Absence of BapA type III effector protein affects Burkholderia pseudomallei intracellular lifecycle in human host cells


Choh L., Ong G., Chua E., Vellasamy K. M. , Mariappan V., Khan A. M. , ...More

PROCESS BIOCHEMISTRY, vol.108, pp.48-59, 2021 (Journal Indexed in SCI) identifier identifier

  • Publication Type: Article / Article
  • Volume: 108
  • Publication Date: 2021
  • Doi Number: 10.1016/j.procbio.2021.05.025
  • Title of Journal : PROCESS BIOCHEMISTRY
  • Page Numbers: pp.48-59
  • Keywords: BapA, Burkholderia pseudomallei, Intracellular lifecycle, Melioidosis, Type III secretion effector, Type III secretion system cluster 3, ENTEROPATHOGENIC ESCHERICHIA-COLI, SECRETION SYSTEM, BACTERIAL INVASION, SHIGELLA-FLEXNERI, IDENTIFICATION, MELIOIDOSIS, INFECTION, VIRULENCE, TIP, PATHOGENESIS

Abstract

The etiological agent of melioidosis, Burkholderia pseudomallei, utilises a type III secretion system cluster 3 (T3SS3) to deliver proteins termed type III effectors (T3SEs) into the host cytoplasm in order to establish an intracellular lifecycle in phagocytic and non-phagocytic cells, thus playing an important role in pathogenesis. To gain insight into possible functional roles for BapA, a putative T3SE with unknown function, in the intracellular lifecycle of B.pseudomallei, bapA gene knockout mutant was constructed. The effect of the knockout on virulence to the otherwise isogenic parental strain, K96243, was studied by cellular infection assays and Caenorhabditis elegans killing assay. The attachment and subsequent entry into A549 cells was significantly (P < 0.05) attenuated in the Delta bapA compared to K96243. However, intracellular replication was not affected. Furthermore, the cell-to-cell spreading capacity of Delta bapA was impaired although the mutant exhibited no evident defect in its actin tail formation. Additionally, phagocytosis and intracellular replication rates of Delta bapA in U937 macrophage cells were significantly reduced relative to K96243 without phagosomal escape being affected. Based on these observations, we conclude that the BapA T3SE could play an important role in B.pseudomallei intracellular lifecycle, especially, in the early stages of attachment and entry into the host cell.