Water inputs across the Namib Desert: implications for dryland edaphic microbiology

Bosch, Jason; Marais, Eugène; Maggs‐Kölling, Gillian; Ramond, Jean‐Baptiste; Lebre, Pedro H.; Eckardt, Frank; Cowan, Don A.

doi:10.21425/f5fbg55302

Cited by 5 publications

(4 citation statements)

References 58 publications

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“…During the development of the hypolithic communities, we observed and inverse relationship in the relative abundances of Cyanobacteria and Bacteroidota/Pseudomonadota, which might be explained by the trophic relationships between these phyla. In open surface soils, phototrophic activity is likely to be very low due to the extended periods of very low water activity (Bosch et al, 2022 ), consistent with the low abundance of Cyanobacteria (León‐Sobrino et al, 2019 ). The fact that trace gas (H 2 /CO) chemotrophy has been suggested as the primary energy acquisition process for community subsistence and growth in desert soils may be particularly significant (Jordaan et al, 2020 ; Ortiz et al, 2021 ).…”

Section: Discussionmentioning

confidence: 83%

“…In this study, two arrays were established at different sites along a precipitation gradient, characterized by a fog‐inundated coastal zone, a hyper‐arid zone 60 km from the coast and a ‘higher rainfall’ zone approximately 120–280 km from the coast (Lancaster et al, 1984 ). The inland array was established in an area estimated to receive between 100 and 150 mm of annual rainfall (Bosch et al, 2022 ), while the ‘station’ array was positioned near the Gobabeb‐Namib Research Institute facilities, located within the central hyper‐arid zone.…”

Section: Resultsmentioning

confidence: 99%

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Kinetics and pathways of sub‐lithic microbial community (hypolithon) development

Bosch,

Lebre,

Marais

et al. 2024

Environ Microbiol Rep

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Type I hypolithons are microbial communities dominated by Cyanobacteria. They adhere to the underside of semi‐translucent rocks in desert pavements, providing them with a refuge from the harsh abiotic stresses found on the desert soil surface. Despite their crucial role in soil nutrient cycling, our understanding of their growth rates and community development pathways remains limited. This study aimed to quantify the dynamics of hypolithon formation in the pavements of the Namib Desert. We established replicate arrays of sterile rock tiles with varying light transmission in two areas of the Namib Desert, each with different annual precipitation regimes. These were sampled annually over 7 years, and the samples were analysed using eDNA extraction and 16S rRNA gene amplicon sequencing. Our findings revealed that in the zone with higher precipitation, hypolithon formation became evident in semi‐translucent rocks 3 years after the arrays were set up. This coincided with a Cyanobacterial ‘bloom’ in the adherent microbial community in the third year. In contrast, no visible hypolithon formation was observed at the array set up in the hyper‐arid zone. This study provides the first quantitative evidence of the kinetics of hypolithon development in hot desert environments, suggesting that development rates are strongly influenced by precipitation regimes.

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Section: Discussionmentioning

confidence: 83%

Section: Resultsmentioning

confidence: 99%

Kinetics and pathways of sub‐lithic microbial community (hypolithon) development

Bosch,

Lebre,

Marais

et al. 2024

Environ Microbiol Rep

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“…Soil microorganisms in extreme, hyperarid deserts such as the AD and the Namib Desert in Namibia must survive protracted periods of aridity between isolated rainfall events. Data from the Namib Desert projected that surface soil microbial communities have active growth for just 184–363 h per year ( Bosch et al, 2022 ). Similarly, soil relative humidity (RH) data recorded in the AD from 2015 to 2018 (sensors at 20 cm depth recording every 2 h) revealed average RH values of just 17–29% across eight hyperarid sites with no values recorded above 52% ( Neilson et al, 2017 ).…”

Section: Introductionmentioning

confidence: 99%

Hyperarid soil microbial community response to simulated rainfall

Demergasso,

Neilson,

Tebes-Cayo

et al. 2023

Front. Microbiol.

