Mycobacterium marinum SecA2 Promotes Stable Granulomas and Induces Tumor Necrosis Factor AlphaIn Vivo

Abstract

ABSTRACTSecA2 is an ATPase present in some pathogenic Gram-positive bacteria, is required for translocation of a limited set of proteins across the cytosolic membrane, and plays an important role in virulence in several bacteria, including mycobacteria that cause diseases such as tuberculosis and leprosy. However, the mechanisms by which SecA2 affects virulence are incompletely understood. To investigate whether SecA2 modulates host immune responsesin vivo, we studiedMycobacterium marinuminfection in two different hosts: an established zebrafish model and a recently described mouse model. Here we show thatM. marinumΔsecA2was attenuated for virulence in both host species and SecA2 was needed for normal granuloma numbers and for optimal tumor necrosis factor alpha response in both zebrafish and mice.M. marinumΔsecA2was more sensitive to SDS and had unique protrusions from its cell envelope when examined by cryo-electron tomography, suggesting that SecA2 is important for bacterial cell wall integrity. These results provide evidence that SecA2 induces granulomas and is required for bacterial modulation of the host response because it affects the mycobacterial cell envelope.