A Novel Method to Detect Genetically Altered Microorganisms in the Environment
Current methods for tracking genetically engineered microorganisms or engineered gene(s) contained in microorganisms are poorly developed. Novel approaches have been undertaken to detect such organisms or gene(s) which utilize selective and/or genetic probe methods. A model recombinant plasmid, called pDC91, was constructed which contains 3-chlorobenzoate (3-CB) degradative genes and a tetracycline-resistance gene (both serve as selective markers), as well as a portion of mouse B-globin gene (serves as a unique genetic marker). The plasmid was introduced into Pseudomonas putida for tracking experiments in simulated natural environments. Freshwater, saltwater, and their sediments were used. It was observed that P. putida/pDC91 survived for a few days in each experimental environment and then decreased rapidly to less than 50 per ml and failed to produce any detectable colonies on the 3-CB-containing plates. Upon addition of 3-CB to each environment, growth of P. putida/pDC91 resumed in the freshwater sediment and, to some extent, in the freshwater, but not in the saltwater or its sediment. pDC91 plasmid DNA was found to be present in colonies that grew from the bacteria in the freshwater and its sediment.