Foundational organization of the cell (biomolecules, enzymes, bioenergy and metabolism, transport through membranes. Transfer of genetic information, action of xenobiotic on the DNA level. Intercellar communication and homeostasis, molecular basis for cancer. Immune mechanisms, allergens, immunotoxicity. Ecosystem, biodiversity and sustainable development. Microorganisms and their importance in the ecosystem metabolism. Interaction of microorganisms with pollutants in biosphere (detergents, pesticides, heavy metals, plastic materials, oil). The concept of bioremediation, bioremediation of oil polluted ecosystems. Application of microorganisms in the ecosystem protection. The concept of trophisity and pollution of water ecosystems. Classification of water ecosystems according to organic production. Microbiological and biological aspect of wastewater processing. Methods and devices for biological water waste treatment (activated sludge, biological filtration, processes in lakes or lagoons). General biological effect of disinfection. Preparation of drinking water. Biological monitoring: biomarkers, bioindicator organisms.