Exploring antibiotic resistance genes and metal resistance genes in plasmid metagenomes from wastewater treatment plants

Abstract

Plasmids operate as independent genetic elements in microorganism communities. Through horizontal gene transfer (HGT), they can provide their host microorganisms with important functions such as antibiotic resistance and heavy metal resistance. In this study, six metagenomic libraries were constructed with plasmid DNA extracted from influent, activated sludge (AS) and digested sludge (DS) of two wastewater treatment plants (WWTPs). Compared with the metagenomes of the total DNA extracted from the same sectors of the wastewater treatment plant, the plasmid metagenomes had significantly higher annotation rates, indicating that the functional genes on plasmids are commonly shared by those studied microorganisms. Meanwhile, the plasmid metagenomes also encoded many more genes related to defense mechanisms, including ARGs. Searching against an antibiotic resistance genes (ARGs) database and a metal resistance genes (MRGs) database revealed a broad-spectrum of antibiotic (323 out of a total 618 subtypes) and MRGs (23 out of a total 23 types) on these plasmid metagenomes. The influent plasmid metagenomes contained many more resistance genes (both ARGs and MRGs) than the AS and the DS metagenomes. Sixteen novel plasmids with a complete circular structure that carried these resistance genes were assembled from the plasmid metagenomes. The results of this study demonstrated that the plasmids in WWTPs could be important reservoirs for resistance genes, and may play a significant role in the horizontal transfer of these genes.

Antimicrobial usage and resistance in beef production

“…Resistance gene clusters 1 and 2 are shown expanded in grey. b Circular distribution of antimicrobial resistance genes by class, and abundance in total annotated antimicrobial genes found six plasmid metagenomes from the influent and sludge from two wastewater treatment plants (modified and reproduced with permission from [192]) …”

“…The authors also detected MGEs in tannery DNA samples, but limitations in methodology restricted investigating linkages with AMR genes. Taking a similar approach, Li et al [192] examined the resistome of plasmids harvested from influent, activated sludge, and digested sludge of two Hong Kong wastewater treatment plants receiving domestic and slaughterhouse (cattle and other production animals) sewage. AMR genes were detected in all of the plasmid metagenomes: the most abundant were tetracycline resistance genes (29% of all AMR gene sequences), quinolone resistance genes (17%), and β-lactam resistance genes (12%) [192].…”

Genetic markers for detection of Escherichia coli K-12 harboring ampicillin-resistance plasmid from an industrial wastewater treatment effluent pond

“…Therefore, microbial communities in WWTP exist as model systems to explore various plasmids carrying genes with important functions for their hosts, including antibiotic resistance, pathogenicity, virulence, biodegradation, and heavy metal resistance (Li et al, 2015). Several studies have reported the presence of immense varieties of plasmids containing antibiotic resistance genes in WWTP (Li et al, 2015).…”

Genetic diversity of Acinetobacter spp. adapted to heavy metal polluted environments

“…Bacterial adaptation mechanisms in environment are metal sorption, accumulation and uptake, mineralization, precipitation, efflux from the cell, oxidation or reduction to less toxic or nontoxic forms (Nies 1999). Genes encoding proteins involved in the mechanisms of biotransformation of toxic heavy metals to less toxic forms are often present on circular plasmid DNA which may be involved in the processes of horizontal gene transfer (Li et al 2015). Heavy -metal tolerant bacterial strains could be used in bioremediation but before their real incorporation into the real processes we must get as much information about these strains.…”