A study on an oligotrophic bacteria and its ecological characteristics in an arid desert area

摘要

An oligotrophic bacterium was isolated from the biological soil crust underlayer in the Xinjiang Gurbantunggut Desert. It was numbered SGB-5, G~+. Cell size is (0.328—0.746) μm × (0.171— 0.240) μm. Raised colony is white, roundness and its diameter is 5 mm. The strain is a facultative aerobe. It was able to grow in conditions of 1 —15 mg·C·L~(-1) culture medium at 10—50℃. The strain's optimum growth temperature is 37℃. The range of its optimum growth pH is 8—9. A large amount of extracellular mucopolysaccharide was secreted during growth. The chemical composition of this mucopolysaccharide consists of arabinose, X sugar, glucose, galactose and mannitol. Mole ratio of these sugars is 1:14:19:6:14. The viscosity of the mucopolysaccharide can reach 6300 mPa-s, when the strain is cultivated for 72 h. After the culture solution in which viscosity was 1500 mPa-s was sprinkled on the quicksand surface, 6 mm bacteria crust of conglutinating sand was formed. This crust could not only stabilize sand, but could also potentially slow the rate of the soil water evaporation.