Overexpression of Small Heat Shock Protein Enhances Heat- and Salt-Stress Tolerance of Bifidobacterium longum NCC2705

Abstract

Bifidobacteria are probiotics that are incorporated live into various dairy products. They confer health-promotive effects via gastrointestinal tract colonization. However, to provide their health-beneficial properties, they must battle the various abiotic stresses in that environment, such as bile salts, acids, oxygen, and heat. In this study, Bifidobacterium longum salt- and heat-stress tolerance was enhanced by homologous overexpression of a small heat shock protein (sHsp). A positive contribution of overproduced sHsp to abiotic stress tolerance was observed when the bacterium was exposed to heat and salt stresses. Significantly higher survival of B. l ongum NCC2705 overexpressing sHsp was observed at 30 and 60 min into heat (55 °C) and salt (5 M NaCl) treatment, respectively. Thermotolerance analysis at 47 °C with sampling every 2 h also revealed the great potential tolerance of the engineered strain. Cell density and acid production rate increased for the sHsp-overexpressing strain after 8 and 10 h of both heat and salt stresses. In addition, tolerance to bile salts, low pH (3.5) and low temperature (4 °C) was also increased by homologous overexpression of the sHsp hsp20 in B. l ongum. Results revealed that hsp20 overexpression in B longum NCC2705 plays a positive cross-protective role in upregulating abiotic responses, ensuring the organism's tolerance to various stress conditions; therefore, sHsp-overexpressing B. l ongum is advised for fermented dairy foods and other probiotic product applications.

Co-diversification of Enterococcus faecium Core Genomes and PBP5: Evidences of pbp5 Horizontal Transfer

“…They are involved in stress responses to salts, pH and ethanol exposure in Clostridium . Hsp20 is a small chaperone protein involved in survival of different abiotic stress conditions including heat (55°C) and salt (5 mM) in Bifidobacterium longum ( Khaskheli et al, 2015 ).…”

Over-Expression of the Heat-Responsive Wheat Gene TaHSP23.9 in Transgenic Arabidopsis Conferred Tolerance to Heat and Salt Stress

“…The over-expression (OE) of sHSPs in plants with transgenic technology can not only enhance the heat tolerance of transgenic plants but also improve the abilities of transgenic plants to tolerate other stresses, such as salinity, drought, heavy metals and disease. Most importantly, the OE of sHSPs in transgenic plants does not cause any adverse or defective phenotypes (Kong et al, 2014;Zhang et al, 2014;Fragkostefanakis et al, 2015;Hu et al, 2015;Khaskheli et al, 2015;Sun et al, 2016;Kuang et al, 2017). For example, the OE of a sHSP gene (MasHSP24.4) from wild banana into tomato significantly enhanced tomato tolerance to high temperatures and drought (Mahesh et al, 2013).…”

In a quest for engineering acidophiles for biomining applications: challenges and opportunities

“…Previous studies have shown that the salt tolerance of Bifidobacterium longum and E. coli can be increased through the increased expression of a small heat shock protein [ 122 ] and the PutP proline transporter gene [ 123 ], respectively. Furthermore, the ectoine genes, ectABC , of the halophilic bacterium Chromohalobacter salexigens has been successfully engineered into an E. coli strain to increase halotolerance [ 124 ], while the heterologous expression of a betaine uptake system, BetL has helped to increase the tolerance of Lactobacillus salivarius UCC118 to multiple stresses, including osmotic stress [ 125 ].…”