Chapter 6: The Breadth and Limits of Life on Earth

Scientific ideas about the potential existence of life elsewhere in the universe are predominantly informed by knowledge about life on Earth. Over the past ∼4 billion years, life on Earth has evolved into millions of unique species. Life now inhabits nearly every environmental niche on Earth that has been explored. Despite the wide variety of species and diverse biochemistry of modern life, many features, such as energy production mechanisms and nutrient requirements, are conserved across the Tree of Life. Such conserved features help define the operational parameters required by life and therefore help direct the exploration and evaluation of habitability in extraterrestrial environments. As new diversity in the Tree of Life continues to expand, so do the known limits of life on Earth and the range of environments considered habitable elsewhere. The metabolic processes used by organisms living on the edge of habitability provide insights into the types of environments that would be most suitable to hosting extraterrestrial life, crucial for planning and developing future astrobiology missions. This chapter will introduce readers to the breadth and limits of life on Earth and show how the study of life at the extremes can inform the broader field of astrobiology.

Evaluation of functional and electrical features of automatic external defibrillators in extreme altitude and temperature environments

Aims

Human exposure to high-altitude and/or low-temperature areas is increasing and cardiac arrest in these circumstances represents an increasing proportion of all treated cardiac arrests. However, little is known about the performance of automated external defibrillators (AED) in these circumstances. The objective of this study is to assess the functional and electrical features of 6 commercially available AEDs in extreme environments.

Methods

Accuracy of shockable rhythm detection, the time required for self-test, rhythm analysis, and capacitor charging, together with total energy, peak voltage, peak current, and phasic duration of defibrillation waveform measured after placing the AEDs in simulated high-altitude, simulated low-temperature, and natural composite high-altitude and low-temperature environment for 30 min, were compared to those measured in the standard environment.

Results

All of the shockable rhythms were correctly detected and all of the defibrillation shocks were successfully delivered by the AEDs. However, the time required for self-test, rhythm detection, and capacitor charging was shortened by 1.2% (3 AEDs, maximum 12.4%) in the simulated high-altitude environment, was prolonged by 3.6% (4 AEDs, maximum 40.8%) in the simulated low-temperature environment, and was prolonged by 4.1% (5 AEDs, maximum 52.1%) in the natural environment. Additionally, the total delivered energy was decreased by 2.5% (2 AEDs, maximum 6.8%) in the natural environment.

Conclusion

All of the investigated AEDs functioned properly in simulated and natural environments, but a large variation in the functional and electrical feature change was observed. When performing cardiopulmonary resuscitation in extreme environments, the impact of environmental factors may need consideration.

The effects of sleep deprivation, acute hypoxia, and exercise on cognitive performance: A multi-experiment combined stressors study

INTRODUCTION

Both sleep deprivation and hypoxia have been shown to impair executive function. Conversely, moderate intensity exercise is known to improve executive function. In a multi-experiment study, we tested the hypotheses that moderate intensity exercise would ameliorate any decline in executive function after i) three consecutive nights of partial sleep deprivation (PSD) (Experiment 1) and ii) the isolated and combined effects of a single night of total sleep deprivation (TSD) and acute hypoxia (Experiment 2).

METHODS

Using a rigorous randomised controlled crossover design, 12 healthy participants volunteered in each experiment (24 total, 5 females). In both experiments seven executive function tasks (2-choice reaction time, logical relations, manikin, mathematical processing, 1-back, 2-back, 3-back) were completed at rest and during 20 min semi-recumbent, moderate intensity cycling. Tasks were completed in the following conditions: before and after three consecutive nights of PSD and habitual sleep (Experiment 1) and in normoxia and acute hypoxia (FIO2 = 0.12) following one night of habitual sleep and one night of TSD (Experiment 2).

RESULTS

Although the effects of three nights of PSD on executive functions were inconsistent, one night of TSD (regardless of hypoxic status) reduced executive functions. Significantly, regardless of sleep or hypoxic status, executive functions are improved during an acute bout of moderate intensity exercise.

CONCLUSION

These novel data indicate that moderate intensity exercise improves executive function performance after both PSD and TSD, regardless of hypoxic status. The key determinants and/or mechanism(s) responsible for this improvement still need to be elucidated. Future work should seek to identify these mechanisms and translate these significant findings into occupational and skilled performance settings.

Information Transmission via Molecular Communication in Astrobiological Environments

The ubiquity of information transmission via molecular communication between cells is comprehensively documented on Earth; this phenomenon might even have played a vital role in the origin(s) and early evolution of life. Motivated by these considerations, a simple model for molecular communication entailing the diffusion of signaling molecules from transmitter to receiver is elucidated. The channel capacity C (maximal rate of information transmission) and an optimistic heuristic estimate of the actual information transmission rate ℐ are derived for this communication system; the two quantities, especially the latter, are demonstrated to be broadly consistent with laboratory experiments and more sophisticated theoretical models. The channel capacity exhibits a potentially weak dependence on environmental parameters, whereas the actual information transmission rate may scale with the intercellular distance d as ℐ ∝ d-4 and could vary substantially across settings. These two variables are roughly calculated for diverse astrobiological environments, ranging from Earth's upper oceans (C ∼ 3.1 × 103 bits/s; ℐ ∼ 4.7 × 10-2 bits/s) and deep sea hydrothermal vents (C ∼ 4.2 × 103 bits/s; ℐ ∼ 1.2 × 10-1 bits/s) to the hydrocarbon lakes and seas of Titan (C ∼ 3.8 × 103 bits/s; ℐ ∼ 2.6 × 10-1 bits/s).

Physiological and performance effects of live high train low altitude training for elite endurance athletes: A narrative review

Altitude training has become an important training application for athletes due its potential for altering physiology and enhancing performance. This practice is commonly used by athletes, with a popular choice being the live high - train low approach. This model recommends that athletes live at high altitude (1250-3000 m), but train at low altitude or sea-level (0-1200 m). Exposure to altitude often leads to hypoxic stress and in turn stimulates changes in total haemoglobin mass, erythropoietin, and soluble transferrin receptors, which alter further underlying physiology. Through enhanced physiology, improved exercise performance may arise through enhancement of the oxygen transport system which is important for endurance events. Previous investigations into the effects of altitude training on exercise performance have been completed in a range of contexts, including running, cycling, swimming, and triathlon. Often following a LHTL altitude intervention, athletes realise improvements in maximal oxygen consumption capacity, time trial performance and peak power outputs. Although heterogeneity exists among LHTL methodologies, i.e., exposure durations and altitude ranges, we synthesised this data into kilometre hours, and found that the most common hypoxic doses used in LHTL interventions ranged from ∼578-687 km h. As this narrative review demonstrates, there are potential advantages to using altitude training to enhance physiology and improve performance for endurance athletes.

Ultrasonic measurement of temperature distributions in extreme environments: Electrical power plants testing in utility-scale steam generators

Thermal heterogeneities within energy conversion and storage, material processing, nuclear processes, aerospace, and military applications are often inaccessible to characterization by insertion sensors. When sensor deployment is possible, conventional pointwise temperature probes quickly degrade when inserted into harsh environments typical of such processes. We developed spatially-resolved ultrasonic thermometry to noninvasively measure the spatial distributions of thermal properties in such applications, even when sizable thermal gradients are present. Our method divides the path of ultrasonic propagation into segments bound by echogenic features, which create echoes in pulse-echo mode, encoding the information about interior temperature distributions. We use the acquired ultrasonic responses to estimate the internal temperature distributions by solving an inverse problem or concatenating segmental estimates. This work describes the implementation and industrial testing of the developed method at a coal-fired electrical power generation plant. We inserted an echogenically segmented Inconel 625 waveguide into the combustion zone of the utility-scale boiler and continuously acquired ultrasonic data while keeping sensitive components away from the damaging combustion environment. The accuracy of the time-dependent temperature distributions reconstructed from the ultrasonic measurements was comparable to that of thermocouples. The resiliency of ultrasonic thermometry to harsh combustion conditions was far superior to conventional insertion sensors. The measurements obtained during plant operation captured daily steam generation cycles in response to changing customer demand and intermittent contributions of renewable power sources to the power grid. These measurements have revealed new insights into the relationship between the dynamic power generation load and the conditions inside the steam generator. The successful industrial testing of spatially-resolved ultrasonic thermometry in solids indicates that the developed technology has matured to become an attractive alternative to conventional sensing in solving challenging problems of long-term thermal characterizations in extreme environments.

