The influence of growth rate and growth-limiting factors on the productionof ice nuclei in Pseudomonas syringae CCM 4073 in continuous culture

The influence of different growth-limiting factors - namely the sources of carbon, nitrogen and phosphorus and the dilution (growth) rate - on the ice -nucleation activity of Pseudomonas syringae CCM 4073 was studied. A higher ice-nucleation activity was observed at a lower dilution (growth) rate (D = 0.1 h(-1)) than at a higher dilution (growth) rate (D = 0.3 h(-1)). Remar kable differences in ice nucleation activity were found in its dependence o n the growth-limiting factor. The highest ice-nucleation activity was obser ved under carbon limitation (T-90 = - 2.7 degrees C), a medium activity und er nitrogen limitation (T-90 = - 5 degrees C) and lowest activity under pho sphorus limitation (T-90 = - 12.3 degrees C). After the addition of excess nitrogen or phosphorus to steady-state cultures, the ice-nucleation activit y was restored.