The ability of a number of microorganisms isolated from highly magnetic soil of the city Mednogorsk to oxidize Fe (II) under conditions of periodic cultivation in a liquid medium was studied. Among the studied microorganisms, two microbial isolates with maximum growth characteristics and iron-oxidizing activity were selected and identified: Bacillus megaterium 69.3 and B. megaterium 69.5. Individual levels of metal resistance of the isolates were determined: maximum tolerated concentration (MTC) for Fe (II) of the isolates B. megaterium 69.3 and B. megaterium 69.5 was 1200 mg L⁻¹, minimum inhibitory concentration (MIC) was 1800 mg L⁻¹. Both microbial isolates actively oxidized Fe (II) by reducing its high concentration in the medium (1.19 g L⁻¹) by 33 and 39% during 14 days of culturing. Total increase in the biomass of B. megaterium 69.3 and B. megaterium 69.5 after 14 days of culturing was 15.3 and 14.7 g L⁻¹; the active parts of the biomass increased 8.7- and 6.9-fold compared to the inoculum dose, respectively. These microbial isolates could be used in future in the biotechnological process of water purification with increased/high levels of Fe (II).

—Biodiagnostics of soil in a settlement with low technogenic impact was performed by the example of the urban settlement of Stepnoe. The number of microorganisms was evaluated in 30 soil samples by inoculation on solid nutrition media: on meat peptone agar for the calculation of the total heterotrophic microorganisms and on the corresponding selective media for hydrocarbon-oxidizing and iron-oxidizing microorganisms. We also analyzed the activity of several soil redox and hydrolytic enzymes (dehydrogenases, catalases, peroxidases, and invertases). The content of the mobile forms of copper, zinc, lead, cadmium, chromium, and nickel was determined to assess the anthropogenic impact on the soil, and the total soil contamination coefficient (Z_c) was calculated. The excess of the MPC of mobile forms of Ni, Cu, and Pb was revealed in the area studied. In general, the total soil contamination coefficient did not exceed 16, indicating favorable environmental and geochemical conditions in the settlement. The analysis of the total number of heterotrophic microorganisms and the amounts of hydrocarbon-oxidizing and iron-oxidizing microorganisms showed deviations from the norm in some regions of the area surveyed, which pointed to anthropogenic transformation of the soil biocenoses. The maximum deviations were typical for the index of hydrocarbon-oxidizing microorganisms, which pointed to soil contamination by hydrocarbons. Our data on the evaluation of the activity of indicator soil enzymes did not exclude possible functional disturbances in the soil. It was found that the activity of soil dehydrogenases and invertases corresponded to low and very low levels of soil enrichment with these enzymes. The activity of soil catalases and peroxidases corresponded to the moderate and high levels of the enzymes, which indicated the absence of pathological changes in the soil. It has been shown that the studied soil microbiological and biochemical parameters are promising for soil health biodiagnostics in areas with low anthropogenic impact.

A soil diagnosis of an urban territory Stepnoe (Saratov region) was conducted within the framework of soil research monitoring of inhabited localities with low levels of anthropogenic impact using chemical and microbiological analysis. Excess over maximum permissible concentration (MPC) of mobile forms of Cr, Zn and Cd were not observed within the researched territory. A universal excess over MPC of mobile forms of Ni, Cu and Pb was established which is most likely connected with anthropogenic contamination. It was discovered that, at the territory of the Stepnoe settlement, mobile forms of heavy metals compounds (HM) in most cases formed paragenetic associations with high correlation coefficient and despite this, an excess over MPC was not significant. This point to a common mineralogical origin of the elements inherited from the parent rock. The values of the total index of chemical contamination were not above 16, which puts the researched samples in a category with permissible contamination. The indices of the total number of heterotrophic bacteria, iron-oxidizing and hydrocarbon-oxidizing bacteria in most samples corresponded to normal indices for chestnut solonetsous and saline soils. In some samples, a deviation from the normal indices was observed justifying the impact of specific contaminants on the soil.

In a long-term model experiment, the abundance dynamics of soil microorganisms was studied as affected by pollution of southern chernozem soils with various concentrations and combinations of iron, nickel and copper ions. In the course of this study, soil microbiocenoses were seeded on solid nutrient media and the following values were estimated: the total numbers of heterotrophic microorganisms on meat–peptone agar, the numbers of iron-oxidizing microorganisms on a selective medium in 0, 30, 90 and 210 days after the introduction of heavy metal ions into the soil. A characteristic diverse impact of heavy metal ions on soil microorganisms was established, and the degree of stability of soil microbocenoses of southern chernozem was revealed. Iron and copper concentrations of 10 and 50 RGCB/MPC in 30 days after soil contamination by individual metal ions or their combinations stimulated the proliferation of heterotrophic microorganisms in the soil microbocenoses and 90 days later the number of this microbial group decreased to the control levels and below. After 210 days, the microbiocenoses returned to a stable state. Nickel ions, introduced into the soil at a concentration of 50 MPC separately and in a number of combinations with other heavy metal ions, did not stimulate the proliferation of heterotrophic microorganisms. Opposite trends were observed in the abundance dynamics of iron-oxidizing microorganisms. With the exception of some model variants such as 10 and 50 MPC of Cu (II), iron, nickel and their combinations in various concentrations inhibited the proliferation of ironoxidizing microorganisms in the first month after soil contamination. The inhibitory effect of a combination of heavy metal ions was stronger than that of individual metals. After 90 days, the numbers of iron-oxidizing microorganisms restored to the control level or even exceeded it. After 210 days, an inhibition of the proliferation of ironoxidizing microorganisms was observed in the microbocenoses, or their abundance corresponded to the value in the control soil sample.

Petromagnetic properties of soils were studied in the territory of Khlebnovsky oil field (Saratov region, Russian Federation). Magnetic susceptibility was measured at low (?lf) and high (?hf) frequencies in soils before and after heating up to 500°C including the frequency dependence of magnetic susceptibility (?fd) and the thermomagnetic coefficient (d?). It was observed that in the studied soils, ?lf varied from 3.05?10-7 m3/kg to 1.56?10-6 m3/kg with an average value of 5.54?10-7 m3/kg; ?hf - from 2.84?10-7 m3 / kg to 1.49?10-6 m3/kg with an average value of 5.21?10-7 m3/kg; ?fd - from 4.13 % to 7.22 % with an average value of 6.21 % and d?- from 0.65 to 21.8 with an average value of 4.4. The thermomagnetic effect (d?) varied from 0.65 to 21.8 with an average value of 4.4. An extensive anomalous zone with thermomagnetic effect values of more than 3 units was formed in the studied territory (we took this as the minimum anomalous value). The zone of anomalous values of thermomagnetic effect in the soils within the Khlebnovsky oil field formed a single area of anomaly in the Northern and Central parts. Anomalies were documented in 26 sample test points. Most of the anomalies were observed in thermomagnetic effect values ranging from 3 to 10 units, and in the Western part of the anomalous zone, a core was formed with values from 10 units and higher. In the center of the core, the maximum value of thermomagnetic effect was 21.8 units. It is possible that both identified anomalies formed a single ring anomaly around the Khlebnovsky oil field, but to confirm this assumption, it is necessary to conduct a more detailed petromagnetic testing of the studied territory. As shown by this research, thermomagnetic coefficient d? was observed to be the most significant of all the measured petromagnetic parameters when detecting accumulations of hydrocarbon deposits.