Abstract: The appearance and spread of antibiotic resistance are considered a highly complex process with many factors affecting the resistance mechanisms, including metals. In order to fully understand the spread of antibiotic resistance in different environments, combined studies including geochemistry and microbiology are becoming imperative. So far, very few such studies have been conducted, and none of them involves the southernmost regions. The aim of this study was, therefore, to examine the biogeochemical characteristics of sediments of the southernmost part of Chile. Sediment geochemistry, as well as the presence of heterotrophic and carbapenem- resistant bacteria (CRB) in the Río de las Minas and neighbouring Strait of Magellan in Punta Arenas (Chile), was investigated to assess the anthropogenic impact of untreated urban wastewater on the accumulation of metals and microbial contaminants in this coastal system. Geochemistry of sediments indicated the influence of both natural processes and anthropogenic activities. Although levels of metals in sediments currently do not represent a toxic effect on organisms, the anthropogenic influence on the sediment composition in the study area cannot be denied. Clinically relevant CRB were found in river sediments (1.9 and 2.7 log CFU / mL). Our findings suggest that the Río de las Minas is under the anthropogenic impact of untreated urban wastewater and represent a significant source of potentially pathogenic CRB to the local environment.

Resumen: La aparición y propagación de la resistencia a los antibióticos se considera un proceso muy complejo, con muchos factores que afectan a los mecanismos de resistencia, incluidos los metales. Con el fin de comprender plenamente la propagación de la resistencia a los antibióticos en diferentes entornos, es imprescindible realizar estudios combinados que incluyan geoquímica y microbiología. Hasta ahora, se han realizado muy pocos estudios de este tipo y ninguno de ellos afecta a las regiones más meridionales. El objetivo de este estudio fue, por lo tanto, examinar las características biogeoquímicas de los sedimentos del extremo sur de Chile. Se investigó la geoquímica de los sedimentos, así como la presencia de bacterias heterótrofas y resistentes a los carbapenemas (BRC) en el Río de las Minas y el Estrecho de Magallanes en Punta Arenas (Chile), para evaluar el impacto antropogénico de las aguas residuales urbanas no tratadas sobre la acumulación de metales y contaminantes microbianos en este sistema costero. La geoquímica de los sedimentos indicaba la influencia tanto de los procesos naturales como de las actividades antropogénicas. Aunque los niveles de metales en los sedimentos actualmente no representan un efecto tóxico sobre los organismos, no se puede negar la influencia antropogénica sobre la composición de los sedimentos en el área de estudio. Se encontraron CCR clínicamente relevantes en los sedimentos de los ríos (1,9 y 2,7 UFC logarítmicos/ ml). Nuestros hallazgos sugieren que el Río de las Minas está bajo el impacto antropogénico de las aguas residuales urbanas no tratadas y representa una fuente significativa de CRB potencialmente patógena para el medio ambiente local.

Abstract The Espinhaço Range, in the Diamantina region (central part of the State of Minas Gerais), is known worldwide as a famous source of associated occurrence of quartz, rutile and/or anatase crystals. The latter is also a classic accompanying mineral of diamonds in the alluvial placers. Primary anatase is related to hydrothermal quartz veins cutting geological units of the Espinhaço Range. In the last decade, outstanding large sized anatase crystals (up to 4 cm) in such veins have been reported from two areas, showing unusual habits and partial intergrowth with rutile. They are colorless, ocher brown, or golden yellowish, often double terminated, and iron rich. Due to their strong adamantine luster and pseudo-octahedral habit, some resemble diamonds. Two different morphological types have been studied: a simple crystal habit solely with {011} faces, and double terminated complex anatase crystals with one or more of the following forms: {011}, {012}, {013}, {017} and {112}. The geological environments as well as general mineralogical characteristics are also described.