An ancient protein balances gene activity and silences foreign DNA in bacteria

Compared to humans, bacteria have a much tidier genome. The tiny microorganisms pack their genes closely together, and don’t carry around a lot of extraneous DNA, so-called junk DNA that fills in the gaps between genes. Some 90 percent of the complete genome sequence of the bacteria E. coli contains sequences of DNA that code for protein, while 90 percent of the human genome is non–coding junk DNA.