abstract book - Clostridia

EXPRESSION OF THE NEUROTOXIN CLUSTER GENES IN
CLOSTRIDIUM BOTULINUM TYPE E AT LOW TEMPERATURE
Y. Chen, H. Korkeala, and M. Lindström.
Centre of Excellence in Microbial Food Safety Research, Department of
Food and Environmental Hygiene, Faculty of Veterinary Medicine,
University of Helsinki, Finland
Being able to grow and produce neurotoxin at refrigeration
temperatures, Clostridium botulinum type E possesses a significant
safety risk for the modern food industry where the chill chain is the main
bacterial growth-inhibiting factor. The expression of all six type E
neurotoxin complex genes was monitored for the first time at either 10
or 30°C using quantitative real-time reverse transcription PCR (qRT-
PCR). Different expression patterns of the toxin complex genes were
observed at the two temperatures. The neurotoxin gene cluster had
early and prolonged expression at 10°C when compared to that at
30°C. The expression levels had only little or no decline after 8 days of
incubation at 10°C in contrast to those at 30°C. The maximal
expression levels at 10°C were similar to (ntnh and p47), 37-65% lower
than (bont/E, orfx2, and orfx3), or 90% lower than (orfx1) at 30°C.
Evidence of different transcriptional mechanisms at 10 and 30°C was
obtained. At 30°C, bont/E, ntnh, and p47, and orfx1, orfx2, and orfx3
seemed to be expressed as two tricistronic operons whereas at 10°C
mono- and bicistronic transcription seemed to prevail. The results
suggest that the botulinum neurotoxin gene cluster has stable activity
for extended time periods at low temperature. Novel strategies and
additional control factors are therefore demanded to ensure the safety
of refrigerated foods.
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