A Metagenomic Time-Series Approach to Assess the Ecological Stability of Microbial Mats in a Seasonally Fluctuating Environment

Microbial mats are complex ecological assemblages that have been present in the rock record since the Precambrian and can still be found in extant marginalized environments. These structures are considered highly stable ecosystems. In this study, we evaluate the ecological stability of dome-forming microbial mats in a modern, water-level fluctuating, hypersaline pond located in the Cuatro Ciénegas Basin, Mexico. We conducted metagenomic sampling of the site from 2016 to 2019 and detected 2250 genera of Bacteria and Archaea, with only <20 belonging to the abundant taxa (>1%). The microbial community was dominated by Proteobacteria, Euryarchaeota, Bacteroidetes, Firmicutes, and Cyanobacteria, and was compositionally sensitive to disturbances, leading to high taxonomic replacement even at the phylum level, with a significant increase in Archaea from [Formula: see text]1-4% to [Formula: see text]33% throughout the 2016-2019 study period. Although a core community represented most of the microbial community (>75%), relative abundances shifted significantly between samples, as demonstrated by changes in the abundance of Coleofasciculus from 10.2% in 2017 to 0.05% in 2019. Although functional differences between seasons were subtle, co-occurrence networks suggest differential ecological interactions between the seasons, with the addition of a new module during the rainy season and the potential shift in hub taxa. Functional composition was slightly more similar between samples, but basic processes such as carbohydrate, amino acid, and nucleic acid metabolisms were widely distributed among samples. Major carbon fixation processes included sulfur oxidation, nitrogen fixation, and photosynthesis (both oxygenic and anoxygenic), as well as the Wood-Ljundgahl and Calvin cycles.

Extreme environments and human health: From the immune microenvironments to immune cells

Exposure to extreme environments causes specific acute and chronic physiological responses in humans. The adaptation and the physiological processes under extreme environments predominantly affect multiple functional systems of the organism, in particular, the immune system. Dysfunction of the immune system affected by several extreme environments (including hyperbaric environment, hypoxia, blast shock, microgravity, hypergravity, radiation exposure, and magnetic environment) has been observed from clinical macroscopic symptoms to intracorporal immune microenvironments. Therefore, simulated extreme conditions are engineered for verifying the main influenced characteristics and factors in the immune microenvironments. This review summarizes the responses of immune microenvironments to these extreme environments during in vivo or in vitro exposure, and the approaches of engineering simulated extreme environments in recent decades. The related microenvironment engineering, signaling pathways, molecular mechanisms, clinical therapy, and prevention strategies are also discussed.

Extremophiles: the species that evolve and survive under hostile conditions

Extremophiles possess unique cellular and molecular mechanisms to assist, tolerate, and sustain their lives in extreme habitats. These habitats are dominated by one or more extreme physical or chemical parameters that shape existing microbial communities and their cellular and genomic features. The diversity of extremophiles reflects a long list of adaptations over millions of years. Growing research on extremophiles has considerably uncovered and increased our understanding of life and its limits on our planet. Many extremophiles have been greatly explored for their application in various industrial processes. In this review, we focused on the characteristics that microorganisms have acquired to optimally thrive in extreme environments. We have discussed cellular and molecular mechanisms involved in stability at respective extreme conditions like thermophiles, psychrophiles, acidophiles, barophiles, etc., which highlight evolutionary aspects and the significance of extremophiles for the benefit of mankind.

Feasibility of chest ultrasound up to 42 m underwater

After recent advancements, ultrasound has extended its applications from bedside clinical practice to wilderness medicine. Performing ultrasound scans in extreme environments can allow direct visualization of unique pathophysiological adaptations but can be technically challenging. This paper summarizes how a portable ultrasound apparatus was marinized to let scientific divers and sonographers perform ultrasound scans of the lungs underwater up to - 42 m. A metallic case protected the ultrasound apparatus inside; a frontal transparent panel with a glove allowed visualization and operation of the ultrasound by the diving sonographer. The inner pressure was equalized with environmental pressure through a compressed air tank connected with circuits similar to those used in SCUBA diving. Finally, the ultrasound probe exited the metallic case through a sealed aperture. No technical issues were reported after the first testing step and the real experiments.

Sponge organic matter recycling: Reduced detritus production under extreme environmental conditions

Sponges are a key component of coral reef ecosystems and play an important role in carbon and nutrient cycles. Many sponges are known to consume dissolved organic carbon and transform this into detritus, which moves through detrital food chains and eventually to higher trophic levels via what is known as the sponge loop. Despite the importance of this loop, little is known about how these cycles will be impacted by future environmental conditions. During two years (2018 and 2020), we measured the organic carbon, nutrient recycling, and photosynthetic activity of the massive HMA, photosymbiotic sponge Rhabdastrella globostellata at the natural laboratory of Bouraké in New Caledonia, where the physical and chemical composition of seawater regularly change according to the tide. We found that while sponges experienced acidification and low dissolved oxygen at low tide in both sampling years, a change in organic carbon recycling whereby sponges stopped producing detritus (i.e., the sponge loop) was only found when sponges also experienced higher temperature in 2020. Our findings provide new insights into how important trophic pathways may be affected by changing ocean conditions.

Shift in rhizospheric and endophytic microbial communities of dominant plants around Sunit Alkaline Lake

Alkaline lakes are a special type of extreme saline-alkali ecosystem, and the dominant plants store a large number of microbial resources with salinity-tolerant or growth-promoting properties in the littoral zones. In this study, high-throughput sequencing technology and molecular ecological networks were used to analyze the bacteria and fungi from different rhizocompartments of three dominant plants along the salinity gradient in the littoral zones of Sunit Alkali Lake. The study found that fungal communities were more tolerant of environmental abiotic stress, and salinity was not the main environmental factor affecting the composition of microbial communities. Mantel test analysis revealed that SOC (soil organic carbon) was the primary environmental factor affecting the rhizosphere bacterial community as well as the rhizosphere endophyte bacteria and fungi, while CO₃^2- (carbonate ions) had a greater impact on the rhizosphere fungal communities. In addition, keystones identified through the associated molecular network play an important role in helping plants resist saline-alkali environments. There were significant differences in the metabolic pathways of microorganisms from different rhizocompartments predicted by the PICRUSt2 database, which may help to understand how microorganisms resist environmental stress. This study is of great importance for understanding the salt environments around alkaline lakes and excavating potential microbial resources.

The effects of manipulating the visual environment on thermal perception: A structured narrative review

When exposed to ambient temperatures that cause thermal discomfort, a human's behavioral responses are more effective than autonomic ones at compensating for thermal imbalance. These behavioral thermal responses are typically directed by an individual's perception of the thermal environment. Perception of the environment is a holistic amalgamation of human senses, and in some circumstances, humans prioritize visual information. Existing research has considered this in the specific case of thermal perception, and this review investigates the state of the literature examining this effect. We identify the frameworks, research rationales, and potential mechanisms that underpin the evidence base in this area. Our review identified 31 experiments, comprising 1392 participants that met the inclusion criteria. Methodological heterogeneity was observed in the assessment of thermal perception, and a variety of methods were employed to manipulate the visual environment. However, the majority of the included experiments (80%) reported a difference in thermal perception after the visual environment was manipulated. There was limited research exploring any effects on physiological variables (e.g. skin and core temperature). This review has wide-ranging implications for the broad discipline of (thermo)physiology, psychology, psychophysiology, neuroscience, ergonomics, and behavior.

Fine-scale heterogeneity reveals disproportionate thermal stress and coral mortality in thermally variable reef habitats during a marine heatwave

Increasing ocean temperatures threaten coral reefs globally, but corals residing in habitats that experience high thermal variability are thought to be better adapted to survive climate-induced heat stress. Here, we used long-term ecological observations and in situ temperature data from Heron Island, southern Great Barrier Reef to investigate how temperature dynamics within various thermally variable vs. thermally stable reef habitats change during a marine heatwave and the resulting consequences for coral community survival. During the heatwave, thermally variable habitats experienced larger surges in daily mean and maxima temperatures compared to stable sites, including extreme hourly incursions up to 36.5 °C. The disproportionate increase in heat stress in variable habitats corresponded with greater subsequent declines in hard coral cover, including a three-times greater decline within the thermally variable Reef Flat (70%) and Deep Lagoon (83%) than within thermally stable habitats along sheltered and exposed areas of the reef slope (0.3-19%). Interestingly, the thermally variable Reef Crest experienced comparatively small declines (26%), avoiding the most severe tidal ponding and resultant heat stress likely due to proximity to the open ocean equating to lower seawater residence times, greater mixing, and/or increased flow. These results highlight that variable thermal regimes, and any acclimatization or adaptation to elevated temperatures that may lead to, do not necessarily equate to protection against bleaching and mortality during marine heatwaves. Instead, thermally stable habitats that have greater seawater exchange with the open ocean may offer the most protection to corals during the severe marine heatwaves that accompany a changing climate.

