title: Release of Cell-Free Ice Nucleators from Three Recombinant Ice Zymomonas mobilis Strains.
abstract: OBJECTIVE
  This work is a study of the ability of three recombinant Zymomonas mobilis strains to release ice nucleators into their growth medium.
  
  
  METHODS
  The recombinant ice(+)Z. mobilis cells were tested for their ability to produce cell-free ice nucleators, under three different growth temperatures and three different glucose concentrations.
  
  
  RESULTS
  Cell-free ice nucleators were obtained from all the recombinant ice(+)Z. mobilis cells tested. The cell-free ice nucleation activity was not affected by the glucose concentration in the growth medium or the growth temperature. The freezing temperature threshold was below -7.6°C, demonstrating a class C nucleating structure of the ice nucleation protein. The size of the ice nucleators was less than 0.22 μm and their density was estimated as 1.024 ± 0.004 g/ml by Percoll density centrifugation. The properties of the detected ice nucleators, in addition to the absence of pyruvate decarboxylase activity in the spent medium (a cytosolic marker), support that the cell-free ice nucleation activity was due to the extracellular release of ice nucleators.
  
  
  CONCLUSIONS
  These findings indicate that the recombinant ice(+)Z. mobilis cells could be valuable for future use as a source of active cell-free ice nucleation protein.
authors.affiliation: Department of Chemistry, University of Ioannina, Ioannina, Greece.
authors.forename: Athanasia
authors.initials: A
authors.lastname: Varsaki
authors.forename: Angelos
authors.initials: A
authors.lastname: Perisynakis
authors.forename: Constantin
authors.initials: C
authors.lastname: Drainas
mesh_terms: D001425:Bacterial Outer Membrane Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D007053:Ice / Q000032:analysis; D013696:Temperature; D017355:Zymomonas / Q000737:chemistry / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*
chemical_list: D001425:Bacterial Outer Membrane Proteins; D007053:Ice; C063113:ice nucleation protein