The DmsABC Sulfoxide Reductase Supports Virulence in Non-typeable Haemophilus influenzae.

Rabeb Dhouib,Dk Seti Maimonah Pg Othman,Marufa Nasreen,Philip M Hansbro,Ulrike Kappler,Alastair G Mcewan,Ama-Tawiah Essilfie,Simon Lee,Daniel Ellis

doi:10.3389/fmicb.2021.686833

Abstract

Although molybdenum-containing enzymes are well-established as having a key role in bacterial respiration, it is increasingly recognized that some may also support bacterial virulence. Here, we show that DmsABC, a putative dimethylsulfoxide (DMSO) reductase, is required for fitness of the respiratory pathogen Haemophilus influenzae (Hi) in different models of infection. Expression of the dmsABC operon increased with decreasing oxygen availability, but despite this, a Hi2019ΔdmsA strain did not show any defects in anaerobic growth on chemically defined medium (CDM), and viability was also unaffected. Although Hi2019ΔdmsA exhibited increased biofilm formation in vitro and greater resistance to hypochlorite killing compared to the isogenic wild-type strain, its survival in contact with primary human neutrophils, in infections of cultured tissue cells, or in a mouse model of lung infection was reduced compared to Hi2019WT. The tissue cell infection model revealed a two-fold decrease in intracellular survival, while in the mouse model of lung infection Hi2019ΔdmsA was strongly attenuated and below detection levels at 48 h post-inoculation. While Hi2019WT was recovered in approximately equal numbers from bronchoalveolar lavage fluid (BALF) and lung tissue, survival of Hi2019ΔdmsA was reduced in lung tissue compared to BALF samples, indicating that Hi2019ΔdmsA had reduced access to or survival in the intracellular niche. Our data clearly indicate for the first time a role for DmsABC in H. influenzae infection and that the conditions under which DmsABC is required in this bacterium are closely linked to interactions with the host.

Highlights

One of the most common types of biomolecular damage caused by oxidative stress is the oxidation of sulfur compounds including amino acids
DmsABC Expression in H. influenzae Is Associated With Anaerobiosis but Shows No Substrate-Dependent Induction In H. influenzae, the DmsABC sulfoxide reductase is encoded by a five-gene operon, dmsABCDE (Hi2019: C645_RS06125– C645_RS06105) (Figure 1A), that is completely conserved in genomes of H. influenzae strains
The gene we have designated dmsE encodes a protein for both the Hi2019 wild-type strain and a Hi2019 mtsZ gene knockout strain where DmsABC is the only S-oxide reductase present (Figure 1D and Supplementary Figure 1). This suggests that in H. influenzae neither the MtsZ nor the DmsABC sulfoxide reductases are induced in the presence of DMSO, which is similar to the situation in E. coli (McNicholas et al, 1997; Constantinidou et al, 2006; Harrington et al, 2009)

Summary

Introduction

One of the most common types of biomolecular damage caused by oxidative stress is the oxidation of sulfur compounds including amino acids Both cysteine and methionine are highly susceptible to oxidative damage, and there is increasing evidence that both thiol-based and molybdenum-containing methionine sulfoxide reductases protect bacterial pathogens from hostinduced oxidative stress and support bacterial virulence (Ezraty et al, 2005, 2017; Denkel et al, 2013; Nasreen et al, 2020; Zhong et al, 2020). The two H. influenzae methionine sulfoxide reductases, MtsZ and MsrAB, are both part of the bacterium’s periplasmic defenses against oxidative stress (Dhouib et al, 2016; Nasreen et al, 2020). MtsZ has been shown to have a role in redox balancing

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Results

Conclusion