title: Inhibition of spontaneous induction of lambdoid prophages in Escherichia coli cultures: simple procedures with possible biotechnological applications.
abstract: BACKGROUND
  Infections of bacterial cultures by bacteriophages are serious problems in biotechnological laboratories. Apart from such infections, prophage induction in the host cells may also be dangerous. Escherichia coli is a commonly used host in biotechnological production, and many laboratory strains of this bacterium harbour lambdoid prophages. These prophages may be induced under certain conditions leading to phage lytic development. This is fatal for further cultivations as relatively low, though still significant, numbers of phages may be overlooked. Thus, subsequent cultures of non-lysogenic strains may be infected and destroyed by such phage.
  
  
  RESULTS
  Here we report that slow growth of bacteria decreases deleterious effects of spontaneous lambdoid prophage induction. Moreover, replacement of glucose with glycerol in a medium stimulates lysogenic development of the phage after infection of E. coli cells. A plasmid was constructed overexpressing the phage 434 cI gene, coding for the repressor of phage promoters which are necessary for lytic development. Overproduction of the cI repressor abolished spontaneous induction of the lambda(imm434) prophage.
  
  
  CONCLUSIONS
  Simple procedures that alleviate problems with spontaneous induction of lambdoid prophage and subsequent infection of E. coli strains by these phages are described. Low bacterial growth rate, replacement of glucose with glycerol in a medium and overproduction of the cI repressor minimise the risk of prophage induction during cultivation of lysogenic bacteria and subsequent infection of other bacterial strains.
authors.affiliation: Laboratory of Molecular Biology, University of Gdansk, Institute of Biochemistry and Biophysics, Polish Academy of Sciences, Kladki 24, 80-822 Gdansk, Poland. czyz@biotech.univ.gda.pl
authors.forename: A
authors.initials: A
authors.lastname: Czyz
authors.forename: M
authors.initials: M
authors.lastname: Los
authors.forename: B
authors.initials: B
authors.lastname: Wrobel
authors.forename: G
authors.initials: G
authors.lastname: Wegrzyn
mesh_terms: D010582:Bacteriophage lambda / Q000187:drug effects / Q000235:genetics / Q000502:physiology*; D001709:Biotechnology; D004268:DNA-Binding Proteins; D004926:Escherichia coli / Q000187:drug effects / Q000254:growth & development / Q000821:virology*; D015967:Gene Expression Regulation, Viral; D005990:Glycerol / Q000494:pharmacology; D008242:Lysogeny / Q000187:drug effects; D010957:Plasmids / Q000235:genetics; D039002:Prophages / Q000187:drug effects / Q000235:genetics / Q000502:physiology*; D012097:Repressor Proteins / Q000235:genetics / Q000378:metabolism; D013997:Time Factors; D014764:Viral Proteins; D054334:Viral Regulatory and Accessory Proteins; D014775:Virus Activation / Q000187:drug effects
chemical_list: D004268:DNA-Binding Proteins; D012097:Repressor Proteins; D014764:Viral Proteins; D054334:Viral Regulatory and Accessory Proteins; C016649:phage repressor proteins; D005990:Glycerol