title: 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.
authors.affiliation: Key Laboratory of Functional Dairy Science of Chinese Ministry of Education and Municipal Government of Beijing, College of Food Science and Nutritional Engineering, China Agricultural University, Beijing, 100083, People's Republic of China.
authors.forename: Gul Bahar
authors.initials: GB
authors.lastname: Khaskheli
authors.forename: FangLei
authors.initials: F
authors.lastname: Zuo
authors.forename: Rui
authors.initials: R
authors.lastname: Yu
authors.forename: ShangWu
authors.initials: S
authors.lastname: Chen
mesh_terms: D001644:Bifidobacterium / Q000187:drug effects* / Q000235:genetics / Q000502:physiology / Q000528:radiation effects*; D015870:Gene Expression; D050888:Heat-Shock Proteins, Small / Q000096:biosynthesis* / Q000235:genetics; D006358:Hot Temperature; D006863:Hydrogen-Ion Concentration; D050296:Microbial Viability / Q000187:drug effects / Q000528:radiation effects; D012492:Salts / Q000633:toxicity*; D013997:Time Factors
chemical_list: D050888:Heat-Shock Proteins, Small; D012492:Salts
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