Natalya Zolotova

Formate as an Energy Source for Microbial Metabolism in Chemosynthetic Zones of Hydrothermal Ecosystems

Formate, a simple organic acid known to support chemotrophic hyperthermophiles, is found in hot springs of varying temperature and pH. However, it is not yet known how metabolic strategies that use formate could contribute to primary productivity in hydrothermal ecosystems. In an effort to provide a quantitative framework for assessing the role of formate metabolism, concentration data for dissolved formate and many other solutes in samples from Yellowstone hot springs were used, together with data for coexisting gas compositions, to evaluate the overall Gibbs energy for many reactions involving formate oxidation or reduction. The result is the first rigorous thermodynamic assessment of reactions involving formate oxidation to bicarbonate and reduction to methane coupled with various forms of iron, nitrogen, sulfur, hydrogen, and oxygen for hydrothermal ecosystems. We conclude that there are a limited number of reactions that can yield energy through formate reduction, in contrast to numerous formate oxidation reactions that can yield abundant energy for chemosynthetic microorganisms. Because the energy yields are so high, these results challenge the notion that hydrogen is the primary energy source of chemosynthetic microbes in hydrothermal ecosystems.

Investigating economic specialization on the central Peruvian coast: A reconstruction of Late Intermediate Period Ychsma diet using stable isotopes

OBJECTIVES Hypothetical models of socioeconomic organization in pre-Columbian societies generated from the rich ethnohistoric record in the New World require testing against the archaeological and bioarchaeological record. Here, we test ethnohistorian Maria Rostworowskis horizontality model of socioeconomic specialization for the Central Andean coast by reconstructing dietary practices in the Late Intermediate Period (c. AD 900-1470) Ychsma polity to evaluate complexities in social behaviors prior to Inka imperial influence. MATERIALS AND METHODS Stable carbon and nitrogen isotope analysis of archaeological human bone collagen and apatite (δ13 Ccol[VPDB], δ15 Ncol[AIR] , δ13 Cap[VPDB] ) and locally available foods is used to reconstruct the diets of individuals from Armatambo (n = 67), associated ethnohistorically with fishing, and Rinconada Alta (n = 46), associated ethnohistorically with agriculture. RESULTS Overall, mean δ15 Ncol[AIR] is significantly greater at Armatambo, while mean δ13 Ccol[VPDB] and mean δ13 Cap[VPDB] are not significantly different between the two sites. Within large-scale trends, adult mean δ13 Cap[VPDB] is significantly greater at Armatambo. In addition, nearly one-third of Armatambo adults and adolescents show divergent δ15 Ncol[AIR] values. DISCUSSION These results indicate greater reliance on marine resources at Armatambo versus Rinconada Alta, supporting the ethnohistoric model of socioeconomic specialization for the Central Andean coast. Deviations from large-scale dietary trends suggest complexities not accounted for by the ethnohistoric model, including intra-community subsistence specialization and/or variation in resource access.

Paleodietary analysis of the sacrificial victims from the Feathered Serpent Pyramid, Teotihuacan

The consumption of different types and quantities of food frequently serves as a practice that expresses and reinforces social distinctions among individuals within complex societies. This study explores the dietary behavior of probable sacrificial victims interred within the offering complex underlying the Feathered Serpent Pyramid as a line of evidence concerning the identities and life experiences of individuals selected for inclusion within one of Teotihuacan’s public monuments. Stable carbon, nitrogen, and oxygen isotope values from rib samples of 12 individuals within the Feathered Serpent Pyramid complex were compared with those of 14 individuals interred in residential contexts within the city. Results provide new information concerning daily subsistence at Classic period Teotihuacan (ca. A.D. 200–600) and highlight the dietary distinctiveness of individuals interred within the Feathered Serpent Pyramid as compared to the general residential population of the site, particularly in terms of the carbon isotope composition of protein sources consumed by a number of the sacrificial victims. Oxygen isotope analysis suggests that most individuals from the Feathered Serpent Pyramid resided within the local Teotihuacan area during the years immediately prior to their deaths, indicating that the unique dietary pattern seen in stable carbon isotope values cannot be attributed to nonlocal residence prior to sacrifice. Rather, these dietary differences may suggest that the group of individuals selected for interment within the Feathered Serpent Pyramid offering complex maintained a distinctive social or economic identity as compared to the rest of the Teotihuacan population during their lives.