TABLE 3.
Chemical characteristics of selected siderophores and their effect on multiplication of AW1-GB6 (ssd) in iron-deficient minimal medium
| Siderophore sourcea | Functional groupb
|
Turbidity (OD600)c
|
||
|---|---|---|---|---|
| Hydroxamate | Catechol | Fe− | Fe+ | |
| None | ND | ND | 0.35 | ND |
| R. solanacearum AW1-GB6 | ND | ND | 0.39 | ND |
| R. solanacearum AW1-PC | − | − | 3.30 | ND |
| R. metallidurans CH34 | − | − | 3.37 | ND |
| B. megaterium ATCC 19213 | + | − | 0.009 | 3.60 |
| Desferrioxamine (10 μM) | + | − | 0.007 | 2.01 |
Bacteria were removed from stationary-phase cultures (e.g., 48 h old) by centrifugation and the supernatant was filter sterilized.
Hydroxamates and catechols were detected with the Csàky and Amow tests, respectively. ND, not done.
Bioassay tubes contained 0.5 ml of MMΔ (amended with 0.25 % [wt/vol] non-deferrated yeast extract, 150 μM 2,2′-dipyridyl, and 20 μg of kanamycin ml−1) and 106 CFU of AW1-GB6 ml−1. Appropriate tubes received 10 μl of a culture supernatant or 10 μl of 0.5 mM desferrioxamine mesylate. Selected tubes also contained 20 μM FeCl3. Turbidity of AW1-GB6 was determined at 48 h; cultures with an OD600 of >1 were diluted 10-fold prior to measurement. Results are from one experiment that was representative of three independent experiments; values are the mean of triplicate tubes.