Mycobacterium tuberculosis is a acid fast bacteria, which can form acid-stable complexes when certain arylmethane dyes are added. All species of mycobacteria have ropelike structures of peptidoglycan that are arranged in such a way to give them properties of an acid fast bacteria. Mycobacteria are abundant in soil and water, but Mycobacterium tuberculosis is mainly identified as a pathogen that lives in the host. Some species in its Mycobacterium tuberculosis complex have adapted their genetic structure specifically to infect human populations.