Limits...
Growth of the obligate anaerobe Desulfovibrio vulgaris Hildenborough under continuous low oxygen concentration sparging: impact of the membrane-bound oxygen reductases.

Ramel F, Brasseur G, Pieulle L, Valette O, Hirschler-Réa A, Fardeau ML, Dolla A - PLoS ONE (2015)

Bottom Line: Effect of constant low oxygen concentration on growth and morphology of the wild-type, single (Δbd, Δcox) and double deletion (Δcoxbd) mutant strains of the genes encoding these oxygen reductases was studied.Time-lapse microscopy revealed that a large majority of the cells were then able to divide (over 97%) but the time to recover a complete division event was longer for single deletion mutant Δbd than for the three other strains.We propose that the pyruvate-ferredoxin oxidoreductase (PFOR) plays a central role in this phenomenon by reversibly switching from an oxidative-sensitive fully active state to an oxidative-insensitive inactive state.

View Article: PubMed Central - PubMed

Affiliation: Aix-Marseille Université, CNRS, LCB-UMR7283, Marseille, France.

ABSTRACT
Although obligate anaerobe, the sulfate-reducing bacterium Desulfovibrio vulgaris Hildenborough (DvH) exhibits high aerotolerance that involves several enzymatic systems, including two membrane-bound oxygen reductases, a bd-quinol oxidase and a cc(b/o)o3 cytochrome oxidase. Effect of constant low oxygen concentration on growth and morphology of the wild-type, single (Δbd, Δcox) and double deletion (Δcoxbd) mutant strains of the genes encoding these oxygen reductases was studied. When both wild-type and deletion mutant strains were cultured in lactate/sulfate medium under constant 0.02% O2 sparging, they were able to grow but the final biomasses and the growth yield were lower than that obtained under anaerobic conditions. At the end of the growth, lactate was not completely consumed and when conditions were then switched to anaerobic, growth resumed. Time-lapse microscopy revealed that a large majority of the cells were then able to divide (over 97%) but the time to recover a complete division event was longer for single deletion mutant Δbd than for the three other strains. Determination of the molar growth yields on lactate suggested that a part of the energy gained from lactate oxidation was derived toward cells protection/repairing against oxidative conditions rather than biosynthesis, and that this part was higher in the single deletion mutant Δbd and, to a lesser extent, Δcox strains. Our data show that when DvH encounters oxidative conditions, it is able to stop growing and to rapidly resume growing when conditions are switched to anaerobic, suggesting that it enters active dormancy sate under oxidative conditions. We propose that the pyruvate-ferredoxin oxidoreductase (PFOR) plays a central role in this phenomenon by reversibly switching from an oxidative-sensitive fully active state to an oxidative-insensitive inactive state. The oxygen reductases, and especially the bd-quinol oxidase, would have a crucial function by maintaining reducing conditions that permit PFOR to stay in its active state.

No MeSH data available.


Related in: MedlinePlus

Biomass formation under various culturing conditions.Final biomass for the four DvH strains cultured under anaerobic conditions only (black bars), with constant 0.02% O2 gas mixture sparging (striped bars) and after growth resumption (open bars). Data are mean values of five independent experiments + SD. Statistical analysis using t-test was used to compare means. Significant differences (p< 0.05) are mentioned by an asterisk.
© Copyright Policy
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC4383621&req=5

pone.0123455.g004: Biomass formation under various culturing conditions.Final biomass for the four DvH strains cultured under anaerobic conditions only (black bars), with constant 0.02% O2 gas mixture sparging (striped bars) and after growth resumption (open bars). Data are mean values of five independent experiments + SD. Statistical analysis using t-test was used to compare means. Significant differences (p< 0.05) are mentioned by an asterisk.

Mentions: In order to determine whether the growth arrest in the presence of 0.02% O2 was due to a complete consumption of substrate (i.e. lactate), lactate and acetate were quantified in the cultures when cells stopped to grow (after ~ 40 h) (Fig 1). Fig 3 shows that under anaerobic conditions, lactate (initial concentration 37 mM) was completely consumed and, accordingly, acetate was produced with an acetate/lactate stoichiometric ratio of about 0.83 for all strains, in agreement with a part of acetate used for biosynthesis. In the cultures with constant 0.02% O2 gas mixture sparging, when growth was stopped, 22.2 ± 4.6 mM lactate was consumed in the wild-type culture and 12.6 ± 1.3, 17.8± 1.3 and 23.4± 0.3 mM lactate were consumed in the Δcox, Δbd and Δcoxbd cultures, respectively and accordingly, less acetate was formed (Fig 3B). However, the acetate/lactate stoichiometric ratio was found slightly lower with an average value of 0.74. These data show that the growth arrest, when cultures were constantly sparged with 0.02% O2, was not the effect of a complete consumption of the energy substrate by the cells. Interestingly, when conditions were then switched to anaerobic by bubbling the cultures with 100% N2 for 15 min to remove oxygen and kept afterwards anaerobic, all strains were able to resume growth and, at the end of the growth, all lactate was consumed (data not shown) in the four strains; however, the final biomasses never reached the value obtained when cells were cultured under anaerobic conditions only, except for the Δcox deletion mutant (Fig 4). When cultured with constant 0.02% O2 sparging, the molar growth yields on lactate (Ylactate) were 70%, 57%, 62% and 65% lower for the wild-type, Δbd, Δcox and Δcoxbd strains, respectively, than when cultured under anaerobic conditions (Fig 5). The single deletion mutant Δbd and Δcox strains exhibited the lowest values while, surprisingly, Ylactate of the double deletion mutant was greater than those of the single deletion mutants and similar to that of the wild-type strain (Fig 5).


