Testing genetically engineered potato, producing the lectins GNA and Con A, on non‐target soil organisms and processes

175

105

The introduction of transgenic plants into agricultural ecosystems has raised the question of the ecological impact of these plants on nontarget organisms, such as soil bacteria. Although differences in both the genetic structure and the metabolic function of the microbial communities associated with some transgenic plant lines have been established, it remains to be seen whether these differences have an ecological impact on the soil microbial communities. We conducted a 2-year, multiple-site field study in which rhizosphere samples associated with a transgenic canola variety and a conventional canola variety were sampled at six times throughout the growing season. The objectives of this study were to identify differences between the rhizosphere microbial community associated with the transgenic plants and the rhizosphere microbial community associated with the conventional canola plants and to determine whether the differences were permanent or depended on the presence of the plant. Community-level physiological profiles, fatty acid methyl ester profiles, and terminal amplified ribosomal DNA restriction analysis profiles of rhizosphere microbial communities were compared to the profiles of the microbial community associated with an unplanted, fallow field plot. Principal-component analysis showed that there was variation in the microbial community associated with both canola variety and growth season. Importantly, while differences between the microbial communities associated with the transgenic plant variety were observed at several times throughout the growing season, all analyses indicated that when the microbial communities were assessed after winter, there were no differences between microbial communities from field plots that contained harvested transgenic canola plants and microbial communities from field plots that did not contain plants during the field season. Hence, the changes in the microbial community structure associated with genetically modified plants were temporary and did not persist into the next field season.

Section: Discussionsupporting

confidence: 70%

mentioning

confidence: 99%

Seasonal Changes in the Rhizosphere MicrobialCommunities Associated with Field-Grown Genetically ModifiedCanola ( Brassicanapus )

Dunfield

Germida

2003

175

105

“…Several previous studies describing the effects of GMOs on the structure of microbial communities have shown that the effect is temporary and depends on the presence or absence of transgenic plants. For example, seasonal variation in the microbial community structure associated with GM plants has been shown, with no persistence into the next field season, at least according to studies on GM canola and potato (17,27). Variable differences in the microbial communities between GM and WT poplars were observed in the present study, which were dependent on the stages of poplar growth, and did not continue into the late growth stage.…”

Section: Discussionmentioning

confidence: 49%

Effect of Genetically Modified Poplars on Soil Microbial Communities during the Phytoremediation of Waste Mine Tailings

Hur

Kim

Song

et al. 2011

149

The application of transgenic plants to clean up environmental pollution caused by the wastes of heavy metal mining is a promising method for removing metal pollutants from soils. However, the effect of using genetically modified organisms for phytoremediation is a poorly researched topic in terms of microbial community structures, despite the important role of microorganisms in the health of soil. In this study, a comparative analysis of the bacterial and archaeal communities found in the rhizosphere of genetically modified (GM) versus wild-type (WT) poplar was conducted on trees at different growth stages (i.e., the rhizospheres of 1.5-, 2.5-, and 3-year-old poplars) that were cultivated on contaminated soils together with nonplanted control soil. Based on the results of DNA pyrosequencing, poplar type and growth stages were associated with directional changes in the structure of the microbial community. The rate of change was faster in GM poplars than in WT poplars, but the microbial communities were identical in the 3-year-old poplars. This phenomenon may arise because of a higher rate and greater extent of metal accumulation in GM poplars than in naturally occurring plants, which resulted in greater changes in soil environments and hence the microbial habitat.Heavy metal pollution threatening human health and the ecosystem is a growing concern worldwide (55). Excessive levels of heavy metals cause serious damage to living organisms that inhabit such environments (3). Furthermore, as a result of the bioaccumulation of heavy metals over time, organisms that do not inhabit contaminated areas may also be subject to higher exposure through the food chain (67). One of the main sources of heavy metal pollution in soil, water, and sediments is the metal purification procedure, which includes mining, smelting, and the tailings from these industries (55). In Korea, approximately 1,000 metal mines have been suspended or closed in the last 30 years, with metal mine tailings amounting to about 10 million tons (40a). The leftover mine tailings contain high concentrations of heavy metals and are a major source of environmental pollution; thus, a number of physicochemical methods have been developed to prevent pollution and/or restore the ecosystem of polluted sites (51).Phytoremediation, which is the use of plants to clean up environmental pollution, has received much attention as a promising method for the removal of metal pollutants in soils (6, 66). Phytoremediation is a cost-effective and environmentally friendly approach compared to other environmentally invasive, expensive, and inefficient cleanup technologies (66). A number of plant species are capable of high-level organic compound degradation or heavy metal hyperaccumulation. Viable candidates for metal phytoremediation include the alpine pennycress Thlaspi caerulescens, the Indian mustard Brassica juncea, the sunflower Helianthusannuus, the yellow poplar Liriodendrontulipifera, and the shrub tobacco Nicotianaglaucum (6). However, slow rates of removal and incomp...

“…In fact, many studies showed that soil microbes represent important key nontarget organisms able to highlight unforeseen collateral effects of transgenic plants on natural and agricultural ecosystems. For example, GM potato lines producing Galanthus nivalis agglutinin and Brassica napus resistant to the herbicide glyphosate modified the composition and diversity of soil and rhizospheric microbial communities (22,63). Other works reported different effects of GM plants on soil microorganisms, mainly at the rhizosphere level, where root exudates directly affect the composition of microbial soil communities, in terms of both structure and function (5,21,37,38,50,60,61,64,66,80).…”

mentioning

confidence: 99%

Impact of Bt Corn on Rhizospheric and Soil Eubacterial Communities and on Beneficial Mycorrhizal Symbiosis in Experimental Microcosms

Castaldini

Turrini²,

Sbrana

et al. 2005

190

123

A polyphasic approach has been developed to gain knowledge of suitable key indicators for the evaluation of environmental impact of genetically modified Bt 11 and Bt 176 corn lines on soil ecosystems. We assessed the effects of Bt corn (which constitutively expresses the insecticidal toxin from Bacillus thuringiensis, encoded by the truncated Cry1Ab gene) and non-Bt corn plants and their residues on rhizospheric and bulk soil eubacterial communities by means of denaturing gradient gel electrophoresis analyses of 16S rRNA genes, on the nontarget mycorrhizal symbiont Glomus mosseae, and on soil respiration. Microcosm experiments showed differences in rhizospheric eubacterial communities associated with the three corn lines and a significantly lower level of mycorrhizal colonization in Bt 176 corn roots. In greenhouse experiments, differences between Bt and non-Bt corn plants were detected in rhizospheric eubacterial communities (both total and active), in culturable rhizospheric heterotrophic bacteria, and in mycorrhizal colonization. Plant residues of transgenic plants, plowed under at harvest and kept mixed with soil for up to 4 months, affected soil respiration, bacterial communities, and mycorrhizal establishment by indigenous endophytes. The multimodal approach utilized in our work may be applied in long-term field studies aimed at monitoring the real hazard of genetically modified crops and their residues on nontarget soil microbial communities.