SinR controls enterotoxin expression in Bacillus thuringiensis biofilms.
The entomopathogen Bacillus thuringiensis produces dense biofilms under various conditions. Here, we report that the transition phase regulators Spo0A, AbrB and SinR control biofilm formation and swimming motility in B. thuringiensis, just as they control biofilm formation and swarming motility in the closely related saprophyte species B. subtilis. However, microarray analysis indicated that in B. thuringiensis, in contrast to B. subtilis, SinR does not control an eps operon involved in exopolysaccharides production, but regulates genes involved in the biosynthesis of the lipopeptide kurstakin. This lipopeptide is required for biofilm formation and was previously shown to be important for survival in the host cadaver (necrotrophism). Microarray analysis also revealed that the SinR regulon contains genes coding for the Hbl enterotoxin. Transcriptional fusion assays, Western blots and hemolysis assays confirmed that SinR controls Hbl expression, together with PlcR, the main virulence regulator in B. thuringiensis. We show that Hbl is expressed in a sustained way in a small subpopulation of the biofilm, whereas almost all the planktonic population transiently expresses Hbl. The gene coding for SinI, an antagonist of SinR, is expressed in the same biofilm subpopulation as hbl, suggesting that hbl transcription heterogeneity is SinI-dependent. B. thuringiensis and B. cereus are enteric bacteria which possibly form biofilms lining the host intestinal epithelium. Toxins produced in biofilms could therefore be delivered directly to the target tissue.
Laboratory for Microbial Dynamics (LaMDa) and Department of Pharmaceutical Biosciences, School of Pharmacy, University of Oslo, Oslo, Norway.
Annette
A
Fagerlund
Micalis, INRA (UMR1319), Domaine de Vilvert, Jouy-en-Josas, France ; Micalis, AgroParistech (UMR1319), Domaine de Vilvert, Jouy-en-Josas, France.
Thomas
T
Dubois
Laboratory for Microbial Dynamics (LaMDa) and Department of Pharmaceutical Biosciences, School of Pharmacy, University of Oslo, Oslo, Norway.
Ole-Andreas
OA
Økstad
Micalis, INRA (UMR1319), Domaine de Vilvert, Jouy-en-Josas, France ; Micalis, AgroParistech (UMR1319), Domaine de Vilvert, Jouy-en-Josas, France.
Emilie
E
Verplaetse
Micalis, INRA (UMR1319), Domaine de Vilvert, Jouy-en-Josas, France ; Micalis, AgroParistech (UMR1319), Domaine de Vilvert, Jouy-en-Josas, France.
Nathalie
N
Gilois
Micalis, INRA (UMR1319), Domaine de Vilvert, Jouy-en-Josas, France ; Micalis, AgroParistech (UMR1319), Domaine de Vilvert, Jouy-en-Josas, France.
Imène
I
Bennaceur
Micalis, INRA (UMR1319), Domaine de Vilvert, Jouy-en-Josas, France ; Micalis, AgroParistech (UMR1319), Domaine de Vilvert, Jouy-en-Josas, France.
Stéphane
S
Perchat
Institut Pasteur, CNRS URA 2172, Unité de Biologie des Bactéries Pathogènes à Gram positif, Paris, France.
Myriam
M
Gominet
Micalis, INRA (UMR1319), Domaine de Vilvert, Jouy-en-Josas, France ; Micalis, AgroParistech (UMR1319), Domaine de Vilvert, Jouy-en-Josas, France.
Stéphane
S
Aymerich
Laboratory for Microbial Dynamics (LaMDa) and Department of Pharmaceutical Biosciences, School of Pharmacy, University of Oslo, Oslo, Norway.
Anne-Brit
AB
Kolstø
Micalis, INRA (UMR1319), Domaine de Vilvert, Jouy-en-Josas, France ; Micalis, AgroParistech (UMR1319), Domaine de Vilvert, Jouy-en-Josas, France.
Didier
D
Lereclus
Micalis, INRA (UMR1319), Domaine de Vilvert, Jouy-en-Josas, France ; Micalis, AgroParistech (UMR1319), Domaine de Vilvert, Jouy-en-Josas, France.
Michel
M
Gohar
D001409:Bacillus cereus / Q000502:physiology; D001413:Bacillus thuringiensis / Q000502:physiology*; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D018441:Biofilms; D004768:Enterotoxins / Q000096:biosynthesis* / Q000235:genetics; D015964:Gene Expression Regulation, Bacterial / Q000502:physiology*; D018085:Regulon / Q000502:physiology*
D001426:Bacterial Proteins; D004768:Enterotoxins; C076733:FlaD protein, Bacteria