The cytotoxic type 3 secretion system 1 of rewires host gene expression to subvert cell death and activate cell survival pathways.

Bacterial effectors potently manipulate host signaling pathways. The marine bacterium () delivers effectors into host cells through two type 3 secretion systems (T3SSs). T3SS1 is vital for survival in the environment, whereas T3SS2 causes acute gastroenteritis in human hosts. Although the natural host is undefined, T3SS1 effectors attack highly conserved cellular processes and pathways to orchestrate nonapoptotic cell death. To understand how the concerted action of T3SS1 effectors globally affects host cell signaling, we compared gene expression changes over time in primary fibroblasts infected with that have a functional T3SS1 (T3SS1) to those in cells infected with lacking T3SS1 (T3SS1). Overall, the host transcriptional response to both T3SS1 and T3SS1 was rapid, robust, and temporally dynamic. T3SS1 rewired host gene expression by specifically altering the expression of 398 genes. Although T3SS1 effectors targeted host cells at the posttranslational level to cause cytotoxicity, T3SS1 also precipitated a host transcriptional response that initially activated cell survival and repressed cell death networks. The increased expression of several key prosurvival transcripts mediated by T3SS1 depended on a host signaling pathway that is silenced posttranslationally later in infection. Together, our analysis reveals a complex interplay between the roles of T3SS1 as both a transcriptional and posttranslational manipulator of host cell signaling.