Group A Streptococci Shift the Balance of Muscular Mitochondrial Dynamics

The most severe form of invasive group A Streptococcus (GAS) disease is necrotizing fasciitis described as rapidly muscle destruction. Muscles are responsible for energetic functions which are mostly provided by proper mitochondrial function. Mitochondria are the highly dynamic organelles, constantly undergoing fusion and fission. Pathogen aim at preserving the bacterial replication niche by targeting to mitochondria and inducing cell death. This prompted us to specifically analyze the effect on muscular mitochondria upon GAS infection. By using electron microscopic analysis of GAS‐infected muscle tissue, the muscle is strongly damaged and the mitochondria are fragmented and structurally abnormal. Further, we found GAS alters the morphology of cell mitochondria, inducing fragmentation of the mitochondria network which accompanied by decreasing the levels of fusion protein in mouse muscle cell, C2C12. Furthermore, our data demonstrate that mitochondrial function is not strictly dependent on morphology. Our results reveal that disruption of fusion induces more profound defects on lacking of fission during GAS infection, and imply that while fusion is required throughout life, fission is more important later in life likely to combat bacterial infection. Overall, our study provides important new insights into the central role of mitochondrial dynamics in innate immunity. Support or Funding Information MOST 108‐2320‐B‐006‐013