Rhizosphere bacteria affected by transgenic potatoes with antibacterial activities compared with the effects of soil, wild-type potatoes, vegetation stage and pathogen exposure

Abstract

A greenhouse experiment was performed to analyze a potential effect of genetically modified potatoes expressing antibacterial compounds (attacin/cecropin, T4 lysozyme) and their nearly isogenic, nontransformed parental wild types on rhizosphere bacterial communities. To compare plant transformation-related variations with commonly accepted impacts caused by altered environmental conditions, potatoes were cultivated under different environmental conditions, for example using contrasting soil types. Further, plants were challenged with the blackleg pathogen Erwinia carotovora ssp. atroseptica. Rhizosphere soil samples were obtained at the stem elongation and early flowering stages. The activities of various extracellular rhizosphere enzymes involved in the C-, P- and N-nutrient cycles were determined as the rates of fluorescence of enzymatically hydrolyzed substrates containing the highly fluorescent compounds 4-methylumbelliferone or 7-amino-4-methyl coumarin. The structural diversity of the bacterial communities was assessed by 16S rRNA-based terminal restriction fragment length polymorphism analysis, and 16S rRNA gene clone libraries were established for the flowering conventional and T4 lysozyme-expressing Desirée lines grown on the chernozem soil, each line treated with and without E. carotovora ssp. atroseptica. Both genetic transformation events induced a differentiation in the activity rates and structures of associated bacterial communities. In general, T4 lysozyme had a stronger effect than attacin/cecropin. In comparison with the other factors, the impact of the genetic modification was only transient and minor, or comparable to the dominant variations caused by soil type, plant genotype, vegetation stage and pathogen exposure.

Antibiotic-resistant soil bacteria in transgenic plant fields

“…Indeed, rhizospheric bacterial diversity is affected more by soil texture or growing season than by cultivation of transgenic varieties (32,34). In contrast, genetically modified potatoes expressing antibacterial compounds were observed to induce different microbial activity rates and structures (35). However, in that study, the impact of the genetic modification cannot be correlated to the transgenic trait, but rather to the plant genotype as the traditional corn was not the isogenic variety of the Bt corn.…”

Exogenous glucosinolate produced by Arabidopsis thaliana has an impact on microbes in the rhizosphere and plant roots

“…Concerns have been raised about the environmental impact associated with genetically modified organisms particularly GM crop. Variable and transient impacts on non-target microorganisms were already shown (De Vries et al, 1999;Lottmann et al, 2000;Dunfield and Germida, 2003;Castaldini et al, 2005;Rasche et al, 2006). We show here that manipulation of glucosinolate content in Brassicaceae could have some repercussions on the microbial community in their close soil environment.…”

Seasonality and resource availability control bacterial and archaeal communities in soils of a temperate beech forest

“…Analysis of variance combined with post hoc Tukey-B tests (SPSS for Windows, version 11.7, SPSS Inc., Chicago, IL, USA) was performed according to Rasche et al (2006) to determine significant treatment effects (tree girdling, seasonality) on abundance and community structure of the investigated microbial groups and functional genes. Pearson's linear correlation coefficients were calculated for assessing significant relations between microbial abundance and geochemical parameters (SPSS for Windows).…”