Bacterial differentiation and phage infection

Caulobacter crescentus undergoes two morphological stages during each cell division cycle. Analysis of the early steps in the infection of this bacterium by the DNA bacteriophage ∅CbK revealed that the phage infects only the free swarmer cell or a predivisional form with swarmer cell characteristics. The kinetics of adsorption and phage DNA injection in both stalked and swarmer populations of wild-type and mutant host cells showed that the selective step in phage infection was DNA injection. The injection of radioactively labeled phage DNA at specific times in the cell cycle was then shown to be an efficient technique to measure cellular differentiation in synchronized populations.