Application of auxin producing bacteria in phytoremediation of oil-contaminated soil

Plant-microbial associations are effective for the remediation of oil-contaminated soils. At the same time, the level of production of phytohormones by bacteria and the effect of petroleum hydrocarbons on the manifestation of the stimulating effect by bacteria remain insufficiently studied. The studies were carried out in a model experiment with plants of Hordeum vulgare L. grown on oil-contaminated sand-soil mixture in artificial lighting. The soil mixture was treated with 10(5) CFU/g of bacteria Pseudomonas plecoglossicida 2,4-D, P. hunanensis IB C7, P. extremaustralis IB K2, Enterobacter asburiae IB UOM3. Bacterial strains were able to destroy hydrocarbons and synthesize indoleacetic acid. By the end of the experiment in the variant polluted with 80 g of oil per 1 kg of soil the number of living plants fell to 67%. The addition of growth-stimulating strains of oil destructors significantly improved the survival of barley plants. The mass of the barley root system was the most sensitive to oil pollution and introduction of bacteria. In the presence of hydrocarbons, a useful adaptive reaction was manifested; it consisted in increasing the mass of the root system. Treatment of barley by bacteria increased the manifestation of this reaction. The introduced bacteria increased the growth of roots more significantly against the background of 80 g/kg than 40 g/kg oil pollution. The revealed stimulation of root growth by microorganisms' introduction accelerated oil decomposition in the soil. Inoculation of contaminated soil with oil destructor strains together with barley plant cultivation reduced pollutant content by 45.0-51.2% and 37.5-41.9% for 21 days (at initial concentration of 40 g/kg and 80 g/kg, respectively). The rate of hydrocarbons' degradation was increased in the row: plant, bacteria, association plant + bacteria.