1)They are primitive organisms.
2)All organisms of the kingdom are prokaryotes.
3)They are present in both living and non-living environment.
4)They can survive in harsh and extreme climatic conditions like in hot springs, acidic soils etc.
5)They are unicellular organisms.Membrane bound nucleus is absent.DNA is in double stranded form, suspended in the cytoplasm of the organism,referred as nucleoid.A rigid cell wall is present.