Soil Acidobacteria Strain AB23 Resistance to Oxidative Stress Through Production of Carotenoids.

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.

Compounds of tucum-do-cerrado (Bactris setosa) fruit with antioxidant activity.

'Tucum-do-cerrado' (Bactris setosa) is an edible fruit from the Brazilian 'Cerrado' biome marked by a high antioxidant potential and polyphenol content when compared to other fruits from the same biome. Its antioxidant activity is higher in the peel than in the pulp. Ethanolic and aqueous peel extracts were analyzed by the ferric reducing antioxidant power (FRAP) assay. We also investigated the aqueous peel extract for its antioxidant mechanism and isolated some of its compounds using high-performance liquid chromatography. Among the extracts tested, the aqueous peel extract exhibited the highest FRAP values, with a predominant free radical scavenger activity. The isolated compounds were identified as two catechins, a cyanidin, a peonidin, and a quercetin. Testing the antioxidant potential of the isolated compounds using the 2-deoxyribose degradation assay revealed that catechin and quercetin showed the highest antioxidant activity. Thus, our results advance the identification of 'tucum-do-cerrado' compounds with antioxidant activity.

Exploring the biological activities and proteome of Brazilian scorpion Rhopalurus agamemnon venom.

Scorpion venoms are formed by toxins harmful to various organisms, including humans. Several techniques have been developed to understand the role of proteins in animal venoms, including proteomics approach. Rhopalurus agamemnon (Koch, 1839) is the largest scorpion in the Buthidae family in the Brazilian Cerrado, measuring up to 110 mm in total length. The accident with R. agamemnon is painful and causes some systemic reactions, but the specie's venom remains uninvestigated. We explore the venom protein composition using a proteomic and a biological-directed approach identifying 230 protein compounds including enzymes like Hyaluronidase, metalloproteinase, L-amino acid oxidase and amylase, the last two are first reported for scorpion venoms. Some of those new reports are important to demonstrate how distant we are from a total comprehension of the diversity about venoms in general, due to their diversity in composition and function. BIOLOGICAL SIGNIFICANCE: In this study, we explored the composition of venom proteins from the scorpion Rhopalurus agamemnon. We identified 230 proteins from the venom including new enzyme reports. These data highlight the unique diversity of the venom proteins from the scorpion R. agamemnon, provide insights into new mechanisms of envenomation and enlarge the protein database of scorpion venoms. The discovery of new proteins provides a new scenario for the development of new drugs and suggests molecular targets to venom components.