| Abstract: | Clostridium perfringens KZ1340 isolated from Antarctic soil was first classified as Clostridium plagarum and later as a lecithinase-negative variant of C. perfringens. Although the strain produced no detectable lecithinase (phospholipase C, PLC) activity in the culture supernatant, it was shown by Southern blot hybridization to possess a PLC-encoding gene (plc). To determine the cause of the PLC deficiency, we cloned and sequenced the plc gene from KZ1340. The deduced amino acid sequence consists of 398 amino acid residues, coinciding with those of the plc genes previously determined. Tyrosine was substituted for histidine at amino acid position 148, which is thought to bind a zinc ion essential for PLC activity. Northern blot analysis revealed that KZ1340 expressed the plc gene at an extremely low level. Furthermore, the plc gene cloned from C. perfringens strain 13 into a plasmid was expressed weakly in KZ1340, compared to that in strain 13. This indicates that the former strain represses plc gene expression in trans. When a phylogenetic tree of plc genes was constructed, the KZ1340 plc gene formed a monophyletic branch along with those of various other C. perfringens strains, supporting the classification of the strain as a variant of C. perfringens. |
