Search Results (506)

Psychrophilic organisms are able to grow at temperatures down to −15 °C, while hyperthermophiles can multiply at temperatures up to 122 °C. What structural changes in extremophile proteins are needed to maintain stable and biochemically active structures under such conditions? Understanding how such extremophiles accomplish this is relevant for human health, biotechnology, and our search for life elsewhere in the universe. The purpose of the current study is to report and compare the structures of four rubredoxins (Rds), the first ever two experimental psychrophile bacteria structures (from Gram-positive Clostridium psychrophilum and Gram-negative Polaromonas glacialis) and two hyperthermophiles from the Gram-negative Thermotoga maritima bacterium and the archaeon Pyrococcus yayanosii, also a piezophile, as part of a program to understand structural variations that support both stability and function under extreme conditions. These structures were obtained using synchrotron radiation X-ray diffraction at 100 K. All four structures had the expected overall rubredoxin fold. Rubredoxin from the only aerobic psychrophilic bacterium Polaromonas glacialis had larger variations in sequence and structure, whereas the other psychrophilic bacterium showed properties closely related to hyperthermophile rubredoxins. Multi-subunit structures showed similar RMSD variability independent from their thermal adaptation status. We propose including functional information in the analysis since temperature optimization may not be the only determinant for a specific protein adaptation. Full article

Chroococcidiopsis sp. was isolated from the endolithic habitat of the Atacama Desert (northern Chile), one of the most challenging-to-life polyextreme environments on Earth. The photosynthetic machinery of microorganisms inhabiting this environment is supposed to be highly adapted to cope with the intense solar radiation of the area. Thus, PAR-red light ranging from 100 to 900 µmol photon·m⁻²·s⁻¹ has been investigated as a strategy to enhance culture productivity and stimulate the synthesis of bioactive molecules in Chroococcidiopsis sp. A control culture was maintained under white light at 100 µmol photon·m⁻²·s⁻¹. The results revealed that red light was utilized more efficiently than white light of similar irradiance, and its modulation enhanced both growth and photosynthetic activity of the cyanobacterium. Furthermore, Chroococcidiopsis sp. appeared to activate mechanisms to mitigate photooxidative stress produced by excess light energy. Specifically, increasing light irradiance induced photoacclimation responses, characterized by a decrease in chlorophyll content and a concomitant increase in carotenoid accumulation, likely aimed at reducing photon flux transduced to photosynthesis. Additionally, scytonemin synthesis was enhanced under high irradiances, contributing to dissipating excess light energy. Overall, this study demonstrates that modulation of red-light irradiance effectively improves the growth of Chroococcidiopsis sp. while promoting the accumulation of antioxidant compounds—primarily carotenoids and, to a lesser extent, scytonemin. Full article

Recent work demonstrated that Cicindelidia hemorrhagica (LeConte) inhabiting geothermal springs in Yellowstone National Park (YNP) possess morphological traits that reduce internal heat load when exposed to bottom-up thermal stress. To investigate whether this pattern extends to other tiger beetle species occupying diverse environments, we quantified the internal abdominal temperatures of six species differing in habitat preference and putative thermal adaptation. Using a water-bath system that simulated surface heating, we compared the temperature differential (ΔT) between beetle-loaded and bare thermocouples across multiple temperatures. Linear mixed-effects models were used to evaluate the influence of location and species on internal temperature. Across all experimental temperatures, C. hemorrhagica exhibited the greatest ΔT values, indicating the lowest internal temperatures relative to the thermal environment, regardless of whether individuals originated from YNP or non-thermal Idaho habitats. In contrast, the warm-resilient Cicindela repanda (Dejean) and non-warm-adapted C. longilabris (Say) showed the smallest ΔT values and therefore the highest internal temperatures. Ventral abdominal coloration—ranging from bright red (C. sedecimpunctata (Klug)) to dark blue-green (C. oregona (Dejean))—did not correlate with internal temperatures, suggesting that it is a poor predictor of heat absorbance or reflectance under bottom-up heat exposure. These results indicate that C. hemorrhagica is uniquely effective at limiting internal heat gain from surface heating, and that it may possess a preadaptive morphological mechanism facilitating thermal resistance in geothermal habitats. Full article

