HIGH-LEVEL EXPRESSION OF THE ICE-NUCLEATING ACTIVITY OF PSEUDOMONAS-SYRINGAE IN RELATION TO ITS GROWTH-CHARACTERISTICS

Optimization of the culture medium is essential for the production of a large biomass of high ice-nucleating-active micro-organisms such as Pseudomonas syringae. Cultures in bioreactors show that optimal substr ate concentrations are approximately the same for ice nucleating activ ity (INA) and total biomass (50-80 g/l of glucose; 28 g/l of peptone) but not for the growth rate. The INA is lowest when the growth rate is highest (50 g/l of glucose, 15 g/l of peptone). We have shown that th e maximal biomass production and INA are related to the C/N ratio (opt imal ratio: 10) rather than to the substrate concentration. These resu lts also contribute to knowledge on the physiology of these bacteria a nd support the sequential maturation of the ice nucleating sites.