9-(4-Bromo-but-yl)-9H-carbazole.

In the title compound, C(16)H(16)BrN, the bromo-butyl group lies on one side of the carbazole ring plane and has a zigzag shape. The dihedral angle between the two benzene rings is 0.55°. In the crystal, mol-ecules are connected by van der Waals inter-actions.

Sludge anaerobic digestion with high concentrations of tetracyclines and sulfonamides: Dynamics of microbial communities and change of antibiotic resistance genes.

This study established two mesophilic anaerobic digesters to ascertain the microbial dynamics and variation characteristics of antibiotic resistance genes (ARGs) during sludge anaerobic digestion (AD) with high concentration of antibiotics. System parameters, microbial community, ARGs (tetA, tetM, tetW, sulI, sulII) and integrase gene of class 1 (intI1) were analyzed. General performance of AD showed methane production was inhibited by 17.1% under the pressure of antibiotics. Microbial 16S rRNA high-throughput sequencing results showed the richness of microbial community decreased, but a higher diversity was found with antibiotics added. Furthermore, microbial community structure at genus level was significantly changed. Real-time quantitative PCR of several target genes demonstrated that the adjunction of high concentration of antibiotics exerted a significant induction influence on ARGs, however, the abundance of intI1 decreased observably. Correlation analysis showed intI1 only played a small role in ARGs' transfer during AD, change of potential hosts was the key factor instead.

Metagenomic analysis reveals the effects of long-term antibiotic pressure on sludge anaerobic digestion and antimicrobial resistance risk.

Continuous stirred-tank digesters with tetracyclines and sulfonamides were operated to investigate the impacts of antibiotic pressure on sludge anaerobic digestion. The versatile methanogen Methanosarcinales and strictly hydrogenotrophic methanogen Methanobacteriales increased and decreased by 21.1% and 10.9% under antibiotic pressure, respectively. KEGG analysis revealed that hydrogenotrophic and acetoclastic methanogenesis pathways were all affected. The decrease in abundance of function genes involved in lipid metabolism, carbohydrate metabolism, and fatty acid degradation, would lead to a reduction in methane production by 25%. Network analysis indicated positive associations among tetracycline residuals, abundance of resistance genes (ARGs), and specific member of potential hosts. Over 1000 ARG subtypes were widely detected in sludge, including macrolide (28%), tetracycline (24%), fluoroquinolone (20%), and peptide (20%) resistance genes. AD process exposed to long-term antibiotic would increase the diversity and abundance of ARG, enhance the association of ARG with specific microbes, and select bacteria able to perform chemotaxis mechanism.

Rapid startup of thermophilic anaerobic digester to remove tetracycline and sulfonamides resistance genes from sewage sludge.

Spread of antibiotic resistance genes (ARGs) originating from sewage sludge is highlighted as an eminent health threat. This study established a thermophilic anaerobic digester using one-step startup strategy to quickly remove tetracycline and sulfonamides resistance genes from sewage sludge. At least 20days were saved in the startup period from mesophilic to thermophilic condition. Based on the results of 16S rDNA amplicons sequencing and predicted metagenomic method, the successful startup largely relied on the fast colonization of core thermophilic microbial population (e.g. Firmicutes, Proteobacteria, Actinobacteria). Microbial metabolic gene pathways for substrate degradation and methane production was also increased by one-step mode. In addition, real-time quantitative PCR approach revealed that most targeted tetracycline and sulfonamides resistance genes ARGs (sulI, tetA, tetO, tetX) were substantially removed during thermophilic digestion (removal efficiency>80%). Network analysis showed that the elimination of ARGs was attributed to the decline of their horizontal (intI1 item) and vertical (potential hosts) transfer-related elements under high-temperature. This research demonstrated that rapid startup thermophilic anaerobic digestion of wastewater solids would be a suitable technology for reducing quantities of various ARGs.