Bacterial communities associated with the rhizosphere of transgenic Bt 176 maize (Zea mays) and its non transgenic counterpart

Abstract

The effect of transgenic Bt 176 maize on the rhizosphere bacterial community has been studied with a polyphasic approach by comparing the rhizosphere of Bt maize cultivated in greenhouse with that of its non transgenic counterpart grown in the same conditions. In the two plants the bacterial counts of the copiotrophic, oligotrophic and sporeforming bacteria, and the community level catabolic profiling, showed no significant differences; differences between the rhizosphere and bulk soil bacterial communities were evidenced. Automated ribosomal intergenic spacer analysis (ARISA) showed differences also in the rhizosphere communities at different plant ages, as well as between the two plant types. ARISA fingerprinting patterns of soil bacterial communities exposed to root growth solutions, collected from transgenic and non transgenic plants grown in hydroponic conditions, were grouped separately by principal component analysis suggesting that root exudates could determine the selection of different bacterial communities.

Ecological compatibility of GM crops and biological control

“…However, another comparison of samples from Bt and non-Bt maize fields revealed a lower abundance of nematodes in Bt fields (Griffiths et al, 2005). The compositions of bacterial communities (Devare et al, 2004;Baumgarte and Tebbe, 2005) and the relative abundances of bacterial classes (Brusetti et al, 2004) did not differ among Bt and non-Bt treatments. It should be noted that Brusetti et al (2004) found no difference in the abundance of spore forming bacteria, which includes Bacillus entomopathogens.…”

“…The compositions of bacterial communities (Devare et al, 2004;Baumgarte and Tebbe, 2005) and the relative abundances of bacterial classes (Brusetti et al, 2004) did not differ among Bt and non-Bt treatments. It should be noted that Brusetti et al (2004) found no difference in the abundance of spore forming bacteria, which includes Bacillus entomopathogens. Protozoa and fungi are also unaffected by some commercialized Bt crops (Saxena and Stotzky, 2001a).…”

Applications (EFSA‐GMO‐RX‐MON810) for renewal of authorisation for the continued marketing of (1) existing food and food ingredients produced from genetically modified insect resistant maize MON810; (2) feed consisting of and/or containing maize MON810, including the use of seed for cultivation; and of (3) food and feed additives, and feed materials produced from maize MON810, all under Regulation (EC) No 1829/2003 from Monsanto

“…In this respect, Widmer (2007) suggested that effects observed on symbiotic microorganisms will only be disadvantageous for the crop itself, without representing a concern for the ecosystem. In addition, a number of other studies (reviewed by Widmer, 2007;Filion, 2008;, performed under laboratory, glasshouse or field conditions covering a large array of classical and more recent analytical tools, revealed only some minor changes in soil microbial community structure with Bt-maize compared to non-Bt-maize (Blackwood and Buyer, 2004;Brusetti et al, 2004;Griffiths et al, 2006;Mulder et al, 2006) or generally show no adverse effects of the Cry1Ab protein released by Bt-maize in root exudates or from biomass incorporated into soil microorganisms or microorganism-mediated processes (Saxena and Stotzky, 2001a;Flores et al, 2005;Anonymous, 2006;Hönemann et al, 2008;. Where effects on microbial communities have been reported, these effects were in general considered spatially and temporally limited, and small compared with those induced by differences in geography, temperature, seasonality, plant variety and soil type (Fang et al, 2005(Fang et al, , 2007Griffiths et al, 2005Griffiths et al, , 2006Lilley et al, 2006;Filion, 2008;.…”

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“…In this respect, Widmer (2007) suggested that effects observed on symbiotic microorganisms living in close association with crops will only be disadvantageous for the crop itself, without representing a concern for the ecosystem. In addition, a number of other studies (reviewed by Widmer, 2007 and, performed under laboratory, glasshouse and field conditions and covering a large array of classical and more recent analytical tools, revealed only some minor changes in soil microbial community structure with Bt-maize compared to non-Bt-maize (Blackwood and Buyer, 2004;Brusetti et al, 2004;Mulder et al, 2005;Griffiths et al, 2006) or generally show no adverse effects of the Cry1Ab protein released by Bt-maize in root exudates or from biomass incorporated into soil on microorganisms or microorganism-mediated processes (Saxena and Stotzky, 2001a;Flores et al, 2005;StMUGV, 2006;Hönemann et al, 2008;. In studies were effects on microbial communities have been reported, these effects were in general considered spatially and temporally limited, and small compared with those induced by differences in geography, temperature, seasonality, plant variety or soil type (Fang et al, 2005(Fang et al, , 2007Griffiths et al, 2005Griffiths et al, , 2006Lilley et al, 2006;.…”