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1007/s00338-022-02328-6.

Evidencing the role of carbonic anhydrase in the formation of carbonate minerals by bacterial strains isolated from extreme environments in Qatar

Calcium carbonate, one of the most abundant minerals in the geological records is considered as primary source of the carbon reservoir. The role of microorganisms in the biotic precipitation of calcium carbonate has been extensively investigated, especially at extreme life conditions. In Qatar, Sabkhas which are microbial ecosystems housing biomineralizing bacteria, have been carefully studied as unique sites of microbial dolomite formation. Dolomite (CaMg(CO₃)₂ is an important carbonate mineral forming oil reservoir rocks; however, dolomite is rarely formed in modern environments. The enzyme carbonic anhydrase is present in many living organisms, performs interconversion between CO₂ and the bicarbonate ion. Thus, carbonic anhydrase is expected to accelerate both carbonate rock dissolution and CO₂ uptake at the same time, serving as carbonite source to carbonites-forming bacteria. This study gathered cross-linked data on the potential role of the carbonic anhydrase excreted by mineral-forming bacteria, isolated from two different extreme environments in Qatar. Dohat Faishakh Sabkha, is a hypersaline coastal Sabkha, from where various strains of the bacterium Virgibacillus were isolated. Virgibacillus can -not only-mediate carbonate mineral formation, but also contributes to magnesium incorporation into the carbonate minerals, leading to the formation of high magnesium calcite. The latter is considered as precursor for dolomite formation. In addition, bacterial strains isolated from marine sediments, surrounding coral reef in Qatar sea, would provide additional knowledge on the role of carbonic anhydrase in mineral formation. Here, the quantification of the two mostly described activities of carbonic anhydrase; esterase and hydration reactions were performed. Mineral-forming strains were shown to exhibit high activities as opposed to the non-forming minerals, which confirms the relation between the presence of active carbonic anhydrase combined with elevated metabolic activity and the biomineralizing potential of the bacterial strains. The highest specific intracellular carbonic anhydrase activity; as both esterase and hydration (i.e., 66 ± 3 and 583000 ± 39000 WAU/10⁸ cells respectively), was evidenced in mineral-forming strains as opposed to non-mineral forming strains (i.e., 6 ±. 0.5 and 1223 ± 61 WAU/10⁸cells) respectively. These findings would contribute to the understanding of the mechanism of microbially mediated carbonate precipitation. This role may be both in capturing CO₂ as source of carbonate, and partial solubilization of the formed minerals allowing incorporation of Mg instead of calcium, before catalyzing again the formation of more deposition of carbonates.

Exploring Space via Astromycology: A Report on the CIFAR Programs Earth 4D and Fungal Kingdom Inaugural Joint Meeting

"Fungi on Mars!": a popular news heading that piques public interest and makes scientists' blood boil. While such a statement is laden with misinformation and light on evidence, the search for past and present extraterrestrial life is an ongoing scientific effort. Moreover, it is one that is increasingly gaining momentum with the recent collection of martian rock cores from Jezero Crater by NASA's Perseverance rover. Despite the increasingly sophisticated approaches guiding the search for microbial life on other planets, fungi remain relatively underexplored compared to their bacterial counterparts, highlighting a gap between the astrobiological and fungal research communities. Through a meeting in April 2021, the CIFAR Earth 4D and Fungal Kingdom research programs worked to bridge this divide by uniting experts in each field. CIFAR is a Canadian-based global research organization that convenes researchers across disciplines to address important questions facing science and humanity. The CIFAR Earth 4D: Subsurface Science & Exploration and Fungal Kingdom: Threats & Opportunities research programs were launched by CIFAR in July 2019, each made up of approximately two dozen international researchers who are experts in their fields. The Earth 4D program, led by co-directors John Mustard (Brown University, USA) and Barbara Sherwood Lollar (University of Toronto, Canada), aims to understand the complex chemical, physical, and biological interactions that occur within and between Earth's surface and subsurface to explore questions on the evolution of planets and life. The Fungal Kingdom program, led by co-directors Leah Cowen (University of Toronto, Canada) and Joseph Heitman (Duke University, USA), seeks to tackle the most pressing threats fungi pose to human health, agriculture, and biodiversity and to harness their extraordinary potential. The programs met to explore areas for synergy within four major themes: (1) the origins of life; (2) the evolution and diversification of life; (3) life in diverse and extreme environments; and (4) extinction: lessons learned and threats. This report covers the research discussed during the meeting across these four themes.

Extreme freeze-tolerance in cryophilic tardigrades relies on controlled ice formation but does not involve significant change in transcription

Subzero temperatures are among the most significant factors defining the distribution of organisms, yet, certain taxa have evolved to overcome this barrier. The microscopic tardigrades are among the most freeze-tolerant animals, with selected species reported to survive milli-Kelvin temperatures. Here, we estimate survival of fully hydrated eutardigrades of the species Ramazzottius varieornatus following exposures to -20 °C and  -80 °C as well as -196 °C with or without initial cooling to -80 °C. The tardigrades easily survive these temperatures, yet with a significant decrease in viability following rapid cooling by direct exposure to -196 °C. Hence, post-freeze recovery of R. varieornatus seems to rely on cooling rate and thus controlled ice formation. Cryophilic organisms are renowned for having cold-active enzymes that secure appropriate reaction rates at low temperatures. Hence, extreme freeze-tolerance in R. varieornatus could potentially involve syntheses of cryoprotectants and de novo transcription. We therefore generated a reference transcriptome for this cryophilic R. varieornatus population and explored for differential gene expression patterns following cooling to -80 °C as compared to active 5 °C controls. Specifically, we tested for fast transcription potentially occurring within 25 min of cooling from room temperature to a supercooling point of ca. -20 °C, at which the tardigrades presumably freeze and enter into the ametabolic state of cryobiosis. Our analyses revealed no evidence for differential gene expression. We, therefore, conclude that extreme freeze-tolerance in R. varieornatus relies on controlled extracellular freezing with any freeze-tolerance related genes being constitutively expressed.

Differential expression profiling of heat stressed tardigrades reveals major shift in the transcriptome

Tardigrades are renowned for their extreme stress tolerance, which includes the ability to endure complete desiccation, high levels of radiation and very low sub-zero temperatures. Nevertheless, tardigrades appear to be vulnerable to high temperatures and thus the potential effects of global warming. Here, we provide the first analysis of transcriptome data obtained from heat stressed specimens of the eutardigrade Ramazzottius varieornatus, with the aim of providing new insights into the molecular processes affected by high temperatures. Specifically, we compare RNA-seq datasets obtained from active, heat-exposed (35 °C) tardigrades to that of active controls kept at 5 °C. Our data reveal a surprising shift in transcription, involving 9634 differentially expressed transcripts, corresponding to >35% of the transcriptome. The latter data are in striking contrast to the hitherto observed constitutive expression underlying tardigrade extreme stress tolerance and entrance into the latent state of life, known as cryptobiosis. Thus, when examining the molecular response, heat-stress appears to be more stressful for R. varieornatus than extreme conditions, such as desiccation or freezing. A gene ontology analysis reveals that the heat stress response involves a change in transcription and presumably translation, including an adjustment of metabolism, and, putatively, preparation for encystment and subsequent diapause. Among the differentially expressed transcripts we find heat-shock proteins as well as the eutardigrade specific proteins (CAHS, SAHS, MAHS, RvLEAM, and Dsup). The latter proteins thus seem to contribute to a general stress response, and may not be directly related to cryptobiosis.

