Modern microbial mats from the Chihuahuan Desert provide insights into ecological stability throughout Earth's history

Microbial mats are complex ecological assemblages that are found in the Precambrian fossil record and in extant extreme environments. Hence, these structures are regarded as highly stable ecosystems. In this work, we assess the ecological stability in a modern, fluctuating, hypersaline pond from the Cuatro Ciénegas Basin. From the 2016 to 2019 metagenomic sampling of this site, we found that this microbial site is sensitive to disturbances, which leads to high taxonomic replacement. Additionally, the mats have shown to be functionally stable throughout time, and could be differentiated between dry and rainy seasonal states. We speculate that this microbial system could represent a modern analog of ancient, hypersaline coastal microbial mats, where functions were preserved over time, whereas taxonomic composition was subject to diversification in the face of local and planetary perturbations.

Diversity of the longhorned beetles (Coleoptera: Cerambycidae) from Cuatro Ciénegas Basin, Coahuila, Mexico

Cerambycidae is one the most diverse families in the order Coleoptera with more than 37,000 species described in all continents. Cerambicyd beetles have a worldwide distribution from sea level to montane sites. In Mexico, more than 1,600 species have been recorded. Nevertheless, the diversity and distribution of this family in the Mexican deserts is poorly known. A first checklist of Cerambycidae from seven localities of Cuatro Ciénegas Basin is presented. This study is the result of sampling carried out between 2009 to 2013. Some material from other collections is also included. The species list includes four subfamilies, 13 tribes, 32 genera and 37 species, from which 13 are new records for the state of Coahuila and three species represent new records for Mexico. These results highlight the paucity of knowledge of insects in the deserts of Mexico.

A new species of Trhypochthoniellus (Acari: Oribatida: Trhypochthoniidae) from Cuatro Ciénegas, Coahuila, Mexico, and a key to the world species

Trhypochthoniellus comprises nine species, being mostly associated to aquatic vegetation; T. chilensis Ermilov & Weigmann as the only known species from North and South America. This genus is recorded for the first time in Mexico. Herein we present the description, illustrations and SEM photographs of Trhypochthoniellus churincensis sp. nov., which was found in association to lignocellulolytic microfungal taxa in the oligotrophic freshwater oasis of Cuatro Ciénegas Basin, Coahuila, México. T. churincensis sp. nov. is morphologically similar to T. longisetus (Berlese) and T. brevisetus Kuriki; however, it differs from both taxa by the presence of nine genital setae (11 to 13 setae), setae h3 subequal to other posterior notogastral setae; subcapitular setae h very short, and notogastral c1 larger. Additionally, we discuss information on food preferences and reproductive mode obtained through the observation of one cultured population maintained under laboratory conditions. A key to the species of Trhypochthoniellus is provided.

Population genomics of Vibrionaceae isolated from an endangered oasis reveals local adaptation after an environmental perturbation.

Background: In bacteria, pan-genomes are the result of an evolutionary "tug of war" between selection and horizontal gene transfer (HGT). High rates of HGT increase the genetic pool and the effective population size (Ne), resulting in open pan-genomes. In contrast, selective pressures can lead to local adaptation by purging the variation introduced by HGT and mutation, resulting in closed pan-genomes and clonal lineages. In this study, we explored both hypotheses, elucidating the pan-genome of Vibrionaceae isolates after a perturbation event in the endangered oasis of Cuatro Ciénegas Basin (CCB), Mexico, and looking for signals of adaptation to the environments in their genomes. Results: We obtained 42 genomes of Vibrionaceae distributed in six lineages, two of them did not showed any close reference strain in databases. Five of the lineages showed closed pan-genomes and were associated to either water or sediment environment; their high Ne estimates suggest that these lineages are not from a recent origin. The only clade with an open pan-genome was found in both environments and was formed by ten genetic groups with low Ne, suggesting a recent origin. The recombination and mutation estimators (r/m) ranged from 0.005 to 2.725, which are similar to oceanic Vibrionaceae estimations. However, we identified 367 gene families with signals of positive selection, most of them found in the core genome; suggesting that despite recombination, natural selection moves the Vibrionaceae CCB lineages to local adaptation, purging the genomes and keeping closed pan-genome patterns. Moreover, we identify 598 SNPs associated with an unstructured environment; some of the genes associated with these SNPs were related to sodium transport.Conclusions: Different lines of evidence suggest that the sampled Vibrionaceae, are part of the rare biosphere usually living under famine conditions. Two of these lineages were reported for the first time. Most Vibrionaceae lineages of CCB are adapted to their micro-habitats rather than to the sampled environments. This pattern of adaptation is concordant with the association of closed pan-genomes and local adaptation.

Draft Genome Sequence of Streptomyces sp. Strain C8S0, Isolated from a Highly Oligotrophic Sediment

Streptomyces spp. are prolific bacteria producing bioactive metabolites. We present the draft genome sequence of Streptomyces sp. strain C8S0, which was isolated from a highly oligotrophic sediment from the Cuatro Cienegas Basin (Mexico). The whole-genome assembly comprised 6,898,902 bp, with 18 biosynthetic gene clusters, including those for nonconventional terpenes, nonribosomal peptides, and polyketides.