TY - JOUR
T1 - A third mode of surface-associated growth
T2 - immobilization of Salmonella enterica serovar Typhimurium modulates the RpoS-directed transcriptional programme
AU - Knudsen, Gitte M.
AU - Nielsen, Maj-Britt
AU - Grassby, Terri
AU - Danino-Appleton, Vittoria
AU - Thomsen, Line Elnif
AU - Colquhoun, Ian J.
AU - Brocklehurst, Tim F.
AU - Olsen, John Elmerdahl
AU - Hinton, Jay C. D.
PY - 2012/8
Y1 - 2012/8
N2 - Although the growth of bacteria has been studied for more than a century, it is only in recent decades that surface-associated growth has received attention. In addition to the well-characterized biofilm and swarming lifestyles, bacteria can also develop as micro-colonies supported by structured environments in both food products and the GI tract. This immobilized mode of growth has not been widely studied. To develop our understanding of the effects of immobilization upon a food-borne bacterial pathogen, we used the IFR Gel Cassette model. The transcriptional programme and metabolomic profile of Salmonella enterica serovar Typhimurium ST4/74 were compared during planktonic and immobilized growth, and a number of immobilization-specific characteristics were identified. Immobilized S. typhimurium did not express motility and chemotaxis genes, and electron microscopy revealed the absence of flagella. The expression of RpoS-dependent genes and the level of RpoS protein were increased in immobilized bacteria, compared with planktonic growth. Immobilized growth prevented the induction of SPI1, SPI4 and SPI5 gene expression, likely mediated by the FliZ transcriptional regulator. Using an epithelial cell-based assay, we showed that immobilized S. typhimurium was significantly less invasive than planktonic bacteria, and we suggest that S. typhimurium grown in immobilized environments are less virulent than planktonic bacteria. Our findings identify immobilization as a third type of surface-associated growth that is distinct from the biofilm and swarming lifestyles of Salmonella.
AB - Although the growth of bacteria has been studied for more than a century, it is only in recent decades that surface-associated growth has received attention. In addition to the well-characterized biofilm and swarming lifestyles, bacteria can also develop as micro-colonies supported by structured environments in both food products and the GI tract. This immobilized mode of growth has not been widely studied. To develop our understanding of the effects of immobilization upon a food-borne bacterial pathogen, we used the IFR Gel Cassette model. The transcriptional programme and metabolomic profile of Salmonella enterica serovar Typhimurium ST4/74 were compared during planktonic and immobilized growth, and a number of immobilization-specific characteristics were identified. Immobilized S. typhimurium did not express motility and chemotaxis genes, and electron microscopy revealed the absence of flagella. The expression of RpoS-dependent genes and the level of RpoS protein were increased in immobilized bacteria, compared with planktonic growth. Immobilized growth prevented the induction of SPI1, SPI4 and SPI5 gene expression, likely mediated by the FliZ transcriptional regulator. Using an epithelial cell-based assay, we showed that immobilized S. typhimurium was significantly less invasive than planktonic bacteria, and we suggest that S. typhimurium grown in immobilized environments are less virulent than planktonic bacteria. Our findings identify immobilization as a third type of surface-associated growth that is distinct from the biofilm and swarming lifestyles of Salmonella.
KW - Faculty of Health and Medical Sciences
KW - Salmonella Typhimurium
KW - immobilization
KW - Metabolism
KW - global expresssion
U2 - 10.1111/j.1462-2920.2012.02703.x
DO - 10.1111/j.1462-2920.2012.02703.x
M3 - Journal article
C2 - 22356617
SN - 1462-2912
VL - 14
SP - 1855
EP - 1875
JO - Environmental Microbiology
JF - Environmental Microbiology
IS - 8
ER -