The Control of the Production and Secretion of Extracellular Ice-nucleating Material of Erwinia uredovora KUIN-3

抄録

The secretion of extracellular ice-nucleating material (EIM) with ice nucleation proteins (INP) from an ice-nucleating bacterium, Erwinia uredovora KUIN-3, increased in proportion to the yeast extract concentration in the ice-nucleating medium. The level of this secretion could be exhibited in terms of the ice-nucleating temperature, T₅₀ (°C), using the ELIZA method with the anti-Ina A antiserum. The secretions and the production on the cell surface of all EIM containing the class A, B and C structures were activated by the addition of yeast extract. Furthermore, based on the examination involving the deletion of various medium components, it was found that lysine (Lys) was closely associated with the secretions of EIM in the class A and B structures. The addition of Lys could affect the polyamine content in the EIM, thereby changing the surface charge of EIM from 5.2 to 4.9. Also, the addition of cadaverine (CAD) could enhance the EIM secretion. Based on these results, the surface charge of the INP aggregate was shown to be essential for the translocation of INP and the secretion of EIM. We found that this secretion, especially the secretion of a class B structure, was inhibited by N, N'- dicyclohexylcarbodiimide (DCCD), which was an H⁺-ATPase inhibitor regardless of normal growth. We also found that this secretion required ATP and the positive charge on the EIM surface. This is the first report on the energy needed to secrete EIM into the culture broth and the possibility for controlling the production of the INP on the cell surface by the reduction of some compounds in the surroundings.