Abbreviation for "Peptide Nucleic Acid - Fluorescence In Situ Hybridization". A peptide is an organic chemical compound resulting from a combination of several amino acids arranged in a defined order (sequence). It is a method by which certain DNA and RNA sequences can be localised in tissues, cells, cell nuclei and chromosomes in minute amounts. An artificially produced probe made of a nucleic acid is used to "hybridize" the nucleic acid to be detected, i.e. it binds and makes it visible. The term "in situ" refers to the fact that the detection is carried out directly in the respective structure and not biochemically in the test tube. The PNA probes used are marked with a fluorescent dye. The method is mainly used in medicine to identify pathogens in human blood.
Growing bacteria and yeast cells also produce a wealth of RNA sequences. In viticulture, the PNA-FISH method is therefore used, for example, to localise the usually undesired yeast species Brettanomyces bruxellensis in wine and the resulting wine defect horse sweat (Brett). Compared to other similar methods, the application is much less cost-intensive and can be carried out quickly. In this case, the visualization is done in the single cell of the yeasts. On the one hand, a statement can be made about the general presence and, in addition, about the germ count and its status. If Brettanomyces is suspected, it is sufficient to take a litre of wine from the barrel or the contents of a bottle. The method is also suitable for the detection of many other organisms. It is to be expected that in the future many other microbiologically based wine defects can be detected with this method.