Balasubramanian Hari Krishnan, Osmani Stephen A
Molecular, Cellular, and Developmental Biology Program, Ohio State University, Columbus, USA, OH.
Molecular, Cellular, and Developmental Biology Program, Ohio State University, Columbus, USA, OH.
Autophagy Rep. 2025 Aug 22;4(1):2547194. doi: 10.1080/27694127.2025.2547194. eCollection 2025.
During chronic infections, biofilms are resistant to both antimicrobial agents as well as the host immune system, often giving rise to recalcitrant persister cells with reduced mitochondrial function rendering biofilm infections difficult to cure. How mitochondrial dynamics and fate are regulated during fungal biofilm formation is poorly understood. In this study, we used live cell microscopy to track mitochondrial morphology during in vitro biofilm formation. We show that mitochondria undergo fragmentation during early biofilm development, and that externally induced oxidative stress similarly induces mitochondrial fragmentation, indicating a role for redox regulation in this process. Deletion of core components of the mitochondrial fission machinery resulted in a swollen mitochondrial phenotype. Mitochondria in the fission-mutant strains are known not to complete fragmentation in response to externally induced oxidative stress, and we show that this results in a "beads on a string" phenotype. We further show that mitochondria remain unfragmented during biofilm formation in the fission-mutant strains, although other biofilm cellular modifications, like disassembly of microtubules, are unaffected. We report that mitophagy is triggered during biofilm development in nitrogen-limiting conditions independently of mitochondrial fission. This indicates mitochondrial fission is dispensable for mitophagy during biofilm development with limiting nitrogen. We further note that general autophagy, but notably not mitophagy, is triggered during biofilm development in carbon-limiting conditions, demonstrating differential regulation of mitochondrial fate in response to specific nutritional limitations during fungal biofilm formation.
在慢性感染期间，生物膜对抗菌剂和宿主免疫系统均具有抗性，常常产生线粒体功能降低的顽固持留菌，这使得生物膜感染难以治愈。目前对于真菌生物膜形成过程中线粒体动力学和命运是如何调控的了解甚少。在本研究中，我们使用活细胞显微镜技术追踪体外生物膜形成过程中的线粒体形态。我们发现，在生物膜发育早期线粒体发生片段化，并且外部诱导的氧化应激同样会诱导线粒体片段化，这表明氧化还原调节在该过程中发挥作用。线粒体分裂机制核心组分的缺失导致线粒体出现肿胀表型。已知裂变突变株中的线粒体在受到外部诱导的氧化应激时不会完成片段化，并且我们发现这会导致“串珠”表型。我们进一步表明，尽管其他生物膜细胞修饰（如微管解聚）不受影响，但在裂变突变株的生物膜形成过程中线粒体仍未发生片段化。我们报道，在氮限制条件下生物膜发育过程中会触发线粒体自噬，且该过程与线粒体裂变无关。这表明在氮限制的生物膜发育过程中，线粒体裂变对于线粒体自噬是可有可无的。我们还注意到，在碳限制条件下生物膜发育过程中会触发一般自噬，但明显不会触发线粒体自噬，这表明在真菌生物膜形成过程中，线粒体命运会因特定营养限制而受到不同的调控。
