Isolation and characterization of two plant growth-promoting bacteria from the rhizoplane of a legume (Lupinus albescens) in sandy soil

Adriana Giongo,Adriana Ambrosini,Marcos Roberto Stroschein,Luciano Kayser Vargas,Maria Helena Bodanese-Zanettini,Luciane Maria Pereira Passaglia,Anelise Beneduzi,Flávio Luiz Eltz

doi:10.1590/s0100-06832010000200009

Abstract

Two bacterial strains that amplified part of the nifH gene, RP1p and RP2p, belonging to the genus Enterobacter and Serratia, were isolated from the rhizoplane of Lupinus albescens. These bacteria are Gram-negative, rod-shaped, motile, facultative anaerobic, and fast-growing; the colonies reach diameters of 3-4 mm within 24 h of incubation at 28 ºC. The bacteria were also able to grow at temperatures as high as 40 ºC, in the presence of high (2-3 % w/v) NaCl concentrations and pH 4 -10. Strain RP1p was able to utilize 10 of 14 C sources, while RP2p utilized nine. The isolates produced siderophores and indolic compounds, but none of them was able to solubilize phosphate. Inoculation of L. albescens with RP1p and RP2p strains resulted in a significant increase in plant dry matter, indicating the plant-growth-promoting abilities of these bacteria.

Highlights

It is widely accepted that rhizosphere and rhizoplane microorganisms can influence plant growth and development
Aiming to identify some of the plant growthpromoting bacteria (PGPB) that inhabit the rhizoplane of L. albescens, small root pieces of plants cultivated in a sandy area of an experimental field in Alegrete, Rio Grande do Sul, Brazil, were collected
Five bacterial strains were randomly selected from this PGPB collection

Summary

Introduction

It is widely accepted that rhizosphere and rhizoplane microorganisms can influence plant growth and development. The term plant growthpromoting bacteria (PGPB) was proposed to designate rhizobacteria that enhance plant growth by other ways (Bashan & Holguin, 1998). Bacteria around plant roots perform a wide range of metabolic activities and are able to make use of a wide range of low molecular mass organic compounds and of some more complex compounds as C and energy sources (Misko & Germida, 2002). These microorganisms play major roles in nutrient transformation and element cycling and influence the availability of these nutrients for plant uptake (Dunfield & Germida, 2001)

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