Cereulide, the emetic toxin of Bacillus cereus, is putatively a product of nonribosomal peptide synthesis.
OBJECTIVE
To determine if cereulide, the emetic toxin produced by Bacillus cereus, is produced by a nonribosomal peptide synthetase (NRPS).


RESULTS
NC Y, an emetic strain of Bacillus cereus, was examined for a NRPS gene using PCR with primers recognizing a fragment of a NRPS gene from the cyanobacterium Microcystis. The amplicon was sequenced and compared with other gene sequences using BLAST analysis, which showed that the amplicon from strain NC Y was similar in sequence to peptide synthetase genes in other micro-organisms, including Bacillus subtilis and B. brevis, while no such sequence was found in the complete genome sequence of a nonemetic strain of B. cereus. Specific PCR primers were then designed and used to screen 40 B. cereus isolates previously implicated in outbreaks of foodborne illness. The isolates were also screened for toxin production using the MTT cell cytotoxicity assay. PCR and MTT assay screening of the B. cereus isolates revealed a high correlation between the presence of the NRPS gene and cereulide production.


CONCLUSIONS
The results indicate that cereulide is produced by a NRPS complex.


CONCLUSIONS
This is the first study to provide evidence identifying the mechanism of production of cereulide, the emetic toxin of B. cereus. The PCR primers developed in the study allow determination of the potential for cereulide production among isolates of B. cereus.
Toh
M
M
Food Science and Technology, School of Chemical Engineering and Industrial Chemistry, The University of New South Wales, Sydney, Australia.
Moffitt
M C
MC
Henrichsen
L
L
Raftery
M
M
Barrow
K
K
Cox
J M
JM
Marquis
C P
CP
Neilan
B A
BA
D001409:Bacillus cereus / Q000235:genetics / Q000378:metabolism*; D001427:Bacterial Toxins / Q000096:biosynthesis*; D016923:Cell Death / Q000187:drug effects; D002851:Chromatography, High Pressure Liquid / Q000379:methods; D047630:Depsipeptides / Q000096:biosynthesis*; D004639:Emetics / Q000378:metabolism; D005516:Food Microbiology; D005798:Genes, Bacterial; D006801:Humans; D046908:Peptide Biosynthesis, Nucleic Acid-Independent; D010453:Peptide Synthases / Q000235:genetics / Q000502:physiology*; D016133:Polymerase Chain Reaction / Q000379:methods
D001427:Bacterial Toxins; D047630:Depsipeptides; D004639:Emetics; C089294:cereulide; D010453:Peptide Synthases; C104385:non-ribosomal peptide synthase