Phenotypic and genotypic characterization of endophytic bacteria associated with transgenic and non-transgenic soybean plants
Endophytic bacteria isolated from non-transgenic and transgenic Roundup Ready® glyphosate-resistant (GR) soybean plants were investigated to analyze the correspondence between phenotypic and genotypic characteristics and to determine whether or not the strains could be grouped based on the source of isolation in transgenic or non-transgenic plants, respectively. Most of the strains recovered from GR plants have shown the ability for plant growth promotion (PGP) by means of IAA production and inorganic phosphate solubilization, and 100% of the strains showed great motility (swarm or swim); in addition, 90% of the strains were able to metabolize the majority of carbon sources tested. GR soybean fields showed higher endophytes abundance than non-transgenic; however, analyzing the phylogenetic trees constructed using the partial 16SrRNA gene sequences, higher diversity was observed in non-transgenic soybean fields. Overall the majority of isolated endophytes could utilize multiple patterns of carbon sources and express resistance to antibiotics, while isolates varied widely in the PGP ability. The greater pattern and frequency of utilization of carbon sources and frequency and intensity of antibiotic resistance compared with PGP ability within the soybean endophytes community suggest that carbon sources metabolism and antibiotic resistance confer a greater relative fitness benefit than PGP ability. In conclusion, cluster analysis of the phenotypes and 16SrRNA gene sequences reveals lack of correspondence between the pattern of bacterial isolates and the transgenic character of plants, and the heterogeneity of clustering suggested that various adaptive processes, such as stress response, could have contributed to generate phenotypic variability to enhance endophytes overall fitness.
KeywordsTransgenic soybean Endophytic bacteria 16SrRNA Antibiotics Carbon sources metabolism Plant growth promotion
This research was supported by CAPES (Coordenação de Aperfeiçoamento de Pessoal de Nível Superior), Program Science Without Borders, Grant 019/2012, and by Fundação Araucária (Brazil), Grant 23265/2011. We thank ICGEB (International Centre For Genetic Engineering and Biotechnology, Trieste, Italy) for the SMART Fellowship to Karla Bianca de Almeida Lopes. We also thank Jennifer Aparecida Schnitzer for laboratory assistance.
Compliance with ethical standards
Conflict of interest
All authors declare that they have no conflict of interest.
Human and animal rights
This article does not contain any studies with animals performed by any of the authors. This study used the GenBank genetic sequence database.
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