Study On Screening And The Role Forming Crust Of Desert Biological Crusting Microorganism

Microbial crust is the primary stage of biological soil crust.Some studies have shown that some microorganisms have the function to promote the formation of biological crusts.In this study,samples?36°31'N,110°08'E?were taken from the well-developed sand fixation sites in Zhongwei project area of"Ningxia Yellow River east bank sand prevention and control forestry project".One year grass grid fixed area,five years grass grid fixed area,ten years grass grid fixed area and Zhongwei sand fixation forest farm were selected as sample plots,which were distributed on both sides of Baolan railway.The microorganisms which could promote the formation of biological crusts were separated from the samples and their function of formation of biological crusts was determined.1.Six hundred and thirty-one strains of bacteria were isolated from the samples of sand crusts.Two strains with the function of forming biological crusts were obtained,labeled ZX1 and ZX16,respectively.The results showed that both ZX1 and ZX16 could form stable crusts.Both ZX1 and ZX16 were identified as Bacillus megaterium by 16S rRNA.2.The results of fermentation optimization experiment showed that the optimal growth temperature of ZX1 is 38^°C,the optimal carbon source,nitrogen source and inorganic salt for ZX1 are glucose,yeast powder and FeSO₄,respectively.The optimal growth temperature of ZX16 is 36^°C,and the optimal carbon source,nitrogen source and inorganic salt of ZX16 are glucose,beef extract and FeSO₄,The number of bacteria increased by 21%after using the optimized medium.3.The results showed that there was no significant difference between ZX1 and ZX16 in the function of biological crust formation.The function of biological crust formation of ZX1 and ZX16 was positively correlated with the amount and concentration of bacterial solution,and it reached the maximum value of the function of biological crust formation when both ZX1 and ZX16 were added into the sand for9 days.Conclusion:Both ZX1 and ZX16 have certain function of biological crust formation,and the function was relatively stable.This experiment has laid a foundation for biological crusting in artificial desert crust.