One of the micro-environmental stresses that fungal pathogens, such as Scedosporium aurantiacum, colonising human lungs encounter in vivo is hypoxia, or deficiency of oxygen. In this work, we studied the impacts of a hypoxic micro-environment (oxygen levels ≤1%) on the growth of a clinical S. aurantiacum isolate (WM 06.482; CBS 136046) and an environmental strain (S. aurantiacum WM 10.136; CBS 136049) on mucin-containing synthetic cystic fibrosis sputum medium. Additionally, profiles of secreted proteases were compared between the two isolates and protease activity was assessed using class-specific substrates and inhibitors. Overall, both isolates grew slower and produced less biomass under hypoxia compared to normoxic conditions. The pH of the medium decreased to 4.0 over the cultivation time, indicating that S. aurantiacum released acidic compounds into the medium. Accordingly, secreted proteases of the two isolates were dominated by acidic proteases, including aspartic and cysteine proteases, with optimal protease activity at pH 4.0 and 6.0 respectively. The clinical isolate produced higher aspartic and cysteine protease activities. Conversely, all serine proteases, including elastase-like, trypsin-like, chymotrypsin-like and subtilisin-like proteases had higher activities in the environmental isolate. Sequence similarities to 13 secreted proteases were identified by mass spectrometry (MS) by searching against other fungal proteases in the NCBI database. Results from MS analysis were consistent with those from activity assays. The clinical highly-virulent, and environmental low-virulence S. aurantiacum isolates responded differently to hypoxia in terms of the type of proteases secreted, which may reflect their different virulence properties.

在人体肺部定居的真菌病原体，如金黄色奇观孢子菌，在体内遇到的一种微环境压力是缺氧或缺氧。在这项工作中，我们研究了缺氧微环境对临床的生长的影响（氧气水平≤1％）S. aurantiacum菌分离物（WM 06.482; CBS 136046）和环境菌株（S.橙黄WM 10.136；CBS 136049）在含粘蛋白的合成性囊性纤维化痰培养基中。另外，比较了两种分离物之间分泌的蛋白酶的概况，并使用类别特异性底物和抑制剂评估了蛋白酶的活性。总体而言，与正常氧条件相比，在低氧条件下，两种分离株的生长速度较慢，生物量较少。随着培养时间的延长，培养基的pH值降低至4.0，这表明金黄色葡萄球菌将酸性化合物释放到培养基中。因此，两个分离株的分泌的蛋白酶主要由酸性蛋白酶（包括天冬氨酸和半胱氨酸蛋白酶）主导，分别在pH 4.0和6.0下具有最佳的蛋白酶活性。临床分离株产生更高的天冬氨酸和半胱氨酸蛋白酶活性。相反，所有丝氨酸蛋白酶，包括弹性蛋白酶样，胰蛋白酶样，胰凝乳蛋白酶样和枯草杆菌蛋白酶样蛋白酶，在环境分离物中均具有较高的活性。通过在NCBI数据库中搜索其他真菌蛋白酶，通过质谱（MS）鉴定了与13种分泌的蛋白酶的序列相似性。MS分析的结果与活性分析的结果一致。临床高毒力和环境低毒力的金黄色葡萄球菌 在分泌的蛋白酶类型方面，分离株对缺氧的反应不同，这可能反映了它们不同的毒力特性。