The highly diverse Antarctic Peninsula soil microbiota as a source of novel resistance genes

The rise of multiresistant bacterial pathogens is currently one of the most critical threats to global health, encouraging a better understanding of the evolution and spread of antimicrobial resistance. In this regard, the role of the environment as a source of resistance mechanisms remains poorly understood. Moreover, we still know a minimal part of the microbial diversity and resistome present in remote and extreme environments, hosting microbes that evolved to resist harsh conditions and thus a potentially rich source of novel resistance genes. This work demonstrated that the Antarctic Peninsula soils host a remarkable microbial diversity and a widespread presence of autochthonous antibiotic-resistant bacteria and resistance genes. We observed resistance to a wide array of antibiotics among isolates, including Pseudomonas resisting ten or more different compounds, with an overall increased resistance in bacteria from non-intervened areas. In addition, genome analysis of selected isolates showed several genes encoding efflux pumps, as well as a lack of known resistance genes for some of the resisted antibiotics, including colistin, suggesting novel uncharacterized mechanisms. By combining metagenomic approaches based on analyzing raw reads, assembled contigs, and metagenome-assembled genomes, we found hundreds of widely distributed genes potentially conferring resistance to different antibiotics (including an outstanding variety of inactivation enzymes), metals, and biocides, hosted mainly by Polaromonas, Pseudomonas, Streptomyces, Variovorax, and Burkholderia. Furthermore, a proportion of these genes were found inside predicted plasmids and other mobile elements, including a putative OXA-like carbapenemase from Polaromonas harboring conserved key residues and predicted structural features. All this evidence indicates that the Antarctic Peninsula soil microbiota has a broad natural resistome, part of which could be transferred horizontally to pathogenic bacteria, acting as a potential source of novel resistance genes.

Endolithic Bacterial Diversity in Lichen-Dominated Communities Is Shaped by Sun Exposure in McMurdo Dry Valleys, Antarctica

The diversity and composition of endolithic bacterial diversity of several locations in McMurdo Dry Valleys (Continental Antarctica) were explored using amplicon sequencing, targeting the V3 and V4 of the 16S region. Despite the increasing interest in edaphic factors that drive bacterial community composition in Antarctic rocky communities, few researchers focused attention on the direct effects of sun exposure on bacterial diversity; we herein reported significant differences in the northern and southern communities. The analysis of β-diversity showed significant differences among sampled localities. For instance, the most abundant genera found in the north-exposed rocks were Rhodococcus and Blastococcus in Knobhead Mt.; Ktedonobacter and Cyanobacteria Family I Group I in Finger Mt.; Rhodococcus and Endobacter in University Valley; and Segetibacter and Tetrasphaera in Siegfried Peak samples. In south-exposed rocks, instead, the most abundant genera were Escherichia/Shigella and Streptococcus in Knobhead Mt.; Ktedonobacter and Rhodococcus in Finger Mt.; Ktedonobacter and Roseomonas in University Valley; and Blastocatella, Cyanobacteria Family I Group I and Segetibacter in Siegfried Peak. Significant biomarkers, detected by the Linear discriminant analysis Effect Size, were also found among north- and south-exposed communities. Besides, the large number of positive significant co-occurrences may suggest a crucial role of positive associations over competitions under the harsher conditions where these rock-inhabiting microorganisms spread. Although the effect of geographic distances in these extreme environments play a significant role in shaping biodiversity, the study of an edaphic factor, such as solar exposure, adds an important contribution to the mosaic of microbial biodiversity of Antarctic bacterial cryptoendolithic communities.

Venus, an Astrobiology Target

We present a case for the exploration of Venus as an astrobiology target-(1) investigations focused on the likelihood that liquid water existed on the surface in the past, leading to the potential for the origin and evolution of life, (2) investigations into the potential for habitable zones within Venus' present-day clouds and Venus-like exo atmospheres, (3) theoretical investigations into how active aerobiology may impact the radiative energy balance of Venus' clouds and Venus-like atmospheres, and (4) application of these investigative approaches toward better understanding the atmospheric dynamics and habitability of exoplanets. The proximity of Venus to Earth, guidance for exoplanet habitability investigations, and access to the potential cloud habitable layer and surface for prolonged in situ extended measurements together make the planet a very attractive target for near term astrobiological exploration.

Isolation of a novel halothermophilic strain of the genus Gracilibacillus from Howz-e Sultan hypersaline lake in Iran

Background and Objectives:

Halothermophilic bacteria are adapted to high osmolarity and can grow in high saline environments and high temperatures. This study was aimed at the isolation of halothermophilic bacteria from Howz-e Sultan hypersaline lake in the central desert zone in Iran.

Materials and Methods:

Samples were collected and after preparing dilutions, the samples were cultured on Molten haloid agar with different salt concentrations (5–35%), then the plates were incubated at 35–70ºC in both aerobic and anaerobic conditions. Biochemical characterizations, utilization of carbon sources, production of exoenzymes and antibiotic susceptibility were investigated. Taxonomic and phylogenetic analyses were performed using 16S rRNA gene sequences.

Results:

One of the isolated bacteria was found to be Gram-positive, hyperhalophilic, thermophilic, endospore-forming, and was named as 1–9 h isolate. The bacterial cells were bacilli-shaped, which produced endospores at a subterminal position. This isolate was an aerobe and facultative anaerobe and grew between pH 5.0 and 10.0 (optimal growth at pH 7.0–7.5), at temperature between 15°C and 65°C (optimal growth at 40–45°C) and at salinity of 9–32% (w/v) NaCl, growing optimally at 18% (w/v) NaCl. On the basis of 16S rRNA gene sequence analysis, isolate 1–9 h belongs to the genus Bacillus within the phylum Firmicutes and showed the closest phylogenetic similarity to Gracilibacillus sp. IBP-V003 (99.0%).

Conclusion:

Based on the results of its phenotypic and genotypic properties, strain 1–9 h represents a novel strain of the genus Gracilibacillus. It can be used in various fields of industry and biotechnology.

Brains in space: the importance of understanding the impact of long-duration spaceflight on spatial cognition and its neural circuitry

Fifty years after the first humans stepped on the Moon, space faring nations have entered a new era of space exploration. NASA’s reference mission to Mars is expected to comprise 1100 days. Deep space exploratory class missions could even span decades. They will be the most challenging and dangerous expeditions in the history of human spaceflight and will expose crew members to unprecedented health and performance risks. The development of adverse cognitive or behavioral conditions and psychiatric disorders during those missions is considered a critical and unmitigated risk factor. Here, we argue that spatial cognition, i.e., the ability to encode representations about self-to-object relations and integrate this information into a spatial map of the environment, and their neural bases will be highly vulnerable during those expeditions. Empirical evidence from animal studies shows that social isolation, immobilization, and altered gravity can have profound effects on brain plasticity associated with spatial navigation. We provide examples from historic spaceflight missions, spaceflight analogs, and extreme environments suggesting that spatial cognition and its neural circuitry could be impaired during long-duration spaceflight, and identify recommendations and future steps to mitigate these risks.

Psychosocial issues in isolated and confined extreme environments

PALINKAS, L.A., and P. SUEDFELD. Psychosocial Issues in Isolated and Confined Extreme Environments. NEUROSCI BIOBEHAV REV (1) XXX-XXX, 2020. Psychosocial elements of behavior and performance will significantly impact the outcomes of long duration missions in space, ranging from individual and team decrements to positive benefits associated with successful adaptation. This paper reviews our current understanding of the individual, interpersonal and organizational issues related to living and working in isolated and confined extreme (ICE) environments. Individual issues include changes in emotions and cognitive performance; seasonal syndromes linked to changes in the physical environment; and positive effects of adapting to ICE environments. Interpersonal issues include processes of crew cohesion, tension and conflict; interpersonal relations and social support; the impact of group diversity and leadership styles on small group dynamics; and crew-mission control interactions. Organizational issues include the influence of organizational culture and mission duration on individual and group performance, crew autonomy, and managerial requirements for long duration missions. Improved screening and selection, leadership, coping and interpersonal skills training, and organizational change are key elements to optimizing adjustment to the environment and preventing decrements during and after long duration missions.

Why are nematodes so successful extremophiles?

Extreme environments constitute the largest habitat on earth, but our understanding of life in such environments is rudimentary. The hostility of extreme environments such as the deep sea, earth’s crust, and toxic lakes limits the sampling, culturing, and studying of extremophiles, the organisms that live in these habitats. Thus, in terms of ecological research, extreme environments are the earth’s final frontier. A growing body of data suggests that nematodes are the most common animal taxon in different types of extreme settings such as the deep-subsurface and sediments in the deep sea. Notably, the reasons for the abundance of nematodes in extreme habitats remain mostly unknown. I propose that a unique combination of several characteristics of nematodes may explain, additively or synergistically, their successful adaptation to extreme habitats. Novel functional genetic and genomic approaches are expected to reveal molecular mechanisms of adaptation of nematodes to the many fascinating extreme environments on earth.

