Wza gene knockout decreases Acinetobacter baumannii virulence and affects Wzy-dependent capsular polysaccharide synthesis

Tianshui Niu; Lihua Guo; Qixia Luo; Kai Zhou; Wei Yu; Yunbo Chen; Chen Huang; Yonghong Xiao

doi:10.1080/21505594.2019.1700659

Wza gene knockout decreases Acinetobacter baumannii virulence and affects Wzy-dependent capsular polysaccharide synthesis

Virulence. 2020 Dec;11(1):1-13. doi: 10.1080/21505594.2019.1700659.

Authors

Tianshui Niu^{1

2}, Lihua Guo¹, Qixia Luo¹, Kai Zhou¹, Wei Yu³, Yunbo Chen¹, Chen Huang¹, Yonghong Xiao¹

Affiliations

¹ Collaborative Initiative Center for Diagnosis and Treatment of Infectious Diseases, State Key Laboratory for Diagnosis & Treatment of Infectious Diseases, the First Affiliated Hospital, college of Medicine, Zhejiang University, Hangzhou, China.
² Hangzhou Red Cross Hospital/Zhe Jiang Chinese Medcine and Western Medcine Integrated Hospital, Hangzhou, China.
³ Zhejiang Provincial People's Hospital, People's Hospital of Hangzhou Medical College, Hangzhou, China.

Abstract

To investigate the virulence of capsular polysaccharide export protein (Wza) in carbapenem-resistant Acinetobacter baumannii and its effect on capsule formation.wza gene knockout and complementation strains were constructed, and changes in bacterial virulence were observed using in vitro adhesion, antiserum complement killing, anti-oxidation experiments, and infections in Galleria mellonella and mice. The effect of wza knockout on the genes wzb and wzc and wzi were assessed by RT-PCR.We successfully constructed wza knockout and complementation strains. Compared with wild-type (WT) strains, wza knockout strains displayed lower adhesion to A549 cells (p = 0.044), lower antiserum complement killing ability (p = 0.001), and lower mortality of G. mellonella (p = 0.010) and mice (p = 0.033). Expression levels of wzb, wzc and wzi were decreased in wza knockout strains. The antioxidant capacity of Wza knockout bacteria was only slightly decreased. Complementation of the wza gene returned the adhesion ability, antiserum complement killing ability, and mortality of G. mellonella and mice to WT levels. Expression of wzb, wzc and wzi was also returned to WT levels following wza complementation.The results clearly demonstrate that Wza is toxic. Wza affects the expression of other proteins of the Wzy capsule polysaccharide synthesis pathway, which affects the assembly, export, and extracellular fixation of capsular polysaccharide, resulting in synergistic effects that decrease bacterial virulence.

Keywords: Acinetobacter baumannii; gene complementation; gene knockout; virulence; wza.

Publication types

Research Support, Non-U.S. Gov't

MeSH terms

A549 Cells
Acinetobacter baumannii / genetics*
Acinetobacter baumannii / pathogenicity
Animals
Bacterial Capsules / metabolism*
Bacterial Outer Membrane Proteins / genetics
Bacterial Outer Membrane Proteins / metabolism
Bacterial Proteins / genetics*
Bacterial Proteins / metabolism*
Disease Models, Animal
Escherichia coli / genetics
Escherichia coli Proteins / genetics
Gene Knockout Techniques
Humans
Mice
Moths
Polysaccharides / genetics*
Polysaccharides / metabolism*
Virulence

Substances

Bacterial Outer Membrane Proteins
Bacterial Proteins
Escherichia coli Proteins
Polysaccharides
Wzi protein, E coli

Grants and funding

This work was supported by the the key research and development program of Zhejiang province [No. 2015C03032];National Key Research and Development Program of China [No. 2017YFC1200203].