Stick together: Isolation and characterization of exopolysaccharide producing bacteria from degraded permafrost soils

Permafrost thaw can result in two distinct environmental landscapes (i.e. “wet condition” soils rich in ice wedges and low drainage, and “dry condition” well-drained areas with higher evapotranspiration). These different conditions influence the bacterial communities and may impact their capacity to produce exopolysaccharides (EPSs), which are crucial for bacterial survival and adaptation. This study aimed to isolate and characterize EPSs-producing bacteria from the active layer of two permafrost degrading landscapes and from undisturbed permafrost soil. A total of 54 bacterial isolates were obtained, representing three phyla: Firmicutes, Actinomycetota, and Pseudomonadota. EPSs production was assessed by determining the polysaccharide content measured as glucose equivalent, and 26 isolates were identified as potential EPSs-producers. Among the isolates, Curtobacterium oceanosedimentum, Frigoribacterium faeni , Streptomyces strains, Neobacillus bataviensis and Mesobacillus subterraneus had the highest polysaccharide yield. They were also found inhabiting in the different horizons of degraded permafrost soil and undisturbed permafrost soil, by determining their relative proportion within the total bacterial community based on 16S rRNA gene sequences similarities.