The Vaginal Lactobacillus gasseri YS1021 Effectively Degraded Mucin by Enzymolysis of M13 Metallopeptidase

Mucin is the core component of the mucus layer barrier in the human reproductive tract and the interaction between mucin and commensal bacteria is crucial for the female reproductive health. In this study, we found that the female reproductive tract isolate Lactobacillus gasseri YS1021 could degrade and utilize mucin to obtain the promoted proliferation. After 48 h of cultivation with 1% mucin added, the biomass of strain YS1021 increased fourfold compared to the control group without mucin. Meanwhile, the addition of mucin induced a 5-fold higher expression of the M13 family metalloprotease encoding gene RS7445, revealing that the enzyme was associated with mucin degradation in the strain YS1201. Moreover, the recombinant strain L. gasseri 7445OE with RS7445 over-expression exhibited an enhanced mucin degradation ability and reached a 7-fold higher biomass than the parent strain YS1021 after 48 h of cultivation with addition of 1% mucin. Furthermore, the gene RS7445 was expressed in Escherichia coli BL21, and the 74 kDa recombinant protein of RS7445 was successfully purified. Enzymatic hydrolysis assay in vitro showed that mucin was decomposed into 39 peptide fragments by the recombinant RS7445, which demonstrated that the M13 family metalloprotease contributes to mucin degradation in L. gasseri YS1021. In sum, this study revealed an important mechanism by which the vaginal L. gasseri YS1021 could degrade and utilize mucin to gain a growth advantage.