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The Terminal Oxidase Cytochrome bd Promotes Sulfide-resistant Bacterial Respiration and Growth.

Forte E, Borisov VB, Falabella M, Colaço HG, Tinajero-Trejo M, Poole RK, Vicente JB, Sarti P, Giuffrè A - Sci Rep (2016)

Bottom Line: E. coli has three respiratory oxidases, the cyanide-sensitive heme-copper bo3 enzyme and two bd oxidases much less sensitive to cyanide.In E. coli respiratory mutants, both O2-consumption and aerobic growth proved to be severely impaired by sulfide when respiration was sustained by the bo3 oxidase alone, but unaffected by ≤200 μM sulfide when either bd enzyme acted as the only terminal oxidase.The impact of this discovery is discussed.

View Article: PubMed Central - PubMed

Affiliation: Department of Biochemical Sciences and Istituto Pasteur- Fondazione Cenci Bolognetti, Sapienza University of Rome, Italy.

ABSTRACT
Hydrogen sulfide (H2S) impairs mitochondrial respiration by potently inhibiting the heme-copper cytochrome c oxidase. Since many prokaryotes, including Escherichia (E.) coli, generate H2S and encounter high H2S levels particularly in the human gut, herein we tested whether bacteria can sustain sulfide-resistant O2-dependent respiration. E. coli has three respiratory oxidases, the cyanide-sensitive heme-copper bo3 enzyme and two bd oxidases much less sensitive to cyanide. Working on the isolated enzymes, we found that, whereas the bo3 oxidase is inhibited by sulfide with half-maximal inhibitory concentration IC50 = 1.1 ± 0.1 μM, under identical experimental conditions both bd oxidases are insensitive to sulfide up to 58 μM. In E. coli respiratory mutants, both O2-consumption and aerobic growth proved to be severely impaired by sulfide when respiration was sustained by the bo3 oxidase alone, but unaffected by ≤200 μM sulfide when either bd enzyme acted as the only terminal oxidase. Accordingly, wild-type E. coli showed sulfide-insensitive respiration and growth under conditions favouring the expression of bd oxidases. In all tested conditions, cyanide mimicked the functional effect of sulfide on bacterial respiration. We conclude that bd oxidases promote sulfide-resistant O2-consumption and growth in E. coli and possibly other bacteria. The impact of this discovery is discussed.

No MeSH data available.


Related in: MedlinePlus

Effect of NaHS and cyanide on respiration of E. coli cells.(Top) Residual respiratory activity measured after the addition of 50 μM NaHS to E. coli cells collected at the reported cell density. (Bottom) Comparison of the effect of cyanide and sulfide on cell respiration: respiratory activity measured after the addition of 50 μM NaHS or 50 μM NaCN to wild-type and mutant E. coli cells. Data (mean ± standard deviation) refer to the control activity measured before the addition of inhibitors (taken as 100%).
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f3: Effect of NaHS and cyanide on respiration of E. coli cells.(Top) Residual respiratory activity measured after the addition of 50 μM NaHS to E. coli cells collected at the reported cell density. (Bottom) Comparison of the effect of cyanide and sulfide on cell respiration: respiratory activity measured after the addition of 50 μM NaHS or 50 μM NaCN to wild-type and mutant E. coli cells. Data (mean ± standard deviation) refer to the control activity measured before the addition of inhibitors (taken as 100%).

Mentions: The striking results obtained with the isolated enzymes prompted us to explore the effect of sulfide on E. coli cell respiration. To this end, we investigated aerobic cultures of E. coli (see Methods for details) and tested the effect of NaHS on cell respiration along cell growth, i.e., at increasing cell density. We initially assayed three mutant strains each expressing a single terminal oxidase (bo3, bd-I or bd-II). The results were remarkably similar to those obtained with the isolated enzymes. O2 consumption by E. coli cells expressing solely cytochrome bo3 was quickly and fully inhibited upon addition of 50 μM NaHS (Fig. 1B). As observed with the isolated bo3 enzyme, the inhibition was promptly and fully restored upon sulfide depletion by the EhOASS/OAS system (Fig. 1B). In contrast, no inhibition was observed following the addition of 50 μM NaHS to E. coli cells expressing either bd-I or bd-II as the only terminal oxidase (Fig. 1B). The results on the three mutant strains proved to be independent of the density at which cells were collected and assayed (Fig. 3, top panel). Similarly to NaHS, cyanide (50 μM) almost completely abolished O2-consumption in E. coli cells expressing only the bo3 oxidase, whereas it was essentially ineffective when respiration was sustained by either bd oxidase (Fig. 3, bottom panel).