Growth of the obligate anaerobe Desulfovibrio vulgaris Hildenborough under continuous low oxygen concentration sparging: impact of the membrane-bound oxygen reductases.

Ramel F, Brasseur G, Pieulle L, Valette O, Hirschler-Réa A, Fardeau ML, Dolla A - PLoS ONE (2015)

Biomass formation under various culturing conditions.Final biomass for the four DvH strains cultured under anaerobic conditions only (black bars), with constant 0.02% O2 gas mixture sparging (striped bars) and after growth resumption (open bars). Data are mean values of five independent experiments + SD. Statistical analysis using t-test was used to compare means. Significant differences (p< 0.05) are mentioned by an asterisk.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4383621&req=5

pone.0123455.g004: Biomass formation under various culturing conditions.Final biomass for the four DvH strains cultured under anaerobic conditions only (black bars), with constant 0.02% O2 gas mixture sparging (striped bars) and after growth resumption (open bars). Data are mean values of five independent experiments + SD. Statistical analysis using t-test was used to compare means. Significant differences (p< 0.05) are mentioned by an asterisk.
Mentions: In order to determine whether the growth arrest in the presence of 0.02% O2 was due to a complete consumption of substrate (i.e. lactate), lactate and acetate were quantified in the cultures when cells stopped to grow (after ~ 40 h) (Fig 1). Fig 3 shows that under anaerobic conditions, lactate (initial concentration 37 mM) was completely consumed and, accordingly, acetate was produced with an acetate/lactate stoichiometric ratio of about 0.83 for all strains, in agreement with a part of acetate used for biosynthesis. In the cultures with constant 0.02% O2 gas mixture sparging, when growth was stopped, 22.2 ± 4.6 mM lactate was consumed in the wild-type culture and 12.6 ± 1.3, 17.8± 1.3 and 23.4± 0.3 mM lactate were consumed in the Δcox, Δbd and Δcoxbd cultures, respectively and accordingly, less acetate was formed (Fig 3B). However, the acetate/lactate stoichiometric ratio was found slightly lower with an average value of 0.74. These data show that the growth arrest, when cultures were constantly sparged with 0.02% O2, was not the effect of a complete consumption of the energy substrate by the cells. Interestingly, when conditions were then switched to anaerobic by bubbling the cultures with 100% N2 for 15 min to remove oxygen and kept afterwards anaerobic, all strains were able to resume growth and, at the end of the growth, all lactate was consumed (data not shown) in the four strains; however, the final biomasses never reached the value obtained when cells were cultured under anaerobic conditions only, except for the Δcox deletion mutant (Fig 4). When cultured with constant 0.02% O2 sparging, the molar growth yields on lactate (Ylactate) were 70%, 57%, 62% and 65% lower for the wild-type, Δbd, Δcox and Δcoxbd strains, respectively, than when cultured under anaerobic conditions (Fig 5). The single deletion mutant Δbd and Δcox strains exhibited the lowest values while, surprisingly, Ylactate of the double deletion mutant was greater than those of the single deletion mutants and similar to that of the wild-type strain (Fig 5).

Bottom Line: Effect of constant low oxygen concentration on growth and morphology of the wild-type, single (Δbd, Δcox) and double deletion (Δcoxbd) mutant strains of the genes encoding these oxygen reductases was studied.Time-lapse microscopy revealed that a large majority of the cells were then able to divide (over 97%) but the time to recover a complete division event was longer for single deletion mutant Δbd than for the three other strains.We propose that the pyruvate-ferredoxin oxidoreductase (PFOR) plays a central role in this phenomenon by reversibly switching from an oxidative-sensitive fully active state to an oxidative-insensitive inactive state.

View Article: PubMed Central - PubMed

Affiliation: Aix-Marseille Université, CNRS, LCB-UMR7283, Marseille, France.

ABSTRACT
Although obligate anaerobe, the sulfate-reducing bacterium Desulfovibrio vulgaris Hildenborough (DvH) exhibits high aerotolerance that involves several enzymatic systems, including two membrane-bound oxygen reductases, a bd-quinol oxidase and a cc(b/o)o3 cytochrome oxidase. Effect of constant low oxygen concentration on growth and morphology of the wild-type, single (Δbd, Δcox) and double deletion (Δcoxbd) mutant strains of the genes encoding these oxygen reductases was studied. When both wild-type and deletion mutant strains were cultured in lactate/sulfate medium under constant 0.02% O2 sparging, they were able to grow but the final biomasses and the growth yield were lower than that obtained under anaerobic conditions. At the end of the growth, lactate was not completely consumed and when conditions were then switched to anaerobic, growth resumed. Time-lapse microscopy revealed that a large majority of the cells were then able to divide (over 97%) but the time to recover a complete division event was longer for single deletion mutant Δbd than for the three other strains. Determination of the molar growth yields on lactate suggested that a part of the energy gained from lactate oxidation was derived toward cells protection/repairing against oxidative conditions rather than biosynthesis, and that this part was higher in the single deletion mutant Δbd and, to a lesser extent, Δcox strains. Our data show that when DvH encounters oxidative conditions, it is able to stop growing and to rapidly resume growing when conditions are switched to anaerobic, suggesting that it enters active dormancy sate under oxidative conditions. We propose that the pyruvate-ferredoxin oxidoreductase (PFOR) plays a central role in this phenomenon by reversibly switching from an oxidative-sensitive fully active state to an oxidative-insensitive inactive state. The oxygen reductases, and especially the bd-quinol oxidase, would have a crucial function by maintaining reducing conditions that permit PFOR to stay in its active state.

No MeSH data available.


Related in: MedlinePlus