Adaptive laboratory evolution of Escherichia coli K-12 MG1655 for growth at high hydrostatic pressure.

Angeliki Marietou,Eric E Allen,Alice T T Nguyen,Douglas Bartlett

doi:10.3389/fmicb.2014.00749

Angeliki Marietou, Eric E Allen + Show 2 more

Open Access

https://doi.org/10.3389/fmicb.2014.00749

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Abstract

Much of microbial life on Earth grows and reproduces under the elevated hydrostatic pressure conditions that exist in deep-ocean and deep-subsurface environments. In this study adaptive laboratory evolution (ALE) experiments were conducted to investigate the possible modification of the piezosensitive Escherichia coli for improved growth at high pressure. After approximately 500 generations of selection, a strain was isolated that acquired the ability to grow at pressure non-permissive for the parental strain. Remarkably, this strain displayed growth properties and changes in the proportion and regulation of unsaturated fatty acids that indicated the acquisition of multiple piezotolerant properties. These changes developed concomitantly with a change in the gene encoding the acyl carrier protein, which is required for fatty acid synthesis.

Highlights

Elevated hydrostatic pressure promotes reduced system volumes and volume changes of activation in chemical equilibria and rates of reactions, respectively (Meersman and McMillan, 2014)
E. coli belongs to the class of Gammaproteobacteria which includes a large proportion of the characterized piezophiles, while as a foodborne pathogen has been subjected to high pressure pasteurization processes potentially promoting the emergence of piezoresistant strains (Vanlint et al, 2012)
GROWTH CONDITIONS E. coli K-12 MG1655 was grown in triplicate lineages (A, B, and C) under fermentative conditions at 37◦C using Luria Bertani (LB) medium supplemented with glucose (11 mM) and HEPES buffer (100 mM, pH 7.5) in 5 ml polyethylene transfer pipette bulbs kept within stainless steel pressure vessels (Figure 1A)

Summary

Introduction

Elevated hydrostatic pressure promotes reduced system volumes and volume changes of activation in chemical equilibria and rates of reactions, respectively (Meersman and McMillan, 2014). Escherichia coli is the most studied piezosensitive microorganism with the ability to grow to pressures of up to 50 MPa (Zobell and Cobet, 1963). It has been successfully used as a model organism to investigate the effects of increasing pressure on cell processes and structures. E. coli belongs to the class of Gammaproteobacteria which includes a large proportion of the characterized piezophiles, while as a foodborne pathogen has been subjected to high pressure pasteurization processes potentially promoting the emergence of piezoresistant strains (Vanlint et al, 2012). High pressure affects many cellular processes in E. coli, including replication, transcription, and translation. Other structural changes under high pressure include a compact nucleoid structure (Welch et al, 1993)

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