Autecology of a genetically modified fluorescent pseudomonad on sugar beet

Abstract

The survival, dispersal and impact of a genetically modified microorganism (GMM) in the phyllosphere of glasshouse grown sugar beet was investigated. The GMM, Pseudomonas fluorescens SBW25EeZY6KX (lacZY and kanr‐xylE) derived from a bacterium originally isolated from field grown sugar beet, was introduced as a seed inoculum. It survived in the phyllosphere throughout the 531‐day study on plants growing in field soil. The bacterium was highly competitive, in some samples representing the largest bacterial population isolated. The GMM also established on a broad range of other plant species when introduced on the seed. Fluctuations in the numbers of GMM correlated with those of the indigenous pseudomonad population, indicating the organism had not been adversely affected by the addition of novel genes. Inoculum density had no significant effect on the number of GMMs detected in the phyllosphere, although it affected the population size in the rhizosphere. The GMM persisted in fallow soil for at least 10 days and subsequently colonised germinating untreated plants. Limited potential for GMM dispersal from the phyllosphere was detected using physical means of transfer, although moisture assisted dispersal from colonised plants. GMM transfer to other plant species growing between treated plants was detected. Insects captured in the glasshouse carried the GMM, indicating a potential for long distance dispersal. Introduction of the wild‐type and GMM on the seed had a transient impact on the number and composition of the bacterial community colonising treated plants. Assessment of community diversity by fatty acid methyl ester (FAME) content of bacterial isolates revealed that the GMM had less impact on the bacterial community than the wild‐type. Both organisms competitively excluded Enterobacteriaceae taxa, although this impact was attributed in part to the low taxa diversity that developed in the artificial conditions of the glasshouse. Instances of the GMM undergoing phenotypic change after introduction on the seed were detected by FAME analysis.

Specific interactions between arbuscular mycorrhizal fungi and plant growth-promoting bacteria: as revealed by different combinations

“…The wheat plant yield was significantly negatively impacted by the presence of SBW25 on healthy plants. Strain SBW25 was originally isolated from the sugar beet phyllosphere (Thompson et al, 1995) and later inoculated onto wheat plants in several greenhouse and field studies. In previous studies, it was shown that SBW25 readily colonizes roots, shoots and seeds of wheat (Unge & Jansson, 2001;Jäderlund et al, 2008).…”

“…Beneficial PGPR included in this study were P. fluorescens SBW25 (Thompson et al, 1995) andP. brasilensis PB177 (von der Weid et al, 2002).…”

“…There is also evidence that combined interactions between AM fungi and bacteria can enhance plant growth (see Artursson et al, 2006, for a review), and that some of these interactions may be very specific . Two examples of plant growth-promoting rhizobacteria (PGPR) are Pseudomonas fluorescens SBW25 (Thompson et al, 1995) and Paenibacillus brasilensis PB177 (von der Weid et al, 2002). Both of these bacteria have previously been shown to attach to vital AM fungal hyphae (Toljander et al, 2006), and P. brasilensis PB177 inoculation was shown to increase the extent of root colonization by the AM fungus Glomus mosseae on clover (Artursson, 2005).…”

Monitoring a genetically modified Pseudomonas sp. released on pine leaves reveals concerted successional patterns of the bacterial phyllospheric community

“…Other studies report survival for over 531 days of a genetically modified Pseudomonas fluorescens on sugarbeet leaves in a greenhouse (Thompson et al 1995a(Thompson et al , 1995b. However, the presence of a positive signal, as well as the insecticidal effect remaining on branches, does not necessarily translate in to corresponding survival of the strain released, as the first phenomenon also may be due to its remaining DNA, and the second to the persisting Cry9a toxin crystals.…”

Use of a novel nonantibiotic triple marker gene cassette to monitor high survival of Pseudomonas fluorescens SBW25 on winter wheat in the field

“…Pseudomonas fluorescens SBW25 was isolated in 1989 from the phyllosphere of sugar beet in the United Kingdom (Thompson et al, 1995a). This bacterium is an effective colonizer of the rhizosphere and phyllosphere of a number of different plants such as cornflower, pea and wheat (Thompson et al, 1995a, b).…”