[A comparative analysis of the ice nucleation activity of pseudomonad cells and lipopolysaccharides]

The paper deals with the study of the ice nucleation activity of the cells, extracellular lipopolysaccharides (ELPSs), lipopolysaccharides (LPSs), and their structural components (lipid A, core oligosaccharide, and O-specific polysaccharide) of Pseudomonas fluorescens, P. syringae, P.fragi, and P. pseudoalcaligenes. The aqueous suspensions of the intact cells of P. syringae IMV 1951 and IMV 185 began to freeze at -1 and -4 degrees C, respectively. This suggests that these cells possess ice nucleation activity. The aqueous cell suspensions of two other strains, P. fluorescens IMV 1433 and IMV 2125, began to freeze at lower temperatures than did distilled water (-9 degrees C), which suggests that the cells of these strains possess antifreeze activity. The ice nucleation activity of the bacterial strains studied did not show any correlation with their taxonomic status. The ice nucleation activity of ELPSs depended little on their concentration (within a concentration range of 0.2-0.4%). In most cases, the ice nucleation activity of ELPSs, LPSs, and their structural components differed from that of the intact cells from which these biopolymers were obtained. This may indicate that the biopolymers under study play a role in ice nucleation, but this role is not crucial. The relationship between the structure of LPSs and their effect on ice nucleation is discussed.