Viruses are abundant and widespread in extreme marine environments, such as sea ice, hydrothermal vents, and ocean trenches. They occur at temperatures up to 122 °C and down to −30 °C and pressures exceeding 100 MPa. Their distribution in these environments is closely correlated with that of their extremophile hosts, which are mostly bacteria, archaea, and microeukaryotes. Viruses have been shown to be capable of long-term survival in conditions simulating interstellar conditions. However, for them to reproduce, they would still need a host. Many recent astro-biological investigations have focused on habitability, specifically the ability of a planet to support the activity of at least one lifeform. The most likely candidates for extraterrestrial habitability in our solar system are the sea ice moons of Jupiter and Saturn, namely Europa and Enceladus. These are both thought to contain subsurface oceans of liquid water and potentially access to the necessary elements for microbial growth. If microorganisms were to be detected in these extraterrestrial environments, viruses might also be found coexisting with their host cells. Full article

Despite their vital physiological roles, oxidative imbalance caused by reactive oxygen, nitrogen, sulphur, and chlorine species damages essential body macromolecules such as proteins, lipids, and nucleic acids through oxidative stress. This stress is strongly associated with cancer, inflammation, neurological and cardiovascular disorders, and other chronic human diseases. Therefore, antioxidants, natural or synthetic, that counteract oxidative damage are important, with increasing interest in their use within the pharmaceutical, food, and cosmetic industries. However, due to toxicity concerns with the synthetic variants, natural antioxidants are increasingly preferred. Extremophile-derived antioxidants, such as superoxide dismutases, catalases, peroxidases, carotenoids, and melanin, are of renewed interest due to their remarkable stability, robustness, and potency under extreme conditions of temperature, pH, and salinity. These make them better than many mesophile-derived antioxidants and excellent candidates for cost-effective biotechnological, research, and industrial processes that require high operational efficiency. This review summarises key classes of selected enzymatic and pigment antioxidants, their mechanisms of action, and their industrial relevance, with a focus on extremophilic microalgae, bacteria, and fungi. The benefits of extremophilic antioxidants are discussed alongside their current applications and existing challenges, including the need to develop efficient delivery systems, scalability issues, and limited characterisation. Full article

2-Phosphoglycerate kinase (2PGK) and cyclic 2,3-diphosphoglycerate synthase (cDPGS) are key enzymes involved in the biosynthesis of cyclic 2,3-diphosphoglycerate (cDPG), an extremolyte known to stabilize proteins in hyperthermophilic Archaea. Using bioinformatics approaches, two candidate genes for each enzyme were identified from a range of thermophilic bacterial and archaeal genomes and metagenomes. Significantly, one gene pair derived from the Taman mud volcano metagenome represents the first indication of a bacterial cDPG biosynthesis pathway. The recombinant expression and purification of these enzymes paved the way to their biochemical and structural characterization. One 2PGK candidate displayed predominant ATPase activity, while the newly identified cDPGS variants demonstrated cDPG synthase activity. Moreover, one of the latter biocatalysts, Ts-cDPGS from the hyperthermophilic archaeon Thermococcus sibiricus, demonstrated a notable thermostability and its 3D structure was resolved at a resolution of 2.2 Å. These findings broaden our understanding of extremophilic enzyme systems and lay the foundation for biotechnological applications involving extremolyte production. Full article

