Carbonaceous particulate matter promotes the horizontal transfer of antibiotic resistance genes.

There is growing concern about the transfer of antibiotic-resistant bacteria (ARB) and antibiotic resistance genes (ARGs) in airborne particulate matter. In this study, we investigated the effects of various types of carbonaceous particulate matter (CPM) on the transfer of ARGs in vitro. The results showed that CPM promoted the transfer of ARGs, which was related to the concentration and particle size. Compared with the control group, the transfer frequency was 95.5, 74.7, 65.4, 14.7, and 3.8 times higher in G (graphene), CB (carbon black), NGP (nanographite powder), GP1.6 (graphite powder 1.6 micron), and GP45 (graphite powder 45 micron) groups, respectively. Moreover, the transfer frequency gradually increased with the increase in CPM concentration, while there was a negative relationship between the CPM particle size and conjugative transfer frequency. In addition, the results showed that CPM could promote the transfer of ARGs by increasing ROS, as well as activating the SOS response and expression of conjugative transfer-related genes (trbBp, trfAp, korA, kroB, and trbA). These findings are indicative of the potential risk of CPM for the transfer of ARGs in the environment, enriching our understanding of environmental pollution and further raising awareness of environmental protection.

Landscape of antibiotic resistance genes and bacterial communities in groundwater on the Tibetan Plateau, and distinguishing their difference with low-altitude counterparts.

Groundwater is a vital source of drinking water for Tibetans. Antibiotic resistance genes (ARGs) and bacterial communities in groundwater on the Tibetan Plateau remain unclear. Furthermore, the characterization of their differences between high-altitude and low-altitude groundwater is still unrevealed. Herein, 32 groundwater samples were collected on the plateau, and intra- and extracellular ARGs (iARGs and eARGs), and bacterial communities were characterised through qPCR assays to 19 ARGs and 16S rRNA sequencing. It showed top four abundant intra- and extracellular last-resort ARGs (LARGs) were blaOXA-48, mcr-1, vanA, and vanB, whereas dominant common ARGs (CARGs) were tetA and ermB, respectively. CARGs had higher abundances than LARGs, and iARGs were more frequently detected than eARGs. Proteobacteria, an invasive resident phylum, and Firmicutes dominated eDNA release. Network analysis revealed all observed LARGs co-occurred with pathogenic and non-pathogenic bacteria. Community diversity was significantly associated with longitude and elevation, while nitrate correlated with ARGs. Comparative analysis demonstrated eARG frequencies and abundances were higher at high altitudes than at low altitudes. Additionally, Acinetobacter and Pseudomonas specifically dominated at high altitudes. This study reveals the widespread prevalence of ARGs, particularly LARGs, in groundwater on the less-disturbed Tibetan Plateau and underlines the potential risks associated with the LARG-carrying bacteria. ENVIRONMENTAL IMPLICATION: Antibiotic resistance genes (ARGs), which are defined as emerging environmental contaminants, are becoming a global concern due to their ability to confer antibiotic resistance to pathogens. Our findings highlight the prevalence of ARGs, particularly LARGs, in groundwater on the Tibetan Plateau, and the possibility that naturally-occurring pathogenic and non-pathogenic bacteria carry multiple LARGs. In addition, we further reveal differences in the distribution of ARGs and bacterial community between high-altitude and low-altitude groundwater. Collectively, our findings offer an important insight into the potential public risks related to groundwater on the Tibetan Plateau.

Enhanced shrub growth in the Arctic increases habitat connectivity for browsing herbivores.

Habitat connectivity is a key factor influencing species range dynamics. Rapid warming in the Arctic is leading to widespread heterogeneous shrub expansion, but impacts of these habitat changes on range dynamics for large herbivores are not well understood. We use the climate-shrub-moose system of northern Alaska as a case study to examine how shrub habitat will respond to predicted future warming, and how these changes may impact habitat connectivity and the distribution of moose (Alces alces). We used a 19 year moose location dataset, a 568 km transect of field shrub sampling, and forecasted warming scenarios with regional downscaling to map current and projected shrub habitat for moose on the North Slope of Alaska. The tall-shrub habitat for moose exhibited a dendritic spatial configuration correlated with river corridor networks and mean July temperature. Warming scenarios predict that moose habitat will more than double by 2099. Forecasted warming is predicted to increase the spatial cohesion of the habitat network that diminishes effects of fragmentation, which improves overall habitat quality and likely expands the range of moose. These findings demonstrate how climate change may increase habitat connectivity and alter the distributions of shrub herbivores in the Arctic, including creation of novel communities and ecosystems.