Unculturable microbes detected by molecular sequences and probes

Nucleic acid probes have revolutionized rapid diagnostics of plant-, animal- and human-pathogenic viroids, viruses, bacteria and protozoa, and have complemented the spectrum of immunological and serological tests. Sequences of genes and rRNA, of proven potential for identification of taxa, are a valuable tool in that both the identity and the phylogenetic position of an isolate can be elucidated. On the other hand, this approach is still laborious and requires sophisticated equipment. Designation of probes does not require information about sequences, although such knowledge is extremely helpful in the formulation of highly specific oligonucleotide probes, e.g. in the case of rDNA probes, where target stretches containing variable sequences are rather short (about 10-30 nucleotides). The application of probe technologies in molecular environmental studies by in situ hybridization, screening of gene libraries and flow cytometry is in its infancy but a logical step towards reconfirmation of the identity of a species in its natural habitat