Class 1 integrons in benthic bacterial communities: abundance, association with Tn402-like transposition modules and evidence for coselection with heavy-metal resistance.
The integron/gene cassette system contributes to lateral gene transfer of genetic information in bacterial communities, with gene cassette-encoded proteins potentially playing an important role in adaptation to stress. Class 1 integrons are a particularly important class as they themselves seem to be broadly disseminated among the Proteobacteria and have an established role in the spread of antibiotic resistance genes. The abundance and structure of class 1 integrons in freshwater sediment bacterial communities was assessed through sampling of 30 spatially distinct sites encompassing different substrate and catchment types from the Greater Melbourne Area of Victoria, Australia. Real-time PCR was used to demonstrate that the abundance of intI1 was increased as a result of ecosystem perturbation, indicated by classification of sample locations based on the catchment type and a strong positive correlation with the first principal component factor score, comprised primarily of the heavy metals zinc, mercury, lead and copper. Additionally, the abundance of intI1 at sites located downstream from treated sewage outputs was associated with the percentage contribution of the discharge to the basal flow rate. Characterization of class 1 integrons in bacteria cultured from selected sediment samples identified an association with complete Tn402-like transposition modules, and the potential for coselection of heavy-metal and antibiotic resistance mechanisms in benthic environments.
Rosewarne
Carly P
CP
Department of Genetics, La Trobe University, Bundoora, Vic., Australia. carly.rosewarne@gmail.com
Pettigrove
Vincent
V
Stokes
Hatch W
HW
Parsons
Yvonne M
YM
D000333:Aeromonas / Q000187:drug effects / Q000235:genetics; D001419:Bacteria / Q000187:drug effects / Q000235:genetics*; D020604:Comamonas testosteroni / Q000187:drug effects / Q000235:genetics; D004251:DNA Transposable Elements; D024881:Drug Resistance, Bacterial / Q000235:genetics*; D017753:Ecosystem; D005618:Fresh Water; D022761:Gene Transfer, Horizontal; D019015:Geologic Sediments / Q000737:chemistry / Q000382:microbiology*; D019426:Integrases / Q000235:genetics; D032023:Integrons; D019216:Metals, Heavy / Q000032:analysis / Q000494:pharmacology*; D016133:Polymerase Chain Reaction; D011549:Pseudomonas / Q000187:drug effects / Q000235:genetics; D012641:Selection, Genetic; D012722:Sewage; D014739:Victoria; D014876:Water Pollution
D004251:DNA Transposable Elements; D019216:Metals, Heavy; D012722:Sewage; D019426:Integrases