Analysis of microbial phospholipids in processes оf biomonitoring of soil condition

Abstract

The purpose of this work was to assess the possibility of applying the method of phospholipid fatty acid analysis in the composition of lipids of cell membranes of soil microorganisms for monitoring the state of the soil in the process of recovery. The experimental part consisted in a determination of phospholipid fatty acids (FFA), including extraction of phospholipids with organic solvents, extraction of the lipid fraction using polar silicate columns, preparation of methyl esters of fatty acids by alkaline methanolysis and analysis of the content of FFA with gas chromatography. The identification of microorganisms was carried out on the basis of an evaluation of the experimental results obtained, which are represented by a combination of chromatogram peaks. The impact of stress factors on microorganisms is determined by the presence of cis-trans-isomerism or cycles of three carbon atoms at the ends of phospholipid fatty acid radicals. In order to verify the objectivity of the results obtained using the proposed method for analysing microorganisms, this work also used the traditional method of controlling soil microorganisms based on the activity of their enzymes - glucosidases, proteases, arylsulphatases and phosphatases. The data obtained indicate the presence of viable soil microorganisms; however, their number does not match the control samples, indicating a failure of the recovery process. The identification results demonstrate the dominance of Gram-negative (Gr - ) bacteria in the control samples in comparison with the samples in conditions of natural recovery. At the same time, in the process of natural restoration, a greater quantity of fungi was found in the soil. According to the data obtained, the largest amounts of cis - isomers and the value of cyclisation of phospholipid fatty acids are characteristic of microorganisms in the control samples, which may be due to the depletion of the substrate when using the soil for agricultural purposes. The experimental data obtained in the course of this work allow us to propose the procedure as an independent method for conducting biological monitoring of ecosystems when analysing phospholipid fatty acids in the composition of cell membrane lipids.