The Cuatro Cienegas basin in the Chihuahuan desert is a system of springs, streams, and pools. These ecosystems support >70 endemic species and abundant living stromatolites and other microbial communities, representing a desert oasis of high biodiversity. Here, we combine data from molecular microbiology and geology to document the microbial biodiversity of this unique environment. Ten water samples from locations within the Cuatro Cienegas basin and two neighboring valleys as well as three samples of wet sediments were analyzed. The phylogeny of prokaryotic populations in the samples was determined by characterizing cultured organisms and by PCR amplification and sequencing of 16S rRNA genes from total community DNA. The composition of microbial communities was also assessed by determining profiles of terminal restriction site polymorphisms of 16S rRNA genes in total community DNA. There were 250 different phylotypes among the 350 cultivated strains. Ninety-eight partial 16S rRNA gene sequences were obtained and classified. The clones represented 38 unique phylotypes from ten major lineages of Bacteria and one of Archaea. Unexpectedly, 50% of the phylotypes were most closely related to marine taxa, even though these environments have not been in contact with the ocean for tens of millions of years. Furthermore, terminal restriction site polymorphism profiles and geological data suggest that the aquatic ecosystems of Cuatro Cienegas are hydrologically interconnected with adjacent valleys recently targeted for agricultural intensification. The findings underscore the conservation value of desert aquatic ecosystems and the urgent need for study and preservation of freshwater microbial communities.

Environmental disasters, ranging from catastrophic floods to extreme temperatures, have caused more than 30,000 deaths per year and more than US$ 250–300 billion a year in economic losses, globally, between 1995 and 2015 (1). Improved infrastructure and planning for extreme events is essential in urban areas, where an increasingly greater fraction of the world’s inhabitants reside. In response, international governmental and private initiatives have placed the goal of resilience at the center stage of urban planning. [For example, The 100 Resilient Cities Initiative (www.100resilientcities.org/); the Global Covenant of Mayors (https://www.compactofmayors.org/globalcovenantofmayors/); and the recent UN Habitat III (https://habitat3.org/the-new-urban-agenda)]. In addition, scientific and policy communities alike now recognize the need for “safe-to-fail” infrastructural design, and the potential role of green and blue infrastructure in mediating hydrological and climatic risks in cities (2). Nevertheless, the social and political norms, values, rules, and relationships that undergird and structure the myriad decisions made by public and private actors—what we call “socio-political infrastructure”—are likely to be as influential in urban vulnerability dynamics as “hard” infrastructure and environmental management. Urban planning for enhanced resilience and sustainability is ultimately a complex social and political process. Socio-political infrastructure creates patterns of behavior and action that shape the built environment. Developing more sustainable pathways of urban development hinges on making this socio-political infrastructure transparent and legible in the tools and approaches available for risk management. We argue that sustainability science is in the position to create the tools, methods, and strategies to identify, represent, and communicate the significance of these social and political processes to decision makers at all levels. In doing so, we can help ensure that these underlying drivers of urban vulnerability become subject to policy intervention. Sustainability science highlights the essential role of socio-political infrastructure in urban resilience. Sustainability is fundamentally about the normative decision process …

The Cuatro Ciénegas Basin (CCB) is a rare oasis in the Chihuahuan Desert in the state of Coahuila, Mexico. It has a biological endemism similar to that of the Galapagos Islands, and its spring-fed ecosystems have very low nutrient content (nitrogen or phosphorous) and are dominated by diverse microbialites. Thus, it has proven to be a distinctive opportunity for the field of astrobiology, as the CCB can be seen as a proxy for an earlier time in Earth's history, in particular the late Precambrian, the biological frontier when prokaryotic life yielded at least partial dominance to eukaryotes and multicellular life. It is a kind of ecological time machine that provides abundant opportunities for collaborative investigations by geochemists, geologists, ecologists, and population biologists in the study of the evolutionary processes that structured Earth-based life, especially in the microbial realm. The CCB is an object of investigation for the identification of biosignatures of past and present biota that can be used in our search for extraterrestrial life. In this review, we summarize CCB research efforts that began with microbial ecology and population biology projects and have since been expanded into broader efforts that involve biogeochemistry, comparative genomics, and assessments of biosignatures. We also propose that, in the future, the CCB is sanctioned as a “Precambrian Park” for astrobiology. Key Words: Microbial mats—Stromatolites—Early Earth—Extremophilic microorganisms—Microbial ecology. Astrobiology 12, 641–647.

Fungi play fundamental ecological roles in terrestrial ecosystems. However, their distribution and diversity remain poorly described in natural communities, particularly in arid and semi-arid ecosystems. In order to identify environmental factors determining fungal community structure in these systems, we assessed their diversity in conjunction with soil physicochemical characteristics in a semi-arid ecosystem in Baja California, Mexico, endemic for Coccidioidomycosis (Valley Fever). Two different microhabitats, burrows (influenced by rodent activity) and topsoil, were compared in winter and summer. Using a metagenomic approach, the ITS1 region of nuclear ribosomal DNA was used as barcode. A total of 1940 Operational Taxonomic Units (OTUs) were identified from 362 332 ITS1 sequences obtained by 454 pyrosequencing. Differences in fungal composition between seasons were clearly identified. Moreover, differences in composition between microhabitats were mainly correlated to significant differences in environmental factors, such as moisture and clay content in topsoil samples, and temperature and electrical conductivity in burrow samples. Overall, the fungal community structure (dominated by Ascomycota and Basidiomycota) was less variable between seasons in burrow than in topsoil samples. Coccidioides spp. went undetected by pyrosequencing. However, a nested PCR approach revealed its higher prevalence in burrows.