Fast and slow milk-coagulating variants of Lactobacillus helveticus HLM 1

Slow milk-coagulating variants were isolated from Lactobacillus helveticus HLM 1, a fast strain which coagulates milk in 16 h at 42 degrees C. Variants were isolated after subculturing in reconstituted skim milk or complex broth media. Analysis of plasmid content revealed that in slow variants a 3.5-megadalton plasmid was missing.