Viral lifestyles modulate prokaryotic community structure and function in thermokarst lakes

Microbes determine the fate of carbon (C) and nitrogen (N) released by rapidly thawing permafrost, with viruses that infect them mediating this process via lysis and metabolic reprogramming. However, little is known about whether and how viruses with different lifestyles modulate microbial community and ecological functions, particularly in thermokarst lakes where studies for viruses were pretty scarce. Here, we conducted metagenome deep sequencing on sediment samples obtained from 60 thermokarst lakes along a 1,100 km permafrost transect, and recovered 4,161 viral and 2,805 microbial genomes from above 3 Tb data, as well as predicted their interactions and functions. We found that viral lifestyles were coupled with microbial life-history strategies along nutrient gradients. Virus-host interactions were more specialized in temperate viruses dominant samples than those in virulent viruses prevailing samples. Further functional predictions revealed that virus-encoded auxiliary metabolic genes (AMGs) exhibited more diverse and higher abundance in virulent viruses dominant community than those in temperate viruses predominant community. What count was that viruses could reduce methane (CH4) emissions from thermokarst lakes via virus-encoded mmoB genes. Overall, these findings highlight the crucial impact of viral life-history strategies on microbial community and key ecosystem function in climate-sensitive thermokarst habitats.