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Characterization of acetic acid-detoxifying Escherichia coli evolved under phosphate starvation conditions.

Moreau PL, Loiseau L - Microb. Cell Fact. (2016)

Bottom Line: We sequenced the genomes of the ancestral and evolved strains, and determined the effects of the genetic changes, tested alone and in combination, on characteristic phenotypes in pure and in mixed cultures.Both processes helped to maintain a residual activity of the tricarboxylic acid cycle, which decreased the production of acetic acid and eventually allowed its re-consumption.Evolved strains rapidly acquired mutations (phnE (+) lapB rpoS trkH and phnE (+) rseP kdpD) that were globally beneficial to growth on glucose and organophosphates, but detrimental to long-term viability.

View Article: PubMed Central - PubMed

Affiliation: Laboratoire de Chimie Bactérienne, UMR 7283, Aix-Marseille Université, Marseille, France. moreau@imm.cnrs.fr.

ABSTRACT

Background: During prolonged incubation of Escherichia coli K-12 in batch culture under aerobic, phosphate (Pi) starvation conditions, excess glucose is converted into acetic acid, which may trigger cell death. Following serial cultures, we isolated five evolved strains in two populations that survived prolonged incubation.

Methods: We sequenced the genomes of the ancestral and evolved strains, and determined the effects of the genetic changes, tested alone and in combination, on characteristic phenotypes in pure and in mixed cultures.

Results: Evolved strains used two main strategies: (1) the constitutive expression of the Trk- and Kdp-dependent K(+) transport systems, and (2) the inactivation of the ArcA global regulator. Both processes helped to maintain a residual activity of the tricarboxylic acid cycle, which decreased the production of acetic acid and eventually allowed its re-consumption. Evolved strains acquired a few additional genetic changes besides the trkH, kdpD and arcA mutations, which might increase the scavenging of organophosphates (phnE (+), lapB, and rseP) and the resistance to oxidative (rsxC) and acetic acid stresses (e14(-)/icd (+)).

Conclusions: Evolved strains rapidly acquired mutations (phnE (+) lapB rpoS trkH and phnE (+) rseP kdpD) that were globally beneficial to growth on glucose and organophosphates, but detrimental to long-term viability. The spread of these mutant strains might give the ancestral strain time to accumulate up to five genetic changes (phnE (+) arcA rsxC crfC e14(-)/icd (+)), which allowed growth on glucose and organophosphates, and provided a long-term survival. The latter strain, which expressed several mechanisms of protection against endogenous and exogenous stresses, might provide a platform for producing toxic recombinant proteins and chemicals during prolonged incubation under aerobic, Pi starvation conditions.

No MeSH data available.


Related in: MedlinePlus

Effects of the kdpD460 and rseP98 mutations on the viability and on the metabolic activity of strains incubated in monoculture. Strains were inoculated 1:500 (time zero) into Pi-limiting medium, further incubated, and the numbers of CFU (a, b) in the cultures, the pH (c, d) and the concentrations of glucose (e, f) and of acetate (g, h) in the spent media were determined
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Fig6: Effects of the kdpD460 and rseP98 mutations on the viability and on the metabolic activity of strains incubated in monoculture. Strains were inoculated 1:500 (time zero) into Pi-limiting medium, further incubated, and the numbers of CFU (a, b) in the cultures, the pH (c, d) and the concentrations of glucose (e, f) and of acetate (g, h) in the spent media were determined

Mentions: All phenotypic traits of the evolved strain ENZ1902 (phnE+kdpD460rseP98) matched with those of ENZ1901 rpoS+ derivatives (phnE+trkH80lapB43): Glg−, RpoS+ (Table 2), Ace+ in pure culture (Fig. 6a, c, e, g), and GPS+ in mixed culture (Fig. 7a). Therefore, we focused on the kdpD460 mutation, which might affect K+ homeostasis like the trkH80 mutation. KdpD belongs to the Kdp system composed of the high-affinity K+ transporter (KdpFABC) and of the two-component system KdpD/KdpE, in which KdpD is the sensor that signals low levels of K+ in the medium. Under K+-limiting conditions, KdpD phosphorylates KdpE, which induces the kdpFABC operon [32, 38].Fig. 6


Characterization of acetic acid-detoxifying Escherichia coli evolved under phosphate starvation conditions.

