title: Characterization of two temperate Lactobacillus paracasei bacteriophages: morphology, kinetics and adsorption.
abstract: OBJECTIVE
  Adsorption and kinetic parameters, latent period, burst size and burst time, are characteristics of phage/host systems and can be affected by several environmental factors. As only few studies have focused on temperate dairy phages, we characterized these parameters on temperate Lactobacillus paracasei phages Φ iLp84 and Φ iLp1308, infective for probiotic strains.
  
  
  METHODS
  Phages were characterized by transmission electron microscopy and genomic DNA restriction. Adsorption under different environmental conditions, phage kinetics and efficiency of plating (EOP) were determined using the double-layer titration method.
  
  
  RESULTS
  Phages Φ iLp84 and Φ iLp1308 belong to the Siphoviridae family and have genome sizes of 38 and 34 kbp, respectively. Adsorption was affected by calcium concentration, pH, temperature and host viability, and reached a limit at very high multiplicity of infection. Latency, burst time and burst size were of 85 min, 131 min and 46 for Φ iLp84, and 51 min, 92 min and 28 for Φ iLp1308, respectively, at 37°C. A clear influence of temperature on phage kinetics was observed. Regarding EOP, Φ iLp84 produced plaques on only 1 out of 8 strains tested.
  
  
  CONCLUSIONS
  Noticeable differences in adsorption, kinetics and EOP were found for two morphologically identical temperate L. paracasei phages of similar origin.
authors.affiliation: Instituto de Lactología Industrial, Facultad de Ingeniería Química, Universidad Nacional del Litoral, Santa Fe, Argentina.
authors.forename: Diego J
authors.initials: DJ
authors.lastname: Mercanti
authors.forename: Hans-Wolfgang
authors.initials: HW
authors.lastname: Ackermann
authors.forename: Andrea
authors.initials: A
authors.lastname: Quiberoni
mesh_terms: D000327:Adsorption; D002118:Calcium; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D007778:Lactobacillus / Q000821:virology*; D017906:Siphoviridae / Q000145:classification* / Q000235:genetics / Q000502:physiology* / Q000648:ultrastructure*; D013696:Temperature
chemical_list: D002118:Calcium