Figure 1

KbvR negatively regulates the expression of type I fimbriae. A mRNA levels of fimA and fimH genes were detected by RT-PCR. The overnight cultures of WT and ΔkbvR strains were diluted 1:100 into fresh LB media and cultured to mid-log phase at 37 °C. Total RNA were extracted and RT-PCR was conducted with 16 S rRNA as the normalized gene. The relative mRNA levels of fimA and fimH genes were analyzed by agarose gel electrophoresis, quantified by densitometry using ImageJ software, and calculated by dividing the densitometry of fimA/fimH gene by the corresponding densitometry of 16 S rRNA. B Yeast agglutination assay. The mid-log phase WT and ΔkbvR cultures (10⁸ CFU/mL, 50 µL) were mixed with equal cell numbers of 50 µL yeast cell suspension and shaken at room temperature for 3 min. Large clumps (with arrows indicated) were observed in the ΔkbvR strain compared with those in WT. C Transmission electron microscopy images of K. pneumoniae NTUH-K2044 and its ΔkbvR mutant, and arrows indicate the fimbriae.