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

Author:
Khaskheli, Gul Bahar, Zuo, FangLei, Yu, Rui, Chen, ShangWu
Source:
Current microbiology 2015 v.71 no.1 pp. 8-15
ISSN:
0343-8651
Subject:
Bifidobacterium longum, bacteria, bile resistance, bile salts, dairy products, gastrointestinal system, heat, heat shock proteins, heat stress, heat tolerance, oxygen, pH, probiotics, salt stress, sodium chloride, stress tolerance, temperature
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.
Agid:
3406857