To obtain a novel matrix metalloproteinase (MMP) inhibitor produced by bacteria, we have focused on the chelating activity of siderophores. Several siderophore-producing bacteria were isolated from soil using chrome azurol S agar plates and then the effect of siderophores on MMP-2 activity was assayed by gelatin zymography. The results showed that partially purified siderophores from ten isolated strains inhibited MMP-2 activity. Among these strains, two were non-fluorescent and eight were fluorescent Pseudomonas species. From these eight strains, pyoverdine-type siderophores were detected. The Zn2+-chelating activity of these siderophores correlated with the inhibition of MMP-2 activity. Therefore, it is considered that siderophores such as pyoverdines inhibit MMP-2 activity by chelating Zn2+ on the active site of MMP-2.