Increase of stress resistance in Lactococcus lactis via a novel food-grade vector expressing a shsp gene from Streptococcus thermophilus

Abstract

The effects of the expression of a small heat shock protein (shsp) gene from Streptococcus thermophilus on stress resistance in Lactococcus lactis under different environmental stresses were investigated in this study.pMG36e-shsp, an expression vector, was first constructed by inserting a shsp open reading frame (ORF) cloned from S. thermophilus strain St-QC into pMG36e. Then, a food-grade expression vector, pMG-shsp, was generated by deleting the erythromycin resistance gene from pMG36e-shsp. The transformation rate of pMG-shsp was comparable to that of pMG36e-shsp when each of these two vectors was introduced into L.lactis. These results demonstrated that the shsp ORF could successfully used as a food-grade selection marker in both pMG-shsp and pMG36e-shsp. Furthermore, the growth characteristics were almost the same between L. lactis ML23 transformants harboring pMG36e or pMG-shsp. The survival rate of L. lactis ML23 expressing the shsp ORF were increased to 0.032%, 0.006%, 0.0027%, 0.03%, and 0.16% under the following environmental stresses: heat, acid, ethanol, bile salt and H 2 O 2, respectively. These results indicated that the expression of the shsp gene in the food-grade vector pMG-shsp conferred resistance to environmental stresses without affecting the growth characteristics of L. lactis ML23.

YocM a small heat shock protein can protect Bacillus subtilis cells during salt stress

“…). It has been shown many times that both heterologous and homologous overexpression of sHsp confers increased tolerance to heat or salt stress, indicating that although a sHsp has evolved its role under specific circumstances it still contributes to protein protection in general (Salas‐Muñoz et al ., ; Tian et al ., ; Kim et al ., ; Wang et al ., ).…”

Microbial response to acid stress: mechanisms and applications

“…The betaine uptake system from Listeria monocytogenes was introduced into Bifidobacterium breve to increase resistance to gastric acid (Sheehan et al 2007). The acid tolerance of L. lactis was enhanced by overexpressing molecular chaperone proteins DnaK (Tian et al 2012) as well as the DNA repair protein RecO (Wu et al 2013). Table 2 lists the genes involving in acid tolerance of microbes which have been verified through genetic manipulation.…”

Hsp from Lactobacillus plantarum Expression in Lactococcus lactis MG1363

“…Because L. lactis itself does not contain Hsp genes, expression of the small heat shock protein Lo18 from O. oeni improved the tolerance of L. lactis to heat and acid conditions [16] . Then, the small heat shock protein gene from Streptococcus thermophilus was expressed in L. lactis ML23, and the results showed that the expression of Hsps inserted in the food-grade vector pMG made L. lactis ML23 resistant to environmental stress [17] . It is resistant to environmental stresses.…”