Research On Population Resource Of Bacteria With ACC Deaminase Activity In Guizhou Karst Landforms

Guizhou Karst landscape is the center of the Karst area in Southwestern China,it has unique soil development and ecological environment.The unique ecosystem makes it possible to contain beneficial microbial populations that are more adaptable to environmental stress,these microorganisms play an important role in the degradation and restoration of karst soils.1-Aminocyclopropane-l-carboxylic acid(ACC)deaminase is capable of degrading ethylene precursors and thus helps plant growth,bacterias with ACC deaminase activity have plant growth promoting effects.This study collected 159 soil samples from five typical Karst landscape regions in Guizhou.First,measured the physical and chemical properties of the soils and counte the number of culturable bacteria in the soil by using a dilution coating method,to explore the influnce of soil properties on the soil bacteria.Then,isolated and identified the bacteria with ACC deaminase from 159 soil samples,and had a preliminary study of these beneficial microbial resources from the aspects of quantitative distribution,species characteristics,colony morphology,gram staining,physiological biochemistry,and enzyme activity.Finally,conducted a pot experiment to investigate the growth-promoting effects under different water conditions of the strain AL30ADF120 that have highest enzyme activity.The results were as follows:(1)The contents of metal elements in the five regions were similar,with the Fe was most,followed by Ca and Ti;The soil pH is basically neutral;The soil moisture content was Zhijin>Pogang>Anlong>Xingyi>Qingshuihe,with an average of 16.9%,and the overall water content was low;The content of soil organic matter was Pogang>Anlong>Xingyi>Qingshuihe>Zhij in;The numbers of bacteria in Pogang,Qingshuihe,Anlong,Zhijin and Xingyi are 6.88×106cfu/g,2.89×105cfu/g,4.47×109cfu/g,9×104cfu/g,4.44×108 cfu/g respectively;The number of bacteria in the Pogang area was significantly positively correlated with soil P element and soil organic matter content,overall,soil Rb element content and elevation had a significant positively correlation with the amount of bacteria in the soil.(2)Isolated and purified 500 strains of ACC deaminase producing bacteria,of which 188 strains were tested for 16S rDNA sequences,the NCBI comparisons showed that there were 14 genera and 63 species.The dominant bacteria were Pseudomonas and Burkholderia,Pseudomonas gessardii was the most common,all bacteria were classified as Proteobacteria and Actinomycetes.The colony shape of 63 strains was mostly round;the colony color of the strains was almost white;most of the strains were rod-shaped and short rod-shaped,and a few were spherical;most of the strains were Gram-positive bacteria.(3)Among the 63 strains of ACC deaminase producing strains,62 strains had ACC deaminase activity greater than 20 nmol ?-KA/(mgPr·h).AL30ADF120(Cup.oxalaticus)showed the highest ACC deaminase activity of 3.641 U/mg,followed by XY08ADF4(Var.paradoxus),and the enzyme activity was 2.204 U/mg.The pot experiment showed that the strain AL30ADF120 had obvious growth-promoting effect on the growth of corn under 35%soil relative water contents.And at the cell level,it promoted the elongation of maize root cells under 35%soil relative water contents.This paper has primarily explored the soil characteristics and beneficial microbial resources with ACC deaminase activity of karst landforms in Guizhou,and has important implications for the protection and utilization of karst landforms and the development of microbial fertilizers.