"Pseudolysogenization" by RNA phage Q beta.

We isolated fairly stable lysogenic-like bacteria from a lysogenic state established between an amber mutant for the maturation protein gene of RNA phage Q beta (Q beta am 205) and its nonpermissive host BE110. These bacteria contained few mature phages intracellularly (less than 10(-3) plaque forming unit per cell), continued to grow with a potentiality to produce Q beta am 205 spontaneously, and showed an immunity-like response against homologous phage infection. These characteristics were maintained by growth in liquid medium containing anti-Q beta serum. We designated these cells as pseudolysogenic bacteria. The relative amounts of RNA genomes in these pseudolysogenic cells (about 10(2) infectious RNA strands per cell) indicated that the RNA genomes could replicate in nonpermissive cells and be distributed in daughter cells synchronizing well with cell division.