Poster Presentation Australian Microbial Ecology 2022

Uncovering the resistome and plasmidome of heavy metal impacted sediment communities (#113)

Brodie F Gillieatt 1 , Nicholas V Coleman 1 , Amy K Cain 2 , Ruth N Zadoks 3
  1. School of Life and Environmental Sciences, The University of Sydney, Camperdown, NSW, Australia
  2. School of Natural Sciences, Macquarie University, Macquarie Park, NSW, Australia
  3. School of Veterinary Science, The University of Sydney, Camperdown, NSW, Australia

The pool of environmental resistance genes, known as the resistome, provides an arsenal of genes that bacteria may acquire to resist chemical stressors. Antibiotics in clinical settings are a well-established example of this, however in many environments such as freshwater sediments, heavy metals dominate as a selective pressure. Metals are suspected to play a role in the co-selection of antibiotic resistance genes (ARGs), although the molecular mechanisms underpinning this phenomenon are unclear. Here, we aimed to understand the relationships of ARGs, metal resistance genes (MRGs), and the mobile genetic elements (MGEs) that carry these, with emphasis on the plasmidome, that is the overall plasmid population. Bacteria resistant to zinc, cadmium, or copper were isolated from sediments in the Lake Macquarie region, which are impacted by metal contamination as a legacy of coal burning and smelting in the area. The resultant strain collection of 81 unique isolates was taxonomically diverse but dominated by the orders Streptomycetales, Micrococcales, Hyphomicrobiales and Burkholderiales. Genome sequencing of eleven isolates revealed novel combinations of MRGs and ARGs, including zinc, cadmium, copper, arsenic, cobalt, chromium, and nickel resistance, and aminoglycoside, aminocoumarin, fluoroquinolone, glycopeptide, macrolide, penam, and phenicol resistance. Four novel resistance plasmids were identified and annotated. One 172 kb plasmid from an Ensifer adhaerens isolate was characterised in detail; this contained an extensive array of MRG operons including czcNCBADRSE, copFGDCBARSNM, cus/silDCBA, arsRNDCH, and aioAB in addition to individual resistance genes acr3, cadR, and pbrA. We have obtained evidence for the presence of diverse metal resistant bacteria and novel combinations of resistance genes and MGEs in local sediments impacted by industrial activities; further analysis of this isolate collection aims to establish whether environmental metals are co-selecting for ARGs, thus informing One Health approaches to tackling the problem of resistance.