Increased temperature selects for antibiotic resistance genes in a model aquatic ecosystem

There is a rising concern that temperature increases associated with climate change might select for antibiotic-resistant bacteria (ARB) and antibiotic resistance genes (ARGs) in aquatic ecosystems, although the extent of this phenomenon remains unknown. This study aimed to determine whether increased temperatures induce ARG selection and modify the transcriptional response in a model aquatic ecosystem using an omics approach. River water microcosms were incubated at 20 °C, at 28 °C (constant temperature increase), and under oscillating temperatures (intervals of 3 days at 20 °C and 4 days at 28 °C to emulate heatwaves) for 28 days. Both the constantly higher temperature and oscillating temperatures altered bacterial community composition and selected for members carrying ARGs, including two Limnohabitans subpopulations that contain the pmrE polymyxin resistance gene and an Alphaproteobacteria carrying the sul2 sulfonamide resistance gene. In addition, metatranscriptomic analyses revealed a lower abundance (p < 0.05) of transcripts related to cell division, bacterial activity/metabolism, antibiotic efflux, stress responses, and cell/gene mobility in samples exposed to oscillating temperatures than in the room temperature controls. This research supports the rising concern that climate change may increase antibiotic resistance in environments exposed to higher temperatures maintained over long periods of time and to repeated short-time heatwave events.