The use of bioassays for environment contamination assessment, in particular for aquatic ecosystems, has gained topicality and found extensive applications over the past decades. The methodologies are well established, but the standardization of bioassay conditions needs to be better defined in order to assure applicability as an efficient analytic tool and that results are ecologically relevant. This paper addresses the analysis of the current international situation and the specifics of Russian practice in culturing and use of test organisms for freshwater bioassays. Standardization of bioassays calls for the utilisation of pertinent sources of test cultures and the provision of appropriate cultivation conditions. The paper discusses and reviews recommendations for the selection of test species and their culturing in the context of established ecotoxicological targets and the assessment of sensitivity to various reference toxicants. The significance of the quality of water utilized for test cultures and sample dilution is highlighted. Strict water quality requirements and synthetic media options are analyzed and due consideration is given to temperature and illumination conditions. Toxkit microbiotests are discussed as an alternative to toxicity bioassays alleviating the need for continuous stock test culturing and maintenance.

Among the living organisms, microscopic fungi are unique in their ability to occupy diverse ecological niches due to the evolutionarily formed mechanisms of adaptation to a broad range of climatic and technogenic factors. One approach to understanding the mechanisms of adaptation to changing environmental conditions is associated with lipid metabolism. The review provides a critical analysis of publications and our own experimental data on the variability of micromycete lipids under the influence of stress factors and of the possible related adaptive mechanisms. The functional, structural, and quantitative changes in fungal lipids were analyzed under the conditions of osmotic, thermal, and cold influences, as well as toxicity. Biochemical variations in the composition of phospholipids and other membrane lipids are characterized as diverse and ambiguous, depending on the degree of exposure, the initial lipid composition, genetic resistance of fungi, and their ability to adapt to extreme conditions. The role of lipid metabolism in the overall integral response of fungal cells to stress is discussed.

Bioassay is a popular method for assessing the ecotoxicological state of different components of urban ecosystems: soils, water bodies, and air. However, l