Isolation and characterization of a marine ice-nucleating bacterium, Pseudomonas sp KUIN-5, which produces cellulose and secretes it in the culture broth

A novel marine ice-nucleating bacterium, KUIN-5 was isolated from a marine algae, Monostroma latissum. Strain KUIN-5 was identified as a Pseudomonas sp, from its characteristics and taxonomics; the optimum temperature and pH for its growth were 25 degrees C and 6.0, respectively, When strain KUIN-5 was aerobically cultured in Carlucci-Pramer medium (pH 6.0) for 50 h at 25 degrees C, the highest ice-nucleating activity of the cells among the media for marine bacteria was obtained, and the ice-nucleating temperature, T-50, was indicated to be -3.2 degrees C, Also, the optimum concentration of NaCl for the growth in this medium, which was prepared with distilled water instead of seawater, was 2.0% (w/v) and then the ice-nucleating activity was inversely proportional to the NaCl concentration, Moreover, when strain KUIN-5 was cultured in Davis medium under optimum conditions, it produced insoluble polysaccharide (IFS) in the culture. The maximum amount of IFS production by strain KUIN-5 was 84.5 mg/ml of medium under optimum conditions, Therefore, this IFS was isolated and could be identified as cellulose, based on TLC or HPLC of the acid hydrolysate, and GC-MS of the acetylated polyalcohol prepared by periodate oxidation and Smith degradation of this polysaccharide. This is the first report of cellulose production by a marine ice-nucleating bacterium.