Taxonomic and functional analyses of intact microbial communities thriving in extreme, astrobiology-relevant, anoxic sites

BACKGROUND

Extreme terrestrial, analogue environments are widely used models to study the limits of life and to infer habitability of extraterrestrial settings. In contrast to Earth's ecosystems, potential extraterrestrial biotopes are usually characterized by a lack of oxygen.

METHODS

In the MASE project (Mars Analogues for Space Exploration), we selected representative anoxic analogue environments (permafrost, salt-mine, acidic lake and river, sulfur springs) for the comprehensive analysis of their microbial communities. We assessed the microbiome profile of intact cells by propidium monoazide-based amplicon and shotgun metagenome sequencing, supplemented with an extensive cultivation effort.

RESULTS

The information retrieved from microbiome analyses on the intact microbial community thriving in the MASE sites, together with the isolation of 31 model microorganisms and successful binning of 15 high-quality genomes allowed us to observe principle pathways, which pinpoint specific microbial functions in the MASE sites compared to moderate environments. The microorganisms were characterized by an impressive machinery to withstand physical and chemical pressures. All levels of our analyses revealed the strong and omnipresent dependency of the microbial communities on complex organic matter. Moreover, we identified an extremotolerant cosmopolitan group of 34 poly-extremophiles thriving in all sites.

CONCLUSIONS

Our results reveal the presence of a core microbiome and microbial taxonomic similarities between saline and acidic anoxic environments. Our work further emphasizes the importance of the environmental, terrestrial parameters for the functionality of a microbial community, but also reveals a high proportion of living microorganisms in extreme environments with a high adaptation potential within habitability borders. Video abstract.

Marine microorganisms as an untapped source of bioactive compounds

The search for novel biologically active molecules has extended to the screening of organisms associated with less explored environments. In this sense, Oceans, which cover nearly the 67% of the globe, are interesting ecosystems characterized by a high biodiversity that is worth being explored. As such, marine microorganisms are highly interesting as promising sources of new bioactive compounds of potential value to humans. Some of these microorganisms are able to survive in extreme marine environments and, as a result, they produce complex molecules with unique biological interesting properties for a wide variety of industrial and biotechnological applications. Thus, different marine microorganisms (fungi, myxomycetes, bacteria, and microalgae) producing compounds with antioxidant, antibacterial, apoptotic, antitumoral and antiviral activities have been already isolated. This review compiles and discusses the discovery of bioactive molecules from marine microorganisms reported from 2018 onwards. Moreover, it highlights the huge potential of marine microorganisms for obtaining highly valuable bioactive compounds.

Heat stress and PPE during COVID-19: impact on healthcare workers' performance, safety and well-being in NHS settings

Personal protective equipment (PPE) can potentiate heat stress, which may have a negative impact on the wearer's performance, safety and well-being. In view of this, a survey was distributed to healthcare workers (HCWs) required to wear PPE during the coronavirus disease 2019 pandemic in the UK to evaluate perceived levels of heat stress and its consequences. Respondents reported experiencing several heat-related illness symptoms, and heat stress impaired both cognitive and physical performance. The majority of respondents stated that wearing PPE made their job more difficult. These, and additional, responses suggest that modification to current working practices is required urgently to improve the resilience of HCWs to wearing PPE during pandemics.

AMADEE-18: Vision-Based Unmanned Aerial Vehicle Navigation for Analog Mars Mission (AVI-NAV)

As a part of the AMADEE-18 analog Mars mission, designed to study challenges associated with human-based exploration of the Red Planet, we focused our team efforts on testing means to localize an unmanned aerial vehicle (UAV) on Mars. Robot helicopters, such as the one selected for a technology demonstration as a part of NASA's Mars 2020 mission, are small and their performance is computationally limited. An essential aspect of navigation and path planning of an autonomous helicopter is accurate localization of the robot. In the absence of a global positioning system, a computationally efficient localization technology that can be applied on Mars is visual-inertial odometry (VIO). The AMADEE-18 mission provided an opportunity to test the feasibility of a state-of-the-art VIO algorithm and the camera in a Mars-like analog environment. The flight datasets included different terrain structures that challenged the functionality of VIO algorithms. The experiment has yielded valuable insights into the desired surface structure, texture, and mission times for surface relative navigation of UAV on Mars.

Under pressure: the extraordinary survival of seal lice in the deep sea

Lice from pinnipeds - sea lions, seals and walruses - are the only insects capable of surviving marine dives. Throughout their evolutionary history, they have adapted to tolerate hypoxia, high salinity, low temperature and, in particular, to tolerate conditions of high hydrostatic pressure. To understand the limits of the capacity of lice to survive during host deep dives, we conducted a series of controlled experiments in the laboratory. We collected lice from elephant seals and submitted the different life stages to high pressure conditions. Lice were first exposed to one of four hydrostatic pressures: 30, 80, 150 or 200 kg cm-2 They were then exposed a second time to higher or lower hydrostatic pressure conditions to test for the impact of the first experience, which could either be deleterious or trigger physiological adaption, allowing them a better tolerance to high pressure. We found that lice from elephant seals can tolerate hydrostatic pressures higher than 200 kg cm-2 (close to 200 atm), which is equivalent to 2000 m depth. Adults exhibited lower recovery times than nymphs after immersion at high hydrostatic pressure. Our findings show that lice have developed unique adaptations to endure extreme marine conditions. We discuss these extreme performances in relation to the morphological characteristics and physiological responses to diving in these insects.

Peptone from casein, an antagonist of nonribosomal peptide synthesis: a case study of pedopeptins produced by Pedobacter lusitanus NL19

Novel natural products are urgently needed to address the worldwide incidence of bacterial resistance to antibiotics. Extreme environments are a major source of novel compounds with unusual chemical structures. Pedobacter lusitanus NL19 is a new bacterial species that was isolated from one such environment and which produces compounds with potent activity against relevant microorganisms in the clinical, food, veterinary and aquaculture areas. The production of antimicrobials by P. lusitanus NL19 was identified in tryptic soy agar (TSA), but not in its equivalent broth (TSB). It was observed that in TSB medium a high concentration of casein peptone (PC) repressed the production of antibacterial compounds. HPLC, MS and MS/MS spectra with de novo sequencing revealed that the bioactivity of P. lusitanus NL19 was due to the production of pedopeptins. Hence, biosynthesis of pedopeptins is inhibited by high concentrations of PC in the broth medium. Furthermore, a nonribosomal peptide synthetase (NRPS) gene cluster was identified in the genome of NL19 encoding the biosynthesis of the peptides. qPCR analysis confirmed that the transcription of these genes is repressed in cells cultivated in high concentrations of PC. It is shown that pedopeptins are nonribosomal peptides with a broad-spectrum activity, including against Gram-positive and Gram-negative bacteria and yeasts.

Composition and predicted functions of the bacterial community in spouting pool sediments from the El Tatio Geyser field in Chile

The El Tatio Geyser Field (ETGF), located in Northern Chile, is the main geyser field in the southern hemisphere. Despite this, details of its microbial ecology are still unknown. Here, we briefly report on  the composition and predicted functions of the bacterial community in spouting pool sediments from the ETGF as revealed by high-throughput sequencing of 16S rRNA genes. Results of this analysis showed that while there were differences in richness and diversity between samples, bacterial communities were primarily dominated by the phyla Proteobacteria, followed Firmicutes, Bacteroidetes, Acidobacteria, and Chloroflexi. Analyses of predicted functional activity indicated that the functions were mostly attributed to chemoheterotrophy and aerobic chemoheterotrophy, followed by sulfur (respiration of sulfur compounds and sulfate) and nitrogen (nitrate reduction, respiration of nitrogen and nitrate) cycling. Taken together, our results suggest a high diversity in taxonomy and predictive functions of bacterial communities in sediments from spouting pools. This study provides fundamentally important  information on the structure and function  predictive functions of microbiota  communities in spouting pools. Moreover, since the ETGF is intensively visited and impacted by tens of thousands of tourists every year, our results can be used to help guide the design of sustainable conservation strategies.

