Structural and functional responses of microbial community with respect to salinity levels in a coastal reclamation land

Investigating microbial responses to soil salinity is of great importance for better understanding of microbial adaptation in reclaimed land. In the present study, a thorough evaluation of soil characteristics was coupled with pyro-sequencing to characterize the bacterial and fungal community structure and diversity of soils with different salinity levels. Soil samples were collected from a reclaimed land and grouped into non-saline (NS) and highly saline (HS) soils based on electrical conductivity (ECse). Principal coordinate analysis (PCoA) demonstrated that bacterial and fungal communities from HS soils clustered separately from NS soils, implying differences in their taxonomic composition. Bacterial phyla Proteobacteria, Actinobacteria and Verrucomicrobia were substantially abundant in HS soils. At species level, Geobacter sp., Candidatus Koribacter and Candidatus Solibacter were dominant in HS soils. Fungal phylum Ascomycota along with its related family Pseudeurotiaceae and genus Pseudogymnoascus sp. were significantly abundant in HS soils. Distance based Linear Model (DistLM) revealed sodium content [Na+] (P < 0.01) and soil ECse (P < 0.001) to be the foremost factors contributing to the shifts in bacterial and fungal community composition respectively. The predicted functional profile analysis revealed bacterial community members in HS soils were characterized by higher abundance of genes encoding proteins and enzymes imparting salinity tolerance (molecular chaperone DnaK, ATP-dependent Clp protease, OmpA-OmpF porins) and synthesizing osmoprotectants (proline and trehalose). The results enabled us to identify the dominant indigenous microflora of the HS soils and their possible adaptation mechanisms, which is believed to provide better understanding for exploring ecological and evolutionary responses of microbes in saline ecosystem.