Increases in the abundance of microbial genes encoding halotolerance and photosynthesis along a sediment salinity gradient

[摘要] Biogeochemical cycles are driven by the metabolic activity of microbialcommunities, yet the environmental parameters that underpin shifts in thefunctional potential coded within microbial community genomes are stillpoorly understood. Salinity is one of the primary determinants of microbialcommunity structure and can vary strongly along gradients within a varietyof habitats. To test the hypothesis that shifts in salinity will also alterthe bulk biogeochemical potential of aquatic microbial assemblages, wegenerated four metagenomic DNA sequence libraries from sediment samplestaken along a continuous, natural salinity gradient in the Coorong lagoon,Australia, and compared them to physical and chemical parameters. A total of392483 DNA sequences obtained from four sediment samples were generated andused to compare genomic characteristics along the gradient. The mostsignificant shifts along the salinity gradient were in the genetic potentialfor halotolerance and photosynthesis, which were more highly represented inhypersaline samples. At these sites, halotolerance was achieved by anincrease in genes responsible for the acquisition of compatible solutes –organic chemicals which influence the carbon, nitrogen and methane cycles ofsediment. Photosynthesis gene increases were coupled to an increase in genesmatching Cyanobacteria, which are responsible for mediating CO₂ andnitrogen cycles. These salinity driven shifts in gene abundance willinfluence nutrient cycles along the gradient, controlling the ecology andbiogeochemistry of the entire ecosystem.

[学科分类] 地球化学与岩石