Dual RNA-seq reveals a type 6 secretion system-dependent blockage of TNF-α signaling and BicA as a virulence factor important during gastrointestinal infection.

Melioidosis is a disease caused by the Gram-negative bacillus (), commonly found in soil and water of endemic areas. Naturally acquired human melioidosis infections can result from either exposure through percutaneous inoculation, inhalation, or ingestion of soil-contaminated food or water. Our prior studies recognized as an effective enteric pathogen, capable of establishing acute or chronic gastrointestinal infections following oral inoculation. However, the specific mechanisms and virulence factors involved in the pathogenesis of during intestinal infection are unknown. In our current study, we standardized an intestinal infection model using primary intestinal epithelial cells (IECs) and demonstrated that requires a functional T6SS for full virulence. Further, we performed dual RNA-seq analysis on -infected IECs to evaluate differentially expressed host and bacterial genes in the presence or absence of a T6SS. Our results showed a dysregulation in the TNF-α signaling via NF-κB pathway in the absence of the T6SS, with some of the genes involved in inflammatory processes and cell death also affected. Analysis of the bacterial transcriptome identified virulence factors and regulatory proteins playing a role during infection, with association to the T6SS. By using a transposon mutant library and isogenic mutants, we showed that deletion of the gene, encoding a putative T3SS/T6SS regulator, ablated intracellular survival and plaque formation by and impacted survival and virulence when using murine models of acute and chronic gastrointestinal infection. Overall, these results highlight the importance of the type 6 secretion system in the gastrointestinal pathogenesis of .