Temperature Exerts Control ofBacillus cereusEmetic Toxin Production on Post-transcriptional Levels.
In recent years, the emetic toxin cereulide, produced byBacillus cereus, has gained high relevance in food production and food safety. Cereulide is synthesized non-ribosomal by the multi-enzyme complex Ces-NRPS, which is encoded on a megaplasmid that shares its backbone with theBacillus anthracispX01 toxin plasmid. Due to its resistance against heat, proteolysis and extreme pH conditions, the formation of this highly potent depsipeptide toxin is of serious concern in food processing procedures including slow cooling procedures and/or storage of intermediate products at ambient temperatures. So far, systematic data on the effect of extrinsic factors on cereulide synthesis has been lacking. Thus, we investigated the influence of temperature, a central extrinsic parameter in food processing, on the regulation of cereulide synthesis on transcriptional, translational and post-translational levels over the growth temperature range of emeticB. cereus. Bacteria were grown in 3°C interval steps from 12 to 46°C and cereulide synthesis was followed fromcesgene transcription to cereulide toxin production. This systematic study revealed that temperature is a cardinal parameter, which primarily impacts cereulide synthesis on post-transcriptional levels, thereby altering the composition of cereulide isoforms. Our work also highlights that the risk of cereulide production could not be predicted from growth parameters or sole cell numbers. Furthermore, for the first time we could show that the formation of the recently identified cereulide isoforms is highly temperature dependent, which may have great importance in terms of food safety and predictive microbiology. Notably the production of isocereulide A, which is about 10-fold more cytotoxic than cereulide, was specifically supported at low temperatures.
Functional Microbiology, Institute of Microbiology, Department of Pathobiology, University of Veterinary Medicine Vienna Vienna, Austria.
Markus
M
Kranzler
Functional Microbiology, Institute of Microbiology, Department of Pathobiology, University of Veterinary Medicine Vienna Vienna, Austria.
Katharina
K
Stollewerk
Food Safety Microbiology, Nestec Ltd, Nestlé Research Center Lausanne, Switzerland.
Katia
K
Rouzeau-Szynalski
Food Safety Microbiology, Nestec Ltd, Nestlé Research Center Lausanne, Switzerland.
Laurence
L
Blayo
Center for Analytical Chemistry, Department of Agrobiotechnology, IFA Tulln, University of Natural Resources and Life Sciences Vienna (BOKU) Vienna, Austria.
Michael
M
Sulyok
Functional Microbiology, Institute of Microbiology, Department of Pathobiology, University of Veterinary Medicine Vienna Vienna, Austria.
Monika
M
Ehling-Schulz
Bacillus cereus; cereulide; food safety; isocereulide; temperature