Bacillus cereus cytotoxins Hbl, Nhe and CytK are secreted via the Sec translocation pathway

BMC Microbiology

Research Article

Toril Lindbäck¹  Per Einar Granum¹  Annette Fagerlund² 

[1] Norwegian School of Veterinary Science, Department of Food Safety and Infection Biology, PO Box 8146 Dep, N-0033, Oslo, Norway;Norwegian School of Veterinary Science, Department of Food Safety and Infection Biology, PO Box 8146 Dep, N-0033, Oslo, Norway;Laboratory for Microbial Dynamics (LaMDa) and Department of Pharmaceutical Biosciences, University of Oslo, PO Box 1068, N-0316, BlindernOslo, Norway;

关键词: Signal Peptide;    Azide;    Signal Peptide Sequence;    Overexpressing Strain;    Toxin Secretion;   

DOI  :  10.1186/1471-2180-10-304

 received in 2010-09-23, accepted in 2010-11-30,  发布年份 2010

来源: Springer

【 摘 要 】

BackgroundBacillus cereus and the closely related Bacillus thuringiensis are Gram positive opportunistic pathogens that may cause food poisoning, and the three secreted pore-forming cytotoxins Hbl, Nhe and CytK have been implicated as the causative agents of diarrhoeal disease. It has been proposed that the Hbl toxin is secreted using the flagellar export apparatus (FEA) despite the presence of Sec-type signal peptides. As protein secretion is of key importance in virulence of a microorganism, the mechanisms by which these toxins are secreted were further investigated.ResultsSec-type signal peptides were identified in all toxin components, and secretion of Hbl component B was shown to be dependent on an intact Sec-type signal peptide sequence. Further indication that secretion of Hbl, Nhe and CytK is dependent on the Sec translocation pathway, the main pathway on which bacterial secretion relies, was suggested by the observed intracellular accumulation and reduced secretion of the toxins in cultures supplemented with the SecA inhibitor sodium azide. Although a FEA deficient strain (a flhA mutant) showed reduced toxin expression and reduced cytotoxicity, it readily secreted overexpressed Hbl B, showing that the FEA is not required for Hbl secretion. Thus, the concurrent lack of flagella and reduced toxin secretion in the FEA deficient strain may point towards the presence of a regulatory link between motility and virulence genes, rather than FEA-dependent toxin secretion.ConclusionsThe Hbl, Nhe and CytK toxins appear to be secreted using the Sec pathway, and the reduced Hbl expression of a FEA deficient strain was shown not to be due to a secretion defect.

【 授权许可】

Unknown   
© Fagerlund et al; licensee BioMed Central Ltd. 2010. This article is published under license to BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.