Arsenic and Its Biological Role: From Early Earth to Current Andean Microbial Ecosystems

Arsenic (As) is present in the Earth's crust and is widely distributed in the environment. It is frequently a component of sulfidic ores in the form of arsenides of nickel, cobalt, copper, and iron. The main sources of As are natural, mostly associated with volcanic areas and hydrothermal vents; further, it can also originate as a result of human activities: mining, waste treatment, and industrial activities, among others.Arsenic is a redox-active metalloid and exists in nature in four oxidation states: arsine [As(-III)], elemental [As(0)], arsenate [As(V)], and arsenite [As(III)]. These states vary according to changes in pH and the redox environment. The first two forms are relatively rare; naturally, As is found as As(V) or As(III). As(V) is predominant in oxygenated aqueous environments, while As(III) is found in reduced or anoxic conditions. Arsenic is a highly dangerous element, as As(III) is 100 times more toxic than As(V). Its greatest toxicity is due to the fact that it can bind to sulfhydryl groups, affecting the correct functioning of many enzymes and proteins. As(V), on the other hand, is a chemical analog of phosphate, so it can interact and eventually replace it in early steps in different ways. On our planet, there are environments with a high arsenic content.Our research group has worked in bioprospecting in Andean microbial ecosystems (AMEs) in the Atacama Desert, Bolivian Altiplano, and Argentine Puna (the so-called Puna?High Andes region). In all of these places, there are hypersaline lakes at altitudes higher than 3000 m above sea level (asl). These lakes share the common characteristic of high concentrations of arsenic, normally ranging between 12 and 230 mg L−1. This range of As concentrations is one of the highest ranges reported for hypersaline lakes.Fil: Saona Acuña, Luis Alberto. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Planta Piloto de Procesos Industriales Microbiológicos; ArgentinaFil: Soria, Mariana Noelia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Planta Piloto de Procesos Industriales Microbiológicos; ArgentinaFil: Villafañe, Patricio Guillermo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Planta Piloto de Procesos Industriales Microbiológicos; ArgentinaFil: Stepanenko, Tatiana Mariel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Planta Piloto de Procesos Industriales Microbiológicos; ArgentinaFil: Farias, Maria Eugenia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Planta Piloto de Procesos Industriales Microbiológicos; Argentin

Integral Prospection of Andean Microbial Ecosystem Project

When microbial ecosystems first started to be reported 10 years ago, nobody reallyhad a notion of the relevance they would have in the Central Andean region.Consequently, the heritage of the microbialites reported in El Peinado, LagunaNegra, Laguna Pozo Bravo, Laguna La Brava, etc. promises to position the Andes asreservoirs of the most relevant modern microbialites on the planet (Table 17.1,Fig. 17.1). Furthermore, the number of different ecosystems is worth paying closeattention to, as it gives rise to questions such as: What favors the development ofthese ecosystems? What are the conditions that influence the precipitation of a carbonaceousor a gypsum system at such a short distance and under similar environmentalconditions, such as at the Atacama salt flat? Why are oncolites distributed so? Untilnow, it has been possible only to survey the systems and to carry out more in-depthstudies in some of them to try to achieve their preservation. Throughout the prospection of the Andean microbial ecosystems (AMEs), some shared characteristics have beenfound from the geological, physical, and chemical points of view [(1) active volcanicincidence: all of the microbial ecosystems that have been found are in some way connectedto areas where active volcanoes are present; (2) underground water input;(3) mixed zones with different salinities: underground low-conductivitywater andsalar thalassic water; (4) two kinds of microbialites found: oncolites (at LagunaNegra, Tres Quebradas, Las Quinoas, etc.) or domes with thrombolites at the bottomand stromatolites at the top surface (at La Brava, Pozo Bravo, Ojos Bravos, and ElPeinado)] and from the biological point of view [(5) predominance of diatoms, themain component in all studied systems; (6) predominance of anaerobic over aerobicphotosynthetic microorganisms; (7) microbial rhodopsin as the main system for producing adenosine triphosphate (ATP); (8) arsenicresistance and bioenergetic mechanisms;and (9) predominance of Carbon fixation pathways other than the Calvincycle]. The biological aspects of these are being studied thoroughly in our lab and arebriefly discussed below.Fil: Farias, Maria Eugenia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Planta Piloto de Procesos Industriales Microbiológicos; ArgentinaFil: Villafañe, Patricio Guillermo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Planta Piloto de Procesos Industriales Microbiológicos; ArgentinaFil: Lencina, Agustina Inés. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro de Investigaciones y Transferencia de Catamarca. Universidad Nacional de Catamarca. Centro de Investigaciones y Transferencia de Catamarca; Argentin