Acidithiobacillus caldus is perpetually exposed to multiple extreme environmental stresses. CsrA, functioning as a post-transcriptional regulator of physiological metabolism, acts as a differential modulator, facilitating more economical and efficient adaptation to extreme environments. The csrA expression recombinant strain was constructed in A. caldus MTH-04 by conjugative transfer technology pJD215. Physiological characterization revealed enhanced acid tolerance, significantly elongated flagella, elevated extracellular secretion, and altered biofilm composition. Notably, intracellular concentrations of free glutamate and aspartate increased to 24.18 mg/L and 16.07 mg/L, respectively. The secondary structure of CsrA protein was determined in vitro through circular dichroism spectroscopy and size-exclusion chromatography. Electrophoretic Mobility Shift Assay (EMSA) successfully demonstrated in vitro binding activity of CsrA to the rpoS leader mRNA. CsrA suppresses rpoS mRNA translation by competing with ribosomes for binding sites, thereby negatively regulating rpoS expression. Critical binding sites were further validated through site-directed mutagenesis. Through EMSA, RT-qPCR and the translation reporter system, it was also found that CsrA has a dual regulatory function for nearby flagella- and motility-related gene clusters (flgC, 07035, motD, 15040), which also implies the global regulatory role of CsrA. In summary, a potential overall post-transcriptional regulatory mechanism based on CsrA and rpoS by extremophile A. caldus was proposed. Finally, the efficiency of bioleaching application by csrA overexpression strain was improved by 20.81%. Full article

Microbial biosurfactants, derived from diverse aquatic and extreme ecosystems, offer a sustainable and environmentally compatible strategy for enhanced oil recovery by fundamentally altering subsurface rock wettability. These biologically produced amphiphiles can efficiently transform oil-wet rock surfaces into water-wet states, thereby mobilizing otherwise trapped crude oil. The primary aim of this review is to provide an integrative understanding of how these biomolecules function at the interface between aquatic microbial ecology and subsurface petroleum engineering, with a particular focus on wettability alteration as a key mechanism for enhancing oil recovery. This review surveys major biosurfactant classes—glycolipids, lipopeptides, and polymeric bioemulsifiers—and their core mechanisms, emphasizing their relevance to challenging reservoir conditions such as high temperature and salinity. A detailed assessment is devoted to persistent hurdles such as stability, adsorption onto rock formations, and economic scalability. Future prospects center on three key approaches: advancing synergistic “bio-hybrid” systems that integrate biosurfactants with complementary agents such as biopolymers and nanomaterials; achieving cost-effective production through the valorization of waste feedstocks; and expanding targeted bioprospecting of microbial diversity from extreme aquatic environments. Together, these strategies are reviewed to drive the advancement of robust, green microbial-enhanced oil recovery (MEOR) technologies, charting a course from fundamental insights to field-scale implementation. Full article

The study of microorganisms inhabiting extreme environments offers a valuable opportunity to explore their potential ecological roles. This study aimed to reveal and compare the microbial taxonomic diversity of largely unexplored permafrost regions located in different climatic zones (dry and wet) in the Chilean Andes, separated by thousands of kilometers. Permafrost active layer samples were collected from the Ojos del Salado (Atacama Desert) and the Torres del Paine (Patagonia) from different sampling depths. Illumina 16S rRNA gene-based amplicon sequencing revealed that the Andean permafrost active layer provides diverse habitats for distinct microbial communities, with higher taxonomic diversity of Bacteria than Archaea. The wet Patagonian Andes samples showed higher diversity, with a greater abundance of Chloroflexota and Bacteroidota, while the dry Ojos del Salado samples were dominated by Actinomycetota, indicating desiccation stress. Archaea were classified as ammonia-oxidizing members of the Thermoproteota phylum. Beta-diversity analyses suggested that differences in environmental conditions (mainly available moisture) contributed more to community structure differentiation than geographical distances. Nevertheless, the effect of sampling depth on microbial diversity was insignificant. Full article

