Comparative Review of the Responses of Listeria monocytogenes and Escherichia coli to Low pH Stress.

Marie-Lucie Feger,Conor P. O’Byrne,Talia Arcari,Jialun Wu,Duarte N. Guerreiro

doi:10.3390/genes11111330

Marie-Lucie Feger, Conor P. O’Byrne + Show 3 more

Open Access

https://doi.org/10.3390/genes11111330

Copy DOI

Journal: Genes	Publication Date: Nov 11, 2020
Citations: 43	License type: CC BY 4.0

Affiliation: Ollscoil na Gaillimhe – University of Galway

Abstract

Acidity is one of the principal physicochemical factors that influence the behavior of microorganisms in any environment, and their response to it often determines their ability to grow and survive. Preventing the growth and survival of pathogenic bacteria or, conversely, promoting the growth of bacteria that are useful (in biotechnology and food production, for example), might be improved considerably by a deeper understanding of the protective responses that these microorganisms deploy in the face of acid stress. In this review, we survey the molecular mechanisms used by two unrelated bacterial species in their response to low pH stress. We chose to focus on two well-studied bacteria, Escherichia coli (phylum Proteobacteria) and Listeria monocytogenes (phylum Firmicutes), that have both evolved to be able to survive in the mammalian gastrointestinal tract. We review the mechanisms that these species use to maintain a functional intracellular pH as well as the protective mechanisms that they deploy to prevent acid damage to macromolecules in the cells. We discuss the mechanisms used to sense acid in the environment and the regulatory processes that are activated when acid is encountered. We also highlight the specific challenges presented by organic acids. Common themes emerge from this comparison as well as unique strategies that each species uses to cope with acid stress. We highlight some of the important research questions that still need to be addressed in this fascinating field.

Highlights

High proton concentrations, which define acidic environments, present a particular challenge for unicellular organisms since the protonation of biological molecules can affect their charge, structure, and function, which have potentially damaging consequences for the cell
We focus on Escherichia coli, perhaps the best studied of all bacterial species, which is a
The particular solutions used by a given species to the problems created by high proton concentrations clearly depends on its natural environment and on its unique physiology and metabolic traits

Summary

Introduction

High proton concentrations, which define acidic environments, present a particular challenge for unicellular organisms since the protonation of biological molecules can affect their charge, structure, and function, which have potentially damaging consequences for the cell. L. monocytogenes is a saprophyte and is characterized by its tolerance to stresses such as low pH, elevated osmolarity, and bile salts and its ability to grow at refrigeration temperatures [6,7,8]. While these bacteria are phylogenetically unrelated, they share the ability to enter the host via contaminated food or water, and both can encounter the gastrointestinal environment, including the extreme acid conditions prevailing in the stomach, as part of their life cycles. We sought to compare and contrast the mechanisms used by these unrelated bacteria with the goal of highlighting common themes as well as individual strategies

Maintaining Intracellular pH under Acidic Conditions

Protective and Repair Mechanisms against Acid Stress

Sensing and Regulatory Processes during Acid Stress

Short-Chain Organic Acid Stress

Findings

Conclusions and Future Perspectives