AUTHOR=Srinon Varintip , Chaiwattanarungruengpaisan Somjit , Korbsrisate Sunee , Stevens Joanne M. 

TITLE=Burkholderia pseudomallei BimC Is Required for Actin-Based Motility, Intracellular Survival, and Virulence

JOURNAL=Frontiers in Cellular and Infection Microbiology

VOLUME=9

YEAR=2019

URL=https://www.frontiersin.org/journals/cellular-and-infection-microbiology/articles/10.3389/fcimb.2019.00063

DOI=10.3389/fcimb.2019.00063

ISSN=2235-2988

ABSTRACT=<p>The intracellular pathogen <italic>Burkholderia pseudomallei</italic>, the etiological agent of melioidosis in humans and various animals, is capable of survival and movement within the cytoplasm of host cells by a process known as actin-based motility. The bacterial factor BimA is required for actin-based motility through its direct interaction with actin, and by mediating actin polymerization at a single pole of the bacterium to promote movement both within and between cells. However, little is known about the other bacterial proteins required for this process. Here, we have investigated the role of the <italic>bimC</italic> gene (<italic>bpss1491</italic>) which lies immediately upstream of the <italic>bimA</italic> gene (<italic>bpss1492</italic>) on the <italic>B. pseudomallei</italic> chromosome 2. Conserved amongst all <italic>B. pseudomallei, B. mallei</italic> and <italic>B. thailandensis</italic> strains sequenced to date, this gene encodes an iron-binding protein with homology to a group of proteins known as the bacterial autotransporter heptosyltransferase (BAHT) family. We have constructed a <italic>B. pseudomallei bimC</italic> deletion mutant and demonstrate that it is defective in intracellular survival in HeLa cells, but not in J774.1 macrophage-like cells. The <italic>bimC</italic> mutant is defective in cell to cell spread as demonstrated by ablation of plaque formation in HeLa cells, and by the inability to form multi-nucleated giant cells in J774.1 cells. These phenotypes in intracellular survival and cell to cell spread are not due to the loss of expression and polar localization of the BimA protein on the surface of intracellular bacteria, however they do correlate with an inability of the bacteria to recruit and polymerize actin. Furthermore, we also establish a role for <italic>bimC</italic> in virulence of <italic>B. pseudomallei</italic> using a <italic>Galleria mellonella</italic> larvae model of infection. Taken together, our findings indicate that <italic>B. pseudomallei</italic> BimC plays an important role in intracellular behavior and virulence of this emerging pathogen.</p>