Soil microbial counts and identification of culturable bacteria in an extreme by arid zone
Su, J.(Chinese Academy of Sciences, Lanzhou (China). State Key Lab. of Frozen Soil and Engineering) | Wu, Y.(Chinese Academy of Sciences, Lanzhou (China). State Key Lab. of Frozen Soil and Engineering) | Ma, X.(Chinese Academy of Sciences, Lanzhou (China). State Key Lab. of Frozen Soil and Engineering) | Zhang, G.(Lanzhou Univ. (China). Key Lab. of Arid and Grass Agro-Ecology of the Ministry of Education) | Feng, H.(Chinese Academy of Sciences, Lanzhou (China). State Key Lab. of Frozen Soil and Engineering)E-mail:[email protected] | Zhang, Y.(Chinese Academy of Sciences, Lanzhou (China). State Key Lab. of Frozen Soil and Engineering)
Sixteen samples of two soil cores (about 550 and 180 cm in depth) were drilled in the lower reach of Heihe river basin (northwest of China) in order to illustrate soil microbial characteristics in an arid environment. Soil water, organic matter and N concentrations, pH, direct cell counts, and culturable microorganism counts were evaluated. The total cell concentration varied from 19 to 1,120/microg, culturable bacteria counts from 0.2 to 10.9 per microg soil. These values were statistically significantly correlated with the concentrations of soil water, organic matter and total N as well as with the amount of surface vegetation. This partly explained the larger bacteria number in the deep first core than in the shallow one. Thirty-two colonies out of 228 were selected for 16S rDNA amplification, sequencing and molecular identification. These 32 isolates were affiliated to 5 major groups of bacteria as follows: alpha-Proteobacteria, beta-Proteobacteria, gamma-Proteobacteria, the high G+C gram-positive bacteria, the low G+C gram-negative bacteria, and the Cytophaga-Flexibacter-Bacteroides group. Twenty-eight species were rod- or short rod shaped, 4 species were cocci. In conclusion, the microbial community in an extremely arid environment was abundant and its density varied depending on soil chemicophysical properties.
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