Bacillus subtilis is traditionally classified as a PGPR that colonizes plant roots through biofilm formation. The current study focused on investigating the influence of various factors on bacilli biofilm formation. In the course of the study, the levels of biofilm formation by the model strain B. subtilis WT 168 and on its basis created regulatory mutants, as well as strains of bacilli with deleted extracellular proteases under conditions of changes in temperature, pH, salt and oxidative stress and presence of divalent metals ions. B. subtilis 168 forms halotolerant and oxidative stress-resistant biofilms at a temperature range of 22 °C–45 °C and a pH range of 6–8.5. The presence of Ca²⁺, Mn²⁺ and Mg²⁺ upsurges the biofilm development while an inhibition with Zn²⁺. Biofilm formation level was higher in protease-deficient strains. Relative to the wild-type strain, degU mutants showed a decrease in biofilm formation, abrB mutants formed biofilms more efficiently. spo0A mutants showed a plummeted film formation for the first 36 h, followed by a surge after. The effect of metal ions and NaCl on the mutant biofilms formation is described. Confocal microscopy indicated that B. subtilis mutants and protease-deficient strains differ in matrix structure. The highest content of amyloid-like proteins in mutant biofilms was registered for degU-mutants and protease-deficient strains.

Due to their capacity to produce antimicrobial peptides that can prevent the growth of diseases, many Bacillus spp. are beneficial to plants. In this study, we looked into the antagonistic activity of the B. pumilus 3-19 strain and its derivatives following targeted genome editing. Two peptide genes with antibacterial action, bacilysin (bac) and bacteriocin (bact), and the sigF gene, which encodes the sigma factor of sporulation, were specifically inactivated using the CRISPR-Cas9 system in the genome of B. pumilus 3-19. Antibacterial activity against B. cereus and Pantoea brenneri decreased as a result of the inactivation of target genes in the B. pumilus 3-19 genome, with a noticeable effect against bacilysin. The growth dynamics of the culture changed when the bac, bact, and sigF genes were inactivated, and the altered strains had less proteolytic activity. An asporogenic mutant of B. pumilus 3-19 was obtained by inactivating the sigF gene. It has been proven that bacilysin plays a unique part in the development of B. pumilus 3-19’s antagonistic action against soil microorganisms.

A novel zinc-dependent metalloendopeptidase of Bacillus intermedius (MprBi) was purified from the culture medium of a recombinant strain of Bacillus subtilis. The amino acid sequence of the...

This work is dedicated to the evaluation of the PGP (plant growth promoting) properties of Bacillus pumilus strain 3-19. This strain is a derivative of Bacillus pumilus 7P, a soil isolate that has developed resistance to streptomycin and increased production of certain extracellular hydrolases. The investigation demonstrated that B. pumilus 3-19 proficiently developed biofilms when cultured in liquid medium at 37°C. Siderophore production by strain 3-19 was identified on the Chrome Azurol S (CAS) agar plate, however, not in the liquid medium. The ability of B. pumilus strain 3-19 to accumulate of biosurfactants on different liquid media was investigated. The strain also demonstrated antimicrobial activity against phytopathogenic bacteria Pectobacterium atrosepticum SCRI1043 and Xanthomonas vesicatoria DSM22252. However, no antagonistic activity was found against the phytopathogenic micromycetes Fusarium oxysporum DR57 and Alternaria solani 12RKL15 was found. Therefore, it is important to investigate the plant growth promoting properties of Bacillus pumilus 3-19 when considering using the strain for crop protection, biofertilisers and biopesticides.