Details

Autor(en) / Beteiligte

• Fazli, Mustafa
• McCarthy, Yvonne
• Givskov, Michael
• Ryan, Robert P.
• Tolker‐Nielsen, Tim

Titel

The exopolysaccharide gene cluster Bcam1330–Bcam1341 is involved in Burkholderia cenocepacia biofilm formation, and its expression is regulated by c‐di‐GMP and Bcam1349

Ist Teil von

• MicrobiologyOpen (Weinheim), 2013-02, Vol.2 (1), p.105-122

Ort / Verlag

England: Blackwell Publishing Ltd

Erscheinungsjahr

2013

Quelle

MEDLINE

Beschreibungen/Notizen

• In Burkholderia cenocepacia, the second messenger cyclic diguanosine monophosphate (c‐di‐GMP) has previously been shown to positively regulate biofilm formation and the expression of cellulose and type‐I fimbriae genes through binding to the transcriptional regulator Bcam1349. Here, we provide evidence that cellulose and type‐I fimbriae are not involved in B. cenocepacia biofilm formation in flow chambers, and we identify a novel Bcam1349/c‐di‐GMP‐regulated exopolysaccharide gene cluster which is essential for B. cenocepacia biofilm formation. Overproduction of Bcam1349 in trans promotes wrinkly colony morphology, pellicle, and biofilm formation in B. cenocepacia. A screen for transposon mutants unable to respond to the overproduction of Bcam1349 led to the identification of a 12‐gene cluster, Bcam1330–Bcam1341, the products of which appear to be involved in the production of a putative biofilm matrix exopolysaccharide and to be essential for flow‐chamber biofilm formation. We demonstrate that Bcam1349 binds to the promoter region of genes in the Bcam1330–Bcam1341 cluster and that this binding is enhanced by the presence of c‐di‐GMP. Furthermore, we demonstrate that overproduction of both c‐di‐GMP and Bcam1349 leads to increased transcription of these genes, indicating that c‐di‐GMP and Bcam1349 functions together in regulating exopolysaccharide production from the Bcam1330–Bcam1341 gene cluster. Our results suggest that the product encoded by the Bcam1330–Bcam1341 gene cluster is a major exopolysaccharide that provides structural stability to the biofilms formed by B. cenocepacia, and that its production is regulated by c‐di‐GMP through binding to and promotion of the activity of the transcriptional regulator Bcam1349. The molecular basis of the wrinkled colony morphotype of Burkholderia cenocepacia H111 that is displayed upon overexpression of the c‐di‐GMP binding CRP/FNR family member Bcam1349 and upon elevated c‐di‐GMP levels is investigated. A novel putative exopolysaccharide is the cause of the wrinkled colony morphology type and also required for pellicle formation and SDS‐resistant flow‐cell biofilm formation. Transcription of genes encoding this exopolysaccharide is upregulated upon Bcam1349 and c‐di‐GMP overexpression and Bcam1349 binds to the promoter region in a c‐di‐GMP dependent fashion.