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The exceptionally long and protracted aridity in the Atacama Desert (AD), Chile, provides an extreme, terrestrial ecosystem that is ideal for studying microbial community dynamics under hyperarid conditions. Our aim was to characterize the temporal response of hyperarid soil AD microbial communities to ex situ simulated rainfall (5% g water/g dry soil for 4 weeks) without nutrient amendment. We conducted replicated microcosm experiments with surface soils from two previously well-characterized AD hyperarid locations near Yungay at 1242 and 1609 masl (YUN1242 and YUN1609) with distinct microbial community compositions and average soil relative humidity levels of 21 and 17%, respectively. The bacterial and archaeal response to soil wetting was evaluated by 16S rRNA gene qPCR, and amplicon sequencing. Initial YUN1242 bacterial and archaeal 16S rRNA gene copy numbers were significantly higher than for YUN1609. Over the next 4 weeks, qPCR results showed significant increases in viable bacterial abundance, whereas archaeal abundance decreased. Both communities were dominated by 10 prokaryotic phyla (Actinobacteriota, Proteobacteria, Chloroflexota, Gemmatimonadota, Firmicutes, Bacteroidota, Planctomycetota, Nitrospirota, Cyanobacteriota, and Crenarchaeota) but there were significant site differences in the relative abundances of Gemmatimonadota and Chloroflexota, and specific actinobacterial orders. The response to simulated rainfall was distinct for the two communities. The actinobacterial taxa in the YUN1242 community showed rapid changes while the same taxa in the YUN1609 community remained relatively stable until day 30. Analysis of inferred function of the YUN1242 microbiome response implied an increase in the relative abundance of known spore-forming taxa with the capacity for mixotrophy at the expense of more oligotrophic taxa, whereas the YUN1609 community retained a stable profile of oligotrophic, facultative chemolithoautotrophic and mixotrophic taxa. These results indicate that bacterial communities in extreme hyperarid soils have the capacity for growth in response to simulated rainfall; however, historic variations in long-term hyperaridity exposure produce communities with distinct putative metabolic capacities.

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“…The hygroscopic disaccharide trehalose, which is accumulated intracellularly in many organisms in response to desiccation [87], is capable of adsorbing and retaining water at atmospheric relative humidity values above 50% [88]. This mechanism of water acquisition by desiccated microbial cells is, at least theoretically, feasible in shallow subsurface microbial communities in both hot [89] and cold desert soils (see Figure 2a,b).…”

Section: Adsorption Of Water From the Atmospherementioning

confidence: 99%

‘Follow the Water’: Microbial Water Acquisition in Desert Soils

Cowan,

Cary,

DiRuggiero

et al. 2023

Microorganisms

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Water availability is the dominant driver of microbial community structure and function in desert soils. However, these habitats typically only receive very infrequent large-scale water inputs (e.g., from precipitation and/or run-off). In light of recent studies, the paradigm that desert soil microorganisms are largely dormant under xeric conditions is questionable. Gene expression profiling of microbial communities in desert soils suggests that many microbial taxa retain some metabolic functionality, even under severely xeric conditions. It, therefore, follows that other, less obvious sources of water may sustain the microbial cellular and community functionality in desert soil niches. Such sources include a range of precipitation and condensation processes, including rainfall, snow, dew, fog, and nocturnal distillation, all of which may vary quantitatively depending on the location and geomorphological characteristics of the desert ecosystem. Other more obscure sources of bioavailable water may include groundwater-derived water vapour, hydrated minerals, and metabolic hydro-genesis. Here, we explore the possible sources of bioavailable water in the context of microbial survival and function in xeric desert soils. With global climate change projected to have profound effects on both hot and cold deserts, we also explore the potential impacts of climate-induced changes in water availability on soil microbiomes in these extreme environments.

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Water inputs across the Namib Desert: implications for dryland edaphic microbiology

Cited by 5 publications

References 58 publications

Kinetics and pathways of sub‐lithic microbial community (hypolithon) development

Kinetics and pathways of sub‐lithic microbial community (hypolithon) development

Hyperarid soil microbial community response to simulated rainfall

‘Follow the Water’: Microbial Water Acquisition in Desert Soils

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