rrndb: the Ribosomal RNA Operon Copy Number Database

The Ribosomal RNA Operon Copy Number Database (rrndb) is an Internet-access ible database containing annotated information on rRNA operon copy number a mong prokaryotes. Gene redundancy is uncommon in prokaryotic genomes, yet t he rRNA genes can vary from one to as many as 15 copies. Despite the widesp read use of 16S rRNA gene sequences for identification of prokaryotes, info rmation on the number and sequence of individual rRNA genes in a genome is not readily accessible. In an attempt to understand the evolutionary implic ations of rRNA operon redundancy, we have created a phylogenetically arrang ed report on rRNA gene copy number for a diverse collection of prokaryotic microorganisms. Each entry (organism) in the rrndb contains detailed inform ation linked directly to external websites including the Ribosomal Database Project, GenBank, PubMed and several culture collections. Data contained i n the rrndb will be valuable to researchers investigating microbial ecology and evolution using 16S rRNA gene sequences. The rrndb web site is directl y accessible on the WWW at http ://rrndb.cme.msu.edu.