Abstract
The extracellular polysaccharide (EPS) matrix embedding microbial cells and soil particles plays an important role in the development of biological soil crusts (BSCs), which is widely recognized as beneficial to soil fertility in dryland worldwide. This study examined the EPS-producing bacterial strains YL24-1 and YL24-3 isolated from sandy soil in the Mu Us Desert in Yulin, Shaanxi province, China. The strains YL24-1 and YL24-3 were able to efficiently produce EPS; the levels of EPS were determined to be 257.22 μg/mL and 83.41 μg/mL in cultures grown for 72 h and were identified as Sinorhizobium meliloti and Pedobacter sp., respectively. When the strain YL24-3 was compared to Pedobacter yulinensis YL28-9T using 16S rRNA gene sequencing, the resemblance was 98.6% and the strain was classified as Pedobacter sp. using physiological and biochemical analysis. Furthermore, strain YL24-3 was also identified as a subspecies of Pedobacter yulinensis YL28-9T on the basis of DNA–DNA hybridization and polar lipid analysis compared with YL28-9T. On the basis of the EPS-related genes of relevant strains in the GenBank, several EPS-related genes were cloned and sequenced in the strain YL24-1, including those potentially involved in EPS synthesis, assembly, transport, and secretion. Given the differences of the strains in EPS production, it is possible that the differences in gene sequences result in variations in the enzyme/protein activities for EPS biosynthesis, assembly, transport, and secretion. The results provide preliminary evidence of various contributions of bacterial strains to the formation of EPS matrix in the Mu Us Desert.
Highlights
Biocrusts are a profitable and functional soil-focused structure that is crucial to the promotion of soil succession, improvement of surface soil moisture, and prevention of soil erosion
This result showed that strain YL24-1 was not a potential novel bacterial species according to the 97% sequence similarity criterion
According to the phylogenetic analysis based on the 16S rRNA gene sequence, the lengths of the 16S rRNA gene sequences of the strain YL24-3 and the strain YL289 were 1484 bp and 1520 bp, respectively, and strain YL24-3 was found to be affiliated with the genus Pedobacter, showing the highest sequence similarity to Pedobacter yulinensis YL28-9T (98.6% sequence similarity) [19]
Summary
Biocrusts are a profitable and functional soil-focused structure that is crucial to the promotion of soil succession, improvement of surface soil moisture, and prevention of soil erosion. EPSs have been shown in studies to have a wide range of biological functions, including preventing cell dehydration, protecting cells, and lowering external pressure. This substance can absorb nutrients from the living environment and is part of the general microbial technique used by oligotrophic bacteria to live in nutrient-deficient environments [7]. Cells can defend themselves from stress such as high pH, antibiotics, or dehydration by secreting EPS into the environment In addition to their natural functions, polysaccharides have long been used in a variety of industrial and technological applications, including cosmetics, food, feed, and pharmaceutics [15]. The associated extracellular polysaccharide-producing genes were identified preliminarily following the design of primers to amplify the genes and TA cloning verification
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
