The lost world of Cuatro Ciénegas Basin, a relictual bacterial niche in a desert oasis

Abstract

Barriers to microbial migrations can lead adaptive radiations and increased endemism. We propose that extreme unbalanced nutrient stoichiometry of essential nutrients can be a barrier to microbial immigration over geological timescales. At the oasis in the Cuatro Ciénegas Basin in Mexico, nutrient stoichiometric proportions are skewed given the low phosphorus availability in the ecosystem. We show that this endangered oasis can be a model for a lost world. The ancient niche of extreme unbalanced nutrient stoichiometry favoured survival of ancestral microorganisms. This extreme nutrient imbalance persisted due to environmental stability and low extinction rates, generating a diverse and unique bacterial community. Several endemic clades of Bacillus invaded the Cuatro Cienegas region in two geological times, the late Precambrian and the Jurassic. Other lineages of Bacillus, Clostridium and Bacteroidetes migrated into the basin in isolated events. Cuatro Ciénegas Basin conservation is vital to the understanding of early evolutionary and ecological processes.

Two Pseudomonas aeruginosa clonal groups belonging to the PA14 clade are indigenous to the Churince system in Cuatro Ciénegas Coahuila, México

“…P. aeruginosa is a very well‐studied species, but in order to explore the possibility of isolating new P. aeruginosa lineages and to understand the origin of its pathogenic potential, we have characterized isolates from diverse environments (Grosso‐Becerra et al ., ). In this work, we explore the Cuatro Ciénegas Basin (CCB) located in the Chihuahuan Desert in the Mexican State of Coahuila, a place previously referred as a lost world due to the presence of ancient bacterial lineages (Souza et al ., ). We have observed that in CCB microbial diversity is extremely high (Souza et al ., ) and a large portion of it seems to include direct descendants of marine organisms (Souza et al ., ; Alcaraz et al ., ) including marine virus (Desnues et al ., ; Taboada et al ., ), which is atypical for lagoons and springs outside CCB.…”

“…In this work, we explore the Cuatro Ciénegas Basin (CCB) located in the Chihuahuan Desert in the Mexican State of Coahuila, a place previously referred as a lost world due to the presence of ancient bacterial lineages (Souza et al ., ). We have observed that in CCB microbial diversity is extremely high (Souza et al ., ) and a large portion of it seems to include direct descendants of marine organisms (Souza et al ., ; Alcaraz et al ., ) including marine virus (Desnues et al ., ; Taboada et al ., ), which is atypical for lagoons and springs outside CCB. We think that this is given in part by the ion composition of its water that is rich in sulphur and magnesium salts and poor in phosphorous and iron.…”

“…Within the diverse and particular CCB water bodies, the most distinct site is the hydrological system of Churince, a particularly vulnerable site due to the overexploitation of its aquifer by alfalfa agriculture (Souza et al ., 2007; De Anda et al ., ; Souza et al ., ). Churince was composed of three interconnected sections: large lagoon, intermediate lagoon and a spring.…”

“…Moreover, the extreme unbalanced nutrimental stoichiometry where the ratio of nitrogen/phosphorous is very high (Elser et al ., ; Lee et al ., , ) can explain most of the endemicity due to extreme selective pressure. It has been proposed that within CCB, oligotrophy not only forces the collaboration within the community to optimize its nutrient cycling (Tapia‐Torres et al ., ; Gomez‐Lunar et al ., ; Rodríguez‐Torres et al ., ), but it acts as an effective sieve against migration (Souza et al ., , ).…”

“…In 2004, the lagoon farthest from the spring, the desiccation lagoon (large lagoon), began to shrink and completely dried in 2006 (Alcaraz et al ., ). Later, the intermediate lagoon began to shrink in 2011 and completely dried in 2017 (Souza et al ., ), now only the main spring maintains some water.…”