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

Abstract

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 modern analogs of ancient microbial mats where functions were preserved over time, whereas composition was subject to diversification in the face of local and planetary perturbations.

Metagenomic comparisons reveal a highly diverse and unique viral community in a seasonally fluctuating hypersaline microbial mat

“…Briefly, as sulphate reduction occurs, cyanobacterial mats are degraded and organic matter oxidizes, which results in chlorophyll Mg 2+ solubilization and bicarbonate production, respectively [73][74][75]. Both, photosynthetic and sulphate-reducing metabolisms have been detected in AD [14].…”

“…If environmental variables are not the main community drivers, it is possible that the community dynamics fit an Eltonian niche concept, which states that community structure is driven by interactions [63,65]. For instance, considering that naked haloarchaeaviruses are only indirectly affected by changes in salinity [53], that AD viral community is dominated by viruses belonging to the order Caudovirales, which are naked viruses, and that a highly diverse and seasonally stable core microbial community has been recently described in AD [14], one could argue that AD viral community will tend to remain stable as long as the host community remains the same. This may be related to the so called 'insurance hypothesis' , which predicts that highly diverse ecosystems remain functionally stable in changing environments [66].…”

“…1c), respectively [9,10]. Despite its fluctuating and extreme nature, AD seem to harbour a seasonally stable microbial core community, with some degree of functionally redundant taxa [10] and a high abundance of alkaline and salt resistance genes [14]. AD is also very diverse in microbes, including more than 6000 ASV in ten samples obtained at a scale of 1.5 m [10].…”

“…AD is a seasonal fluctuating site, with the N:P ratio, pH and salinity ranging from 10 : 1, 9.5 and low hypersaline (5.3 %) during the wet season () to 78 : 1, 5.5 and high hypersaline (saturation) during the dry season (), respectively [9, 10]. Despite its fluctuating and extreme nature, AD seem to harbour a seasonally stable microbial core community, with some degree of functionally redundant taxa [10] and a high abundance of alkaline and salt resistance genes [14]. AD is also very diverse in microbes, including more than 6000 ASV in ten samples obtained at a scale of 1.5 m [10].…”