Genomic Insights into the Polysaccharide-Degrading Potential of Rhizosphere-Associated Niallia sp. M35 Isolated from Saline Soils in the Aydarkul Lake Region

The aim of this study was to obtain culturable bacterial isolates, which are resistant to heat and salt stress, from saline soil samples enriched with plant residues, collected in the coastal zone of Lake Aydarkul (Uzbekistan). When all the 21 isolates, belonging to the family Bacillaceae, obtained in a cultivation medium with 60 g/L salinity, were tested for the ability to degrade plant polysaccharides, such as pectin and hemicellulose (xylan), the new isolate, Niallia sp. M35, was selected as the most interesting for application in plant residues hydrolysis under salt stress. The strain was actively growing on citrus pectin and birchwood xylan, degrading 46 ± 9 and 71 ± 5% of added polysaccharides, respectively. Genome sequencing revealed a very broad spectrum of carbohydrate-active enzymes (CAZymes), including 96 glycosyl hydrolases, as well as two extracellular polysaccharide lyases of families 8 and 11. Complete pathways of rhamnogalacturonan and xylan degradation were revealed in the M35 genome. Moreover, this isolate possessed the complete genomic potential for the mineralization of other polysaccharides. Overall, our data indicate that Niallia sp. M35 exhibits versatile metabolic and degradation potential useful not only for various biotechnological applications but also representing an important resource for the recycling of plant residues, thereby increasing the fertility of saline soils typically depleted in organic matter.