SulA-induced filamentation in Salmonella enterica serovar Typhimurium: effects on SPI-1 expression and epithelial infection.

Salmonella enterica serovar Typhimurium is capable of adopting a filamentous phenotype in response to damage. How this adaptive response affects bacterial virulence is unclear. We have examined the hypothesis that filamentation affects the ability of Salmonella to infect host cells. Expression of the cell division inhibitor SulA in Salm. Typhimurium SL1344 from an arabinose-inducible plasmid resulted in filamentation. We examined expression of the type 3 secretion system (T3SS) encoded by Salmonella pathogenicity island 1 (SPI-1) using SL1344 expressing a chromosomal PprgH-gfp reporter. Single cell analysis of SulA-induced SL1344 PprgH-gfp revealed a relationship between increasing cell length and decreasing propensity for prgH expression, but there was no evidence of a significant change in prgH expression evident at the whole population level. Filamentous Salm. Typhimurium were capable of initiating membrane ruffling on MDCK epithelial cells, but only nonfilamentous bacteria (< 6 μm) invade.   Induction of SulA expression in Salmonella inhibits septation. Increasing filament length is associated with down-regulation of SPI-1 gene expression, but a significant proportion of filaments retain the ability to produce SPI-1 T3SS and induce membrane ruffles on epithelia. Despite an active SPI-1 T3SS, filamentous Salmonella are unable to invade epithelial cells. Our findings that filamentous Salmonella can express an invasive phenotype but fail to invade cells suggest that their presence in food does not constitute an immediate risk of infection until septation occurs. The described SulA expression model provides a convenient model for studying the impact of filamentation in the absence of additional stresses.

Humphrey S ，Macvicar T ，Stevenson A ，Roberts M ，Humphrey TJ ，Jepson MA ... -  《-》

Differences in Salmonella enterica serovar Typhimurium strain invasiveness are associated with heterogeneity in SPI-1 gene expression.

Clark L ，Perrett CA ，Malt L ，Harward C ，Humphrey S ，Jepson KA ，Martinez-Argudo I ，Carney LJ ，La Ragione RM ，Humphrey TJ ，Jepson MA ... -  《-》

LuxS-based quorum sensing does not affect the ability of Salmonella enterica serovar Typhimurium to express the SPI-1 type 3 secretion system, induce membrane ruffles, or invade epithelial cells.

Perrett CA ，Karavolos MH ，Humphrey S ，Mastroeni P ，Martinez-Argudo I ，Spencer H ，Bulmer D ，Winzer K ，McGhie E ，Koronakis V ，Williams P ，Khan CM ，Jepson MA ... -  《-》

Spatial segregation of virulence gene expression during acute enteric infection with Salmonella enterica serovar Typhimurium.

Laughlin RC ，Knodler LA ，Barhoumi R ，Payne HR ，Wu J ，Gomez G ，Pugh R ，Lawhon SD ，Bäumler AJ ，Steele-Mortimer O ，Adams LG ... -  《mBio》

Enhanced recovery of Salmonella Typhimurium DT104 from exposure to stress at low temperature.

Humphrey S ，Clark LF ，Humphrey TJ ，Jepson MA ... -  《-》