SEARCH FOR THE FUNCTION OF THE NUCLEASE NUCM OF ERWINIA-CHRYSANTHEMI

Erwinia chrysanthemi synthesizes a periplasmic nuclease, NucM. To try to determine the function of NucM, we studied the efficiency of variou s DNA transfer techniques, i.e. electroporation, transformation, phage infection, in a nucM mutant. No difference was observed, except for e lectroporation but only when the bacteria were grown at high temperatu re. The high frequency of electroporation obtained allowed the develop ment of a new method for marker exchange recombination in E. chrysanth emi. The pathogenicity of the nucM mutant was tested on potato tubers and on potato vitro plants: NucM does not seem to play an important ro le in E chrysanthemi phytopathogenicity. The gene nucM was localized o n the E. chrysanthemi chromosome near the ser386 marker.