Polymerase Chain Reaction (PCR) Overview

For the last 150 years, fungi have been identified based on macro and microscopic examination of morphological characteristics and biochemical assays. This would often entail growing the fungi on synthetic media for long periods of time at varying temperatures to achieve sporulation and the production of conidia. Often this could take upwards of several weeks to a month to complete.

Recently, with the development of more rapid molecular-based techniques to identify microorganisms appearing in journal after journal, researchers at the US EPA's National Exposure Research Center have developed and patented a method for the rapid identification of common indoor air fungal contaminants. The researchers identified unique Deoxyribonucleic acid (DNA) sequences for many of the problematic fungal species and designed a molecular-based assay to identify and quantify these organisms rapidly. This new technology is based on the detection of genetic material (DNA) of a target organism by Polymerase Chain Reaction (PCR). The licensed technology will rapidly replace the subjective identification of fungi by optical microscopy. In its most basic form, it is the cycled amplification of a sequence-specific segment of DNA utilizing a thermostable DNA polymerase, (an enzyme which catalyzes the addition or synthesis of DNA by adding complementary nucleotides to a growing chain or backbone of “denatured single stranded template” to form the common double helix structure of DNA) and sequence specific primer oligonucleotides.

Since this technique is based on the identification of unique DNA sequences and not the experience of the microscopist conducting the analysis, it is accurate, reproducible, and very rapid.

Learn how the PCR process works