IntroductionMany nitrogen-fixing bacteria (NFB) can synthesize siderophores. However, the contribution of NFB siderophore synthesis to plant growth has not been evaluated, and its impact on NFB’s antifungal activity remains unclear.MethodsThe type of siderophore synthesized by the nitrogen-fixing bacterium (NFB) Kosakonia radicincitans GXGL-4A was determined. The effects of NFB siderophore production on plant growth were examined by inoculating cucumber with GXGL-4A and the mutant ΔguaA (which d