Environmental DNA: ecological and genetic aspects
Authors: Pomohaibo V. M. , Orlova L. D. , Vlasenko N. A. 
Published: February 2018

Attention to environmental DNA (eDNA) was motivated by problem of undesirable gene transfer possibility from genetically modified plants to wild bacteria and other organisms. First studies have already examined persistence of DNA from these plants in soil, and also in the samples of nearby groundwater and river for a few kilometers from the place of cultivating. In soil it persists long time enough – from a few days to a few years, and in water – from a few hours to a few days. eDNA excreted from different sources – frozen ice cores, sediments of lakes, soil, caves, water of lakes, rivers and oceans, contains genetic information about biodiversity of present and ancient organisms. Researches revealed an important fact: data of eDNA and other sources, for example pollen, macrofossils, living animals and plants, complement each other, showing more reliable information about the variety of species, than used separately. Therefore the analysis eDNA needs to be not of considered alternative method of ecological researches, but an additional to traditional methods. In the process of study of eDNA it is necessary to take into account five aspects at least: its origin, physical state, conversion, transport and technical challenges. The origin of eDNA remains studied not enough. From a few publications it is known that eDNA comes in different composition excretions, leaves, hair, peeling etc., or as a result of released plasmids and chromosomal DNA from living prokaryotes. There are also possible secondary sources of eDNA – dead bodies and excretions of predators, scavengers, detritivores and coprovores. On the amount of the genetic material, released by organisms in an environment, various ontogenetic, trophic and other factors can have considerably influence. eDNA can be presented in both intracellular and extracellular forms.. Over time intracellular eDNA releases outside by influence of different ecological factors – activity of microorganisms, presence of extracellular enzymes, mechanical destruction etc. In further extracellular eDNA can break in corpuscles of different sizes – mainly within the limits of 1–10 μm. It can be free, adsorbed by other substances or dissolved. At certain conditions the period of eDNA persistence can be very great – from a few hours (in water) to hundred thousands of years (in frozen ice cores). Ancient eDNA is very fragmented and chemically changed by various physical, chemical and biological factors of environment. Substantive eDNA amount is taken up by bacteria and protozoa. Here it quickly metabolizes, but some its fragments can be integrated in a local genome. eDNA is able to be transported to great distance (from a few meters to 10 kilometers) that can appreciably influence on the results of its research. Also the laboratory experiment has certain problems – design (equipment, sequence of operations and condition of it realization), realization of experiment, authenticity of it will depend on quality of equipment and reagents, competence and honesty of scientific personnel etc.), ability of skilled researcher to give interpretation of results. Data that given in our review testifies that the active study of eDNA only began, and further intensive efforts of environmentalists and geneticists are needed in direction of it research. The results of such researches will allow to create the effective methods of scientifically reasonable recreating nature application.