ARS | Publication request: UTILIZATION OF HETEROLOGOUS SIDOEPRHORES BY A BACTERIUM IN THE RHIZOSPHERE

Submitted to: International Congress of Plant Pathology Abstracts and Proceedings
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: December 31, 1997
Publication Date: N/A

Technical Abstract: An iron sensor (pvd-inaZ), comprised of a transcriptional fusion of the ice nucleation reporter (inaZ) to an iron-regulated promoter, was used to evaluate the capacity of Pseudomonas putida N1R to utilize heterologous siderophores in the rhizosphere as iron sources. Ice nucleation activity (INA) expressed by N1R or its pyoverdine-deficient mutant (N1R Pvd-) containing pvd-inaZ was inversely related to iron in a growth medium. Siderophores produced by Enterobacter cloacae EcCT-501 (aerobactin and enterobactin) and P. putida WCS358 (pseudobactin-358) were used as sources of iron by N1R Pvd- in culture. When a medium was supplemented with pseudobactin-358, INA expressed by N1R Pvd- decreased, indicating that levels of iron available to the bacterium increased. In the rhizosphere of cucumber under gnotobiotic conditions, N1R Pvd- (pvd-inaZ) expressed less INA in the presence of EcCT-501 or WCS358 than in the presence of their siderophore-minus mutants. Results indicate that siderophores produced by its coinhabitants in the rhizosphere were utilized by N1R Pvd-, thereby enhancing levels of iron available to the bacterium.