Dual staining of natural bacterioplankton with 4',6-diamino-2-phenylindole and fluorescent oligonucleotide probes targeting kingdom-level 16S rRNA sequences

A dual staining technique using 4', 6-diamidino-2-phenylindole and fluoresent oligonucleotide probes specific for kingdom-level 16S rRNA sequence was developed. The method increased the sensitivity and visibility of natural bacterioplankton, thus allowing the microscopic characterization and quantification of specific phylogenetic group in dilute aquatic communities. The specific oligonucleotide probes could also be used at other taxonomic levels.