Moreau PL, Loiseau L - Microb. Cell Fact. (2016)

Effects of the kdpD460 and rseP98 mutations on the viability and on the metabolic activity of strains incubated in monoculture. Strains were inoculated 1:500 (time zero) into Pi-limiting medium, further incubated, and the numbers of CFU (a, b) in the cultures, the pH (c, d) and the concentrations of glucose (e, f) and of acetate (g, h) in the spent media were determined
© Copyright Policy - OpenAccess
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC4759930&req=5

Fig6: Effects of the kdpD460 and rseP98 mutations on the viability and on the metabolic activity of strains incubated in monoculture. Strains were inoculated 1:500 (time zero) into Pi-limiting medium, further incubated, and the numbers of CFU (a, b) in the cultures, the pH (c, d) and the concentrations of glucose (e, f) and of acetate (g, h) in the spent media were determined
Mentions: All phenotypic traits of the evolved strain ENZ1902 (phnE+kdpD460rseP98) matched with those of ENZ1901 rpoS+ derivatives (phnE+trkH80lapB43): Glg−, RpoS+ (Table 2), Ace+ in pure culture (Fig. 6a, c, e, g), and GPS+ in mixed culture (Fig. 7a). Therefore, we focused on the kdpD460 mutation, which might affect K+ homeostasis like the trkH80 mutation. KdpD belongs to the Kdp system composed of the high-affinity K+ transporter (KdpFABC) and of the two-component system KdpD/KdpE, in which KdpD is the sensor that signals low levels of K+ in the medium. Under K+-limiting conditions, KdpD phosphorylates KdpE, which induces the kdpFABC operon [32, 38].Fig. 6

Bottom Line: We sequenced the genomes of the ancestral and evolved strains, and determined the effects of the genetic changes, tested alone and in combination, on characteristic phenotypes in pure and in mixed cultures.Both processes helped to maintain a residual activity of the tricarboxylic acid cycle, which decreased the production of acetic acid and eventually allowed its re-consumption.Evolved strains rapidly acquired mutations (phnE (+) lapB rpoS trkH and phnE (+) rseP kdpD) that were globally beneficial to growth on glucose and organophosphates, but detrimental to long-term viability.

View Article: PubMed Central - PubMed

Affiliation: Laboratoire de Chimie Bactérienne, UMR 7283, Aix-Marseille Université, Marseille, France. moreau@imm.cnrs.fr.

ABSTRACT

Background: During prolonged incubation of Escherichia coli K-12 in batch culture under aerobic, phosphate (Pi) starvation conditions, excess glucose is converted into acetic acid, which may trigger cell death. Following serial cultures, we isolated five evolved strains in two populations that survived prolonged incubation.

Methods: We sequenced the genomes of the ancestral and evolved strains, and determined the effects of the genetic changes, tested alone and in combination, on characteristic phenotypes in pure and in mixed cultures.

Results: Evolved strains used two main strategies: (1) the constitutive expression of the Trk- and Kdp-dependent K(+) transport systems, and (2) the inactivation of the ArcA global regulator. Both processes helped to maintain a residual activity of the tricarboxylic acid cycle, which decreased the production of acetic acid and eventually allowed its re-consumption. Evolved strains acquired a few additional genetic changes besides the trkH, kdpD and arcA mutations, which might increase the scavenging of organophosphates (phnE (+), lapB, and rseP) and the resistance to oxidative (rsxC) and acetic acid stresses (e14(-)/icd (+)).

Conclusions: Evolved strains rapidly acquired mutations (phnE (+) lapB rpoS trkH and phnE (+) rseP kdpD) that were globally beneficial to growth on glucose and organophosphates, but detrimental to long-term viability. The spread of these mutant strains might give the ancestral strain time to accumulate up to five genetic changes (phnE (+) arcA rsxC crfC e14(-)/icd (+)), which allowed growth on glucose and organophosphates, and provided a long-term survival. The latter strain, which expressed several mechanisms of protection against endogenous and exogenous stresses, might provide a platform for producing toxic recombinant proteins and chemicals during prolonged incubation under aerobic, Pi starvation conditions.

No MeSH data available.


Related in: MedlinePlus