Microbial response to environmental stresses: from fundamental mechanisms to practical applications

Abstract

Environmental stresses are usually active during the process of microbial fermentation and have significant influence on microbial physiology. Microorganisms have developed a series of strategies to resist environmental stresses. For instance, they maintain the integrity and fluidity of cell membranes by modulating their structure and composition, and the permeability and activities of transporters are adjusted to control nutrient transport and ion exchange. Certain transcription factors are activated to enhance gene expression, and specific signal transduction pathways are induced to adapt to environmental changes. Besides, microbial cells also have well-established repair mechanisms that protect their macromolecules against damages inflicted by environmental stresses. Oxidative, hyperosmotic, thermal, acid, and organic solvent stresses are significant in microbial fermentation. In this review, we summarize the modus operandi by which these stresses act on cellular components, as well as the corresponding resistance mechanisms developed by microorganisms. Then, we discuss the applications of these stress resistance mechanisms on the production of industrially important chemicals. Finally, we prospect the application of systems biology and synthetic biology in the identification of resistant mechanisms and improvement of metabolic robustness of microorganisms in environmental stresses.

Enhancing 5‐aminolevulinic acid tolerance and production by engineering the antioxidant defense system of Escherichia coli

“…To protect cells from the damage caused by ROS, microorganisms have developed a variety of defense mechanisms against oxidative stress (Guan et al, ). Enzymatic systems play major roles in the antioxidant mechanisms.…”

“…These results suggest that reinforcing the antioxidant defense system may be a universal strategy to combat ROS generated by different target products or intermediates. Moreover, several environmental stresses also lead to oxidative stress (Guan et al, ). By using a combination of SOD and heat shock protein genetic devices, the thermotolerance and ethanol production of Saccharomyces cerevisiae were improved (Sun et al, ; K. Xu et al, ).…”

The Response of Haloferax volcanii to Salt and Temperature Stress: A Proteome Study by Label‐Free Mass Spectrometry

“…The heat shock response has been well studied in all three domains of life, leading to the identification of several heat shock protein families . As only few members of these families were actually found to be upregulated upon continuous growth at high temperature, we systematically inspected all Haloferax proteins classified into one of the known heat shock protein families.…”

“…This confirmed that most of these are not upregulated upon continuous growth at high temperature (for full details see Text S5, Supporting Information). This is not surprising in itself as the heat shock response is rapid but transient . Among the few proteins that are strongly affected by growth temperature is the adjacently encoded gene pair HVO_O450 and HVO_O451, both members of the Hsp20‐type heat shock protein family (also known as short Heat Shock Proteins, sHSPs).…”

Structural and proteomic changes in viable but non-culturableVibrio cholerae

“…Changes in the physical and chemical properties of their environment, such as heat, cold and salt stress, oxygen and nutrient deprivation, desiccation and changes in osmolarity, threaten the survival of bacteria, and they have therefore evolved various strategies to evade detrimental effects [1][2][3].…”