Screening, Resistance and Growth-Promoting Effect of Endophytic Bacteria with ACC Deaminase Activity Isolated from Soybean Nodules

Objective:We screened endophytic bacteria containing ACC (1-aminocyclopropane-1-carboxylate) deaminase from soybean nodules, and evaluated salt-alkaline resistance, phylogenetic status and the growthpromoting of representative strain.Methods:The features of strains producing ACC deaminase were determined by using the ACC as a sole nitrogen source, adopting standard curve method, colorimetric method, solid medium screening method, bacterial morphology, physio-biochemical characteristics, similarity analysis of 16S rRNA gene, inoculation tests.Results:Eight endophytic bacteria containing ACC deaminase were screened from soybean nodules collected from 36 points of 13 cities (regions)in Henan province. Enzymaticactivity of DD132 was the highest (15.712 U/mg). Screened strain tolerated to medium of 4%-6% NaCl concentration. Among of them, DD165 and DD132 could tolerate 9% NaCl concentration. Five bacteria growing well under pH 11, showing that these strains had stronger alkali resistance. Eight strains containing ACC deaminase activity were affiliated to four genera: Bacillus, Enterobacter, Stenotrophomonas and Pantoea. Inoculation test showed that DD132 had a significant growthpromoting effect on wheat seedlings.Conclusions:Endophytic bacteria containing high ACC deaminase activity from soybean nodules have stronger salt-alkaline resistance. DD132 has obvious growth-promoting effect on wheat seedlings.