FIG 5.

Capsular polysaccharide biosynthesis test. (A) A precipitation test was performed with centrifugation at 10,000 × g for 5 min, and the resultant pellet was checked for mucoid appearance. The WT and C-frwC strains were found to have denser pellets than the ΔfrwC mutant. M, DL 2000 DNA marker. (B) String test. The strains were grown on 5% sheep blood plates at 37°C for 16 h, and the WT and C-frwC strains displayed viscous filaments stretched by a tip, but the ΔfrwC mutant colony was stretched as a whole. (C) RT-PCR. The expression levels of 16S rRNA and magA (a gene identified as responsible for the hypermucoviscous phenotype) of K. pneumoniae strains were monitored by RT-PCR. The magA transcript level was increased in the ΔfrwC strain. (D) magA expression. The magA transcript level was quantified with Image Lab software. (E) CPS quantification. CPS was isolated and expressed as the amount of glucuronic acid per 10⁹ CFU of bacterial cells. The error bars represent the standard errors of three biological replicates. The P value for the frwC mutant was calculated by ANOVA.