title: Molecular aspects of microbial ice nucleation.
abstract: Certain organisms nucleate the crystallization of ice. This requires a small volume of water to be induced, probably by lattice-matching with a solid template, to form an 'ice embryo'--a region sharing at least some of the characteristics of macroscopic ice. It is of particular interest to understand the structure and function of biological structures capable of lattice-matching (or otherwise inducing a quasi-crystalline state). Some strains of the Gram-negative eubacterial genera Erwinia, Pseudomonas, and Xanthomonas, and the mycobionts of certain lichens, display ice-nucleating activity. In bacteria, the activity is conferred by a protein that contains three nested periodicities of repetition, which probably reflects a hierarchy of three motifs of structural repetition. Thus the tertiary structure of the ice-nucleation protein is likely to be regular, consistent with the expectation of its forming a template for lattice-matching. Even within a clonal culture, the nucleating sites formed by bacteria and lichens vary considerably in the threshold temperatures at which they display activity; this indicates wide variations in either the size of the template, or its structural regularity, or both. However, ice-nucleating sites of lichen and bacterial origin are clearly differentiated by their sensitivities to experimental treatments.
authors.affiliation: DNA Plant Technology Corporation, Oakland, California 94608.
authors.forename: G
authors.initials: G
authors.lastname: Warren
authors.forename: P
authors.initials: P
authors.lastname: Wolber
mesh_terms: D000595:Amino Acid Sequence; D018407:Bacterial Physiological Phenomena; D003460:Crystallization; D007053:Ice; D008011:Lichens / Q000502:physiology*; D008969:Molecular Sequence Data; D013696:Temperature; D013698:Templates, Genetic
chemical_list: D007053:Ice