Northern blot analysis of cpb2 mRNAs from C. perfringens. (A) Expression of cpb2 mRNAs from SD isolates. RNA was extracted from tje specified C. perfringens cultures grown at 37°C for 3 h, and 10 μg of RNA from each was subjected to Northern blot analysis using a 560-bp AlkPhos-labeled cpb2-specific probe. Results are shown for control isolates CWC245 (a cpb2-positive, pig GI disease isolate) and 106527 (a cpb2-negative strain) and for representative SD isolates 4370/94, 2728/94, 4828/94, and 5422/94. The cpb2 mRNA (1.2 kb) isindicated by an arrowhead. (B) Comparative expression of cpb2 mRNAs from representative SD isolates versus CWC245. Various amounts of RNAs extracted from CWC245, 2728/94, 4828,94, 3409/94, 4178/94, and 5282/94 cultures grown at 37°C for 3 h were subjected to Northern blot analysis using a 560-bp AlkPhos-labeled cpb2-specific probe. The relative levels of cpb2 mRNAs in SD isolates were determined as described in Materials and Methods. The cpb2 mRNA (1.2 kb) is indicated by an arrowhead. The various amounts of RNA loaded on the gel are indicated at the bottom.