AUTHOR=Cai Ruopeng , Wang Gang , Le Shuai , Wu Mei , Cheng Mengjun , Guo Zhimin , Ji Yalu , Xi Hengyu , Zhao Caijun , Wang Xinwu , Xue Yibing , Wang Zijing , Zhang Hao , Fu Yunhe , Sun Changjiang , Feng Xin , Lei Liancheng , Yang Yongjun , ur Rahman Sadeeq , Liu Xiaoyun , Han Wenyu , Gu Jingmin 

TITLE=Three Capsular Polysaccharide Synthesis-Related Glucosyltransferases, GT-1, GT-2 and WcaJ, Are Associated With Virulence and Phage Sensitivity of Klebsiella pneumoniae

JOURNAL=Frontiers in Microbiology

VOLUME=10

YEAR=2019

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2019.01189

DOI=10.3389/fmicb.2019.01189

ISSN=1664-302X

ABSTRACT=<p><italic>Klebsiella pneumoniae</italic> (<italic>K. pneumoniae</italic>) spp. are important nosocomial and community-acquired opportunistic pathogens, which cause various infections. We observed that <italic>K. pneumoniae</italic> strain K7 abruptly mutates to rough-type phage-resistant phenotype upon treatment with phage GH-K3. In the present study, the rough-type phage-resistant mutant named K7R<sup>R</sup> showed much lower virulence than K7. Liquid chromatography-tandem mass spectrometry (LC-MS-MS) analysis indicated that WcaJ and two undefined glycosyltransferases (GTs)- named GT-1, GT-2- were found to be down-regulated drastically in K7R<sup>R</sup> as compared to K7 strain. <italic>GT-1</italic>, <italic>GT-2</italic>, and <italic>wcaJ</italic> are all located in the gene cluster of capsular polysaccharide (CPS). Upon deletion, even of single component, of <italic>GT-1</italic>, <italic>GT-2</italic>, and <italic>wcaJ</italic> resulted clearly in significant decline of CPS synthesis with concomitant development of GH-K3 resistance and decline of virulence of <italic>K. pneumoniae</italic>, indicating that all these three GTs are more likely involved in maintenance of phage sensitivity and bacterial virulence. Additionally, K7R<sup>R</sup> and GT-deficient strains were found sensitive to endocytosis of macrophages. Mitogen-activated protein kinase (MAPK) signaling pathway of macrophages was significantly activated by K7R<sup>R</sup> and GT-deficient strains comparing with that of K7. Interestingly, in the presence of macromolecular CPS residues (&gt;250 KD), K7(Δ<italic>GT-1</italic>) and K7(Δ<italic>wcaJ</italic>) could still be bounded by GH-K3, though with a modest adsorption efficiency, and showed minor virulence, suggesting that the CPS residues accumulated upon deletion of <italic>GT-1</italic> or <italic>wcaJ</italic> did retain phage binding sites as well maintain mild virulence. In brief, our study defines, for the first time, the potential roles of GT-1, GT-2, and WcaJ in <italic>K. pneumoniae</italic> in bacterial virulence and generation of rough-type mutation under the pressure of bacteriophage.</p>