Hemerythrins in the microaerophilic bacterium Campylobacter jejuni help protect key iron–sulphur cluster enzymes from oxidative damage

Abstract

Microaerophilic bacteria are adapted to low oxygen environments, but the mechanisms by which their growth in air is inhibited are not well understood. The citric acid cycle in the microaerophilic pathogen Campylobacter jejuni is potentially vulnerable, as it employs pyruvate and 2-oxoglutarate:acceptor oxidoreductases (Por and Oor), which contain labile (4Fe-4S) centres. Here, we show that both enzymes are rapidly inactivated after exposure of cells to a fully aerobic environment. We investigated the mechanisms that might protect enzyme activity and identify a role for the hemerythrin HerA (Cj0241). A herA mutant exhibits an aerobic growth defect and reduced Por and Oor activities after exposure to 21% (v/v) oxygen. Slow anaerobic recovery of these activities after oxygen damage was observed, but at similar rates in both wild-type and herA strains, suggesting the role of HerA is to prevent Fe-S cluster damage, rather than promote repair. Another hemerythrin (HerB; Cj1224) also plays a protective role. Purified HerA and HerB exhibited optical absorption, ligand binding and resonance Raman spectra typical of μ-oxo-bridged di-iron containing hemerythrins. We conclude that oxygen lability and poor repair of Por and Oor are major contributors to microaerophily in C. jejuni; hemerythrins help prevent enzyme damage microaerobically or during oxygen transients.

Genome‐wide association of functional traits linked with Campylobacter jejuni survival from farm to fork

“…The nuoK gene encodes a membrane-bound subunit of the 14 subunit oxidoreductase complex I, which in C. jejuni, unlike classical complex I NADH dehydrogenases, transfers electrons from reduced flavodoxin, formed from 2-oxoacid oxidation by Oor (and possibly Por) enzymes, to the respiratory chain (Weerakoon et al, 2009;Kendall et al, 2014) (Fig. The nuoK gene encodes a membrane-bound subunit of the 14 subunit oxidoreductase complex I, which in C. jejuni, unlike classical complex I NADH dehydrogenases, transfers electrons from reduced flavodoxin, formed from 2-oxoacid oxidation by Oor (and possibly Por) enzymes, to the respiratory chain (Weerakoon et al, 2009;Kendall et al, 2014) (Fig.…”

“…The nuoK gene encodes a membrane-bound subunit of the 14 subunit oxidoreductase complex I, which in C. jejuni, unlike classical complex I NADH dehydrogenases, transfers electrons from reduced flavodoxin, formed from 2-oxoacid oxidation by Oor (and possibly Por) enzymes, to the respiratory chain (Weerakoon et al, 2009;Kendall et al, 2014) (Fig. This has been proposed to partially explain the microaerophilic nature of C. jejuni (Pan and Imlay, 2001;Kelly, 2008;Kendall et al, 2014). Por and Oor, which convert pyruvate to acetyl-CoA and 2-oxoglutarate to succinyl-CoA, respectively, are oxygen sensitive Fe-cluster enzymes, usually found in obligate anaerobes, which replace the oxygen stable pyruvate and 2-oxoglutarate dehydrogenases of aerobes.…”

“…NuoK is a proton-translocating subunit of the inner membrane respiratory complex I, referred to as NDH-1 or the Nuo complex (Fig. In C. jejuni, flavodoxin is reduced by 2-oxoglutarate:acceptor oxidoreductase (Oor) and possibly by pyruvate:acceptor oxidoreductase (Por) enzymes (Weerakoon et al, 2009;Kendall et al, 2014). In most bacteria the function of complex I is to link NADH oxidation to the reduction of quinone in electron transport chain (ETC) for energy conservation; however the C. jejuni genome lacks the genes encoding nuoE and nuoF, responsible for NADH dehydrogenase activity (Kelly, 2008;Weerakoon et al, 2009).…”

Productivity, metabolism and physiology of free-living chemoautotrophic Epsilonproteobacteria

“…Supporting this, even epsilonproteobacterial genera that associate with terrestrial animals, such as Campylobacter, Helicobacter and Wolinella, retain physiological characteristics reflective of a hydrothermal environment where they most likely evolved. These include a need for high CO 2 (Al-Haideri et al, 2016), intolerance to high levels of O 2 (Kendall et al, 2014), and the ability to use hydrogen as an electron donor (Wolin et al, 1961). Below, the underlying geochemistry of deep-sea vents and its effect on the growth conditions of the microbes inhabiting this habitat are discussed.…”

PerR controls oxidative stress defence and aerotolerance but not motility-associated phenotypes of Campylobacter jejuni

“…When exposed to such conditions, C. jejuni will be under oxidative stress; hence, its ability to deal with such stresses is thought to contribute significantly to its success as a bacterial pathogen. C. jejuni expresses an array of factors combatting oxidative stresses, including several peroxidases (Atack et al, 2008;Baillon et al, 1999;Kendall et al, 2014) and an iron-cofactored superoxide dismutase (Purdy et al, 1999), and the absence of these factors severely affects important aspects of C. jejuni food chain survival and transmission (Oh & Jeon, 2014;Stead & Park, 2000) as well as virulence .…”