Bacillati

Bacillati, formerly known as "Terrabacteria", is a kingdom containing approximately two-thirds of prokaryote species, including those in the gram positive phyla (Actinomycetota and Bacillota) as well as the phyla Cyanobacteriota and Chloroflexota.

It derives its name (terra = "land") from the evolutionary pressures of life on land. Bacillati possess important adaptations such as resistance to environmental hazards (e.g., desiccation, ultraviolet radiation, and high salinity) and oxygenic photosynthesis. Also, the unique properties of the cell wall in gram-positive taxa, which likely evolved in response to terrestrial conditions, have contributed toward pathogenicity in many species. These results now leave open the possibility that terrestrial adaptations may have played a larger role in prokaryote evolution than currently understood.