Use of a lux reporter system for monitoring rapid changes in α-toxin gene expression in Clostridium perfringens during growth

To determine whether the luxA– luxB reporter system is suitable as a sensitive reporter for rapid real-time measurements of α-toxin gene ( cpa) expression in Clostridium perfringens, and to widen the range of α-toxin-producing C. perfringens strains examined with respect to cpa expression during growth, the reporter plasmid pPS14 (possessing the α-toxin promoter region plus 0.7 kb of upstream region linked to the luxA– luxB genes), was used in batch growth experiments of C. perfringens P90.2.2, an α-toxin-producing strain with no known association with disease. Levels of in vivo bioluminescence obtained during growth were broadly in agreement with previous mRNA and reporter studies of cpa expression (Bullifent et al., FEMS Microbiol. Lett. 131 (1995) 99–105), confirming the suitability of lux as an accurate reporter system in this organism, but the sensitive nature of the lux reporter permitted the in vivo detection of a very rapid reduction in expression during late-exponential phase that was not attributable to loss in cell viability or limiting bioluminescence assay substrates. There was also a small peak in cpa expression in early- to mid-exponential phase cells, that was not detected in previous studies with other reporters. This may be indicative of the exquisite sensitivity of the lux reporter, or this may be a difference in cpa expression that occurs specifically in this C. perfringens strain. Whichever is the case, these results confirm the complexity of α-toxin gene expression in different strains of this pathogenic bacterium.