Identification of estrone-degrading Betaproteobacteria in activated sludge by microautoradiography fluorescent in situ hybridization

Microbial degradation of steroid sex hormones: implications for environmental and ecological studies

Steroid hormones modulate development, reproduction and communication in eukaryotes. The widespread occurrence and persistence of steroid hormones have attracted public attention due to their endocrine-disrupting effects on both wildlife and human beings. Bacteria are responsible for mineralizing steroids from the biosphere. Aerobic degradation of steroid hormones relies on O2 as a co-substrate of oxygenases to activate and to cleave the recalcitrant steroidal core ring. To date, two oxygen-dependent degradation pathways - the 9,10-seco pathway for androgens and the 4,5-seco pathways for oestrogens - have been characterized. Under anaerobic conditions, denitrifying bacteria adopt the 2,3-seco pathway to degrade different steroid structures. Recent meta-omics revealed that microorganisms able to degrade steroids are highly diverse and ubiquitous in different ecosystems. This review also summarizes culture-independent approaches using the characteristic metabolites and catabolic genes to monitor steroid biodegradation in various ecosystems.

Functional Response of MBR Microbial Consortia to Substrate Stress as Revealed by Metaproteomics

Bacterial consortia have a primary role in the biological degradations occurring in activated sludge for wastewater treatment, for their capacities to metabolize the polluting matter. Therefore, the knowledge of the main metabolic pathways for the degradation of pollutants becomes critical for a correct design and operation of wastewater treatment plants. The metabolic activity of the different bacterial groups in activated sludge is commonly investigated through respirometry. Furthermore, in the last years, the development of "omic" approaches has offered more opportunities to integrate or substitute the conventional microbiological assays and to deeply understand the taxonomy and dynamics of complex microbial consortia. In the present work, an experimental membrane bioreactor (MBR) was set up and operated for the treatment of municipal wastewater, and the effects of a sudden decrease of the organic supply on the activated sludge were investigated. Both respirometric and metaproteomic approaches revealed a resistance of autotrophic bacteria to the substrate stress, and particularly of nitrifying bacteria. Furthermore, metaproteomics allowed the identification of the taxonomy of the microbial consortium based on its protein expression, unveiling the prevalence of Sorangium and Nitrosomonas genera both before and after the organic load decrease. Moreover, it confirmed the results obtained through respirometry and revealed a general expression of proteins involved in metabolism and transport of nitrogen, or belonging to nitrifying species like Nitrosomonas europeae, Nitrosomonas sp. AL212, or Nitrospira defluvii.

Transformation, CO2 formation and uptake of four organic micropollutants by carrier-attached microorganisms

A tiered process was developed to assess the transformation, CO₂ formation and uptake of four organic micropollutants by carrier-attached microorganisms from two municipal wastewater treatment plants. At the first tier, primary transformation of ibuprofen, naproxen, diclofenac, and mecoprop by carrier-attached microorganisms was shown by the dissipation of the target compounds and the formation of five transformation products using LC-tandem MS. At the second tier, the microbial cleavage of the four organic micropollutants was confirmed with ¹⁴C-labeled micropollutants through liquid scintillation counting of the ¹⁴CO₂ formed. At the third tier, microautoradiography coupled with fluorescence in situ hybridization (MAR-FISH) was used to screen carrier-attached microorganisms for uptake of the four radiolabeled micropollutants. Results from the MAR-FISH screening indicated that only a small fraction of the microbial community (≤1‰) was involved in the uptake of the radiolabeled micropollutants and that the responsible microorganisms differed between the compounds. At the fourth tier, the microbial community structure of the carrier-attached biofilms was analyzed by 16S rRNA gene amplicon sequencing. The sequencing results showed that the MAR-FISH screening targeted ∼80% of the microbial community and that several taxonomic families within the FISH-probed populations with MAR-positive signals (i.e. Firmicutes, Gammaproteobacteria, and Deltaproteobacteria) were present in both biofilms. From the broader perspective of organic micropollutant removal in biological wastewater treatment, the MAR-FISH results of this study indicate a high degree of microbial substrate specialization that could explain differences in transformation rates and patterns between micropollutants and microbial communities.

Removal of nutrients and pharmaceuticals and personal care products from wastewater using periphyton photobioreactors

In this work, periphyton photobioreactors were built and were used for the treatment of synthetic wastewater spiked with PPCPs under different operational conditions. The removal rates of total nitrogen were relatively stable and varied from 39% to 77% overtime in different treatments. However, the removal rates of soluble reactive phosphorus decreased overtime from 42% to 68% on day 2 to 15.8% to 44% on day 22. For the selected PPCPs, only bisphenol A was effectively removed (72%-86.4%), hydrochlorothiazide and ibuprofen were moderately removed (26.2%-48.7%), and carbamazepine and gemfibrozil were poorly removed (6.45%-20.6%). Longer hydraulic retention time enhanced the treatment efficiency but illumination period showed contrasting effects on the removal of the nutrients and the PPCPs.