Biodiversity risk assessment of genetically modified Chaetoceros gracilis for outdoor cultivation

[摘要] A genetically modified (GM) strain of the diatomChaetoceros gracilis expressing the phosphite dehydrogenase gene (ptxD), which is a useful gene bothfor the biological containment and the avoidance ofmicrobial contamination, was characterized to estimate the risk against the biodiversity by laboratoryexperiments. GM strain could grow in the mediumcontaining phosphite as a sole source of phosphorus,while its general characteristics such as growth, salttolerance, heat and dehydration resistance in thenormal phosphate-containing medium were equivalent to those of wild type (WT) strain. The increasein potential toxicity of GM strain against plant,crustacean, fish and mammal was also disproved.The dispersal ability of WT strain cultured in anoutdoor raceway pond was investigated for 28 daysby detecting the psb31 gene in vessels, settled atvariable distances (between 5 and 60 m) from thepond. The diatom was detected only in one vesselplaced 5 m apart. To estimate the influence on theenvironment, WT and GM strains were inoculatedinto freshwater, seawater and soil. The influence onthe microbiome in those samples was assessed by16S rRNA gene amplicon sequencing, in additionto the analysis of the survivability of those strainsin the freshwater and the seawater. The results indicated that the effect to the microbiome and the survivability were comparable between WT and GMstrains. All results showed that the introduction ofthe ptxD gene into the diatom had a low risk onbiodiversity.

[学科分类] 微生物学和免疫学

[关键词] biodiversity;diatom;geneticallymodified microorganisms;microalgae;microbiome;outdoor cultivation;ptxD gene;toxicity