Ziziphus lotus (L.) Lam., an extremophyte shrub native to the Mediterranean basin, yields underexplored fruits as a source of therapeutic agents. This study combined in vitro and in silico approaches to evaluate the antioxidant potential of Z. lotus fruits and predict their potential to inhibit xanthine oxidase (XO), a key enzyme in reactive oxygen species generation and oxidative stress-related pathologies. The ethyl acetate extract from the hydroalcoholic macerate was enriched in total phenolics (281.33 ± 1.5 μg GAE/mg) and flavonoids (127.26 ± 5.89 μg RE/mg) and displayed remarkable effects against the ABTS^•+ radical cation (IC₅₀ = 18.49 ± 1.47 μg/mL) and phenanthroline reducing power (A_0.5 = 8.38 ± 0.69 μg/mL), together with measurable xanthine oxidase inhibition (IC₅₀ = 170.4 ± 5.90 μg/mL). The compounds tentatively identified by full-scan UHPLC-QtoF-HRMS were docked against XO (PDB ID: 3NVY), with phytosphingosine (−8.5 kcal/mol) and rutin (−8.3 kcal/mol) exhibiting the strongest binding affinities, forming favorable predicted interactions with critical catalytic residues, followed by 6‴-feruloylspinosin, 3′,5′-di-C-β-glucopyranosylphloretin and hexadecasphinganine (ranging from −7.8 to −7.6 kcal/mol). Predictive structure–activity relationships were also observed. These results provide insights into the antioxidant potential of Z. lotus phytochemicals and highlight the value of this extremophile plant as sustainable resource for phytotherapy and the management of oxidative stress-related diseases. Full article

Hypersaline solar saltworks represent unique ecological niches that harbor extremophilic microalgae with considerable biotechnological potential. Within these environments, members of the genus Dunaliella are particularly noteworthy due to their remarkable metabolic plasticity and ability to accumulate high-value biomolecules. In the present study, we investigated the biodiversity of Dunaliella in hypersaline saltworks by isolating and identifying autochthonous strains and assessing their growth kinetics and biomass biochemical composition in the context of potential biotechnological applications. Specifically, sixteen strains of Dunaliella were isolated from evaporation and crystallizer ponds of the Kalloni saltworks in Lesvos, Greece, and subjected to an integrative characterization combining morphological observations, molecular phylogenetics, growth kinetics, and biochemical profiling. Phylogenetic analyses based on four genetic markers (18S, ITS, rbcL, tufA) consistently resolved the isolates into three distinct clades: one corresponding to Dunaliella salina/D. minutissima, one to D. parva, and a third representing a clearly divergent lineage. Growth assays revealed marked variability in cell density, biomass productivity and specific growth rate, with certain strains exhibiting enhanced proliferation under controlled conditions. Biochemical analyses demonstrated distinct allocation patterns, with evaporation pond isolates comparatively enriched in proteins (up to 60.8% DW), whereas crystallizer pond isolates accumulated higher levels of carbohydrates (up to 19.0% DW), carotenoids (up to 7.34% mg g⁻¹ DW) and phenolic compounds (up to 8.68% mg GAE g⁻¹ DW). Antioxidant assays (FRAP, TEAC) further indicated significantly elevated reducing and radical scavenging activities among crystallizer isolates. These findings expand current knowledge on the biodiversity of autochthonous Dunaliella strains and support their potential as sustainable sources of bioactive compounds for applications in the agri-food, nutraceutical, pharmaceutical, and cosmeutical sectors. Full article

The hypersaline soils of the Odiel Saltmarshes Natural Area in Southwest Spain harbor highly diverse microbial communities adapted to extreme conditions. However, their genomic diversity remains largely unexplored. In addition to high salinity, these soils are contaminated with heavy metals, creating a hostile environment of great interest for studying extremophilic microorganisms and their metabolic adaptations. This study aims to characterize the uncovered prokaryotic taxa as Candidatus species inhabiting the hypersaline soils of the Odiel Saltmarshes, based on their metagenomic assembled genomic sequences. The reconstructed genomes were assessed for quality based on completeness and contamination thresholds and subsequently taxonomically classified. Comparative genomic analysis of six high-quality MAGs revealed key metabolic traits related to survival under extreme salinity and heavy metal conditions. The findings provide new insights about microbial diversity of hypersaline environments and expand the catalog of known prokaryotic genomes. Detailed characterization of six novel Candidatus taxa highlights the unique adaptations of these microorganisms, enhancing our understanding of life in extreme habitats. Full article

