Bacteria Producing Ectoine in the Rhizosphere of Plants Growing on Technogenic Saline Soil

Abstract

Bacterial communities producing ectoine were studied in the rhizosphere of red goosefoot (Chenopodium rubrum L.) and weeping alkaligrass (Puccinellia distans (Jacq.) Parl.) growing on technogenic soil (Technosol) near the salt dump of the Solikamsk Potash Industrial Ore Administration 2 (SPIOA 2) of Uralkali PJSC (Solikamsk, Perm region) in order to assess the effect of this osmoprotective compound on plants under the conditions of technogenic salinization. It was found that most of bacteria in the studied soil are capable of synthesizing ectoine. The content of ectoine in the soil, as well as the number of producing bacteria, was higher in the rhizosphere than in the soil without plants. The concentration of ectoine was 167.4 ± 9.8 µmol/kg in the rhizosphere of red goosefoot, 92.9 ± 14.1 µmol/kg in the rhizosphere of weeping alkaligrass, and 23.9 ± 8.4 µmol/kg in the soil without plants. Bacteria belonging to the Pseudomonas genus predominated in the bacterial community of the rhizosphere of red goosefoot, and representatives of the Halomonas genus predominated in the rhizosphere of weeping alkaligrass. A stimulating effect on the growth of seedling roots under the conditions of salt stress was found for the following ectoine-producing strains: Halomonas sp. MK 2-1, Pseudomonas sp. BR 19-12, and Dietzia sp. PMK 9. The data obtained indicate the existence of positive effect of rhizosphere bacterial communities on plants under salinization due to the production of ectoine and may be used to develop biotechnologies that increase the productivity of plants growing on saline soils.