Bioremediation, as a process of removing pollutants from natural ecosystems, can be implemented due to the ability of saprophytic microorganisms to biodegradation of organic substances. Biodegradation plays an important role in the circulation of chemical elements in the nature, as well as in the processes of self-purification of soil and aquatic ecosystems. More than 30 genera of microorganisms have ability to degrade hydrocarbons and phenols. Quantitative analysis of phenol-degrading (PhD) and petrol-degrading (PD) microorganisms in bacterioplankton community of water body can be used for environmental assessment of these pollutions. The investigation of fluvial bacterioplankton was carried out in the framework of scientific comprehensive monitoring with the aim of assessing the functioning of hydrobiont communities, habitat status and level of eutrophication of different type aquatic ecosystems. Water samples were collected seasonally during 2015 at the 11 stations (sampling sites) of the Dniester River Basin within the boundaries of the Republic of Moldova: 12 samples at the middle sector of the river, 9 samples in the Dubossary reservoir and 12 samples at the lower sector. The sampling techniques that are regulated by the international standards ISO 5667–4:1987 and ISO 5667–6:2005 (approved at the national level) were used for collecting of fluvial bacterioplankton. The cultivation of water microorganisms was carried out on the elective nutrient media at 22°C. Numeration was done by the direct method of colony counting. Cells number was reported as colony-forming units (CFUs) per 1 ml. Water quality was assessed according classification of Vinogradov at al. (2001). The phenol-degrading and petrol-degrading microorganisms were recorded in all sectors of the Dniester River. Number density of these microorganisms varied in the range of 9 – 353 CFU/ml (PhD) and 34 – 928 CFU/ml (PD). Two peak numbers have been registered during the analyzed period: PhD microorganisms at the station Sucleia in summer and PD microorganisms at the station Goiani in autumn (Fig. 1). According to used classification, water quality of the Dubossary reservoir and middle sector of the river varies between categories “relatively pure” – „moderately polluted”; water quality of the lower sector corresponds to the category „relatively pure”. The most polluted part is the sector Naslavcea – Camenca with maximum at the station Soroca. However, considering quality of water in the downstream sector, self-cleaning capacity of the Dniester River can be assessed as satisfactory.