isothiocyanate and hot concentrated HCl yielded particulate material that had the physical and chemical characteristics of melanins. No pigment formation was observed when C. neoformans was exposed to live Escherichia coli or heat-killed K. aerogenes. Analysis of K. aerogenes supernatants revealed the presence of dopamine, which can be a substrate for melanin synthesis by C. neoformans. Our findings illustrate a remarkable interaction between a pathogenic fungus and a gram-negative bacterium, in which the bacterium produces a substrate that promotes fungal melanization. This observation provides a precedent that could explain the source of a substrate for C. neoformans melanization in the environment.
在研究新型隐球菌与盘基网柄菌的相互作用时，我们注意到，在含有产气克雷伯菌饲养菌苔的琼脂中，酵母菌落呈褐色。这一发现很有趣，因为新型隐球菌菌落除非有黑色素形成的前体物质，否则不会产生色素。所有新型隐球菌血清型的菌株在22℃、30℃和37℃下，对产气克雷伯菌均产生褐色色素。色素产生需要真菌漆酶，且高浓度葡萄糖会抑制色素产生。用异硫氰酸胍和热浓盐酸处理褐色细胞，得到了具有黑色素物理和化学特征的颗粒物质。当新型隐球菌暴露于活的大肠杆菌或热灭活的产气克雷伯菌时，未观察到色素形成。对产气克雷伯菌上清液的分析表明，其中存在多巴胺，它可以作为新型隐球菌合成黑色素的底物。我们的研究结果表明，一种致病真菌与一种革兰氏阴性细菌之间存在显著的相互作用，其中细菌产生促进真菌黑色素形成的底物。这一观察结果提供了一个先例，可解释环境中新型隐球菌黑色素形成底物的来源。
