The phylum Verrucomicrobia is made up of six groups of gram-negative, spherical or rod-shaped bacteria that consume other plants or animals for energy and nutrients (heterotrophic). They are distributed throughout freshwater, marine, and soil habitats, as well as vertebrae digestive tracts including those of humans. The bacteria within this group exist as a free-living organisms or symbiont (organisms that live in close physical association) with eukaryotic hosts from nematode worms and marine sponges to the gut of sea cucumber, clam worm, and humans.