Adaptations, life-history traits and ecological mechanisms of parasites to survive extremes and environmental unpredictability in the face of climate change

Climate change is increasing weather unpredictability, causing more intense, frequent and longer extreme events including droughts, precipitation, and both heat and cold waves. The performance of parasites, and host-parasite interactions, under these unpredictable conditions, are directly influenced by the ability of parasites to cope with extremes and their capacity to adapt to the new conditions. Here, we review some of the structural, behavioural, life history and ecological characteristics of parasitic nematodes that allow them to persist and adapt to extreme and changing environmental conditions. We focus primarily, but not exclusively, on parasitic nematodes in the Arctic, where temperature extremes are pronounced, climate change is happening most rapidly, and changes in host-parasite interactions are already documented. We discuss how life-history traits, phenotypic plasticity, local adaptation and evolutionary history can influence the short and long term response of parasites to new conditions. A detailed understanding of the complex ecological processes involved in the survival of parasites in extreme and changing conditions is a fundamental step to anticipate the impact of climate change in parasite dynamics.

Origin, distribution, and geochemistry of arsenic in the Altiplano-Puna plateau of Argentina, Bolivia, Chile, and Perú

Elevated concentrations of arsenic in water supplies represent a worldwide health concern. In at least 14 countries of South America, high levels have been detected relative to international standards and guidelines. Within these countries, the high plateau referred to as the "Altiplano-Puna", encompassing areas of Argentina, Bolivia, Chile, and Perú, exhibits high arsenic concentrations that could be affecting 3 million inhabitants. The origins of arsenic in the Altiplano-Puna plateau are diverse and are mainly natural in origin. Of the natural sources, the most important correspond to mineral deposits, brines, hot springs, and volcanic rocks, whereas anthropogenic sources are related to mining activities and the release of acid mine drainage (AMD). Arsenic is found in all water types of the Altiplano-Puna plateau over a wide range of concentrations (0.01 mg·L^-1 < As in water > 10 mg·L^-1) which in decreasing order correspond to: AMD, brines, saline waters, hot springs, rivers affected by AMD, rivers and lakes, and groundwater. Despite the few studies which report As speciation, this metalloid appears mostly in its oxidized form (As[V]) and its mobility is highly susceptible to the influence of dry and wet seasons. Once arsenic is released from its natural sources, it also precipitates in secondary minerals where it is generally stable in the form of saline precipitates and Fe oxides. In relation to human health, arsenic adaptation has been detected in some aboriginal communities of the Puna together with an efficient metabolism of this metalloid. Also, the inefficient methylation of inorganic As in women of the Altiplano might lead to adverse health effects such as cancer. Despite the health risks of living in this arsenic-rich environment with limited water resources, not all of the Altiplano-Puna is properly characterized and there exists a lack of information regarding the basic geochemistry of arsenic in the region.

The art of adapting to extreme environments: The model system Pseudoalteromonas

Extremophilic microbes have adapted to thrive in ecological niches characterized by harsh chemical/physical conditions such as, for example, very low/high temperature. Living organisms inhabiting these environments have developed peculiar mechanisms to cope with extreme conditions, in such a way that they mark the chemical-physical boundaries of life on Earth. Studying such mechanisms is stimulating from a basic research viewpoint and because of biotechnological applications. Pseudoalteromonas species are a group of marine gamma-proteobacteria frequently isolated from a range of extreme environments, including cold habitats and deep-sea sediments. Since deep-sea floors constitute almost 60% of the Earth's surface and cold temperatures represent the most common of the extreme conditions, the genus Pseudoalteromonas can be considered one of the most important model systems for studying microbial adaptation. Particularly, among all Pseudoalteromonas representatives, P. haloplanktis TAC125 has recently gained a central role. This bacterium was isolated from seawater sampled along the Antarctic ice-shell and is considered one of the model organisms of cold-adapted bacteria. It is capable of thriving in a wide temperature range and it has been suggested as an alternative host for the soluble overproduction of heterologous proteins, given its ability to rapidly multiply at low temperatures. In this review, we will present an overview of the recent advances in the characterization of Pseudoalteromonas strains and, more importantly, in the understanding of their evolutionary and chemical-physical strategies to face such a broad array of extreme conditions. A particular attention will be given to systems-biology approaches in the study of the above-mentioned topics, as genome-scale datasets (e.g. genomics, proteomics, phenomics) are beginning to expand for this group of organisms. In this context, a specific section dedicated to P. haloplanktis TAC125 will be presented to address the recent efforts in the elucidation of the metabolic rewiring of the organisms in its natural environment (Antarctica).

The Dallol Geothermal Area, Northern Afar (Ethiopia)-An Exceptional Planetary Field Analog on Earth

The Dallol volcano and its associated hydrothermal field are located in a remote area of the northern Danakil Depression in Ethiopia, a region only recently appraised after decades of inaccessibility due to severe political instability and the absence of infrastructure. The region is notable for hosting environments at the very edge of natural physical-chemical extremities. It is surrounded by a wide, hyperarid salt plain and is one of the hottest (average annual temperature_Dallol: 36-38°C) and most acidic natural systems (pH_Dallol ≈0) on Earth. Spectacular geomorphologies and mineral deposits produced by supersaturated hydrothermal waters and brines are the result of complex interactions between active and inactive hydrothermal alteration of the bedrock, sulfuric hot springs and pools, fumaroles and geysers, and recrystallization processes driven by hydrothermal waters, degassing, and rapid evaporation. The study of planetary field analog environments plays a crucial role in characterizing the physical and chemical boundaries within which life can exist on Earth and other planets. It is essential for the definition and assessment of the conditions of habitability on other planets, including the possibility for biosignature preservation and in situ testing of technologies for life detection. The Dallol area represents an excellent Mars analog environment given that the active volcanic environment, the associated diffuse hydrothermalism and hydrothermal alteration, and the vast acidic sulfate deposits are reminiscent of past hydrothermal activity on Mars. The work presented in this paper is an overview of the Dallol volcanic area and its hydrothermal field that integrates previous literature with observations and results obtained from field surveys and monitoring coupled with sample characterization. In so doing, we highlight its exceptional potential as a planetary field analog as well as a site for future astrobiological and exploration programs.

Using Science-Driven Analog Research to Investigate Extravehicular Activity Science Operations Concepts and Capabilities for Human Planetary Exploration

Biologic Analog Science Associated with Lava Terrains (BASALT) is a science-driven exploration program seeking to determine the best tools, techniques, training requirements, and execution strategies for conducting Mars-relevant field science under spaceflight mission conditions. BASALT encompasses Science, Science Operations, and Technology objectives. This article outlines the BASALT Science Operations background, strategic research questions, study design, and a portion of the results from the second field test. BASALT field tests are used to iteratively develop, integrate, test, evaluate, and refine new concepts of operations (ConOps) and capabilities that enable efficient and productive science. This article highlights the ConOps investigated during BASALT in light of future planetary extravehicular activity (EVA), which will focus on scientific exploration and discovery, and serves as an introduction to integrating exploration flexibility with operational rigor, the value of tactical and strategic science planning and execution, and capabilities that enable and enhance future science EVA operations.

Environmental parameters, and not phylogeny, determine the composition of extracellular polymeric substances in microbial mats from extreme environments

The ability to establish biofilms is a key trait for microorganisms growing in extreme environments. The extracellular polymeric substances (EPS) present in biofilms provide not only surface attachment, but also protection against all kinds of environmental stressors, including desiccation, salinity, temperature or heavy metal pollution. The acquisition of suitable biofilm characteristics might thus be an important process mediating the adaptation of microorganisms to novel environmental conditions. In this work we have characterized the EPS of 20 phylogenetically diverse biofilms collected in situ from five contrasting extreme environments, including two geothermal areas (Copahue, Argentina; Seltun, Iceland), two cold areas (Pastoruri glacier, Peru; Byers Peninsula, Antarctica) and one extremely acidic river (Río Tinto, Spain). Biofilms were subjected to biochemical characterization, glycan profiling and immunoprofiling with an antibody microarray. Our results showed that environmental conditions strongly influence biofilm characteristics, with microorganisms from the same environment achieving similar EPS compositions regardless of the phylogeny of their main species. The concentration of some monosaccharides in the EPS could be related to environmental conditions such as temperature or heavy metal toxicity, suggesting that in some cases stress resistance can be mediated by specific sugars. Overall, our results highlight the existence of conserved EPS compositional patterns for each extreme environment, which could in turn be exploited to engineer ecological adaptations in genetically modified microorganisms.

