Enhancing plant growth under municipal wastewater irrigation by plant growth promoting rhizospheric Bacillus spp

Abstract

Wastewater treatment is often addressed with phytoremediation. However, excessive amount of salts in wastewater can cause toxicity in plants. To mitigate the problem, plant growth-promoting rhizobacteria (PGPR) can be used to promote plant growth under this stressful condition. This research aimed to screen PGPR for their application in enhancing plant growth under municipal wastewater irrigation and to identify their characteristics. We isolated PGPR from soil contaminated with municipal wastewater and from weeds grown around solid waste dump. The isolates were tested in vitro for their plant growth promotion characteristics such as phosphate solubilization, auxin phytohormone and siderophore production. The isolates showing high ability of siderophore production were chosen and tested for plant growth promotion in vivo. Inoculation of certain isolates, including Bacillus amyloliquefaciens isolate WE15, to Chinese kale increased its root and shoot weight when it was irrigated with sterile tap water or municipal wastewater containing high concentration of ammonium, magnesium, and iron ions. Additionally, Bacillus firmus isolate WD19 reduces iron ions in culture medium. Thus, B. amyloliquefaciens isolate WE15 and B. firmus isolate WD19 are potential candidates for phytoremediation enhancement of iron ions contaminated soil. © 2018 The Authors