Andean Microbial Ecosystems: Traces in Hypersaline Lakes About Life Origin

High-altitude Andean lakes (HAALs) represent unique environments on the Earth where one can study the biological chemistry of life in one of its most extreme versions. The Atacama Desert, Argentine Puna, and Bolivian Altiplano harbor hypersaline lakes where polyextremophilic Andean Microbial Ecosystems (AMEs) inhabit microbial mats, evaporitic mats, biofilms (BF), evaporites (EV), and microbialites (Mi). These AMEs have two remarkable characteristics: (i) they are the only ones in the world that inhabit areas ranging from 3100 to 4200 masl; and (ii) they are excellent modern analogues of those which populated the primitive Earth ~3 billion years ago. In this chapter, we will delve into the different kinds of AMEs present in the HAAL, their formation, structure, and their adaptation to conditions largely influenced by volcanic activity, UV radiation, arsenic content, high salinity, low dissolved oxygen content, extreme daily temperature fluctuation, and oligotrophic conditions. All of these physicochemical parameters recreate the early Earth and even extraterrestrial conditions. The relevance of studying these ecosystems does not lie only in scientific-descriptive and/or economic interest. The scientific research community has a great responsibility to address climate change. In this scenario, the AMEs could have played a key role, influencing changes that allowed the origin of aerobic life and those who have faced the great climatic events of the Earth.Fil: Saona Acuña, Luis Alberto. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Planta Piloto de Procesos Industriales Microbiológicos; ArgentinaFil: Soria, Mariana Noelia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Planta Piloto de Procesos Industriales Microbiológicos; ArgentinaFil: Villafañe, Patricio Guillermo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Planta Piloto de Procesos Industriales Microbiológicos; ArgentinaFil: Lencina, Agustina Inés. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Planta Piloto de Procesos Industriales Microbiológicos; ArgentinaFil: Stepanenko, Tatiana Mariel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Planta Piloto de Procesos Industriales Microbiológicos; ArgentinaFil: Farias, Maria Eugenia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Planta Piloto de Procesos Industriales Microbiológicos; Argentin

Modern microbial mats and endoevaporites systems in Andean lakes a general approach

Puna wetlands and salars are a unique extreme environment all over the world, since their locations are in high-altitude saline deserts, largely influenced by volcanic activity. Ultraviolet radiation, arsenic content, high salinity, and low dissolved oxygen content, together with extreme daily temperature fluctuations and oligotrophic conditions, shape an environment that recreates the early Earth and, even more so, extraterrestrial conditions. Microbes inhabiting extreme environments face these conditions with different strategies, including formation of intricate microbial communities with an increasing degree of complexity. In that way, biofilms, mats, endoevaporitic mats, domes, and microbialites have been found to exist in association with salars, lagoons, and even volcanic fumaroles in Central Andean extreme environments. They form microbial ecosystems, where light and O2 availability decrease with depth stratification, promoting functional group diversity. This microbial diversity, together with the geochemistry, may favor the precipitation of minerals. This chapter summarizes general concepts in the environmental microbiology of extreme Andean ecosystems, which are explored throughout this book.Fil: Farias, Maria Eugenia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Planta Piloto de Procesos Industriales Microbiológicos; ArgentinaFil: Saona Acuña, Luis Alberto. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Planta Piloto de Procesos Industriales Microbiológicos; Argentin

Biological synthesis of nanosized sulfide semiconductors: current status and future prospects

There have been extensive and comprehensive reviews in the field of metal sulfide precipitation in the context of environmental remediation. However, these works have focused mainly on the removal of metals from aqueous solutions-usually, metal-contaminated effluents-with less emphasis on the precipitation process and on the end-products, frequently centering on metal removal efficiencies. Recently, there has been an increasing interest not only in the possible beneficial effects of these bioremediation strategies for metal-rich effluents but also on the formed precipitates. These metal sulfide materials are of special relevance in industry, due to their optical, electronic, and mechanical properties. Hence, identifying new routes for synthesizing these materials, as well as developing methodologies allowing for the control of the shape and size of particulates, is of environmental, economic, and practical importance. Multiple studies have shown proof-of-concept for the biological synthesis of inorganic metallic sulfide nanoparticles (NPs), resorting to varied organisms or cell components, though this information has scarcely been structured and compiled in a systematic manner. In this review, we overview the biological synthesis methodologies of nanosized metal sulfides and the advantages of these strategies when compared to more conventional chemical routes. Furthermore, we highlight the possibility of the use of numerous organisms for the synthesis of different metal sulfide NPs, with emphasis on sulfate-reducing bacteria (SRB). Finally, we put in perspective the potential of these methodologies in the emerging research areas of biohydrometallurgy and nanobiotechnology for the uptake of metals in the form of metal sulfide nanoparticles. A more complete understanding of the principles underlying the (bio)chemistry of formation of solids in these conditions may lead to the large-scale production of such metal sulfides, while simultaneously allowing an enhanced control over the size and shape of these biogenic nanomaterials