Exploring the biogeochemical cycle of iron in an extremely acidic natural environmental gradient.

DIAZ GONZALEZ FERNANDO; ROJAS VILLALOBO CAMILA; ISSOTA FRANCISCO; MOYA BELTRAN ANA; GALLARDO YASNA; CARRASCO HÉCTOR; GIAVENO ALEJANDRA; TEMPORETTI PEDRO; QUATRINI RAQUEL

Pucón

Congreso; XLV Congreso Chileno de Microbiología; 2023

Sociedad Chilena de Microbiología

>Iron (Fe) is the most abundant element on the planet, accounting for 32.1% of its total mass. Thesolubility and bioavailable concentration of the redox species of Fe, ferrous [Fe(II)] and ferric ions[Fe(III)], vary with the environmental pH. Thus, pH is a determining factor in the biogeochemicalcycling of the metal. In acidic-oxic environments, Fe(II) serves as an electron donor for acidophilicFe-oxidizing microorganisms, while in microaerobic or anoxic environments, Fe(III) acts as anelectron acceptor for both acidophilic and acid-tolerant Fe-reducing microorganisms. The Febiogeochemical cycle has been extensively studied in aquatic systems where vertical redox andpH gradients form in the water-sediment interphase. However, little is known about the diversityand distribution patterns of Fe-cycling microorganisms in longitudinal transitional environments(pH gradient) under variant community contexts. The Agrio River, located in the acidic geothermalsystem of Copahue-Caviahue-ChanchoCó, serves as an ideal natural model to study themicrobial Fe-cycle under such conditions. The river's waters, volcanic-glacial in origin, exhibitample changes along its course in total metal concentration, temperature and pH. Usingmetagenomic strategies, we have studied the microbial communities in the water column at 15points along the physicochemical gradient of the river. Based on a meta-analysis of the knownuniverse of Fe-cycling microorganisms, we analyzed the presence and abundance of taxaassociated with the Fe-cycle at each site, establishing their occurrence ranges in the system andcorrelating their distribution with the collected abiotic/biotic metadata. The results demonstratethat the system harbors a great diversity of Fe-oxidizing and Fe-reducing microorganisms, whichdistribute differentially along the gradient, with a higher presence of Fe-oxidizers in sites closer tothe source. There is a clear transition towards metabolisms related to Fe respiration from themidpoint of the system onwards, linked to the input of organic matter into the system. This workdiscusses the findings in an eco-physiological context, aiming to understand the role of pH inshaping the microbiota assembly in this extreme system.