TheESX-5 secretion system enables carbon source utilization and growth in mice.

Abstract

uses several ESX type VII protein secretion systems for pathogenesis.ESX-5 is only partially characterized because it is essential for growth in standard lab culture conditions. To circumvent ESX-5 essentiality, we made anstrain in which the central ESX-5 membrane component EccDcan be conditionally depleted. Here, we use this strain to demonstrate thatrequires the ESX-5 secretion system to grow using specific carbon sources, to grow in cultured macrophages, and to replicate and disseminate in aerosol-infected mice.requires ESX-5 to use glycerol or glucose as the sole carbon source. Use of glycerol and glucose also depends on the outer membrane protein PPE51. We show thatrequires ESX-5 activity for outer membrane export and surface exposure of PPE51. Expression of the outer membrane porin MspA enabled growth of ESX-5-deficienton glycerol, suggesting that the main function of ESX-5is to export nutrient transporters to the outer membrane. Depletion of EccDin acutely infected mice caused clearance offrom lung tissues, demonstrating the critical importance of ESX-5 activity during infection. Our findings suggest that ESX-5 promotespathogenesis by mediating export of outer membrane proteins that enable nutrient acquisition.IMPORTANCEESX type VII secretion systems play important roles in pathogenesis, but the functions of ESX-5 are not well characterized because it is essential for growth in standard lab culture conditions. We used a strain that conditionally expresses a central membrane component of the ESX-5 secretion apparatus to determine how ESX-5 impacts growth in lab cultures and in a mouse infection model. We found thatrequires ESX-5 to grow using several carbon sources and to grow in the lungs of infected mice. Inhibiting production of the ESX-5 secretion system in mice also led to clearance offrom lung tissues. Our results demonstrate that theESX-5 system is a critical virulence factor and suggest that ESX-5 is a strong candidate for antitubercular drug development.