Image from W.H. Freeman and Sinauer Associates, used by permission. Operons are either inducible or repressible according to the control mechanism. Seventy-five different operons controlling 250 structural genes have been identified for E. coli . Bacteria have flagella with a different microtubule structure than the flagella of eukaryotes. Cell walls of bacteria contain peptidoglycan instead of the cellulose found in cell walls of plants and some algae.
Ribosomes are the structures in cells where proteins are assembled.
Bacterial ribosomes have different sized ribosomal subunits than do eukaryotes. Transmission electron micrograph of several bacterial flagella. Unicellular, they often stick together forming clumps or filaments. Scanning electron m icrographs illustrating external features of the rod-shaped bacterium E. coli . Shapes and grouping forms of various bacteria.