RAPD, RFLP, T-RFLP, AFLP, RISA

Abstract

Traditional methods of identifying microorganisms through culturing and microscopy techniques can be somewhat tedious and time consuming. A faster and more accurate method for identifying microorganisms is through the sequencing of its ribosomal gene. Classification of microorganisms by ribosomal gene sequencing has become widely accepted within the scientific community. Although this method is quite definitive in its ability to identify the microorganism being studied, it usually involves a pure culture and then the cloning and sequencing of its ribosomal gene. In order to look at complex communities and uncultured microorganisms, many researches have removed the culturing step and moved towards the generation of 16S clone libraries (see Chapter 5.1). Data generated from numerous 16S clone libraries from countless environments have produced databases full of ribosomal sequences that may have never been gathered if culturing of the microorganism had been a prerequisite. Ribosomal clone libraries are still quite time consuming, especially if one is interested in detecting differences between complex community structures under varying conditions, such as the effect, diet can impose on the rumen microbial community. Rapid screening methods that allow for the presentation of phylogenetic ribosomal diversity patterns from complex communities in an easy-to-interpret and reproducible manner have all benefited from the knowledge gained from ribosomal clone libraries. Restriction fragment length polymorphism (RFLP) and terminal restriction fragment length polymorphism (T-RFLP) are two such techniques that will be described in this chapter. Other methods such as ribosomal intergenic spacer analysis (RISA), which determines diversity through differences, found in the transcribed spacer region between the highly conserved ribosomal genes can also be employed. RISA is a particularly powerful tool for attempting to discriminate between closely related species and strains 9. Two methods that do not focus on the conserved ribosomal regions for phylogenetic diversity studies are those that amplify up random genomic sequences. The two most common methods are random amplified polymorphic DNA (RAPD) 13 and amplified fragment length polymorphism (AFLP) 11. (cont in article)

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