Геномные перестройки влияют на устойчивость биопленок почвенных бактерий Azospirillum brasilense к абиотическим стрессам

Abstract

The bacteria Azospirillum brasilense, used as biofertilizers, have a significant positive effect on the growth and development of plants. The genome of the strain A. brasilense Sp7 is represented by a chromosome and numerous plasmids with molecular weight of 90, 115, and over 300 MDa. Genomic rearrangements that cause changes in the “plasmid profile” can contribute to the formation of subpopulations or phenotypic variants in a bacterial population. There is little data on the role of such rearrangements in the adaptation of A. brasilense to dynamic environmental conditions. The ability of azospirilla to form biofilms also has a determined significance for the successful functioning of the plant-microbial association and the resistance of bacteria and plants to various abiotic stresses. The purpose of this work consisted of the analysis of the genomic rearrangements in spontaneous derivatives of A. brasilense Sp7 and the assessment of the resistance of their biofilms to drying, water stress and oxidative stress. PCR analysis to detect changes in the structure of genomic DNA was performed using primers corresponding to known conservative motifs in repetitive bacterial nucleotide sequences. The relative amount of the biofilm biomass was assessed by measuring the crystal violet A540 desorbed after staining. The level of relative respiratory activity of cells in biofilms was determined by the fluorometric resazurin test. The non-penetrating osmotic agent PEG 6000 was used to create the osmotic/water stress model. It was shown that rearrangements in genomic DNA contribute to the formation of stable phenotypic variants of the Sp7 strain, which form biofilms in different ways under water stress conditions. A derived strain of A. brasilense Sp7.8, the biofilm population of which is more resistant to water stress compared to the parent strain was selected.