Direct DNA analysis is the most widely used approach for microorganism characterization in natural and built environments; therefore, reliable and effective methods of nucleic acid extraction for samples from particular types of environments are needed. In this study, we compared three commercial kits for metagenomic DNA extraction from three types of biomass: activated sludge, biofilm, and anaerobic digestate. The yield, purity, and quality of DNA were measured, and the effect that the DNA kit had on the subsequent microbial community analysis was assessed with amplified ribosomal intergenic spacer analysis (ARISA). Amplicons were analyzed automatically utilizing capillary electrophoresis. For the activated sludge and digestate, the suggested kit is FastDNA™ Spin Kit for Soil (MP Biomedicals). This kit allowed the highest DNA yield to be obtained and provided the highest biodiversity. For biofilm with a high content of extracellular polymeric substances, the FavorPrep™ Soil DNA Isolation Mini Kit (FAVORGEN) is recommended. This kit allowed to obtain the highest biodiversity and provided the most reliable results of genetic distance assessment in this type of biomass.

Wastewater treatment plants (WWTPs) offer the possibility of recovering valuable substances produced by microorganisms, such as extracellular polymeric substances (EPSs). This study aimed to investigate the generation and properties of biopolymers and microbial communities of activated sludge from a large, full-scale WWTP. EPS composition in the activated sludge changed mostly during the transition period from winter to spring. Higher temperatures favored higher protein (PN) concentrations and a higher PN/PSs (polysaccharides) ratio in tightly-bound EPS, stimulating bacterial aggregation. In the sludge, filamentous Microthrix sp. were abundant (~6%) but the settling properties of the sludge improved with increasing PN content in the bound EPS fraction. The content of alginate (ALE)-like polymers averaged 55–60 mg/g Mixed Liquor Suspended Solids, and ALE content in sludge and characteristics were stable during the year. The abundance of Nitrospira sp. and the marine group NS9 in activated sludge correlated with the ALE content in the biomass, pointing to the importance of biopolymer production for nitrogen-transforming microorganisms. The most common EPS-producer was, Candidatus Competibacter (3–4%). The abundance of the Roseiflexaceae family significantly increased in summer, as did the abundance of Trichoccus sp. and Flavobacterium sp. in winter. The study shows that seasonal temperature fluctuations do not significantly affect the production of polymers, especially alginate, which favors commercial ALE recovery. The non-uniform composition of ALE-like polymers shows the possibility of their use in areas that do not require a specific polymer composition, e.g., as environmentally friendly coating materials or sorbents. The study contributes to biopolymer recovery and valorization of activated sludge.

Microcystin-LR (MC-LR) is a potent hepatotoxin that has also been pointed out of causing neurotoxicity, but the exact mechanisms of action still remain ambiguous and need to be elucidated. Data from studies on mammals show that pathology of astrocyte cells points to perturbations of microRNA signaling. Glial fibrillary acidic protein (GFAP), a neuronal cell/astrocyte-specific protein, and a microRNA-124-3p (MiR124-3p) are among putative triggers and regulators of neuronal cell/astrocyte reactivity. In the present study on whitefish (Coregonus lavaretus), we found that gfap mRNA contains a putative target site for MIR124-3p, to potentially affect its expression changes. qPCR expression study of gfap:MiR124-3p pair in the midbrain of juvenile whitefish, during 28 days of exposure to a repeated subacute dose of MC-LR (100 μg kg⁻¹ body mass), showed marginally significant up-regulation of gfap only on the 7th day of exposure period which suggests neuronal toxicity. During the whole exposure period, neither midbrain nor blood plasma levels of MiR124-3p were changed. Furthermore, double luciferase gene reporter assay confirmed the lack of MiR124-3p involvement in mediating control over gfap mRNA expression. These data show that, although MC-LR may trigger neuronal toxicity in whitefish, this does not involve MiR124-3p in response to the treatment.

Aeruginosamides (AEGs) are classified as cyanobactins, ribosomally synthesized peptides with post-translational modifications. They have been identified in cyanobacteria of genera Microcystis, Oscillatoria, and Limnoraphis. In this work, the new data on the in vitro activities of three AEG variants, AEG A, AEG625 and AEG657, and their interactions with metabolic enzymes are reported. Two aeruginosamides, AEG625 and AEG657, decreased the viability of human breast cancer cell line T47D, but neither of the peptides was active against human liver cancer cell line Huh7. AEGs also did not change the expression of MIR92b-3p, but for AEG625, the induction of oxidative stress was observed. In the presence of a liver S9 fraction containing microsomal and cytosolic enzymes, AEG625 and AEG657 showed high stability. In the same assays, quick removal of AEG A was recorded. The peptides had mild activity against three cytochrome P450 enzymes, CYP2C9, CYP2D6 and CYP3A4, but only at the highest concentration used in the study (60 µM). The properties of AEGs, i.e., cytotoxic activity and in vitro interactions with important metabolic enzymes, form a good basis for further studies on their pharmacological potential.