Fouling Autopsy - Foulant Analysis

Fluorescent in situ hybridization (FISH)

FISH (Fluorescent in situ hybridization) is a cytogenetic technique that can be used to detect and localize the presence or absence of specific DNA sequences on chromosomes. It uses fluorescent probes that bind to only those parts of the chromosome with which they show a high degree of sequence similarity. Fluorescence microscopy can be used to find out where the fluorescent probe bound to the chromosome. FISH is often used for finding specific features in DNA. These features can be used in genetic counseling, medicine, and species identification. In foulant analysis this method is used to detect Gram negative bacteria with phylogenetic probes monitoring of a-, b- and c-Proteobacteria, of the main ammonia-oxidizing bacteria
(AOB) and nitrite-oxidizing bacteria of the Nitrobacter and Nitrospira genera.

FISH is independent from the culturability of the bacteria and it is increasingly applied as it allows the evaluation of the presence and distribution of specific micro-organisms in activated sludge flocs. Despite the recent increase of FISH applications to activated sludge, the literature is mainly concerned with the investigation of strains with specific characteristics or with the biomass selected in the most common applications (CASP and domestic wastewater treatment).