Isolation, screening, identification, and characterization of arsenic resistant plant growth promoting rhizobacteria isolated from Pennisetum purpureum

Abstract

Microbes that can progress plant productivity and health are recognized as PGPR. Rhizobacteria perform a main role in the phytoremediation process by increasing phytoremediation efficacy, thus the need to identify the superior rhizobacteria has been gaining serious attention. In the present study, Pennisetum purpureum were exposed to a series of As-polluted sand including control (0, 5, 20, 40, 60, and 80 mg kg−1) in plastic crates in a greenhouse environment. Four weeks after exposure, the plants could survive with toxicity of As pollution up to 40 mg kg−1. A total of 22 groups of bacterial isolates were confirmed based on the morphological characteristics, biochemical characteristics, and Gram staining. Preliminary and secondary As screening tests were also conducted. Identification was directed utilizing a molecular identification system. After As screening tests, 17 rhizobacterial isolates presented possible tolerance to As. Based on the molecular identification, 9 bacterial isolates were confirmed which were two [28N A UPM (Bacillus subtilis) and 28N U UPM (Bacillus australimaris)] gram-positive and seven [28N H UPM (Burkholderia seminalis), 28N G UPM (Enterobacter cloacae), 28N D UPM (Pseudomonas stutzeri), 28N I UPM (Sphingobacterium thalpophilum), 28N M UPM (Proteus mirabilis), 28N K UPM (Neisseria perflava) and 28N S UPM (Pseudomonas boreopolis)] gram-negative bacteria. All the nine identified rhizobacteria showed excellent results in terms of PGP characters. Among them, 28N U UPM (Bacillus australimaris) performed the highest PGP traits. The findings revealed that these highly As-resistant rhizobacteria have the potential to produce PGP traits and can help P. purpureum growth and productivity.