Biofilm Formation by Mutant Strains of Bacilli under Different Stress Conditions.

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 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. 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 Ca, Mn and Mg upsurges the biofilm development while an inhibition with Zn. Biofilm formation level was higher in protease-deficient strains. Relative to the wild-type strain, mutants showed a decrease in biofilm formation, mutants formed biofilms more efficiently. 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 mutants and protease-deficient strains differ in matrix structure. The highest content of amyloid-like proteins in mutant biofilms was registered for -mutants and protease-deficient strains.