ABSTRACT

Candida albicans is the most prevalent fungal pathogen in humans, particularly in immunocompromised patients. In this study, by screening a C. albicans mutant library, we first identified that the MSS2 gene, an ortholog of Saccharomyces cerevisiae MSS2 required for mitochondrial respiration, mediates chitosan resistance. Upon treatment with 0.2% chitosan, the growth of mss2Δ strains was strikingly impaired, and MSS2 expression was significantly repressed by chitosan. Furthermore, mss2Δ strains exhibited slow growth on medium supplemented with glycerol as the sole carbon source. Similar to the chitosan-treated wild-type strain, the mss2Δ strain exhibited a significantly impaired ATP production ability. These data suggest that an antifungal mechanism of chitosan against C. albicans acts by inhibiting MSS2 gene expression, leading to repression of mitochondrial function. Normal respiratory function is suggested to be required for fungal virulence. Interestingly, the mss2Δ mutant strains exhibited significantly impaired invasive ability in vitro and ex vivo but retained normal hyphal development ability in liquid medium. Furthermore, the MSS2 deletion strains could not form robust biofilms and exhibited significantly reduced virulence. Collectively, these results demonstrated that the antifungal effect of chitosan against C. albicans is mediated via inhibition of mitochondrial biogenesis. These data may provide another strategy for antifungal drug development via inhibition of fungal mitochondria.

摘要

白色念珠菌是人类中最普遍的真菌病原体，尤其是在免疫功能低下的患者中。在这项研究中，通过筛选白色念珠菌突变体文库，我们首先确定了线粒体呼吸所需的酿酒酵母MSS2直系同源物MSS2基因介导了壳聚糖抗性。用0.2％的壳聚糖处理后，mss2Δ菌株的生长显着受损，并且壳聚糖显着抑制了MSS2表达。此外，mss2Δ菌株在补充有甘油作为唯一碳源的培养基上显示出缓慢的生长。与壳聚糖处理的野生型菌株类似，mss2Δ菌株表现出明显的ATP产生能力受损。这些数据表明壳聚糖针对白色念珠菌的抗真菌机制通过抑制MSS2基因表达而起作用，导致线粒体功能受到抑制。建议真菌毒力需要正常的呼吸功能。有趣的是，mss2Δ突变株在体外和离体时均表现出明显的侵袭能力受损，但在液体培养基中仍保持正常的菌丝发育能力。此外，MSS2缺失菌株不能形成坚固的生物膜，并且显示出显着降低的毒力。总的来说，这些结果表明壳聚糖对白色念珠菌的抗真菌作用是通过抑制线粒体的生物发生而介导的。这些数据可能为抑制真菌线粒体提供了另一种抗真菌药物开发的策略。