Microbial hitchhikers harbouring antimicrobial-resistance genes in the riverine plastisphere

Abstract

Background The widespread nature of plastic pollution has given rise to wide scientific and social concern regarding the capacity of these materials to serve as vectors for pathogenic bacteria and reservoirs for Antimicrobial Resistance Genes (ARG). In- and ex-situ incubations were used to characterise the riverine plastisphere taxonomically and functionally in order to determine whether antibiotics within the water influenced the ARG profiles in these microbiomes and how these compared to those on natural surfaces such as wood and their planktonic counterparts. Results We show that plastics support a taxonomically distinct microbiome containing potential pathogens and ARGs. While the plastisphere was similar to those biofilms that grew on wood, they were distinct from the surrounding water microbiome. Hence, whilst potential opportunistic pathogens (i.e. Pseudomonas aeruginosa, Acinetobacter and Aeromonas) and ARG subtypes (i.e. those that confer resistance to macrolides/lincosamides, rifamycin, sulfonamides, disinfecting agents and glycopeptides) were predominant in all surface-related microbiomes, especially on weathered plastics, a completely different set of potential pathogens (i.e. Escherichia, Salmonella, Klebsiella and Streptococcus) and ARGs (i.e. aminoglycosides, tetracycline, aminocoumarin, fluoroquinolones, nitroimidazole, oxazolidinone and fosfomycin) dominated in the planktonic compartment. Our genome-centric analysis allowed the assembly of 215 Metagenome Assembled Genomes (MAGs), linking ARGs and other virulence-related genes to their host. Interestingly, a MAG belonging to Escherichia –that clearly predominated in water– harboured more ARGs and virulence factors than any other MAG, emphasising the potential virulent nature of these pathogenic-related groups. Finally, ex-situ incubations using environmentally-relevant concentrations of antibiotics increased the prevalence of their corresponding ARGs, but different riverine compartments –including plastispheres– were affected differently by each antibiotic. Conclusions Our results provide insights into the capacity of the riverine plastisphere to harbour a distinct set of potentially pathogenic bacteria and function as a reservoir of ARGs. The environmental impact that plastics pose if they act as a reservoir for either pathogenic bacteria or ARGs is aggravated by the persistence of plastics in the environment due to their recalcitrance and buoyancy. Nevertheless, the high similarities with microbiomes growing on natural co-occurring materials and even more worrisome microbiome observed in the surrounding water highlights the urgent need to integrate the analysis of all environmental compartments when assessing risks and exposure to pathogens and ARGs in anthropogenically-impacted ecosystems.

Effects of microplastics on Daphnia-associated microbiomes in situ and in vitro

“…By applying metagenome shotgun sequencing to field samples, we quantified specific functional genes in Daphnia microbiomes that could be associated with MP presence, including ARGs and hydrolytic enzymes involved in polyester biodegradation. Recently, plastispheres have been identified as hotspots for ARGs (Zhu et al, 2022; Vlaanderen et al, 2023; Zadjelovic et al, 2023) and hence their higher abundances in the host microbiomes from high-MP ponds was not unexpected. Since high-MP ponds are close to human activity hubs, they are at greater risk of antibiotic contamination through sewage runoff.…”

Recent advances in microbial and enzymatic engineering for the biodegradation of micro- and nanoplastics

“…Microplastics pose a serious ecological concern due to their capacity to adsorb heavy metals, harbor bacterial pathogens, carry multidrug-resistant E. coli , and act as a vector for persistent pollutants. 257–260 The risks are further intensified by the combined effects of manufacturing chemicals and organic contaminants that are attached to microplastics. Microplastics also support the development of various microbial communities and create biofilms made up of algae, bacteria, and fungi.…”

The antibiotic crisis: On the search for novel antibiotics and resistance mechanisms

“…It forms a myriad of microniches (i.e. microplastics) dispersed throughout terrestrial and marine ecosystems, serving as reservoirs and refuges for ARGs and potential pathogens (Zadjelovic et al., 2023 ; Zhu et al., 2022 ). Moreover, the extended residence time in the environment and high microbial load can promote HGT among cells, accelerating the spill‐over and global spread of ARGs.…”