Klebsiella pneumoniae BolA contributes to cell morphology, siderophore production, stresses challenge, cell adhesion and virulence

Klebsiella pneumoniae infection is one of the important reasons for the increased of morbidity and mortality. The main virulence factors of K. pneumoniae include capsule polysaccharide, lipopolysaccharide, fimbriae, outer membrane proteins and siderophores. BolA homologues form a broadly conserved family of proteins in prokaryotes and eukaryotes. In Escherichia coli, bolA expression is quickly induced in response to different stresses or stationary phase that rapidly adapt to changing environments. In this report, we confirmed that bolA mutant strain exhibited increased sensitivity to bile and oxidative stresses. In addition, gene deletion showed that bolA has an important role for the adherence of K. pneumoniae to host cell and establishment in mice, including liver, spleen, kidney and lung tissues, and induce the formation of liver abscess in mice. Our results also demonstrated that K. pneumoniae bolA increases the production of siderophore and virulence in Galleria mellonella larvae. Collectively, our results demonstrated that K. pneumoniae BolA is a new virulence factor which contributes to survival in different stresses and overcome host defense. These findings are helpful for the research of new treatment strategies for K. pneumoniae infection. IMPORTANCEKlebsiella pneumoniae is an important conditional pathogen causing nosocomial infections and community-acquired infections. It can resistant to multiple antibiotics, causing refractory infections and public health threat. Therefore, new treatments are required to fight the pathogen, and a better understanding of its virulence factors are needed to develop new drugs. Here, we unraveled the role of BolA in survival under different stresses and overcome host defense. Our results suggested that bolA actively contributes to cell morphology, stresses challenge, cell adhesion and siderophore production that are tightly related to bacterial virulence. Therefore, bolA mutant strain reduces the virulence of K. pneumoniae in G. mellonella larvae and its colonization ability in mice. These results reported bolA is a key virulence factor in K. pneumoniae, and they are helpful for research of new therapies to treat this increasingly problematic pathogen.