INACTIVATION OF THE SAPA TO SAPF LOCUS OF ERWINIA-CHRYSANTHEMI REVEALS COMMON FEATURES IN PLANT AND ANIMAL BACTERIAL PATHOGENESIS

We investigated the role in pathogenesis of bacterial resistance to pl ant antimicrobial peptides. The sapA to sapF (for sensitive to antimic robial peptides) operon from the pathogenic bacterium Erwinia chrysant hemi has been characterized. It has five open reading frames that are closely related (71% overall amino acid identity) and are in the same order as those of the sapA to sapF operon from Salmonella typhimurium. An E. chrysanthemi sap mutant strain was constructed by marker exchan ge. This mutant was more sensitive than was the wild type to wheat a-t hionin and to snakin-1, which is the most abundant antimicrobial pepti de from potato tubers. This mutant was also less virulent than was the wild-type strain in potato tubers: lesion area was 37% that of the co ntrol, and growth rate was two orders of magnitude lower. These result s indicate that the interaction of antimicrobial peptides from the hos t with the sapA to sapF operon from the pathogen plays a similar role in animal and in plant bacterial pathogenesis.