A greater challenge is to understand how many operons are regulated coordinately. The paradigm is bacteriophage lambda. Although lambda has only 7 operons, they control two completely different modes of bacteriophage growth inside the E. coli host cell. Bacteriophage lambda was discovered by Joshua and Esther Lederberg . They were using UV light to mutagenize strains of E. coli when they found that one of the strains was, in fact, a lysogen.
Bacteriophage lambda has two different life cycles.
It can infect its host, E. coli , replicate and synthesize new phage, then lysing and killing the host as the phage burst from the cell. Or, the phage can infect the cell and enter a dormant phase within the cell in which the phage is present but its genes are generally not being expressed. Then under certain circumstances, the phage will leave dormancy and resume lytic growth. It was difficult to know whether the sudden appearance of phage in bacterial cultures was due to some contaminant in the cultures or due to some intrinsic but unknown part of the bacteria themselves. Lysogeny, the hereditary ability to produce phage, occupies a unique position at the junction of genetics and virology.