Metagenomic studies revealed the prevalence of Acidobacteria in soils, but the physiological and ecological reasons for their success are not well understood. Many Acidobacteria exhibit 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 by Acidobacteria strain AB23 isolated from a savannah-like soil and to identify putative carotenoid genes in Acidobacteria genomes. Phylogenetic analysis revealed that strain AB23 belongs to the Occallatibacter genus from the class Acidobacteriia (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 of Acidobacteriia with available genomes possess the complete gene cluster for phytoene production. Some Acidobacteriia members 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 among Acidobacteriia. 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 for Acidobacteria in soils.

元基因组学研究揭示了酸性细菌在土壤中的流行，但对其成功的生理和生态原因尚不十分了解。许多酸性细菌表现出类胡萝卜素相关的色素，可能与它们对环境压力的耐受性有关。这项工作的目的是调查酸性细菌菌株AB23从稀树草原样土壤中分离产生的橙色色素的作用，并鉴定酸性细菌基因组中假定的类胡萝卜素基因。系统发育分析表明，菌株AB23属于酸杆菌属的Occallatibacter属。（细分1）。在光和维生素存在下，AB23菌株产生类胡萝卜素。然而，当细胞暴露于光下时，生长速率和生物量下降。类胡萝卜素的存在导致对过氧化氢的耐受性。比较基因组学表明，具有可用基因组的嗜酸细菌的所有成员都具有完整的植物六氢番茄红素基因簇。一些嗜酸细菌成员具有额外的基因簇，可能与有色类胡萝卜素的产生有关。有色和无色类胡萝卜素都参与对氧化应激的耐受性。这些结果表明类胡萝卜素基因的存在在酸性细菌中很普遍。轻和大气中的氧气会刺激类胡萝卜素的合成，但是土壤中还有其他自然的氧化应激源。对类胡萝卜素提供的环境氧化应激的耐受性可能为土壤中的酸性细菌提供竞争优势。