Lac as a marker gene to track microbes in the environment

The environmental use of microorganisms as a means to combat pests and diseases, to remediate contaminated land and act as bio-fertilisers and plant growth promoters has been a focus for research for many years. However, the successful application of living microbial inocula is dependent on a thorough understanding of the behaviour of the organisms involved in relation to the environment into which they are released [8]. In order to gain this type of understanding, a large variety of selective and semi-selective media have been developed that allow selective recovery of organisms from environmental samples. Such media make use of specific characteristics that are inherent to the organism under study. Such characteristics include, growth conditions (temperature, pH, etc), resistance to antibiotics and heavy metals, tolerance to osmotic pressure and/or expression of phenotypic characteristics such as fluorescent pigments, coloration and morphology. In this way, media have been designed for the isolation and quantification of many ecologically important bacteria [27] Recent advances in recombinant technology have allowed the identification, characterisation and isolation of genes that encode for useful characteristics in relation to environmental applications. After isolation, and introduction into suitable vector systems, such genes can subsequently be introduced into a single recipient organism, allowing the creation of a genetically modified microorganism (GMM) with potentially ‘improved’ characteristics for environmental use. However, public concerns over the possible (negative) consequences of releasing functionally ‘improved’ organisms into the environment has increased the need for the development of sensitive detection techniques for microorganisms in environmental samples. The need to detect GMMs in the environment has created an impetus for the development of detection methods employing molecular techniques. Besides genes that encode for functional characteristics that are aimed to improve the environmental performance of a GMM, a variety of genes have been isolated from several organisms to facilitate detection of a particular GMM in the environment. Depending on the type of genetic marker employed, a GMM may be tracked phenotypically, relying on the expression of the marker gene by the GMM. Alternatively,