Isolation, identification, and growth-promotion function of Streptomyces sp. in wetland rhizosphere

Abstract

Wetlands are the most biologically diverse ecosystems on Earth. The isolation of Streptomyces strains from wetlands is helpful to study their diversity and functions in such habitats. In this study, six strains of Streptomyces were isolated from the rhizosphere soil of three plant species in Huaxi Wetland of Guiyang and were identified as Streptomyces galilaeus, S. avidinii, S. albogriseolus, S. hydrogenans, S. spororaveus, and S. cellulosae, respectively. The six strains all solubilized phosphate, fixed nitrogen, and produced ACC deaminase and siderophores, and four strains also secreted indole-3-acetic acid. The six strains grew well in the ranges of 0%–3% NaCl, 0%–25% PEG, and pH 5.0–10.0, which showed that the screened strains were tolerant to certain degrees of salinity, drought, and acidic/alkaline pH stress. In addition, the S. avidinii WL3 and S. cellulosae WL9 strains (especially the former) significantly promoted seed germination of mung bean, pepper, and cucumber. A pot experiment further showed that WL3 significantly promoted the growth of cucumber seedlings compared with that of the control, with plant height, root length, lateral root number, and fresh weight increased by 104.99%, 49.99%, 94.12%, and 82.86%, respectively. Thus, strains of six species of Streptomyces with multiple plant growth-promoting characteristics were isolated from the wetland. These results lay a foundation for their potential use as microbial agents and seed-coating treatments.

An update about plant growth promoting Streptomyces species

“…Thus, ACC is a non-protein amino acid that functions as ethylene's direct precursor. These physiological mechanisms are crucial for biocontrol properties of Streptomyces such as antifungal activity of Streptomyces hydogenans was found associated with the high rates for synthesizing IAA and thoroughly utilized ACC deaminase [11,12].…”