The cytochrome d oxidase complex regulated by fexA is an Achilles' heel in the in vivo survival of Vibrio vulnificus

Wenzhi Tan,Kwangjoon Jeong,Raghunath Pendru,Sao Puth,Seol Hee Hong,Shee Eun Lee,Joon Haeng Rhee

doi:10.1080/22221751.2019.1665972

Wenzhi Tan, Kwangjoon Jeong + Show 5 more

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https://doi.org/10.1080/22221751.2019.1665972

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Abstract

ABSTRACT Vibrio vulnificus is a halophilic estuarine bacterium causing severe opportunistic infections. To successfully establish an infection, V. vulnificus must adapt to redox fluctuations in vivo. In the present study, we show that deletion of V. vulnificus fexA gene caused hypersensitivity to acid and reactive oxygen species. The ΔfexA mutant exhibited severe in vivo survival defects. For deeper understanding the role of fexA gene on the successful V. vulnificus infection, we analyzed differentially expressed genes in ΔfexA mutant in comparison with wild type under aerobic, anaerobic or in vivo culture conditions by genome-scale DNA microarray analyses. Twenty-two genes were downregulated in the ΔfexA mutant under all three culture conditions. Among them, cydAB appeared to dominantly contribute to the defective phenotypes of the ΔfexA mutant. The fexA deletion induced compensatory point mutations in the cydAB promoter region over subcultures, suggesting essentiality. Those point mutations (PcydSMs) restored bacterial growth, motility, cytotoxicity ATP production and mouse lethality in the ΔfexA mutant. These results indicate that the cydAB operon, being regulated by FexA, plays a crucial role in V. vulnificus survival under redox-fluctuating in vivo conditions. The FexA-CydAB axis should serve an Achilles heel in the development of therapeutic regimens against V. vulnificus infection.

Highlights

Vibrio vulnificus is a halophilic estuarine bacterium that causes opportunistic infection with high mortality [1]
These results indicate that FexA plays an important role in V. vulnificus growth under wide spectrum redox status
In V. vulnificus, deletion of fexA, an arcA ortholog, attenuated a plethora of V. vulnificus functions, including in vitro growth and in vivo survival, resistance to reactive oxygen species (ROS) and acidic pH, motility, cytotoxicity and mouse lethality, all of which contribute to pathogenicity in vivo

Summary

Introduction

Vibrio vulnificus is a halophilic estuarine bacterium that causes opportunistic infection with high mortality [1]. The growth defects of ΔfexA mutant were fully recovered in the fexA revertant in all culture conditions and a compensatory point mutation in the cydAB promoter region (ΔfexA/PcydSM1) restored bacterial growth in 0.2% succinate MEM media (Figure 5(D)). These results corroborate that FexA directly regulates cydAB, critical components of complex III in the electron transfer system of V. vulnificus using succinate for proton generation and that the FexA plays a pivotal role in in vivo proliferation of V. vulnificus via regulation of expression of the cydAB.

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