A factor produced by Escherichia coli K-12 inhibits the growth of E. coli mutants defective in the cytochrome bd quinol oxidase complex: enterochelin rediscovered

Abstract

Escherichia coli produces an extracellular factor that inhibits the aerobic growth of Cyd' mutants, defective in the synthesis or assembly of the cytochrome bd-type quinol oxidase. This paper shows that such a factor is the iron-chelating siderophore enterochelin. Mutants in entA or aroB, defective in the production of enterochelin, did not produce the factor that inhibits the growth of cydAB and cydDC mutants; purified enterochelin inhibited the growth of Cyd' mutants, but not that of wild-type cells. Other iron-chelating agents, particularly ethylenediamine-di(ohydroxypheny1acetic acid) (EDDHA), whose complex with Fe(lll) has a large stability constant (log K = 33*9), also inhibited the growth of Cyd' mutants at micromolar concentrations, but not that of wild-type cells. Supplementation of agar plates with Fe(lll) or boiled catalase prevented the inhibition of Cyd' mutants by the extracellular factor. Spontaneous mutants isolated by being able to grow in the presence of the extracellular factor on plates also showed increased resistance to iron chelators. The reducing agent ascorbate, ascorbate plus In(lll), ascorbate plus Ga(lll), or Ga(lll) alone, also alleviated inhibition by the extracellular factor, presumably by reducing iron to Fe(ll) and complexing of the siderophore with alternative trivalent metal cations. The preferential inhibition of Cyd' mutants by the extracellular factor and other iron chelators is not due to decrease in expression, activity or assembly of cytochrome bo', the major alternative oxidase mediating quinol oxidation. Cyd' mutants overproduce siderophores, presumably reflecting intracellular iron deprivation. 2TN, UK

Interruption of the cydB Locus in Brucella abortus Attenuates Intracellular Survival and Virulence in the Mouse Model of Infection

“…Low pH also promotes the release of iron bound to transferrin receptors internalized within endocytic vacuoles (17), and pathogens having a strict requirement for iron depend on macrophage acidification for growth (55). E. coli and A. vinelandii cyd mutants have been shown to overproduce siderophores and are deficient in intracellular iron (12,19). Growth inhibition is relieved under microaerobic conditions preventing oxygen overload or by the addition of ferrous iron sulfate, perhaps by stimulating SOD.…”

Membrane topology and mutational analysis of Escherichia coli CydDC, an ABC-type cysteine exporter required for cytochrome assembly

“…Strains were challenged on zincazide medium (ZnSO 4 -NaN 3 , 0?15 mM each) supplemented with Casamino acids (ZABC plates; Poole et al, 1989) and on nutrient agar containing 0?1 mM of the metal-chelating agent ethylenediaminedi(o-hydroxyphenyl acetic acid) (EDDHA) (Cook et al, 1998).…”

“…Cyd 2 mutants have a complex phenotype, including sensitivity to: (i) zinc and azide, inhibitors of the remaining cytochrome o-mediated respiratory chain (Poole et al, 1989); (ii) iron chelators (Cook et al, 1998) and (iii) H 2 O 2 (Delaney et al, 1992;Lindqvist et al, 2000). We exploited these sensitivities to test strain AN2343 (cydD1) that had been transformed with pRKP1602 (bearing the wild-type cydDC genes) or site-directed cydD mutant derivatives, by plating on ZABC medium (containing Zn 2+ and azide ions) or plates supplemented with EDDHA or H 2 O 2 .…”

“…Loss of cytochrome bd causes a complex phenotype that extends beyond the lack of a functional oxidase. The Cyd 2 phenotype in E. coli includes (i) an inability to exit aerobically from stationary phase at 37 uC (Siegele et al, 1996); (ii) sensitivity to high temperature (Delaney et al, 1992), (iii) increased sensitivity to H 2 O 2 (Delaney et al, 1992); (iv) sensitivity to iron chelators (Cook et al, 1998); and loss of motility and increased benzylpenicillin sensitivity (Pittman et al, 2002). The need to understand cytochrome bd assembly is underlined by the importance of this oxidase in many bacteria.…”

Global Transcriptome Analysis ofStaphylococcus aureusResponse to Hydrogen Peroxide

“…Cytochrome d oxidase catalyzes the last step of oxygen respiration and prevails under oxygen-limiting conditions (26). Interestingly, it was speculated that cytochrome d oxidase is required under conditions of environmental stress and may have crucial roles in cellular physiology other than acting as an oxidase (12). Further, prior studies revealed that cytochrome d oxidase plays an imperative part in cellular protection against oxidative stress, at least under microaerobic growth conditions, by showing that mutation or deletion of the genes encoding the enzyme increases sensitivity to oxidative stress in E. coli and Azotobacter vinelandii (18,23,35).…”