A cold-responsive <i>fimACD</i> chaperone–usher operon tunes motility and biofilm formation in <i>Pseudomonas fragi</i> D12

locus with altered fimbrial architecture, motility behavior, and biofilm robustness, while separating these effects from bulk growth. The results support a view in which fimbriae in a psychrotolerant bacterium operate as adjustable elements that influence when cells favor long-range swimming versus surface-associated growth. Such information may provide direct genetic and phenotypic evidence for functional specialization of the fimbrial system under cold stress, offering new insight into the molecular strategies that enable microbial survival in low-temperature habitats.