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Influence of the ^B Stress Factor and yxaB, the Gene for a Putative Exopolysaccharide Synthase under ^B Control, on Biofilm Formation

Krzysztofa Nagórska,¹ Krzysztof Hinc,² Mark A. Strauch,³ and Micha Obuchowski^2*

Department of Molecular Biology, University of Gdask, Gdask, Poland,¹ Department of Medical Biotechnology, Intercollegiate Faculty of Biotechnology, Medical University of Gdask, Gdask, Poland,² Department of Biomedical Sciences, Dental School, University of Maryland, Baltimore, Maryland³

Received 15 October 2007/ Accepted 22 February 2008

Bacillus subtilis forms structured communities of biofilms encased in an exopolysaccharide matrix on solid surfaces and at the air-liquid interface. It is postulated that nonoptimal growth conditions induce this multicellular behavior. We showed that under laboratory conditions a strain deleted for sigB was unable to form a floating pellicle on the surface of a liquid medium. However, overexpression of yxaB, encoding a putative exopolysaccharide synthase, from a p_Spac promoter in a sigB-deleted strain resulted in partial recovery of the wild-type phenotype, indicating the participation of the YxaB protein in this multicellular process. We present data concerning the regulation of transcription of genes yxaB and yxaA, encoding a putative glycerate kinase. Both genes are cotranscribed as a single transcription unit from a ^A-dependent promoter during vegetative growth of a liquid bacterial culture. The promoter driving transcription of the yxaAB operon is regulated by AbrB. In addition, the second gene in the operon, yxaB, possesses its own promoter, which is recognized by RNA polymerase containing the ^B subunit. This transcription start site is used under general stress conditions, resulting in increased expression.

Published ahead of print on 7 March 2008.