Microbial strains isolated from CO2-venting Kolumbo submarine volcano show enhanced co-tolerance to acidity and antibiotics

As ocean acidification intensifies, there is growing global concern about the impacts that future pH levels are likely to have on marine life and ecosystems. By analogy, a steep decrease of seawater pH with depth is encountered inside the Kolumbo submarine volcano (northeast Santorini) as a result of natural CO₂ venting, making this system ideal for ocean acidification research. Here, we investigated whether the increase of acidity towards deeper layers of Kolumbo crater had any effect on relevant phenotypic traits of bacterial isolates. A total of 31 Pseudomonas strains were isolated from both surface- (SSL) and deep-seawater layers (DSL), with the latter presenting a significantly higher acid tolerance. In particular, the DSL strains were able to cope with H⁺ levels that were 18 times higher. Similarly, the DSL isolates exhibited a significantly higher tolerance than SSL strains against six commonly used antibiotics and As(III). More importantly, a significant positive correlation was revealed between antibiotics and acid tolerance across the entire set of SSL and DSL isolates. Our findings imply that Pseudomonas species with higher resilience to antibiotics could be favored by the prospect of acidifying oceans. Further studies are required to determine if this feature is universal across marine bacteria and to assess potential ecological impacts.

A Desert Cyanobacterium under Simulated Mars-like Conditions in Low Earth Orbit: Implications for the Habitability of Mars

In the ESA space experiment BIOMEX (BIOlogy and Mars EXperiment), dried Chroococcidiopsis cells were exposed to Mars-like conditions during the EXPOSE-R2 mission on the International Space Station. The samples were exposed to UV radiation for 469 days and to a Mars-like atmosphere for 722 days, approaching the conditions that could be faced on the surface of Mars. Once back on Earth, cell survival was tested by growth-dependent assays, while confocal laser scanning microscopy and PCR-based assay were used to analyze the accumulated damage in photosynthetic pigments (chlorophyll a and phycobiliproteins) and genomic DNA, respectively. Survival occurred only for dried cells (4-5 cell layers thick) mixed with the martian soil simulants P-MRS (phyllosilicatic martian regolith simulant) and S-MRS (sulfatic martian regolith simulant), and viability was only maintained for a few hours after space exposure to a total UV (wavelength from 200 to 400 nm) radiation dose of 492 MJ/m² (attenuated by 0.1% neutral density filters) and 0.5 Gy of ionizing radiation. These results have implications for the hypothesis that, during Mars's climatic history, desiccation- and radiation-tolerant life-forms could have survived in habitable niches and protected niches while transported.

Michel Jouvet and "exotic" sleep

Michel Jouvet directed my medical thesis on paradoxical sleep in cats obtained in 1969, and my research on sleep in extreme environments (Antarctica, Arctic winter cold, physical exercise), which was the subject of my Ph.D. dissertation in 1984. As a military MD and scientist, I was posted in "exotic" (far away) places (Antarctica, Canada, Niger) and participated in several remote field trials (Canada, Côte d'Ivoire, Congo, Angola). Michel Jouvet supervised my research activity, allowing me the use of his laboratory facilities. He co-authored the work on sleep in Antarctica in 1987. In 1988, he was invited to Niamey (Niger) to preside on the international jury of medical doctorate dissertations. He then examined one of my patients with narcolepsy-like sleep attacks, suspect of sleeping sickness. Jouvet also co-authored our work on nitric oxide in the rat model of sleeping sickness. His scientific curiosity led him to study REM sleep eye movements in Bassari people, an isolated ethnic group in Senegal. With Monique Gessain, he co-authored a book on the Bassari oneiric activity. He was convinced that research in electricity-free villages was capital for understanding past mankind story. The present contribution recognizes the tremendous work capacity and scientific curiosity of Michel Jouvet.

Effects of acute or chronic heat exposure, exercise and dehydration on plasma cortisol, IL-6 and CRP levels in trained males

This study examined the acute and chronic effects of euhydrated and hypohydrated heat exposure, on biomarkers of stress and inflammation. Eight trained males [mean (SD) age: 21 (3) y; mass: 77.30 (4.88) kg; V̇O_2max: 56.9 (7.2) mL kg^-1 min^-1] undertook two heat acclimation programmes (balanced cross-over design), once drinking to maintain euhydration and once with restricted fluid-intake (permissive dehydration). Days 1, 6, and 11 were 60 min euhydrated exercise-heat stress tests (40 °C; 50% RH, 35% peak power output), days 2-5 and 7-10 were 90 min, isothermal-strain (target rectal temperature: 38.5 °C) exercise-heat sessions. Plasma was obtained pre- and post- exercise on day 1, 2, and 11 and analysed for cortisol, interleukin-6 (IL-6), and C-reactive protein (CRP). Cortisol and CRP were also assessed on day 6. IL-6 was elevated following the initial (acute) 90 min isothermal heat strain exercise-heat exposure (day 2) with permissive dehydration ((pre exercise: 1.0 pg mL^-1 [0.9], post-exercise: 1.8 pg mL^-1 [1.0], P = .032) and when euhydrated (pre-exercise: 1.0 pg mL^-1 [1.4], post-exercise: 1.6 pg mL^-1 [2.1], P = .048). Plasma cortisol levels were also elevated but only during permissive dehydration (P = .032). Body mass loss was strongly correlated with Δcortisol (r = -0.688, P = .003). Although there was a trend for post-exercise cortisol to be decreased following both heat acclimation programmes (chronic effects), there were no within or between intervention differences in IL-6 or CRP. In conclusion, acute exercise in the heat increased IL-6 and cortisol only when fluid-intake is restricted. There were no chronic effects of either intervention on biomarkers of inflammation as evidenced by IL-6 and CRP returning to basal level at the end of heat acclimation.

Sodium bicarbonate supplementation improves severe-intensity intermittent exercise under moderate acute hypoxic conditions

Acute moderate hypoxic exposure can substantially impair exercise performance, which occurs with a concurrent exacerbated rise in hydrogen cation (H⁺) production. The purpose of this study was therefore, to alleviate this acidic stress through sodium bicarbonate (NaHCO₃) supplementation and determine the corresponding effects on severe-intensity intermittent exercise performance. Eleven recreationally active individuals participated in this randomised, double-blind, crossover study performed under acute normobaric hypoxic conditions (FiO₂% = 14.5%). Pre-experimental trials involved the determination of time to attain peak bicarbonate anion concentrations ([HCO₃⁻]) following NaHCO₃ ingestion. The intermittent exercise tests involved repeated 60-s work in their severe-intensity domain and 30-s recovery at 20 W to exhaustion. Participants ingested either 0.3 g kg bm⁻¹ of NaHCO₃ or a matched placebo of 0.21 g kg bm⁻¹ of sodium chloride prior to exercise. Exercise tolerance (+ 110.9 ± 100.6 s; 95% CI 43.3–178 s; g = 1.0) and work performed in the severe-intensity domain (+ 5.8 ± 6.6 kJ; 95% CI 1.3–9.9 kJ; g = 0.8) were enhanced with NaHCO₃ supplementation. Furthermore, a larger post-exercise blood lactate concentration was reported in the experimental group (+ 4 ± 2.4 mmol l⁻¹; 95% CI 2.2–5.9; g = 1.8), while blood [HCO₃⁻] and pH remained elevated in the NaHCO₃ condition throughout experimentation. In conclusion, this study reported a positive effect of NaHCO₃ under acute moderate hypoxic conditions during intermittent exercise and therefore, may offer an ergogenic strategy to mitigate hypoxic induced declines in exercise performance.

HaloDom: a new database of halophiles across all life domains

Background

Halophilic organisms may thrive in or tolerate high salt concentrations. They have been studied for decades and a considerable number of papers reporting new halophilic species are being published every year. However, an extensive collection of these salt-loving organisms does not exist nowadays. Halophilic life forms have representatives from all three life domains, Archaea, Bacteria and Eukarya. The purpose of this study was to search for all documented halophilic species in the scientific literature and accommodate this information in the form of an online database.

Results

We recorded more than 1000 halophilic species from the scientific literature. From these, 21.9% belong to Archaea, 50.1% to Bacteria and 27.9% to Eukaryotes. Our records contain basic information such as the salinity that a particular organism was found, its taxonomy and genomic information via NCBI and other links. The online database named “HaloDom” can be accessed at http://www.halodom.bio.auth.gr.

Conclusions

Over the last few years, data on halophiles are growing fast. Compared to previous efforts, this new halophiles database expands its coverage to all life domains and offers a valuable reference system for studies in biotechnology, early life evolution and comparative genomics.

