Prokaryotic Community Structure and Metabolisms in Shallow Subsurface of Atacama Desert Playas and Alluvial Fans After Heavy Rains: Repairing and Preparing for Next Dry Period

Abstract

The Atacama Desert, the oldest and driest desert on Earth, displays significant rains only once per decade. To investigate how microbial communities take advantage of these sporadic wet events, we carried out a geomicrobiological study a few days after a heavy rain event in 2015. Different physicochemical and microbial community analyses were conducted on samples collected from playas and an alluvial fan from surface, 10, 20, 50, and 80 cm depth. Gravimetric moisture content peaks were measured in 10 and 20 cm depth samples (from 1.65 to 4.1% w/w maximum values) while, in general, main anions such as chloride, nitrate, and sulfate concentrations increased with depth, with maximum values of 13–1,125; 168–10,109; and 9,904–30,952 ppm, respectively. Small organic anions such as formate and acetate had maximum concentrations from 2.61 to 3.44 ppm and 6.73 to 28.75 ppm, respectively. Microbial diversity inferred from DNA analysis showed Actinobacteria and Alphaproteobacteria as the most abundant and widespread bacterial taxa among the samples, followed by Chloroflexi and Firmicutes at specific sites. Archaea were mainly dominated by Nitrososphaerales, Methanobacteria, with the detection of other groups such as Halobacteria. Metaproteomics showed a high and even distribution of proteins involved in primary metabolic processes such as energy production and biosynthetic pathways, and a limited but remarkable presence of proteins related to resistance to environmental stressors such as radiation, oxidation, or desiccation. The results indicated that extra humidity in the system allows the microbial community to repair, and prepare for the upcoming hyperarid period. Additionally, it supplies biomarkers to the medium whose preservation potential could be high under strong desiccation conditions and relevant for planetary exploration.

Phospholipid biomarkers in Mars-analogous soils of the Atacama Desert

“…(2018) was between 5 × 10 4 and 5 × 10 6 cells per gram of soils, generally lower than this study. The lower biomass and different PLFA compositions might be a result of the timing of sampling: they sampled 1 month after an even more massive rainfall (33.3 mm) in 2015 that could damage most microbial communities in a short period, with Proteobacteria and Firmicutes being the dominant survivors (Azua-Bustos et al ., 2018; Fernandez-Martinez et al ., 2019). Sampling of this study was performed 6 months after the heavy rainfall in 2017, and microbial communities could partly recover (Orlando et al ., 2010; Armstrong et al ., 2016; Uritskiy et al ., 2019) to pre-disturbance abundance (Connon et al ., 2007; Lester et al ., 2007; Shirey, 2013; Valdivia-Silva et al ., 2016; Finstad et al ., 2017; Knief et al ., 2019).…”

“…The viable cell numbers and the number of individual PLFAs were not significantly different between Yungay and BBS-1 (Table 2 and Fig. 3a), since heavy rainfall not only brought moisture but also caused osmotic damages to microbial communities (Armstrong et al ., 2016; Azua-Bustos et al ., 2018; Fernandez-Martinez et al ., 2019). As for the classes of PLFAs, the proportions of normal saturated, hydroxy and polyunsaturated fatty acids were higher in BBS-1, while cyclopropyl and monounsaturated fatty acids were higher in Yungay.…”

Natural Holobiome Engineering by Using Native Extreme Microbiome to Counteract the Climate Change Effects

“…For example, desert (also known as dry/arid environments) represent about a third of the planet's biomes, which are characterized by significant absence of rainfall, extreme fluctuations in temperature, generally low nutrient status, high levels of incident UV radiation and strong winds (Chamizo et al, 2012;Stomeo et al, 2013). The microorganisms associated with these environments are generally represented by Bacteria, Fungi, and Archaea (Makhalanyane et al, 2015;Fernández-Martínez et al, 2019). Bacterial communities present in desert soils typically contain a number of ubiquitous phyla including Actinobacteria, Bacteroidetes and Proteobacteria (Fierer et al, 2009).…”

Spatial and Temporal Variability of Microbial Communities and Salt Distributions Across an Aridity Gradient Before and After Heavy Rains in the Atacama Desert

“…Instantaneously after rainfall, microorganisms start producing proteins and metabolites that are crucial in fundamental biosynthetic pathways, energy supplements, desiccation resistance, radiation protection, and oxidation defense for the preparation of the upcoming hyperarid period (Fernandez-Martinez et al 2019).…”