Eubacteria, known to most simply as bacteria, are found in every ecosystem on Earth. They have a vast amount of diversity; some varieties such as salmonella and E. coli are deadly to humans, while others live within the body and assist with biological processes.
Eubacteria are prokaryotes, which means that they do not have a nucleus. Their DNA floats within the cell or in a structure called a nucleoid. In some conditions, eubacteria engage in gene transfer methods to steal genes from bacteria and other organisms. This process makes eubacteria the fastest evolving organism on Earth. They reproduce by creating genetically identical copies of themselves.