Metagenomic studies revealed the prevalence ofAcidobacteriain soils, but the physiological and ecological reasons for their success are not well understood. ManyAcidobacteriaexhibit carotenoid-related pigments, which may be involved in their tolerance of environmental stress. The aim of this work was to investigate the role of the orange pigments produced byAcidobacteriastrain AB23 isolated from a savannah-like soil and to identify putative carotenoid genes inAcidobacteriagenomes. Phylogenetic analysis revealed that strain AB23 belongs to theOccallatibactergenus from the classAcidobacteriia(subdivision 1). Strain AB23 produced carotenoids in the presence of light and vitamins; however, the growth rate and biomass decreased when cells were exposed to light. The presence of carotenoids resulted in tolerance to hydrogen peroxide. Comparative genomics revealed that all members ofAcidobacteriiawith available genomes possess the complete gene cluster for phytoene production. SomeAcidobacteriiamembers have an additional gene cluster that may be involved in the production of colored carotenoids. Both colored and colorless carotenoids are involved in tolerance to oxidative stress. These results show that the presence of carotenoid genes is widespread amongAcidobacteriia. Light and atmospheric oxygen stimulate carotenoid synthesis, but there are other natural sources of oxidative stress in soils. Tolerance to environmental oxidative stress provided by carotenoids may offer a competitive advantage forAcidobacteriain soils.