<i>Delftia</i> as a small-molecule chassis: lessons from delftibactin and harmane

<i>Delftia</i> spp. occur in diverse environmental and host-associated settings, but their small-molecule capabilities are not uniform across the genus. In this Minireview, we use a strain-resolved "small-molecule chassis" framework to examine cases in which exported, low-molecular-weight metabolites can be linked to extracellular phenotypes. We focus on two anchor systems: delftibactin, a siderophore-like nonribosomal peptide metallophore associated with Au(III) detoxification and gold biomineralization in <i>Delftia acidovorans</i>, and harmane, a β-carboline linked to inhibition of early <i>Plasmodium</i> development by <i>Delftia tsuruhatensis</i> TC1 in mosquitoes. These systems do not represent the same level of mechanistic resolution, with delftibactin providing the tighter genotype→metabolite→phenotype chain and TC1 spanning both a harmane-linked mosquito phenotype and a less resolved low-molecular-weight supernatant phenotype in sand flies. Comparative genomics further supports the idea that these activities are strain- and lineage-specific rather than genus-wide. We argue that the small-molecule chassis framework is most useful not as a blanket label for <i>Delftia</i>, but as a way to identify which strains justify deeper mechanistic study and cautious translation.