Ultramafic geoecology of South and Southeast Asia

Globally, ultramafic outcrops are renowned for hosting floras with high levels of endemism, including plants with specialised adaptations such as nickel or manganese hyperaccumulation. Soils derived from ultramafic regoliths are generally nutrient-deficient, have major cation imbalances, and have concomitant high concentrations of potentially phytotoxic trace elements, especially nickel. The South and Southeast Asian region has the largest surface occurrences of ultramafic regoliths in the world, but the geoecology of these outcrops is still poorly studied despite severe conservation threats. Due to the paucity of systematic plant collections in many areas and the lack of georeferenced herbarium records and databased information, it is not possible to determine the distribution of species, levels of endemism, and the species most threatened. However, site-specific studies provide insights to the ultramafic geoecology of several locations in South and Southeast Asia. The geoecology of tropical ultramafic regions differs substantially from those in temperate regions in that the vegetation at lower elevations is generally tall forest with relatively low levels of endemism. On ultramafic mountaintops, where the combined forces of edaphic and climatic factors intersect, obligate ultramafic species and hyperendemics often occur. Forest clearing, agricultural development, mining, and climate change-related stressors have contributed to rapid and unprecedented loss of ultramafic-associated habitats in the region. The geoecology of the large ultramafic outcrops of Indonesia's Sulawesi, Obi and Halmahera, and many other smaller outcrops in South and Southeast Asia, remains largely unexplored, and should be prioritised for study and conservation.

Acid rock drainage in Nevado Pastoruri glacier area (Huascarán National Park, Perú): hydrochemical and mineralogical characterization and associated environmental implications

The generation of acid rock drainage (ARD) was observed in an area of Nevado Pastoruri as a result of the oxidative dissolution of pyrite-rich lutites and sandstones. These ARDs are generated as abundant pyrite becomes exposed to atmospheric conditions as a result of glacier retreat. The proglacial zone contains lagoons, springs, streams and wetlands, scant vegetation, and intense fluvioglacial erosion. This work reports a comprehensive identification and the results of sampling of the lagoons and springs belonging to the microbasin, which is the headwaters of the Pachacoto River, as well as mapping results based on the hydrochemical data obtained in our study. The physical properties and water chemistry of 12 springs and 22 lagoons from the proglacial zone are also presented. Water springs are far from being chemically uniform, with pH and EC values ranging between 2.55-6.42 and 23-1110 μS/cm respectively, which suggests a strong geologic control on water chemistry. Fe-SO₄^-2 concentrations confirm the intense process of pyrite oxidative dissolution. Many of the lagoons are affected by ARD, with low pH (~ 3), and high EC (256-1092 μS/cm) values when compared with unaffected lagoons (EC between 7 and 59 μS/cm), indicating a high degree of mineralization. The affected lagoons show higher concentrations of SO₄^2- and SiO₂, and elements as Fe, Al, Mg, Mn, Zn, Co, and Ni, which are related to the alteration of pyrite and the dissolution of aluminosilicate minerals. Schwertmannite-goethite appears to be the most important mineral phases controlling the Fe solubility at a pH of 2-3.5. Moreover, they act as a sorbent of trace elements (As, Sb, V, Pb, Zn, Cr), which is an efficient mechanism of natural attenuation. Despite of this, the water flowing out from the basin is acid (pH 3.1) and contains significant concentrations of Fe (0.98 mg/L) and Al (3.76 mg/L) that confer mineral acidity to water. The Pachacoto River located 5.5 km downstream from this point showed a strong natural attenuation, with a pH of 6.9 and low concentration of metals. This mitigating process is possible due to (i) the formation of precipitates that retain toxic elements and (ii) the mixing with natural waters that promote dilution, which favor the increase of pH until circumneutral conditions.

Rhizobacterial Community Structures Associated with Native Plants Grown in Chilean Extreme Environments

Chile is topographically and climatically diverse, with a wide array of diverse undisturbed ecosystems that include native plants that are highly adapted to local conditions. However, our understanding of the diversity, activity, and role of rhizobacteria associated with natural vegetation in undisturbed Chilean extreme ecosystems is very poor. In the present study, the combination of denaturing gradient gel electrophoresis and 454-pyrosequencing approaches was used to describe the rhizobacterial community structures of native plants grown in three representative Chilean extreme environments: Atacama Desert (ATA), Andes Mountains (AND), and Antarctic (ANT). Both molecular approaches revealed the presence of Proteobacteria, Bacteroidetes, and Actinobacteria as the dominant phyla in the rhizospheres of native plants. Lower numbers of operational taxonomic units (OTUs) were observed in rhizosphere soils from ATA compared with AND and ANT. Both approaches also showed differences in rhizobacterial community structures between extreme environments and between plant species. The differences among plant species grown in the same environment were attributed to the higher relative abundance of classes Gammaproteobacteria and Alphaproteobacteria. However, further studies are needed to determine which environmental factors regulate the structures of rhizobacterial communities, and how (or if) specific bacterial groups may contribute to the growth and survival of native plants in each Chilean extreme environments.

Microbial diversity of extreme habitats in human homes

High-throughput sequencing techniques have opened up the world of microbial diversity to scientists, and a flurry of studies in the most remote and extreme habitats on earth have begun to elucidate the key roles of microbes in ecosystems with extreme conditions. These same environmental extremes can also be found closer to humans, even in our homes. Here, we used high-throughput sequencing techniques to assess bacterial and archaeal diversity in the extreme environments inside human homes (e.g., dishwashers, hot water heaters, washing machine bleach reservoirs, etc.). We focused on habitats in the home with extreme temperature, pH, and chemical environmental conditions. We found a lower diversity of microbes in these extreme home environments compared to less extreme habitats in the home. However, we were nonetheless able to detect sequences from a relatively diverse array of bacteria and archaea. Habitats with extreme temperatures alone appeared to be able to support a greater diversity of microbes than habitats with extreme pH or extreme chemical environments alone. Microbial diversity was lowest when habitats had both extreme temperature and one of these other extremes. In habitats with both extreme temperatures and extreme pH, taxa with known associations with extreme conditions dominated. Our findings highlight the importance of examining interactive effects of multiple environmental extremes on microbial communities. Inasmuch as taxa from extreme environments can be both beneficial and harmful to humans, our findings also suggest future work to understand both the threats and opportunities posed by the life in these habitats.

Description of a halocin-producing Haloferax larsenii HA1 isolated from Pachpadra salt lake in Rajasthan

Haloarchaea grow in the extreme environment, such as high salt concentration, and secrete antimicrobial peptides known as halocins. Identification of Haloferax larsenii strain HA1 was carried out using biochemical and molecular methods. Strain HA1 was found as a strict aerobe, catalase positive and Gram negative. It was able to grow optimally at 15 % NaCl (w/v), 42 °C and pH 7.2. Strain HA1 was sensitive to bile acid, was resistant to chloramphenicol and could not utilize arginine. Halocin, produced by strain HA1, was stable up to 100 °C and in a pH range of 5.0-9.0. Antimicrobial activity was not affected by organic solvents, surfactants and detergents, but it was completely lost in the presence of proteinase K, suggesting proteinaceous nature of the compound. It was halocidal against indicator strain Hfx. larsenii HA10. The molecular weight of halocin HA1 was found to be ~14 kDa. These properties of halocin HA1 may be applicable to the preservation of salted foods.

Pyrosequencing-Based Assessment of the Microbial Community Structure of Pastoruri Glacier Area (Huascarán National Park, Perú), a Natural Extreme Acidic Environment

The exposure of fresh sulfide-rich lithologies by the retracement of the Nevado Pastoruri glacier (Central Andes, Perú) is increasing the presence of heavy metals in the water as well as decreasing the pH, producing an acid rock drainage (ARD) process in the area. We describe the microbial communities of an extreme ARD site in Huascarán National Park as well as their correlation with the water physicochemistry. Microbial biodiversity was analyzed by FLX 454 sequencing of the 16S rRNA gene. The suggested geomicrobiological model of the area distinguishes three different zones. The proglacial zone is located in the upper part of the valley, where the ARD process is not evident yet. Most of the OTUs detected in this area were related to sequences associated with cold environments (i.e., psychrotolerant species of Cyanobacteria or Bacteroidetes). After the proglacial area, an ARD-influenced zone appeared, characterized by the presence of phylotypes related to acidophiles (Acidiphilium) as well as other species related to acidic and cold environments (i.e., acidophilic species of Chloroflexi, Clostridium and Verrumicrobia). Sulfur- and iron-oxidizing acidophilic bacteria (Acidithiobacillus) were also identified. The post-ARD area was characterized by the presence of OTUs related to microorganisms detected in soils, permafrost, high mountain environments, and deglaciation areas (Sphingomonadales, Caulobacter or Comamonadaceae).