Regulation of ECP fimbriae‐related genes by the transcriptional regulator RcsAB in Klebsiella pneumoniae NTUH‐K2044

Abstract

Klebsiella pneumoniae is one of the major pathogens causing nosocomial infections.The regulator of capsule synthesis (Rcs) system is a complex signal transduction pathway that is involved in the regulation of virulence factors of K. pneumoniae as an important transcriptional regulator. The RcsAB box-like sequence was found to be present in the promoter-proximal regions of ykgK, one of the ECP fimbriaerelated genes, which suggested the expression of ECP fimbriae may be regulated by RcsAB. The ykgK gene in K. pneumoniae has 86% similarity to the ecpR gene in Escherichia coli. Nucleotide sequence alignment revealed a similar ECP fimbriae gene cluster including six genes in K. pneumoniae, which was proved to be on the same operon in this study. The electrophoretic mobility shift assay and DNase I assay, relative fluorescence expression, β-galactosidase activity, and relative gene expression of ykgK in the wild-type and mutant strains were performed to determine the transcriptional regulation mechanism of RcsAB on ECP fimbriae. The mutant ΔykgK and complementary strain ΔykgK/cΔykgK were constructed to complete the Galleria mellonella larvae infection experiment and biofilm formation assay. This study showed that RcsAB binds directly to the promoter region of the ykgK gene to positively regulate ECP fimbriae-related gene clusters, and then positively affect the biofilm formation. K E Y W O R D S ECP fimbriae-related gene, Klebsiella pneumoniae, RcsAB, transcriptional regulator, ykgK gene 1 | INTRODUCTION Klebsiella pneumoniae is a common opportunistic pathogen that can cause urinary and respiratory tract infections, pneumonia, bacteraemia, and sepsis [1]. Current research on the virulence of K. pneumoniae has also attracted much attention. The known virulence factors of K. pneumoniae mainly include capsular polysaccharide (CPS), lipopolysaccharide, fimbriae, urease, biofilm formation-related factors, and the iron capture

Transcriptional regulation of the yersiniabactin receptor fyuA gene by the ferric uptake regulator in Klebsiella pneumoniae NTUH‐K2044

“…The formula for calculating the relative formation of biofilm was as follows: the relative formation of biofilm = 1000 × OD 570 /(OD 600 × V1 × V2). V1 represents the initial volume of the bacterial suspension, and V2 represents the volume of DMSO [31,32]. The average relative biofilm formation was measured by three independent experiments, which indirectly reflected the biofilm formation ability.…”