Decoupling adhesion from carbon metabolism via FimA deletion in Klebsiella pneumoniae type 1 pili.

Klebsiella pneumoniae can naturally synthesize commercially valuable metabolites, such as 1,3-propanediol (1,3-PD), 2,3-butanediol (2,3-BD), and 3-hydroxypropionic acid (3-HP). While its pili are pivotal for colonization and infection, their influence on metabolite biosynthesis remains unclear. Here, we report that eliminating type 1 pili does not significantly compromise growth and the production of aforementioned metabolites. Base editing of fimA, which encodes the major component of type 1 pili, yielded mutants with reduced piliation, motility, adhesion and biofilm formation but growth comparable to that of the wild type. Molecular dynamics simulations showed that disruption of salt bridges, attenuation of hydrogen bonding to water, and abatement of hydrophobic interactions collectively impair fimbrial assembly. Shake-flask and bioreactor fermentations showed that the ΔfimA strain consumed glycerol or glucose and produced metabolites at levels comparable to the fimA-intact strain. Transcriptomics revealed that deleting fimA caused a downregulation of two nitrogen-utilizing genes but an upregulation of four quorum sensing (QS) genes-an overexpression-dependent compensatory response mechanism of QS-although QS ultimately collapsed. Overall, type 1 pili are not tightly integrated into glycerol or glucose metabolism, underscoring the flexibility of the metabolic network and the dispensability of these pili for sustainable bioproduction of value-added metabolites in K. pneumoniae.