EVOLUTIONARY ADAPTATION TO ENVIRONMENTAL pH IN EXPERIMENTAL LINEAGES OF ESCHERICHIA COLI

Hughes, Bradley S.; Cullum, Alistair J.; Bennett, Albert A.

doi:10.1111/j.1558-5646.2007.00139.x

Cited by 59 publications

(75 citation statements)

References 35 publications

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“…A fin de colonizar el tracto gastrointestinal de los mamíferos, E. coli se ha adaptado para sobrevivir y crecer en valores de pH comprendidos entre 4,5 y 9, (de Jonge et al, 2003). Fuera de estos límites, E. coli reduce significativamente su crecimiento y su sobrevida (Hughes et al, 2007). Dentro de este intervalo de valores de pH, E. coli preserva su actividad enzimática, la estructura de sus proteínas y de su ácido nucleico, manteniendo su pH intra-citoplasmático entre valores de 7,2 a 7, 8 (Sloneczewki et al, 1981;Salmond et al, 1984;Zilberstein et al, 1984).…”

Section: Introductionunclassified

“…La tolerancia de E. coli a bajos valores de pH, le permite sobrevivir en el tracto gastrointestinal de los mamíferos, donde debe resistir la acidez del medio gástrico antes de alcanzar un ambiente menos ácido en el intestino (Hughes et al, 2007). Teniendo en cuenta estos aspectos debería considerarse cuál sería la verdadera actividad de CFX si ésta actuara sobre bacterias de localización extracelular en tejidos inflamados a causa de una infección bacteriana.…”

Section: Introductionunclassified

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Actividad antibacteriana in vitro de Ciprofloxacina sobre una cepa autóctona de Escherichia coli: efecto del pH sobre su potencia y efecto de la persistencia bacteriana sobre su modo de acción

Patricelli¹,

Dell'elce²,

Weidmann³

et al. 2017

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RESUMEN. En este trabajo se evaluó in vitro:(i) el efecto del pH sobre la actividad bactericida de ciprofloxacina (CFX) frente a una cepa autóctona de Escherichia coli y (ii) el efecto de las bacterias persistentes sobre el modo de acción concentración dependiente de CFX. La actividad antibacteriana de CFX disminuyó a causa del descenso del pH, por lo que los valores de concentración inhibitoria mínima (CIM), concentración bactericida mínima (CBM) y concentración de erradicación bacteriana mínima (CEBM) se incrementaron cuando el pH del medio de cultivo descendió de 7,4 a valores de 6,5 y 5,5. La cinética de eliminación bacteriana de CFX fue bifásica a causa de la selección de una sub-población de bacterias persistentes que presentaron una velocidad de eliminación más lenta. Por lo tanto la actividad bactericida de CFX fue definida por su concentración en relación a la CIM y el tiempo durante el cual se mantuvo la exposición de las bacterias a ésta.SUMMARY. In vitro antibacterial activity of ciprofloxacin against a native strain of Escherichia coli: effect of pH on its potency and effect of bacterial persistence on its mode of action. In this in vitro assay was evaluated: (i) the effect of pH on the bactericidal activity of ciprofloxacin (CFX) against a native strain of Escherichia coli, (ii) the effect of persister bacteria on the concentration-dependent mode of action of CFX. The antibacterial activity of CFX decreased with reductions of pH, so the values of minimum inhibitory concentration (MIC), minimum bactericidal concentration (MBC) and minimum eradication bacterial concentration (MEBC) were increased when the pH of the culture medium decreased from 7.4 to 6.5 and 5.5. The kinetics of bacterial elimination of CFX presented a biphasic pattern because of the selection of a sub-population of persistent bacteria which presented a slower elimination rate. Therefore, the antibacterial activity of CFX was determined by its concentration in reference to MIC values and the time during which the exposure of the bacteria was maintained.Palabras clave: Escherichia coli, eficacia, modo de acción, pH, bacterias persistentes.

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Section: Introductionunclassified

Actividad antibacteriana in vitro de Ciprofloxacina sobre una cepa autóctona de Escherichia coli: efecto del pH sobre su potencia y efecto de la persistencia bacteriana sobre su modo de acción

Patricelli¹,

Dell'elce²,

Weidmann³

et al. 2017

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“…E. coli experimental evolution in moderate acid (pH 5.3) yields an acid-dependent fitness increase, but genome sequence analysis has not been used to identify the underlying genetic changes (31). In another study, populations that evolved for 1,000 generations with 20 rounds of exposure to pH 2.5 showed 20 new mutations, including mutations in evgS alleles that relieve logphase repression of extreme-acid resistance (32).…”

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Acid-Adapted Strains of Escherichia coli K-12 Obtained by Experimental Evolution

