Extremophile microbiomes in acidic and hypersaline river sediments of <scp>W</scp>estern <scp>A</scp>ustralia

Present-day terrestrial analogue sites are crucial ground truth proxies for studying life in geochemical conditions close to those assumed to be present on early Earth or inferred to exist on other celestial bodies (e.g. Mars, Europa). Although hypersaline sapropels are border-of-life habitats with moderate occurrence, their microbiological and physicochemical characterization lags behind. Here, we study the diversity of life under low water activity by describing the prokaryotic communities from two disparate hypersaline sapropels (Transylvanian Basin, Romania) in relation to geochemical milieu and pore water chemistry, while inferring their role in carbon cycling by matching taxa to known taxon-specific biogeochemical functions. The polyphasic approach combined deep coverage SSU rRNA gene amplicon sequencing and bioinformatics with RT-qPCR and physicochemical investigations. We found that sapropels developed an analogous elemental milieu and harbored prokaryotes affiliated with fifty-nine phyla, among which the most abundant were Proteobacteria, Bacteroidetes and Chloroflexi. Containing thirty-two candidate divisions and possibly undocumented prokaryotic lineages, the hypersaline sapropels were found to accommodate one of the most diverse and novel ecosystems reported to date and may contribute to completing the phylogenetic branching of the tree of life.

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“…S2). As expected, Bacteria dominated the sapropels (Table 1), harboring similar numbers with the ones reported for hypersaline sediments 17, 18 .…”

Section: Resultssupporting

confidence: 86%

Hypersaline sapropels act as hotspots for microbial dark matter

Andrei

Baricz

Robeson

et al. 2017

Sci Rep

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“…Indeed, all three Acidiphilium isolates tested in this study were able to aggregate to some extent, even without PEA addition. This morphological feature observed in Acidiphilium isolates has been previously documented, for example, the salt-tolerant Acidiphilium strain, AusYE3-1, also forms flocs and alters cell shapes from rod-shaped or coccobacillus to filamentous structures when stressed under high salt concentrations [68].…”

Section: Discussionsupporting

confidence: 70%

“…Acidiphilium spp. have been also directly isolated from acidic mine drainage waters and sediments [14,67] and from acidic hypersaline river sediments in Australia, where they can make up high relative fractions of the microbial community [68].…”

Section: Discussionmentioning

confidence: 99%

Molecular Mechanisms Underpinning Aggregation in Acidiphilium sp. C61 Isolated from Iron-Rich Pelagic Aggregates

Cooper

Wegner

et al. 2020

Microorganisms

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Iron-rich pelagic aggregates (iron snow) are hot spots for microbial interactions. Using iron snow isolates, we previously demonstrated that the iron-oxidizer Acidithrix sp. C25 triggers Acidiphilium sp. C61 aggregation by producing the infochemical 2-phenethylamine (PEA). Here, we showed slightly enhanced aggregate formation in the presence of PEA on different Acidiphilium spp. but not other iron-snow microorganisms, including Acidocella sp. C78 and Ferrovum sp. PN-J47. Next, we sequenced the Acidiphilium sp. C61 genome to reconstruct its metabolic potential. Pangenome analyses of Acidiphilium spp. genomes revealed the core genome contained 65 gene clusters associated with aggregation, including autoaggregation, motility, and biofilm formation. Screening the Acidiphilium sp. C61 genome revealed the presence of autotransporter, flagellar, and extracellular polymeric substances (EPS) production genes. RNA-seq analyses of Acidiphilium sp. C61 incubations (+/− 10 µM PEA) indicated genes involved in energy production, respiration, and genetic processing were the most upregulated differentially expressed genes in the presence of PEA. Additionally, genes involved in flagellar basal body synthesis were highly upregulated, whereas the expression pattern of biofilm formation-related genes was inconclusive. Our data shows aggregation is a common trait among Acidiphilium spp. and PEA stimulates the central cellular metabolism, potentially advantageous in aggregates rapidly falling through the water column.

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“…The copyright holder for this preprint this version posted December 18, 2020. ; https://doi.org/10.1101/2020.12.17.423355 doi: bioRxiv preprint Diversity dynamics of Lake Magic responsible for the lowering of pH in the sediment (Lu et al, 2016;Zaikova et al, 2018). The Alicyclobacillus genus members are reported to be involved in iron oxidation along with archaea in other acid saline lakes in WA (Johnson et al, 2015;Lu et al, 2016). The members of the genus are also capable of reducing iron (Yahya et al, 2008;Lu et al, 2010).…”

Section: Discussionmentioning

confidence: 99%

Temporal Microbial Community Dynamics within a Unique Acid Saline Lake

Ghori

Wise

Whiteley

2020

Preprint

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Lake Magic is one of the acidic hypersaline lakes (ca. 1 km in diameter) present within the Yilgarn Craton in WA. This unique lake exhibits extremely low pH (<1.6) coupled to very high salinity (32% TDS) with the highest concentration of aluminium (1774 mg/L) and silica (510 mg/L) in the world. Previous studies on Lake Magic diversity has revealed that the lake hosts acidophilic, acidotolerant, halophilic and halotolerant bacterial species. These studies provide indicators of the population residing within the lake. However, they do not emphasize the survival mechanisms adopted by the resident microorganisms and how the diversity of microbial populations residing within the lake changes during the dynamic stages of flooding, evapo-concentration and desiccation. We have studied the bacterial and fungal diversity in Lake Magic via amplicon sequencing and functional analysis through different stages of the lake in a span of one year, in the salt and sediment layer. Our results highlight that the diversity in Lake Magic is strongly driven by the pH and salt concentrations at different stages of the lake. The microbial community becomes more specialised in specific functions during more extreme stages. This also suggests that microbial interactions are involved in stabilising the ecosystem and is responsible for the resistance and resilience of these communities as the interactions of these microbes create a safe haven for other microbes to survive during more extreme stages.

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Extremophile microbiomes in acidic and hypersaline river sediments of Western Australia

Cited by 14 publications

References 53 publications

Hypersaline sapropels act as hotspots for microbial dark matter

Hypersaline sapropels act as hotspots for microbial dark matter

Molecular Mechanisms Underpinning Aggregation in Acidiphilium sp. C61 Isolated from Iron-Rich Pelagic Aggregates

Temporal Microbial Community Dynamics within a Unique Acid Saline Lake

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