ARS | Publication request: Evidence that a DEGS homologue in Enterobacter clocae is important for colonization and disease suppression on cucumber

Submitted to: Microbial Ecology International Symposium
Publication Type: Abstract Only
Publication Acceptance Date: May 1, 2008
Publication Date: August 31, 2008
Citation: Roberts, D.P., Lohrke, S.M., Mckenna, L.F., Lakshman, D.K. 2008. Evidence that a DEGS homologue in Enterobacter clocae is important for colonization and disease suppression on cucumber [abstract]. Microbial Ecology International Symposium.

Technical Abstract: Enterobacter cloacae 501R3 shows promise as a biocontrol agent for damping-off of cucumber caused by Pythium ultimum. Enterobacter cloacae C10 is a mini-Tn5 Km transposon mutant of 501R3 that was reduced in colonization of cucumber roots and in suppression of damping-off of cucumber. Molecular characterization of C10 indicated that mini-Tn5 Km was inserted in a region of the E. cloacae genome with a high degree of DNA sequence similarity to degS, a periplasmic serine protease. In the closely related bacterium Escherichia coli, degS is an essential gene and consequently recovery of degS mutants requires a suppressor mutation. To demonstrate the importance of degS for plant-beneficial activities, pBeloBAC11 constructs containing wild-type E. cloacae or E. coli degS were introduced into C10 and 501R3 by electroporation and the resultant strains tested for colonization and disease suppression. C10 containing wild-type E. cloacae or E. coli degS was significantly better than C10 containing pBeloBAC11 alone in colonization of cucumber roots and in suppression of P. ultimum damping-off of cucumber. In E. coli, DegS is required for RpoE mediated gene expression in response to extracytoplasmic stress. This study demonstrates a role for degS, and by extension, the RpoE-mediated stress response in colonization and disease suppression.