Questioning the reliability of marker/reporter genes in GMO risk assessment

A commercially available biocontrol agent, Bacillus subtilis MBI600, was transformed with plasmids containing a luciferase luxAB fusion cassette under the control of a constitutive promoter, as well as two promoter-less plasmids, containing either a luxAB fusion cassette or luxA and luxB genes. Introduction of these genes did not alter the growth rate, but subsequent expression of the luciferase enzyme resulted in a consistently compromised in vitro biocontrol activity. The expressed luciferase gene product (rather then the insertion of the novel genes) appeared to have undesired side effects on the phenotype of the transformed organism, demonstrating why caution should be exercised when using marker/reporter gene systems for investigating biocontrol.