SPI1 and infection: SPI1 effectors invF and SPI1 master regulator hilA were significantly upregulated in STM ΔchiA mutant 2 hours post-infection (hpi), whereas SPI2 encoded ssaV expression was similar in both STM WT and STM ΔchiA strains at 16 hpi (Fig 1F and 1G), suggesting that the reduced bacterial invasion in the epithelial cells by ΔchiA mutant is independent of SPI1 gene expression.