Soil salinization represents a significant abiotic constraint to global agricultural sustainability. The potential of extremophile plant growth-promoting bacteria (PGPB) to alleviate such stress in maize was investigated in this study. Siderophore-producing PGPB enhance plant growth and improve the rhizosphere microenvironment by increasing nutrient availability and inducing systemic resistance. Two salt-tolerant, high-siderophore-producing PGPB strains, Bacillus toyonensis TRM58010 and Peribacillus frigoritolerans TRM58009, were isolated and identified from soil samples collected on the Pamir Plateau. In this study, we found that B. toyonensis TRM58010 synthesized catechol-type siderophores, which enhanced iron availability for maize in saline–alkaline conditions, thereby improving iron nutrition and directly promoting root and stem growth under salt stress. P. frigoritolerans TRM58009 produced hydroxamate-type siderophores, which increased maize iron uptake and stimulated antioxidant enzyme activity, mitigating oxidative stress caused by salinity and alkalinity and supporting overall plant health. Both strains demonstrated robust tolerance to extreme alkaline and saline conditions. Hydroponic and pot experiments showed that these strains significantly improved maize germination rate, root and stem development, plant height, leaf growth, antioxidant enzyme activities, and chlorophyll content under saline–alkaline stress. Notably, the application of P. frigoritolerans TRM58009 bacterial suspension increased maize leaf catalase, peroxidase, and superoxide dismutase activities by 15.712%, 11.584%, and 2.820%, respectively (all p < 0.05), while decreasing malondialdehyde (MDA) content by 15.685% (p < 0.05). P. frigoritolerans TRM58009 elevated chlorophyll a content by 23.4% (p < 0.05). These findings demonstrate the potential of extremophile PGPB strains to mitigate the impact of saline–alkaline stress on maize growth. The distinct growth-promoting effects of these strains, isolated from Pamir Plateau meadow soils, present a promising strategy for bioremediation of saline–alkaline lands and the development of efficient microbial fertilizers. By advancing the use of salt-tolerant siderophore-producing bacteria, this study lays the foundation for innovative approaches to enhance crop resilience and productivity in challenging environments. Full article

Hot springs represent unique geothermal ecosystems where extreme physicochemical conditions intersect with remarkable microbial diversity and metabolic innovation. These natural laboratories harbor specialized communities of thermophilic and hyperthermophilic microorganisms that have evolved exceptional adaptations to elevated temperatures, extreme pH, and high salinity. This review synthesizes current understanding of hot spring systems as multifunctional natural resources, examining their roles in fundamental microbiology, biotechnology, and sustainable development. We explore the ecological principles governing microbial community assembly, the taxonomic and functional diversity of prokaryotic and eukaryotic microorganisms, and the genomic mechanisms underlying thermophilic adaptation. Hot springs yield enzymes revolutionizing molecular biology and industrial catalysis, bioactive metabolites with pharmaceutical potential, and novel bioremediation capabilities including plastic degradation. Beyond biological significance, these systems contain valuable minerals and rare earth elements, supporting an emerging bioeconomy integrating wellness tourism, bioprospecting, and sustainable resource extraction. However, critical knowledge gaps remain regarding viral ecology, horizontal gene transfer, eukaryotic diversity, and climate change impacts. We emphasize that hot springs merit renewed interdisciplinary attention as model systems for understanding extremophile physiology, early life evolution, and the development of nature-based biotechnological solutions. Realizing their full potential requires balanced management strategies that preserve ecosystem integrity while enabling responsible utilization of these irreplaceable geobiological resources. Full article