The use of bioluminescence as a reporter to study the adherence of the plant growth promoting rhizopseudomonads 7NSK2 and ANP15 to canola roots

Abstract

The adherence of the plant growth promoting rhizopseudomonads Pseudomonas aeruginosa 7NSK2 and Pseudomonas fluorescens ANP15 to canola roots (Brassica campestris L. c.v. Tobin) was examined by means of a bacterial bioluminescence system. The bioluminescence broad host range vector pDLUX-I was constructed from pLAFR-I and the lux A–E genes of Vibrio fischerii. This vector was conjugally transferred into the plant growth promoting rhizopseudomonads 7NSK2 and ANP15. The transformed strains were constitutively bioluminescent at an optimal temperature of 21 °C. The measured bioluminescence was directly proportional to the density of the bacteria in suspension and was the same for both planktonic and sessile bacteria adhering to the root surface. The adherence of the plant growth promoting rhizopseudomonads was proportional to the density of the bacterial inoculum, approached saturation at 60 min, and was reversible. The kinetics of the microbial adhesion was described by a Freundlich isotherm suggesting that the adherence of the bacteria to the canola root surface does not involve specific receptors. We conclude that the pDLUX-I vector is an easy and accurate way to study the kinetics of microbial adherence to the rhizoplane.Key words: rhizopseudomonads, bioluminescence, adhesion, plant growth promotion.not available