Appearance of the arginine phenotype in Lactococcus lactis subsp. cremoris 2204 following phage transduction

An induced phage 2204-T from an arginine-positive Lactococcus lactis subsp. lactis 2204 L strain was used in transduction experiments with Lactococcus lactis subsp. cremoris 2204 (an arginine-negative strain containing the chloramphenicol resistance plasmid pFX3). Arginine-positive transductants were isolated at a low frequency (< 10−10 arginine-positive isolates per initial recipient cell). Hybridization experiments with labelled DNA from phage 2204-T showed the presence of the temperate phage (2204-T) genome in total DNA of the transductant 2204 LT strains. No hybridization was observed with DNA from the arginine-negative strain 2204. A mitomycin C treated derivative of 2204 LT that was arginine negative also showed no hybridization, indicating that the prophage had been eliminated. The presence of the chloramphenicol resistance plasmid pFX3 in both transductants and mitomycin C cured derivatives was demonstrated by hybridization, confirming the origin of the arginine-positive isolates as derivatives of 2204.