Abstract:[Background] Biological soil crusts play a crucial role in windbreak and sand fixation, and oligotrophic microorganisms adaptive to nutrient-poor conditions are the main contributors to crust formation in deserts. [Objective] To investigate the sand-fixing function of Paenarthrobacter sp. AMU7 cultured with different carbon sources and analyze its exopolysaccharides, thus providing elite microbial resources for ecological management of deserts. [Methods] The oligotrophic sand-fixing strain AMU7, isolated and screened from the moss crust sample of Mu Us Sandy Land, was identified by 16S rRNA gene sequencing, morphological observation, and physiological and biochemical tests. Strain AMU7 was cultured in the media with different carbon sources. The crust thickness and pressure-bearing capacity were measured with a vernier caliper and a pressure gauge, respectively, to evaluate the effect of strain AMU7 in promoting crust formation. The exopolysaccharides in fermentation broth samples under different treatments were measured by the phenol-sulfuric acid method and the sand-fixing effects were determined, on the basis of which the types and location of the sand-fixing substances produced by strain AMU7 were determined. [Results] Strain AMU7 was identified as Paenarthrobacter sp. AMU7. With glucose as the carbon source, strain AMU7 formed stable crusts with the thickness consistently exceeding 1.74 cm. The 24 h pressure-bearing capacity of the crusts produced by the fermentation broth of strain AMU7 was stably over 25 N higher than that by the glucose synthetic medium (control), which indicated that strain AMU7 significantly enhanced the compressive strength of the crust. The sand-fixing substances of Paenarthrobacter sp. AMU7 were not secondary metabolites secreted in large quantities during the stable growth phase, but exopolysaccharides produced in the extracellular mucous layer formed during the rapid proliferation and growth of bacterial cells. Moreover, the content of exopolysaccharides was higher in the mucous layer during the early logarithmic growth phase. [Conclusion] Paenarthrobacter sp. AMU7 has an efficient sand-fixing capability, demonstrating significant application potential in the ecological management of deserts.