Harden

Creamer

et al. 2015

Appl Environ Microbiol

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Enteric bacteria encounter a wide range of pHs throughout the human intestinal tract. We conducted experimental evolution of Escherichia coli K-12 to isolate clones with increased fitness during growth under acidic conditions (pH 4.5 to 4.8). Twenty-four independent populations of E. coli K-12 W3110 were evolved in LBK medium (10 g/liter tryptone, 5 g/liter yeast extract, 7.45 g/liter KCl) buffered with homopiperazine-N,N=-bis-2-(ethanosulfonic acid) and malate at pH 4.8. At generation 730, the pH was decreased to 4.6 with HCl. By 2,000 generations, all populations had achieved higher endpoint growth than the ancestor at pH 4.6 but not at pH 7.0. All evolving populations showed a progressive loss of activity of lysine decarboxylase (CadA), a major acid stress enzyme. This finding suggests a surprising association between acid adaptation and moderation of an acid stress response. At generation 2,000, eight clones were isolated from four populations, and their genomes were sequenced. Each clone showed between three and eight missense mutations, including one in a subunit of the RNA polymerase holoenzyme (rpoB, rpoC, or rpoD). Missense mutations were found in adiY, the activator of the acid-inducible arginine decarboxylase (adiA), and in gcvP (glycine decarboxylase), a possible acid stress component. For tests of fitness relative to that of the ancestor, lacZ::kan was transduced into each strain. All acid-evolved clones showed a high fitness advantage at pH 4.6. With the cytoplasmic pH depressed by benzoate (at external pH 6.5), acid-evolved clones showed decreased fitness; thus, there was no adaptation to cytoplasmic pH depression. At pH 9.0, acid-evolved clones showed no fitness advantage. Thus, our acid-evolved clones showed a fitness increase specific to low external pH.

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“…Adaptive trade-offs are a cornerstone of evolutionary ecology [6][7][8], frequently explaining the maintenance of polymorphisms at range margins [9] and along environmental gradients [10,11]. Nonetheless, direct evidence of adaptive trade-offs is surprisingly rare [5] and most often represented by studies of experimental evolution in laboratory conditions [5,12,13]. Evidence of adaptive trade-offs in natural populations is lacking or surprisingly equivocal [6]; patterns attributed to fitness trade-offs resulting from environmental differences can often be attributed to alternative mechanisms [5].…”

Section: Introductionmentioning

confidence: 99%

Why are not all chilies hot? A trade-off limits pungency

et al. 2011

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Evolutionary biologists increasingly recognize that evolution can be constrained by trade-offs, yet our understanding of how and when such constraints are manifested and whether they restrict adaptive divergence in populations remains limited. Here, we show that spatial heterogeneity in moisture maintains a polymorphism for pungency (heat) among natural populations of wild chilies (Capsicum chacoense) because traits influencing water-use efficiency are functionally integrated with traits controlling pungency (the production of capsaicinoids). Pungent and non-pungent chilies occur along a cline in moisture that spans their native range in Bolivia, and the proportion of pungent plants in populations increases with greater moisture availability. In high moisture environments, pungency is beneficial because capsaicinoids protect the fruit from pathogenic fungi, and is not costly because pungent and non-pungent chilies grown in well-watered conditions produce equal numbers of seeds. In low moisture environments, pungency is less beneficial as the risk of fungal infection is lower, and carries a significant cost because, under drought stress, seed production in pungent chilies is reduced by 50 per cent relative to non-pungent plants grown in identical conditions. This large difference in seed production under water-stressed (WS) conditions explains the existence of populations dominated by non-pungent plants, and appears to result from a genetic correlation between pungency and stomatal density: non-pungent plants, segregating from intra-population crosses, exhibit significantly lower stomatal density (p ¼ 0.003), thereby reducing gas exchange under WS conditions. These results demonstrate the importance of trait integration in constraining adaptive divergence among populations.

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EVOLUTIONARY ADAPTATION TO ENVIRONMENTAL pH IN EXPERIMENTAL LINEAGES OF ESCHERICHIA COLI

Abstract: This study uses the enteric bacterium

Cited by 59 publications

References 35 publications

Actividad antibacteriana in vitro de Ciprofloxacina sobre una cepa autóctona de Escherichia coli: efecto del pH sobre su potencia y efecto de la persistencia bacteriana sobre su modo de acción

Actividad antibacteriana in vitro de Ciprofloxacina sobre una cepa autóctona de Escherichia coli: efecto del pH sobre su potencia y efecto de la persistencia bacteriana sobre su modo de acción

Acid-Adapted Strains of Escherichia coli K-12 Obtained by Experimental Evolution

Why are not all chilies hot? A trade-off limits pungency

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