Bacterial antibiotic resistance is often a part of mobile genetic elements that move from one bacterium to another. By interfering with the horizontal movement and the maintenance of these elements, it is possible to remove the resistance from the population. Here, we show that a so-called plasmid-dependent bacteriophage causes the initially resistant bacterial population to become susceptible to antibiotics. However, this effect is efficiently countered when the system also contains a predator that feeds on bacteria. Moreover, when the environment contains antibiotics, the survival of resistance is dependent on the resistance mechanism. When bacteria can help their contemporaries to degrade antibiotics, resistance is maintained by only a fraction of the community. On the other hand, when bacteria cannot help others, then all bacteria remain resistant. The concentration of the antibiotic played a less notable role than the antibiotic used. This report shows that the survival of antibiotic resistance in bacterial communities represents a complex process where many factors present in real-life systems define whether or not resistance is actually lost.

In contrast to earlier assumptions, there is now mounting evidence for the role of tundra soils as important sources of the greenhouse gas nitrous oxide (N2O). However, the microorganisms involved in the cycling of N2O in these soils remain largely uncharacterized. In this study, we manually binned and curated 541 metagenome-assembled genomes (MAGs) from tundra soils in northern Finland. We then searched for MAGs encoding enzymes involved in denitrification, the main biotic process driving N2O emissions. Denitrifying communities were dominated by poorly characterized taxa with truncated denitrification pathways, i.e. lacking one or more denitrification genes. Among these, MAGs with the metabolic potential to produce N2O comprised the most diverse functional group. Re-analysis of a previously published metagenomic dataset from soils in northern Sweden supported these results, suggesting that truncated denitrifiers are dominant throughout the tundra biome.

Background In contrast to earlier assumptions, there is now mounting evidence for the role of tundra soils as important sources of the greenhouse gas nitrous oxide (N2O). However, the microorganisms involved in the cycling of N2O in this system remain largely uncharacterized. Since tundra soils are variable sources and sinks of N2O, we aimed at investigating differences in community structure across different soil ecosystems in the tundra. Results We analysed 1.4 Tb of metagenomic data from soils in northern Finland covering a range of ecosystems from dry upland soils to water-logged fens and obtained 796 manually binned and curated metagenome-assembled genomes (MAGs). We then searched for MAGs harbouring genes involved in denitrification, an important process driving N2O emissions. Communities of potential denitrifiers were dominated by microorganisms with truncated denitrification pathways (i.e., lacking one or more denitrification genes) and differed across soil ecosystems. Upland soils showed a strong N2O sink potential and were dominated by members of the Alphaproteobacteria such as Bradyrhizobium and Reyranella. Fens, which had in general net-zero N2O fluxes, had a high abundance of poorly characterized taxa affiliated with the Chloroflexota lineage Ellin6529 and the Acidobacteriota subdivision Gp23. Conclusions By coupling an in-depth characterization of microbial communities with in situ measurements of N2O fluxes, our results suggest that the observed spatial patterns of N2O fluxes in the tundra are related to differences in the composition of denitrifier communities.

Global warming changes the activity of soil microbial communities in high latitudes, which might result in higher greenhouse gas emissions. However, these microbial processes involved in GHG production and consumption are not thoroughly understood. We analyzed 116 soil metatranscriptomes from 73 tundra sites and investigated how bacterial and archaeal communities and their functions vary horizontally (i.e. vegetation type) and vertically (i.e. topsoil organic and mineral layers) during the summer season, in soil types that differed in pH, moisture, soil organic matter (SOM), and carbon and nitrogen content. Active microbial communities were significantly different in the organic and mineral soil layers. Additionally, the communities differed significantly between the different vegetation types both in the organic and mineral layers. Various plant polymer degraders were particularly active in shrub-dominated ecosystems with high SOM and low pH, less known mixotrophic groups (such as Chloroflexi) were active lower SOM and higher pH. Additionally, we detected transcripts of alphaproteobacterial methanothrophs, which potentially moderate methane release from tundra soils in deeper soil layer. Our results provide new insights into the diversity and activity of microbial communities of high latitudes under climate change.

Due to climate change, increased microbial activity in high-latitude soils may lead to higher greenhouse gas (GHG) emissions. However, microbial GHG production and consumption mechanisms in tundra soils are not thoroughly understood. To investigate how the diversity and functional potential of bacterial and archaeal communities vary across vegetation types and soil layers, we analyzed 116 soil metatranscriptomes from 73 sites in the Finnish sub-Arctic. Meadow soils were characterized by higher pH and lower soil organic matter (SOM) and carbon/nitrogen ratio. In contrast, dwarf shrub-dominated ecosystems had higher SOM and lower pH. Although Actinobacteria, Acidobacteria, Alphaproteobacteria, and Planctomycetes were dominant in all communities, there were significant differences at the genus level between vegetation types; plant polymer degrading groups were more active in shrub-dominated soils than in meadows. Given that climate-change scenarios predict the expansion of shrubs at high latitudes, our results indicate that tundra soil microbial communities harbor potential decomposers of increased plant litter, which may affect the rate of carbon turnover in tundra soils. Additionally, transcripts of methanotrophs were detected in the mineral layer of all soils, which may moderate methane fluxes. This study provides new insights into possible shifts in tundra microbial diversity and activity due to climate change.