Abstract
Understanding of the metabolic pathways connected with a removal of micropollutant bisphenol A (BPA) may help to better design effective wastewater treatment processes. The aim of this study was to determine changes in gene expression in an aerobic granular sludge (AGS) community exposed to BPA. In the study, AGS adapted to BPA degradation was used. In this sludge, BPA was dosed; as a control sample, granules without BPA addition were used. mRNA was isolated from both samples and sequenced using the Illumina platform. Metatranscriptome analysis of AGS exposed to BPA indicated direct biodegradation as the main mechanism of BPA removal from wastewater. High expression of genes coding pilus and flagellin proteins in the BPA-exposed biomass indicated that exposition to BPA stimulated aggregation of microbial cells and formation of biofilm. In the BPA-exposed biomass, nitrogen was mainly used as an energy source, as indicated by the presence of genes coding nitrification enzymes and urease. Moreover, exposition to BPA stimulated expression of genes coding proteins responsible for xenobiotic degradation, including enzymes responsible for benzoate degradation. These results increase knowledge about BPA metabolism in complex microbial communities in wastewater treatment systems and indicate that AGS is suitable for efficiently removing BPA from wastewater.
Highlights
Accelerated urbanization and significant industrial development in recent years have increased the occurrence of micropollutants in aquatic environments
Nitrogen metabolism in the control sample was mostly related to nitrogen assimilation, while in the Bisphenol A (BPA)-exposed sample, nitrogen was mainly used as an energy source
The study of changes in gene expression in aerobic granular sludge allows to obtain information about mechanisms responsible for BPA removal, indirectly indicating the dominant microbiological changes leading to effective wastewater treatment
Summary
Accelerated urbanization and significant industrial development in recent years have increased the occurrence of micropollutants in aquatic environments. Many wastewater treatment plants (WWTPs) are not adapted for the elimination of those toxic compounds, and as a result, many of these micropollutants pass through the treatment process, enter surface waters, and become a danger to wildlife and a problematic issue for the drinking water industry [1]. Research by Bolz et al [3] detected BPA in German surface waters at concentrations up to 0.4 μg/L. Another study showed that in the United States, 41% of examined streams were polluted with BPA in concentrations ranging from 0.14 μg/L to 12 μg/L [4]. Even small BPA concentrations of 1–10 μg/L cause serious toxicity to aquatic organisms—fish, algae, and invertebrates [5]. Matsumura et al [6] indicated that low BPA concentrations in soil (1 mg BPA/g) do not affect the microbial community, but high BPA concentrations (100 mg/g) significantly suppress microbial activity and growth
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