Rapidly growing E. coli cells have up to 70,000 ribosomes.
Slower ones have less.
54 genes for ribosomal proteins all organized in operons. Rate of synthesis is adjusted according to the rate of rRNA synthesis Ribosomal proteins are translationally autoregulated. One protein of each operon binds to the mRNA of that operon. If lots of rRNA is present in the cell, most of the protein is bound to rRNA and so the mRNA is translated to produce more ribosomal protein. However, if there is little rRNA in the cell, the protein will bind to the mRNA and prevent translation.