The Effect of Bacillus pumilus 3-19 Metalloproteinase Gene Knockout on the Expression of Minor Proteases of the Strain Degradome and Its PGP Properties.

The Bacillus pumilus 3-19 strain exhibits increased secretion of various hydrolases, including proteases, and is a promising plant growth-promoting (PGP) agent. A unique secreted minor metalloproteinase, MprBp, which has no homologs among prokaryotic enzymes, has been identified in its genome. The role of the enzyme in B. pumilus cells is poorly understood. Using CRISPR/Cas9 genome editing, a deletion mutant of B. pumilus 3-19 with an inactivated mprBp gene was obtained. Comparative analysis of the mutant and native strains by quantitative reverse transcription PCR (RT-qPCR) revealed a significant decrease in the expression of other minor proteases. The mutant strain also demonstrated a two-fold increase in biofilm formation, suggesting that MprBp acts as a negative regulator of this process. Additionally, seed treatment with B. pumilus ΔmprBp led to an increase in the morphometric parameters of barley seedlings (Hordeum vulgare L.).