Manganese impairs the QoxABCD terminal oxidase leading to respiration‐associated toxicity

Abstract

Cell physiology relies on metalloenzymes and can be easily disrupted by imbalances in metal ion pools. Bacillus subtilis requires manganese for growth and has highly regulated mechanisms for import and efflux that help maintain homeostasis. Cells defective for manganese (Mn) efflux are highly sensitive to intoxication, but the processes impaired by Mn excess are often unknown. Here, we employed a forward genetics approach to identify pathways affected by manganese intoxication. Our results highlight a central role for the membrane‐localized electron transport chain in metal intoxication during aerobic growth. In the presence of elevated manganese, there is an increased generation of reactive radical species associated with dysfunction of the major terminal oxidase, the cytochrome aa3 heme‐copper menaquinol oxidase (QoxABCD). Intoxication is suppressed by diversion of menaquinol to alternative oxidases or by a mutation affecting heme A synthesis that is known to convert QoxABCD from an aa3 to a bo3‐type oxidase. Manganese sensitivity is also reduced by derepression of the MhqR regulon, which protects cells against reactive quinones. These results suggest that dysfunction of the cytochrome aa3‐type quinol oxidase contributes to metal‐induced intoxication.

The coordinated population redistribution between Bacillus subtilis submerged biofilm and liquid-air pellicle

“…S1 ), and the qoxABCD operon (encoding cytochrome aa 3 quinol oxidase, the major oxidase in aerated cultures, represented as qoxA gene in Fig. S1 ) [ 50 ]. For efficient aerobic growth, cells require either CydABCD or QoxABCD [ 50 ].…”

“…S1 ) [ 50 ]. For efficient aerobic growth, cells require either CydABCD or QoxABCD [ 50 ]. In the first hour only cydA appears to be upregulated ( Fig.…”

MntP and YiiP Contribute to Manganese Efflux in Salmonella enterica Serovar Typhimurium under Conditions of Manganese Overload and Nitrosative Stress

“…Manganese excess has been shown to affect electron transport chain function and function of Fe-S cluster enzymes in central energy-generating pathways. ( 15 – 17 ). These proteins are also targets of oxidants, which could explain, at least in part, why enhanced sensitivity to oxidants is seen for some species, but the mechanisms underlying the requirement for manganese efflux remain incompletely understood.…”

“…Together, these effects can result in inhibition of energy-generating and biosynthetic pathways. In Bacillus subtilis , which requires manganese for growth, excess manganese has been associated with impaired function of the cytochrome aa 3 heme-copper menaquinol oxidase (QoxABCD) of the electron transport chain ( 17 ). Therefore, while increased cellular manganese may benefit bacteria when challenged with a specific physiological or chemical stress, efflux of manganese may be necessary upon alleviation of the aforementioned stress.…”

A Central Role for Magnesium Homeostasis during Adaptation to Osmotic Stress

“…Ion homeostasis relies on the tight regulation of both import and efflux ( 2 – 5 ), and mutants lacking efflux have an increased sensitivity to metal intoxication ( 6 – 10 ). Previously, we recovered mpfA mutations as suppressors of Mn 2+ sensitivity in strains defective for Mn 2+ efflux ( 5 , 11 ). Strains lacking MpfA have an ∼50% increase in intracellular Mg 2+ ( 5 ), consistent with the assignment of MpfA as a major Mg 2+ efflux system ( 5 , 12 ).…”