Identification, functions, and growth-promoting characteristics of an endophytic bacterium from Stipagrostis pennata

Abstract:

[Background] With tenacious vitality, Stipagrostis pennata is a pioneer plant species in the desert, which features fast reproduction, high seed yield, and wide spread of seeds. [Objective] To test the growth-promoting endophytic bacteria of S. pennata. [Methods] The endophytic strain Z1 was isolated from the seeds of S. pennata and the biochemical characteristics, fermentation conditions, and growth-promoting performance were explored. [Results] The colonies of Z1 were spherical, yellow, and opaque, with small protrusions in the center and wrinkled and wet margins. Microscopy showed that it was straight rod-shaped with fine flagella on the surface and the size of (0.5-1.0) μm×(1.0-3.0) μm. The Gram staining test, indole test, oxidase test, starch hydrolysis test, V-P test, and gelatin liquefaction test all demonstrated positive results, while the methyl red test and urea hydrolysis test showed negative result. Moreover, it was identified as a Pantoea strain. Z1 produced Indole-3-acid, with the yield of 3.14 mg/L. Moreover, it can solubilize phosphorus and potassium and secrete iron carrier. The optimum fermentation conditions of Z1 are as follows: peptone as nitrogen source, soluble starch as carbon source, calcium carbonate as inorganic salt, and pH 9.0. The wheat growth-promoting effect of Z1 was obvious 10 days after the inoculation, as the leaf width, plant height, and root length were 60.0%, 13.5%, and 8.0% larger, respectively, and the leaf water content, total chlorophyll content, nitrogen content, and soluble protein of wheat seedlings were significantly increased (P<0.05). [Conclusion] Z1 is a functional bacterium with growth-promoting potential, which can be used for microbe-plant interaction and desertification control.