Transfer of T6SS_SPI-19 from Salmonella Gallinarum to Salmonella Typhimurium Lacking T6SS_SPI-6 Complements its Colonization Defect in Mice

Salmonella genus harbors five Type VI Secretion System (T6SS) gene clusters. The T6SS encoded in SPI-6 (T6SS_SPI-6) contributes to Salmonella Typhimurium colonization of chickens and mice, while the T6SS encoded in SPI-19 (T6SS_SPI-19) of Salmonella Gallinarum contributes to chicken colonization. Interestingly, the T6SS_SPI-19 of Salmonella Gallinarum complemented the defect in chicken colonization of a Salmonella Typhimurium strain that lacks the T6SS_SPI-6, suggesting that both T6SSs are interchangeable. Here we show that the transfer of Salmonella Gallinarum T6SS_SPI-19 complemented the defect in mice colonization of a Salmonella Typhimurium ΔT6SS_SPI-6 strain, indicating that both T6SSs are functionally redundant during host colonization.