Attenuation of Yersinia pestis fyuA Mutants Caused by Iron Uptake Inhibition and Decreased Survivability in Macrophages

Yulu Chen; Kai Song; Xin Chen; Ye Li; Ruichen Lv; Qingwen Zhang; Yujun Cui; Yujing Bi; Yanping Han; Yafang Tan; Zongmin Du; Ruifu Yang; Zhizhen Qi; Yajun Song

doi:10.3389/fcimb.2022.874773

Attenuation of Yersinia pestis fyuA Mutants Caused by Iron Uptake Inhibition and Decreased Survivability in Macrophages

Front Cell Infect Microbiol. 2022 May 4:12:874773. doi: 10.3389/fcimb.2022.874773. eCollection 2022.

Authors

Yulu Chen^{1

2}, Kai Song^{1

2}, Xin Chen³, Ye Li¹, Ruichen Lv⁴, Qingwen Zhang^{5

6}, Yujun Cui¹, Yujing Bi¹, Yanping Han¹, Yafang Tan¹, Zongmin Du¹, Ruifu Yang^{1

6}, Zhizhen Qi^{5

6}, Yajun Song^{2

3

6}

Affiliations

¹ State Key Laboratory of Pathogen and Biosecurity, Beijing Institute of Microbiology and Epidemiology, Academy of Military Medical Sciences (AMMS), Beijing, China.
² Lab for Bacteriology, State Key Laboratory of Pathogen and Biosecurity, Beijing Institute of Microbiology and Epidemiology, Academy of Military Medical Sciences (AMMS), Beijing, China.
³ School of Basic Medicine, Anhui Medical University, Hefei, China.
⁴ Huadong Research Institute for Medicine and Biotechniques, Nanjing, China.
⁵ Qinghai Institute for Endemic Disease Prevention and Control, Xining, China.
⁶ National Health Commission - Qinghai Co-construction Key Laboratory for Plague Control, Xining, China.

Abstract

Yersinia pestis is the etiological agent of plague, a deadly infectious disease that has caused millions of deaths throughout history. Obtaining iron from the host is very important for bacterial pathogenicity. Y. pestis possesses many iron uptake systems. Yersiniabactin (Ybt) plays a major role in iron uptake in vivo and in vitro, and in virulence toward mice as well. FyuA, a β-barrel TonB-dependent outer membrane protein, serves as the receptor for Ybt. In this study, we examined the role of the fyuA gene in Y. pestis virulence using different challenging ways and explored the underlying mechanisms. The BALB/c mouse infection assay showed that the virulence of the mutant strains (ΔfyuA and ΔfyuA_GCAdel) was lower when compared with that of the wild-type (WT) strain 201. Furthermore, the attenuation of virulence of the mutant strains via subcutaneous and intraperitoneal challenges was far greater than that via intravenous injection. Iron supplementation restored lethality during subcutaneous challenge with the two mutants. Thus, we speculated that the attenuated virulence of the mutant strains toward the mice may be caused by dysfunctional iron uptake. Moreover, ΔfyuA and ΔfyuA_GCAdel strains exhibited lower survival rates in murine RAW264.7 macrophages, which might be another reason for the attenuation. We further explored the transcriptomic differences between the WT and mutant strains at different temperatures and found that the expressions of genes related to Ybt synthesis and its regulation were significantly downregulated in the mutant strains. This finding indicates that fyuA might exert a regulatory effect on Ybt. Additionally, the expressions of the components of the type III secretion system were unexpectedly upregulated in the mutants, which is inconsistent with the conventional view that the upregulation of the virulence genes enhances the virulence of the pathogens.

Keywords: Ybt system; Yersinia pestis; fyuA; iron uptake system; pathogenicity; virulence.

Publication types

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

MeSH terms

Animals
Bacterial Proteins / genetics
Bacterial Proteins / metabolism
Iron / metabolism
Macrophages / metabolism
Mice
Plague* / microbiology
Virulence / genetics
Yersinia pestis*

Substances

Bacterial Proteins
Iron