Transfer of T6SSSPI-19from SalmonellaGallinarum to SalmonellaTyphimurium Lacking T6SSSPI-6Complements its Colonization Defect in Mice

Salmonellagenus harbors five Type VI Secretion System (T6SS) gene clusters. The T6SS encoded in SPI-6 (T6SSSPI-6) contributes to SalmonellaTyphimurium colonization of chickens and mice, while the T6SS encoded in SPI-19 (T6SSSPI-19) of SalmonellaGallinarum contributes to chicken colonization. Interestingly, the T6SSSPI-19of SalmonellaGallinarum complemented the defect in chicken colonization of a SalmonellaTyphimurium strain that lacks the T6SSSPI-6, suggesting that both T6SSs are interchangeable. Here we show that the transfer of SalmonellaGallinarum T6SSSPI-19complemented the defect in mice colonization of a SalmonellaTyphimurium ΔT6SSSPI-6strain, indicating that both T6SSs are functionally redundant during host colonization.