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Journal of Bacteriology, July 2007, p. 5302-5313, Vol. 189, No. 14
0021-9193/07/$08.00+0     doi:10.1128/JB.00239-07
Copyright © 2007, American Society for Microbiology. All Rights Reserved.

Low Concentrations of Bile Salts Induce Stress Responses and Reduce Motility in Bacillus cereus ATCC 14570{triangledown} ,{dagger}

Simen M. Kristoffersen,1,2 Solveig Ravnum,2 Nicolas J. Tourasse,2 Ole Andreas Økstad,2 Anne-Brit Kolstø,2 and William Davies1*

Department of Molecular Biosciences, University of Oslo, PB 1041 Blindern, 0316 Oslo, Norway,1 Department of Pharmaceutical Biosciences, School of Pharmacy, University of Oslo, PB 1068 Blindern, 0316 Oslo, Norway2

Received 13 February 2007/ Accepted 30 April 2007

Tolerance to bile salts was investigated in forty Bacillus cereus strains, including 17 environmental isolates, 11 dairy isolates, 3 isolates from food poisoning outbreaks, and 9 other clinical isolates. Growth of all strains was observed at low bile salt concentrations, but no growth was observed on LB agar plates containing more than 0.005% bile salts. Preincubation of the B. cereus type strain, ATCC 14579, in low levels of bile salts did not increase tolerance levels. B. cereus ATCC 14579 was grown to mid-exponential growth phase and shifted to medium containing bile salts (0.005%). Global expression patterns were determined by hybridization of total cDNA to a 70-mer oligonucleotide microarray. A general stress response and a specific response to bile salts were observed. The general response was similar to that observed in cultures grown in the absence of bile salts but at a higher (twofold) cell density. Up-regulation of several putative multidrug exporters and transcriptional regulators and down-regulation of most motility genes were observed as part of the specific response. Motility experiments in soft agar showed that motility decreased following bile salts exposure, in accordance with the transcriptional data. Genes encoding putative virulence factors were either unaffected or down-regulated.

* Corresponding author. Mailing address: Department of Molecular Biosciences, University of Oslo, PB1041 Blindern, 0316 Oslo, Norway. Phone: 47 22 85 45 91. Fax: 47 22 85 46 05. E-mail: william.davies{at}imbv.uio.no

{triangledown} Published ahead of print on 11 May 2007.

{dagger} Supplemental material for this article is available at http://jb.asm.org/.

Journal of Bacteriology, July 2007, p. 5302-5313, Vol. 189, No. 14
0021-9193/07/$08.00+0     doi:10.1128/JB.00239-07
Copyright © 2007, American Society for Microbiology. All Rights Reserved.



This article has been cited by other articles:

  • den Besten, H. M. W., Mols, M., Moezelaar, R., Zwietering, M. H., Abee, T. (2009). Phenotypic and Transcriptomic Analyses of Mildly and Severely Salt-Stressed Bacillus cereus ATCC 14579 Cells. Appl. Environ. Microbiol. 75: 4111-4119 [Abstract] [Full Text]  


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