title: Small Bacillus cereus ATCC 14579 subpopulations are responsible for cytotoxin K production.
abstract: OBJECTIVE
  Bacillus cereus diarrhoeal food poisoning can be caused by several potential enterotoxins, including the nonhaemolytic enterotoxin (Nhe), haemolysin BL (Hbl) and cytotoxin K (CytK). To get more insights into the CytK expression, a fluorescent reporter strain was created for CytK expression.
  
  
  METHODS
  Bacillus cereus ATCC 14579 was used as the reporter strain that contained the cyan fluorescent protein (CFPopt) gene under control of the cytK promoter. Transcription of enterotoxin genes nheB, hblC and cytK was assessed by messenger RNA analysis (RT-qPCR), and their full expression was assessed by immunological protein detection in the case of Nhe and Hbl and fluorescence microscopy in the case of CytK, using the reporter gene CFPopt.
  
  
  RESULTS
  Transcription of enterotoxins Nhe, Hbl and CytK showed similar kinetics with a peak during the late exponential growth phase. Toxin expression of the reporter strain was unaltered in comparison with the wild type. However, fluorescence, and thus CytK expression, only occurred in a small (1-2%) portion of the cell population.
  
  
  CONCLUSIONS
  These results suggest that a small subpopulation of B. cereus ATCC 14579 is responsible for CytK production in a homogeneous monoculture.
  
  
  CONCLUSIONS
  Future research is warranted to determine whether genetically homogeneous B. cereus populations utilize differential gene expression for other toxins and virulence genes than CytK and whether this also applies to other B. cereus strains. If so, differential expression of toxin genes could be used by these bacteria to increase the fitness and survival chances of their population by diversification and specialization into different subpopulations.
authors.affiliation: Laboratory of Food Microbiology and Food Preservation, Faculty of Bioscience Engineering, Ghent University, Gent, Belgium.
authors.forename: S
authors.initials: S
authors.lastname: Ceuppens
authors.forename: S
authors.initials: S
authors.lastname: Timmery
authors.forename: J
authors.initials: J
authors.lastname: Mahillon
authors.forename: M
authors.initials: M
authors.lastname: Uyttendaele
authors.forename: N
authors.initials: N
authors.lastname: Boon
mesh_terms: D001409:Bacillus cereus / Q000235:genetics / Q000378:metabolism* / Q000472:pathogenicity; D003603:Cytotoxins / Q000096:biosynthesis*; D004768:Enterotoxins / Q000096:biosynthesis*; D005517:Foodborne Diseases / Q000382:microbiology; D015964:Gene Expression Regulation, Bacterial; D017930:Genes, Reporter; D008856:Microscopy, Fluorescence; D011401:Promoter Regions, Genetic
chemical_list: D003603:Cytotoxins; D004768:Enterotoxins