Role of FimK in Mediating Host Urinary Bladder Epithelial Cell Association of Uropathogenic Klebsiella Pneumoniae and Quasipneumoniae


December 2021


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Klebsiella spp. commonly cause both uncomplicated urinary tract infection (UTI) and recurrent UTI (rUTI). K. quasipneumoniae, a relatively newly defined species of Klebsiella, has been shown to be metabolically distinct from K. pneumoniae, but its urovirulence mechanisms have not been defined. Type 1 and type 3 fimbriae, encoded by fim and mrk operons respectively, mediate attachment of Klebsiella spp. to host epithelial cells. fimK is a regulatory gene unique to the Klebsiella fim operon that encodes an N-terminal DNA binding domain and a C-terminal phosphodiesterase domain that has been hypothesized to cross-regulate type 3 fimbriae via modulation of cellular levels of cyclic di-GMP. Comparative genomic analysis between K. pneumoniae and K. quasipneumoniae revealed a conserved premature stop codon in K. quasipneumoniae fimK that results in loss of the C-terminal phosphodiesterase domain (PDE). We hypothesized that this truncation would ablate cross-regulation of type 3 fimbriae in K. quasipneumoniae. Here, we report that K. quasipneumoniae KqPF9 bladder epithelial cell association and invasion is dependent on type 3 but not type 1 fimbriae. Further, we show that basal expression of both type 1 and type 3 fimbrial operons as well as bladder epithelial cell association are higher in KqPF9 than in K. pneumoniae TOP52. Interestingly, complementation of KqPF9∆fimK with the TOP52 fimK allele markedly reduced type 3 fimbrial expression and bladder epithelial cell attachment, a phenotype that was rescued by mutation of the C-terminal PDE active site. Taken together these data suggest that C-terminal PDE of FimK modulates type 3 fimbrial expression in K. pneumoniae and its absence in K. quasipneumoniae leads to a loss of type 3 fimbrial cross-regulation.



Biology, Molecular, Biology, Microbiology, Biology, Genetics