Osmotolerance in Escherichia coli Is Improved by Activation of Copper Efflux Genes or Supplementation with Sulfur-Containing Amino Acids

Abstract

Improvement in the osmotolerance of Escherichia coli is essential for the production of high titers of various bioproducts. In this work, a cusS mutation that was identified in the previously constructed high-succinate-producing E. coli strain HX024 was investigated for its effect on osmotolerance. CusS is part of the twocomponent system CusSR that protects cells from Ag(I) and Cu(I) toxicity. Changing cusS from strain HX024 back to its original sequence led to a 24% decrease in cell mass and succinate titer under osmotic stress (12% glucose). When cultivated with a high initial glucose concentration (12%), introduction of the cusS mutation into parental strain Suc-T110 led to a 21% increase in cell mass and a 40% increase in succinate titer. When the medium was supplemented with 30 g/liter disodium succinate, the cusS mutation led to a 120% increase in cell mass and a 492% increase in succinate titer. Introducing the cusS mutation into the wild-type strain ATCC 8739 led to increases in cell mass of 87% with 20% glucose and 36% using 30 g/liter disodium succinate. The cusS mutation increased the expression of cusCFBA, and gene expression levels were found to be positively related to osmotolerance abilities. Because high osmotic stress has been associated with deleterious accumulation of Cu(I) in the periplasm, activation of CusCFBA may alleviate this effect by transporting Cu(I) out of the cells. This hypothesis was confirmed by supplementing sulfurcontaining amino acids that can chelate Cu(I). Adding methionine or cysteine to the medium increased the osmotolerance of E. coli under anaerobic conditions. IMPORTANCE In this work, an activating Cus copper efflux system was found to increase the osmotolerance of E. coli. In addition, new osmoprotectants were identified. Supplementation with methionine or cysteine led to an increase in osmotolerance of E. coli under anaerobic conditions. These new strategies for improving osmotolerance will be useful for improving the production of chemicals in industrial bioprocesses.

Assessing the Involvement of Selected Phenotypes of Pseudomonas simiae PICF7 in Olive Root Colonization and Biological Control of Verticillium dahliae

“…This TCS has been demonstrated to be required for copper and silver resistance in this bacterium [ 76 ]. Furthermore, the CusR/CusS system is essential for the regulation of the cusCFBA operon, responsible for exporting both metals outside the cells [ 76 , 77 ].…”

Multiomic Fermentation Using Chemically Defined Synthetic Hydrolyzates Revealed Multiple Effects of Lignocellulose-Derived Inhibitors on Cell Physiology and Xylose Utilization in Zymomonas mobilis

“…These results underscore the importance of efflux pumps in helping Z. mobilis alleviate LDI toxicity. Recent work in E. coli found that upregulation of the cusCFBA efflux system was able to increase osmotolerance (Xiao et al, 2017), suggesting that upregulation of efflux systems in Z. mobilis may similarly contribute to osmotolerance in addition to LDI detoxification.…”

Efflux mediated chlorpyrifos tolerance inEscherichia coliBL21(DE3)

“…The cusCBA system transports Ag(I) and Cu(I) across the membranes to protect the bacterial cells from potential toxicity caused by the accumulation of free metal ions prevalent during the stress (Mealman et al, 2012). Improvement in the osmotolerance of E. coli on activation of copper efflux genes was suggested by Xiao et al, (2017). Pal et al .…”