Isolation and identification of hydrogen-oxidizing bacteria producing 1-aminocyclopropane-1-carboxylate deaminase and the determination of enzymatic activity

Abstract:

Abstract: [Objective] We used Medicago sativa rhizosphere in Shaanxi province of China to isolate and identify hydrogen-oxidizing bacteria that produced ACC (1-aminocyclopropane-1-carboxylate) deaminase, and then studied the mechanism why they can promote the growth of plants. [Methods] Hydrogen-oxidizing bacteria were isolated by gas-cycle incubation system. We studied the morphological character, physiological characteristics, 16S rDNA sequence analysis and built the phylogenic tree. Thin layer chromatography was used to isolate the strain that produced ACC deaminase. Ninhydrin reaction was used to test the enzyme activity. [Results] In total 37 strains were isolated, 8 of which could oxidize H2 strongly and grow chemolithoautotrophically. We initially identified them as hydrogen-oxidizing bacteria. Only strain WMQ-7 produced ACC deaminase among these 8 strains. Morphological and physiological characteristics analysis showed that strain WMQ-7 was essentially consistent with Pseudomonas putida. The 16S rDNA sequence analysis (GenBank accession number EU807744) suggested that strain WMQ-7 was clustered together with Pseudomonas putida in phylogenetic tree, with the sequence identity of 99 %. Based on all these results, strain WMQ-7 was identified as Pseudomonas putida. The enzyme activity of strain WMQ-7 was 0.671 U/μg. [Conclusion] A strain producing ACC deaminase was identified and tested.