Rhizospheric bacteria from the Atacama Desert hyper-arid core: cultured community dynamics and plant growth promotion

Abstract

The Atacama Desert is the oldest and driest desert on Earth, with environmental conditions including great temperature variations, high UV-radiation, drought, high salinity, making it a natural laboratory to study the limits of life and resistance strategies. However, it shows great biodiversity harboring vast forms of adapted life and can be used as a model of desertification processes. While desertification is increasing as result of climate change and human activities, is necessary to optimize soil and water usage, where stress-resistant crops are possible solutions. As many studies have revealed the great impact of rhizobiome over plant growth efficiency and resistance to abiotic stress, we set up to explore the rhizospheric soils of Suaeda foliosa and Distichlis spicata from the Atacama Desert. By culturing these soils and using 16S rRNA amplicon sequencing, we address the community taxonomy composition dynamics, the stability through time and the ability to promote lettuce plants growth. The rhizospheric soil communities were dominated by the families Pseudomonadaceae, Bacillaceae and Planococcaceae for S. foliosa and Porphyromonadaceae and Haloferacaceae for D. spicata. Nonetheless, the cultures were completely dominated by the Enterobacteriaceae family (up to 98%). Effectively, lettuce plants supplemented with the cultures showed greater size and biomass accumulation, we identify 12 candidates that could be responsible of these outcomes, of which 5 (Enterococcus, Pseudomonas, Klebsiella, Paenisporosarcina and Ammoniphilus) were part of the built co-occurrence network, being Klebsiella a major participant. We aim to contribute to the efforts to characterize the microbial communities as key for the plants survival in extreme environments, and as a possible source of consortia with plant growth promotion traits aiming agricultural applications. IMPORTANCEThe current scenario of climate change and desertification represents a series of incoming challenges for all living organisms, also as the human population grows rapidly, so is rising the demand for food and natural resources; thus, it is necessary to make agriculture more efficient by optimizing soil and water usages thus ensuring future food supplies. Particularly, the Atacama Desert (northern Chile) is considered the most arid place on Earth as a consequence of geological and climatic characteristics, such as the naturally low precipitation patterns and high temperatures, which makes it an ideal place to carry out research that seeks to aid agriculture to the future sceneries, which are predicted to resemble these. The use of microorganism consortia from plants thriving under these extreme conditions to promote plant growth, improve crops and make "unsuitable" soils farmable is our main interest. TWEETCultures of rhizospheric soils from Atacama Desert resilient plants were enriched in Klebsiella, Bacillus and Brevibacillus which promoted lettuce growth