Laboratory Stock Variants of the Archetype Silver Resistance Plasmid pMG101 Demonstrate Plasmid Fusion, Loss of Transmissibility, and Transposition of Tn7/pco/sil Into the Host Chromosome

Journal article

University of Technology Sydney. Faculty of Science.The application of nanoparticles, the product of nanotechnology, has been rapidly growing as they are being used in a broad range of industries. Among those nanoparticles, nanosilver (NAg) is one the most widely used due to its antimicrobial properties, making it common in medical devices and a wide range of consumer products. The widespread use of NAg has led to the release of the nanoparticles into the environment, and furthermore may lead to the accumulation of silver in the environment. The uncontrolled release of NAg to natural environments may affect microbial communities, facilitating the development of antibiotic-resistant microbes through the co-selection of antimicrobial resistance genes (ARGs). This thesis herein unravels the potential of NAg and ionic silver (Ag+) in shifting the microbial community structures as well as the profile of antimicrobial resistance (ARGs), metal resistance (MRGs), and oxidative-stress related genes in water-sediment microcosms constructed from the marine environment Port Botany, New South Wales, Australia. The concentration of silver influences the extent of its impact on microbial communities as well as ARGs, MRGs, and even oxidative-stress genes. A higher Ag concentration (50 mg/L) resulted in greater enrichments of certain ARGs, MRGs, and oxidative stress-associated genes, compared to the lower concentration of 0.5 mg/L Ag, which showed only up to 3-fold increase. Notably, there were distinct impact between NAg and Ag+ in shifting the microbial communities, as evident from the Ward D2 hierarchical cluster analysis. Furthermore, assembly-based metagenomics analysis revealed that MAGs impacted by the silver exposure host multiple ARGs and MRGs, indicating the potential co-selection driven by silver. While the mechanism underlying the distinct impact between NAg and Ag+ is still unclear, it is hypothesised that NAg and Ag+ interact with microbes differently. Interestingly, the impact of Ag exposure is more pronounced in water microcosms (with a maximum 101-fold increase in specific functional genes) when compared to sediments (up to 8-fold increase). This difference is likely due, at least in part, to the physicochemical transformation of silver in sediments, which reduces its bioavailability. The findings of this work are expected to contribute to the development of strategies for managing the use and disposal of NAg-containing products which are currently ineffective

Authors: Hooton, SPT; Pritchard, ACW; Asiani, K; Gray-Hammerton, CJ; Stekel, DJ

• Publication status: Published
• Peer review status: Peer reviewed
• Publisher: Frontiers Media
• Journal: Frontiers in Microbiology
• Volume: 12
• Pages: 723322-723322
• Article number: 723322
• Publication date: 2021-08-19
• DOI: 10.3389/fmicb.2021.723322
• EISSN: 1664-302X
• ISSN: 1664-302X
• Language: English
• Keywords: Insertion sequence; Gene; Plasmid; Biology; Genetics; Genome; Microbiology; Chromosome; Transposable element; Molecular biology; Escherichia coli