Abstract
The conversion of cattle manure into biogas in anaerobic digestion (AD) processes has been gaining attention in recent years. However, antibiotic consumption continues to increase worldwide, which is why antimicrobial concentrations can be expected to rise in cattle manure and in digestate. This study examined the long-term synergistic effects of antimicrobials on the anaerobic digestion of cattle manure. The prevalence of antibiotic resistance genes (ARGs) and changes in microbial biodiversity under exposure to the tested drugs was investigated using a metagenomic approach. Methane production was analyzed in lab-scale anaerobic bioreactors. Bacteroidetes, Firmicutes, and Actinobacteria were the most abundant bacteria in the samples. The domain Archaea was represented mainly by methanogenic genera Methanothrix and Methanosarcina and the order Methanomassiliicoccales. Exposure to antibiotics inhibited the growth and development of methanogenic microorganisms in the substrate. Antibiotics also influenced the abundance and prevalence of ARGs in samples. Seventeen types of ARGs were identified and classified. Genes encoding resistance to tetracyclines, macrolide–lincosamide–streptogramin antibiotics, and aminoglycosides, as well as multi-drug resistance genes, were most abundant. Antibiotics affected homoacetogenic bacteria and methanogens, and decreased the production of CH4. However, the antibiotic-induced decrease in CH4 production was minimized in the presence of highly drug-resistant microorganisms in AD bioreactors.
Highlights
This study demonstrated that biomass supplementation with increasing concentrations This ENRO
The metaanalysis revealed that prolonged mesophilic anaerobic digestion (AD) of cattle manure in the presence of all three genomic analysis revealed that prolonged mesophilic AD of cattle manure in the presence of all three tested antibiotics can modify the resistome profile and increase the relative abundance of individual antibiotic resistance genes (ARGs) in digestates
ARGs in an environment where genes can be transferred from the digestate to farmland, tested antibiotics can modify the resistome profile and increase the relative abundance of individual ARGs in digestates
Summary
The most popular classes of antibiotics include beta-lactams (such as amoxicillin, AMO) [8], fluoroquinolones (such as enrofloxacin, ENRO) [9], and nitroimidazole derivatives (such as metronidazole, MET) [10]. These antimicrobials inhibit the AD process, induce changes in microbial communities, promote the spread of drug resistance (DR), and influence the efficiency of biogas and CH4 production [11]. MET is used mainly to treat infections caused by anaerobic bacteria [13]. This antimicrobial can be accumulated for up to 42 days in the host organism [10]. The presence and spread of broad-spectrum betalactamases in the environment pose a serious threat to public health around the world [17]
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