Detailed analysis of c-di-GMP mediated regulation of csgD expression in Salmonella typhimurium.
BACKGROUND
The secondary messenger cyclic di-GMP promotes biofilm formation by up regulating the expression of csgD, encoding the major regulator of rdar biofilm formation in Salmonella typhimurium. The GGDEF/EAL domain proteins regulate the c-di-GMP turnover. There are twenty- two GGDEF/EAL domain proteins in the genome of S. typhimurium. In this study, we dissect the role of individual GGDEF/EAL proteins for csgD expression and rdar biofilm development.


RESULTS
Among twelve GGDEF domains, two proteins upregulate and among fifteen EAL domains, four proteins down regulate csgD expression. We identified two additional GGDEF proteins required to promote optimal csgD expression. With the exception of the EAL domain of STM1703, solely, diguanylate cyclase and phosphodiesterase activities are required to regulate csgD mediated rdar biofilm formation. Identification of corresponding phosphodiesterases and diguanylate cyclases interacting in the csgD regulatory network indicates various levels of regulation by c-di-GMP. The phosphodiesterase STM1703 represses transcription of csgD via a distinct promoter upstream region.


CONCLUSIONS
The enzymatic activity and the protein scaffold of GGDEF/EAL domain proteins regulate csgD expression. Thereby, c-di-GMP adjusts csgD expression at multiple levels presumably using a multitude of input signals.
Department of Microbiology, Tumor and Cell Biology, Karolinska Institutet, Stockholm, Sweden.|Present Address: Department of Molecular Biology, Umeå University, Umeå, Sweden.|Department of Allied Health Sciences, University of Health Sciences, Lahore, Pakistan.
Irfan
I
Ahmad
Department of Microbiology, Tumor and Cell Biology, Karolinska Institutet, Stockholm, Sweden.
Annika
A
Cimdins
Department of Microbiology, Tumor and Cell Biology, Karolinska Institutet, Stockholm, Sweden.|Present Address: Department of Biology, Laboratory for Microbiology, Philipps-University Marburg, Marburg, Germany.
Timo
T
Beske
Department of Microbiology, Tumor and Cell Biology, Karolinska Institutet, Stockholm, Sweden. ute.romling@ki.se.
Ute
U
Römling
D001426:Bacterial Proteins / Q000235:genetics* / Q000302:isolation & purification / Q000378:metabolism*; D018441:Biofilms / Q000254:growth & development; D006152:Cyclic GMP / Q000031:analogs & derivatives* / Q000378:metabolism; D029968:Escherichia coli Proteins / Q000378:metabolism; D017353:Gene Deletion; D015964:Gene Expression Regulation, Bacterial / Q000235:genetics; D009154:Mutation; D010641:Phenotype; D010727:Phosphoric Diester Hydrolases / Q000378:metabolism; D019761:Phosphorus-Oxygen Lyases / Q000378:metabolism; D000072417:Protein Domains / Q000235:genetics; D012486:Salmonella typhimurium / Q000201:enzymology / Q000235:genetics / Q000378:metabolism* / Q000502:physiology*; D015398:Signal Transduction; D015854:Up-Regulation
D001426:Bacterial Proteins; D029968:Escherichia coli Proteins; C062025:bis(3',5')-cyclic diguanylic acid; D010727:Phosphoric Diester Hydrolases; D019761:Phosphorus-Oxygen Lyases; C060720:diguanylate cyclase; D006152:Cyclic GMP
CsgD; GGDEF/EAL domain proteins; Salmonella typhimurium; biofilm formation; c-di-GMP; rdar morphotype