The Terminal Oxidase Cytochrome bd Promotes Sulfide-resistant Bacterial Respiration and Growth.

Forte E, Borisov VB, Falabella M, Colaço HG, Tinajero-Trejo M, Poole RK, Vicente JB, Sarti P, Giuffrè A - Sci Rep (2016)

Effect of NaHS and cyanide on respiration of E. coli cells.(Top) Residual respiratory activity measured after the addition of 50 μM NaHS to E. coli cells collected at the reported cell density. (Bottom) Comparison of the effect of cyanide and sulfide on cell respiration: respiratory activity measured after the addition of 50 μM NaHS or 50 μM NaCN to wild-type and mutant E. coli cells. Data (mean ± standard deviation) refer to the control activity measured before the addition of inhibitors (taken as 100%).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4815019&req=5

f3: Effect of NaHS and cyanide on respiration of E. coli cells.(Top) Residual respiratory activity measured after the addition of 50 μM NaHS to E. coli cells collected at the reported cell density. (Bottom) Comparison of the effect of cyanide and sulfide on cell respiration: respiratory activity measured after the addition of 50 μM NaHS or 50 μM NaCN to wild-type and mutant E. coli cells. Data (mean ± standard deviation) refer to the control activity measured before the addition of inhibitors (taken as 100%).
Mentions: The striking results obtained with the isolated enzymes prompted us to explore the effect of sulfide on E. coli cell respiration. To this end, we investigated aerobic cultures of E. coli (see Methods for details) and tested the effect of NaHS on cell respiration along cell growth, i.e., at increasing cell density. We initially assayed three mutant strains each expressing a single terminal oxidase (bo3, bd-I or bd-II). The results were remarkably similar to those obtained with the isolated enzymes. O2 consumption by E. coli cells expressing solely cytochrome bo3 was quickly and fully inhibited upon addition of 50 μM NaHS (Fig. 1B). As observed with the isolated bo3 enzyme, the inhibition was promptly and fully restored upon sulfide depletion by the EhOASS/OAS system (Fig. 1B). In contrast, no inhibition was observed following the addition of 50 μM NaHS to E. coli cells expressing either bd-I or bd-II as the only terminal oxidase (Fig. 1B). The results on the three mutant strains proved to be independent of the density at which cells were collected and assayed (Fig. 3, top panel). Similarly to NaHS, cyanide (50 μM) almost completely abolished O2-consumption in E. coli cells expressing only the bo3 oxidase, whereas it was essentially ineffective when respiration was sustained by either bd oxidase (Fig. 3, bottom panel).

Bottom Line: E. coli has three respiratory oxidases, the cyanide-sensitive heme-copper bo3 enzyme and two bd oxidases much less sensitive to cyanide.In E. coli respiratory mutants, both O2-consumption and aerobic growth proved to be severely impaired by sulfide when respiration was sustained by the bo3 oxidase alone, but unaffected by ≤200 μM sulfide when either bd enzyme acted as the only terminal oxidase.The impact of this discovery is discussed.

View Article: PubMed Central - PubMed

Affiliation: Department of Biochemical Sciences and Istituto Pasteur- Fondazione Cenci Bolognetti, Sapienza University of Rome, Italy.

ABSTRACT
Hydrogen sulfide (H2S) impairs mitochondrial respiration by potently inhibiting the heme-copper cytochrome c oxidase. Since many prokaryotes, including Escherichia (E.) coli, generate H2S and encounter high H2S levels particularly in the human gut, herein we tested whether bacteria can sustain sulfide-resistant O2-dependent respiration. E. coli has three respiratory oxidases, the cyanide-sensitive heme-copper bo3 enzyme and two bd oxidases much less sensitive to cyanide. Working on the isolated enzymes, we found that, whereas the bo3 oxidase is inhibited by sulfide with half-maximal inhibitory concentration IC50 = 1.1 ± 0.1 μM, under identical experimental conditions both bd oxidases are insensitive to sulfide up to 58 μM. In E. coli respiratory mutants, both O2-consumption and aerobic growth proved to be severely impaired by sulfide when respiration was sustained by the bo3 oxidase alone, but unaffected by ≤200 μM sulfide when either bd enzyme acted as the only terminal oxidase. Accordingly, wild-type E. coli showed sulfide-insensitive respiration and growth under conditions favouring the expression of bd oxidases. In all tested conditions, cyanide mimicked the functional effect of sulfide on bacterial respiration. We conclude that bd oxidases promote sulfide-resistant O2-consumption and growth in E. coli and possibly other bacteria. The impact of this discovery is discussed.

No MeSH data available.


Related in: MedlinePlus