Open AccessAcidic pH is required for the functional assembly of the type III secretion system encoded by Salmonella pathogenicity island 2
Author(s) -
Rappl Catherine,
Deiwick Jörg,
Hensel Michael
Publication year - 2003
Publication title -
fems microbiology letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.899
H-Index - 151
eISSN - 1574-6968
pISSN - 0378-1097
DOI - 10.1016/s0378-1097(03)00638-4
Subject(s) - secretion , salmonella , pathogenicity island , type three secretion system , effector , biology , salmonella enterica , operon , microbiology and biotechnology , flagellum , intracellular , biochemistry , bacteria , virulence , gene , escherichia coli , genetics
Salmonella enterica employs two type III secretion systems (T3SS) for interactions with host cells during pathogenesis. The T3SS encoded by Salmonella pathogenicity island 2 (SPI2) is required for the intracellular replication of Salmonella and the survival inside phagocytes. During growth in vitro, acidic pH is a signal that promotes secretion of proteins by this T3SS. We analyzed protein levels and subcellular localization of various T3SS subunits under in vitro conditions at acidic or neutral pH, inducing or ablating secretion, respectively. Growth at acidic pH resulted in higher levels of SsaC, a protein forming the outer membrane secretin, without increasing expression of the operon containing ssaC . Acidic pH also induced oligomerization of SsaC subunits, a prerequisite for a functional secretin pore. It has previously been described that environmental stimuli resembling the intraphagosomal habitat of Salmonella control the expression of SPI2 genes. Here we propose that such stimuli also modulate the assembly of a functional T3SS that is capable of translocation of effector proteins into the host cell.