Pyoverdines, a group of peptide siderophores produced by Pseudomonas species, function not only in iron acquisition, but also in their virulence in hosts. Thus, chemical inhibition of pyoverdine production may be an effective strategy to control Pseudomonas virulence. In the plant pathogen Pseudomonas cichorii SPC9018 (SPC9018), pyoverdine production is required for virulence on eggplant. We screened microbial culture extracts in a pyoverdine-production inhibition assay of SPC9018 and found Streptomyces sp. RM-32 as a candidate-producer. We isolated two active compounds from RM-32 cultures, and elucidated their structures to be actinomycins X₂ and D. Actinomycins X₂ and D inhibited pyoverdine production by SPC9018 with IC₅₀ values of 17.6 and 29.6 μM, respectively. Furthermore, pyoverdine production in other Pseudomonas bacteria, such as the mushroom pathogen P. tolaasii, was inhibited by the actinomycins. Therefore, these actinomycins may be useful as chemical tools to examine pyoverdine functions and as seed compounds for anti-Pseudomonas virulence agents.

Pyoverdines是由假单胞菌（Pseudomonas）物种产生的一组肽铁载体，不仅在铁的获取中起作用，而且在寄主中也具有毒力。因此，化学抑制吡啶酮的产生可能是控制假单胞菌毒力的有效策略。在植物病原体Pseudomonas cichorii SPC9018（SPC9018）中，为了在茄子上产生毒力，需要生产过碘。我们在SPC9018的化脓性生产抑制试验中筛选了微生物培养物提取物，并发现了链霉菌。RM-32作为候选制作人。我们从RM-32培养物中分离了两种活性化合物，并阐明了其结构分别为放线菌素X ₂和D。放线菌素X ₂D和D抑制SPC9018产生的嘧啶过量，IC ₅₀值分别为17.6和29.6μM 。此外，放线菌素抑制了其他假单胞菌细菌（如蘑菇病原体P. tolaasii）中的泛素定产生。因此，这些放线菌素可作为化学工具来检查pyoverdine的功能，并可用作抗假单胞菌毒力剂的种子化合物。