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Rezumat articol ediţie STUDIA UNIVERSITATIS BABEŞ-BOLYAI
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Rezumat: Microorganisms either independently or in association with other organisms play a very important role to the plant nutrients recycling. Soil pollutant concentrations above certain limits disrupt the ecosystems and as a result the nutrient cycling process. The paper presents the seasonal evolution of the bacterial community structure in the most representative polluted soils from Cluj County: urban roadside soil, industrial polluted soils including metallurgy and refractory products manufacturing sector, soils affected by zootechnical residues, soil contaminated with hexachlorocyclohexane pesticide residue and soil polluted by uncontrolled dumping of municipal solid waste. The following 7 ecophysiological groups were investigated: aerobic heterotrophic bacteria, ammonifying bacteria, nitrifying bacteria (ammonium and nitrite oxidizing bacteria), denitrifying bacteria, iron-reducing bacteria and sulphate reducing bacteria. Enumeration of viable soil microorganisms was accomplished by serial dilution and plate count technique (aerobic heterotrophic bacteria) or most probable number method (all other analyzed bacteria). Based on the obtained results, the bacterial indicator of the soil quality (BISQ) was calculated for each soil sample. The BISQ values ranged between 2.047 and 3.708, indicating a moderate density of the bacterial groups. Quantitative analysis of soil microbial populations shows a marked decrease in total culturable numbers of the different microbial groups of the contaminated soil samples. Aerobic heterotrophic bacterial populations were particularly sensitive to pollution. Organic matter decomposition and nitrogen mineralization, which are carried out by various groups of microorganisms, have also been affected by increased pollutants concentration in the soils. A negative correlation between the bacterial indicators of soil quality and heavy metals was established.
Keywords: bacterial communities, bacterial indicator of soil quality, soil pollution
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