HUN-REN Szegedi Biológiai Kutatóközpont 
2024. okt. 31. | News
Roland Wirth and his colleagues from the Microbial and Algal Genomics Research Group led by Gergely Maróti in the Institute of Plant Biology of the HUN-REN Biological Research Centre investigated the antibiotic resistance genes (ARGs) of anaerobic degradation microbiomes in industrial-scale biogas plants. The study revealed a limited correlation between the abundance and activity of antibiotic resistance genes in anaerobic environments. Certain resistance genes appeared to be “silent” under the anaerobic degradation conditions examined. Additionally, the study demonstrated that the expression and activity of ARGs in potentially pathogenic microbes were significantly lower compared to those in non-pathogenic bacteria within the microbiome. This suggests that anaerobic treatment and degradation of various organic materials can effectively reduce the risk posed by antibiotic resistance genes associated with potentially pathogenic microbes. The study was published in the Water Research journal.
The genes that enable microbes to resist antibiotics are of ancient origin. However, anthropogenic pressure is exerting selection pressure on microbes carrying different types of antibiotic resistance. Concurrently, human antibiotic use has increased the threat posed by antibiotic-resistant pathogenic microbes. The anaerobic degradation that results in biomethane—a clean and sustainable energy source— is also a bioremediation process that effectively reduces the prevalence of pathogenic bacteria in various types of wastewater. However, the efficient degradation of different organic materials requires a certain time, so that an exchange of different antibiotic resistance genes between pathogenic and non-pathogenic microbes can occur. Currently, our scientific understanding of anaerobic resistance in microorganisms living in anaerobic environments is limited. This is complicated by the fact that most microorganisms living in anaerobic environments cannot survive without microbial partners. Thus, the identification of antibiotic resistant microbes in such communities requires a specific approach. Advanced metagenomic techniques and innovative bioinformatic algorithms offer promising solutions. In this study, the authors reconstructed microbial genomes by analyzing and combining metagenomic and metatranscriptomic data from industrial-scale biogas reactors, identified antibiotic resistance genes and assessed their expression.
1. Figure. Expression of antibiotic-resistant bacteria and their resistance gene families in the biogas plants investigated (MWBP: Szeged Wastewater Treatment Plant biogas plant; SZBP: Szeged Karotin Ltd. biogas plant).
The results of this research showed that microorganisms living in anaerobic environments carried a wide range of genes linked to antibiotic resistance. The most prevalent among these are multidrug resistance genes, which encode membrane-bound proteins capable of expelling multiple types of antibiotics from the cell. These genes also enhance microbial pathogenicity by releasing substances that promote cell adhesion, thereby increasing antibiotic resistance in microbes harmful to humans. The authors noted a limited correlation between the relative abundance and expression (activity) of antibiotic resistance genes, suggesting that not all resistance genes are actively expressed under anaerobic degradation conditions. Furthermore, the study examined the genomic locations of these resistance genes, with results indicated that most ARGs were situated on bacterial chromosomes. However, resistance genes on plasmids demonstrated higher activity. These findings underscore the importance of gene expression analysis for accurately assessing ARG-related risks. The observed activity of resistance genes implies that both natural and anthropogenic factors influence the microbiomes that thrive in different types of wastewater. The findings also suggest that anaerobic treatment effectively reduces ARG activity in potentially pathogenic microbes. Nevertheless, some microbial groups harmful to humans, such as Staphylococcus species, demonstrated resistance to anaerobic degradation treatment highlighting the need for further develoments in wastewater treatment and bioremediation approaches.