Pseudomonas aeruginosa Predominates as Multifaceted Rhizospheric Bacteria with Combined Abilities of P-solubilization and Biocontrol

Abstract

Use of multifunctional plant growth promoting rhizobacteria (PGPR) for managing plant growth and health could not only facilitate higher positive effects on plants but also enable their predominant rhizospheric prevalence. While multi-functional PGPR are common, those harbouring both direct and indirect traits of growth promotion are relatively fewer. The present work aimed at isolating and characterizing the otherwise unusual multipotential PGPR with P-solubilizing ability in combination with broad-spectrum biocontrol abilities from diverse soils and analysing their relative prevalence. Primary screening yielded 50 isolates with varying P-solubilizing potential; of which only 8 showed In vitro antibiosis of E. coli. Selected 14 isolates with varying degree of P-solubilizing and antibacterial potential were evaluated for siderophore, HCN and indole-3-acetic acid (IAA) production. While all selected isolates produced HCN, 13 of them produced IAA and 10 showed siderophore production, at varying levels. Biochemical characterization of these isolates indicated that siderophore production was maximum with fluorescent Pseudomonas isolates while isolates of Enterobacteriaceae family were best IAA producers. However, molecular characterization of isolates capable of efficient P-solubilization along with strong ability to exhibit all the three biocontrol traits, identified them as Pseudomonas spp., typically P. aeruginosa. Overall, these results indicate that categorically P. aeruginosa species are likely to predominate as rhizobacteria with co-existence of discrete abilities to solubilize P as well as produce IAA, siderophore and HCN. The study also implies relatively higher metabolic versatility of P. aeruginosa species as compared to other members of fluorescent Pseudomonas family; thus, accounting for their rhizospheric abundance.

Keywords

• multipotential pgpr
• rhizospheric pseudomonas aeruginosa
• p-solubilization
• biocontrol.