In E.  coli  there  are  seven  rRNA  transcription  units  scattered  by  the genome,  each of that contains one copy of every of the 16S, 23S  and 5S rRNA genes and one to four copies of several tRNA genes which is shown in the diagram. This gene assembly is transcribed by the single prokaryotic RNA polymerase to yield a one 30S pre-rRNA transcript about 6000 nt in the size. This arrangement make sures that stoichiometric   amounts   of   the   several   rRNAs   are   synthesized   for   ribosome assembly.  Subsequently  transcription,  the  30S  pre-rRNA  molecule  forms  internal base  paired  regions  to  provide  a  series  of  stem-loop  structures  and  ribosomal proteins  bind  to form  a ribonucleoprotein (RNP)  difficult. 

                Figure:  Transcription and processing of prokaryotic rRNA.