Institute of Plant Biology, Department of Microbiology, University of Zurich, Zurich, Switzerland.
Proteomics. 2010 May;10(9):1819-30. doi: 10.1002/pmic.200900691.
Fungi and bacteria are key players in the decomposition of leaf litter, but their individual contributions to the process and their interactions are still poorly known. We combined semi-quantitative proteome analyses (1-D PAGE-LC-MS/MS) with qualitative and quantitative analyses of extracellular degradative enzyme activities to unravel the respective roles of a fungus and a bacterium during litter decomposition. Two model organisms, a mesophilic Gram-negative bacterium (Pectobacterium carotovorum) and an ascomycete (Aspergillus nidulans), were grown in both, pure culture and co-culture on minimal medium containing either glucose or beech leaf litter as sole carbon source. P. carotovorum grew best in co-culture with the fungus, whereas growth of A. nidulans was significantly reduced when the bacterium was present. This observation suggests that P. carotovorum has only limited capabilities to degrade leaf litter and profits from the degradation products of A. nidulans at the expense of fungal growth. In accordance with this interpretation, our proteome analysis revealed that most of the extracellular biodegradative enzymes (i.e. proteases, pectinases, and cellulases) in the cultures with beech litter were expressed by the fungus, the bacterium producing only low levels of pectinases.
真菌和细菌是分解落叶的关键参与者，但它们在该过程中的各自贡献及其相互作用仍知之甚少。我们结合半定量蛋白质组分析（1-D PAGE-LC-MS/MS）与细胞外降解酶活性的定性和定量分析，揭示了在落叶分解过程中一种真菌和一种细菌的各自作用。两种模式生物，一种嗜温革兰氏阴性菌（果胶杆菌）和一种子囊菌（构巢曲霉），在含有葡萄糖或山毛榉落叶作为唯一碳源的基础培养基上，分别在纯培养和共培养中生长。果胶杆菌在与真菌共培养时生长最好，而当细菌存在时，构巢曲霉的生长则显著减少。这一观察结果表明，果胶杆菌分解落叶的能力有限，并且以牺牲真菌生长为代价，从构巢曲霉的降解产物中获益。与这一解释一致，我们的蛋白质组分析显示，在含有山毛榉落叶的培养物中，大多数细胞外生物降解酶（即蛋白酶、果胶酶和纤维素酶）都是由真菌表达的，而细菌只产生低水平的果胶酶。
