Bacterial ribosomal RNA in pieces

The exact knowledge on the ribosomal RNA (rRNA) structure is an important prerequisite for work with rRNA sequences in bioinformatic analyses and in experimental research. Most available rRNA sequences of bacteria are based on gene sequences and on similarity analyses using Escherichia coli rRNA as a standard. Therefore, it is often overlooked that many bacteria harbour mature rRNA 'in pieces'. In some cases, the processing steps during the fragmentation lead to the removal of rRNA segments that are usually found in the ribosome. In this review, the current knowledge on the mechanisms of rRNA fragmentation and on the occurrence of fragmented rRNA in bacteria is summarized, and the physiological implications of this phenomenon are discussed.