Screening of Microorganisms for Biodegradation of Simazine Pollution (Obsolete Pesticide Azotop 50 WP)

The capability of environmental microorganisms to biodegrade simazine—an active substance of 2-chloro-s-triazine herbicides (pesticide waste since 2007)—was assessed. An enormous metabolic potential of microorganisms impels to explore the possibilities of using them as an alternative way for thermal and chemical methods of utilization. First, the biotope rich in microorganisms resistant to simazine was examined. Only the higher dose of simazine (100 mg/l) had an actual influence on quantity of bacteria and environmental fungi incubated on substrate with simazine. Most simazine-resistant bacteria populated activated sludge and biohumus (vermicompost); the biggest strain of resistant fungi was found in floral soil and risosphere soil of maize. Compost and biohumus were the sources of microorganisms which biodegraded simazine, though either of them was the dominant considering the quantity of simazine-resistant microorganisms. In both cases of periodic culture (microorganisms from biohumus and compost), nearly 100% of simazine (50 mg/l) was degraded (within 8 days). After the repeated enrichment culture with simazine, the rate of its degradation highly accelerated, and just after 24 h, the significant decrease of simazine (20% in compost and 80% in biohumus) was noted. Although a dozen attempts of isolating various strains responsible for biodegradation of simazine from compost and biohumus were performed, only the strain identified as Arthrobacter urefaciens (NC) was obtained, and it biodegraded simazine with almost 100% efficiency (within 4 days)

Functional Repertoire of Antibiotic Resistance Genes in Antibiotic Manufacturing Effluents and Receiving Freshwater Sediments

Environments polluted by direct discharges of effluents from antibiotic manufacturing are important reservoirs for antibiotic resistance genes (ARGs), which could potentially be transferred to human pathogens. However, our knowledge about the identity and diversity of ARGs in such polluted environments remains limited. We applied functional metagenomics to explore the resistome of two Croatian antibiotic manufacturing effluents and sediments collected upstream of and at the effluent discharge sites. Metagenomic libraries built from an azithromycin-production site were screened for resistance to macrolide antibiotics, whereas the libraries from a site producing veterinary antibiotics were screened for resistance to sulfonamides, tetracyclines, trimethoprim, and beta-lactams. Functional analysis of eight libraries identified a total of 82 unique, often clinically relevant ARGs, which were frequently found in clusters and flanked by mobile genetic elements. The majority of macrolide resistance genes identified from matrices exposed to high levels of macrolides were similar to known genes encoding ribosomal protection proteins, macrolide phosphotransferases, and transporters. Potentially novel macrolide resistance genes included one most similar to a 23S rRNA methyltransferase from Clostridium and another, derived from upstream unpolluted sediment, to a GTPase HflX from Emergencia. In libraries deriving from sediments exposed to lower levels of veterinary antibiotics, we found 8 potentially novel ARGs, including dihydrofolate reductases and beta-lactamases from classes A, B, and D. In addition, we detected 7 potentially novel ARGs in upstream sediment, including thymidylate synthases, dihydrofolate reductases, and class D beta-lactamase. Taken together, in addition to finding known gene types, we report the discovery of novel and diverse ARGs in antibiotic-polluted industrial effluents and sediments, providing a qualitative basis for monitoring the dispersal of ARGs from environmental hotspots such as discharge sites of pharmaceutical effluents