Extremophiles最新文献

Psychrophily is a phenotype describing microbial growth at low temperatures; elucidating the biomolecular and genomic adaptations necessary for survival in the cold is important for understanding life in extreme environments on Earth and in outer space. We used comparative genomics and temperature growth experiments of bacteria from the family Colwelliaceae to identify genomic factors correlated with optimal growth temperature (OGT). A phylogenomic analysis of 67 public and 39 newly sequenced strains revealed three main clades of Colwelliaceae. Temperature growth experiments revealed significant differences in mean OGT by clade, wherein strains of Colwelliaceae had similar growth rates at -1 °C but varied in their ability to tolerate 17 °C. Using amino acid compositional indices, a multiple linear regression model was constructed to predict the OGT of these organisms (RMSE 5.2 °C). Investigation of Colwelliaceae functional genes revealed a putative cold-adaptive gene cassette that was present in psychrophilic strains but absent in a closely related strain with a significantly higher OGT. This study also presents genomic evidence suggesting that the clade of Colwelliaceae containing Colwellia hornerae should be investigated as a new genus. These contributions offer key insights into the psychrophily phenotype and its underlying genomic foundation in the family Colwelliaceae.

Knufia petricola is a black fungus that colonizes sun-exposed surfaces as extreme and oligotrophic environments. As ecologically important heterotrophs and biofilm-formers on human-made surfaces, black fungi form one of the most resistant groups of biodeteriorating organisms. Due to its moderate growth rate in axenic culture and available protocols for its transformation and CRISPR/Cas9-mediated genome editing, K. petricola is used for studying the morpho-physiological adaptations shared by extremophilic and extremotolerant black fungi. In this study, the bacteria-derived tetracycline (TET)-dependent promoter (Tet-on) system was implemented to enable controllable gene expression in K. petricola. The functionality i.e., the dose-dependent inducibility of TET-regulated constructs was investigated by using GFP fluorescence, pigment synthesis (melanin and carotenoids) and restored uracil prototrophy as reporters. The newly generated cloning vectors containing the Tet-on construct, and the validated sites in the K. petricola genome for color-selectable or neutral insertion of expression constructs complete the reverse genetics toolbox. One or multiple genes can be expressed on demand from different genomic loci or from a single construct by using 2A self-cleaving peptides, e.g., for localizing proteins and protein complexes in the K. petricola cell or for using K. petricola as host for the expression of heterologous genes.

Today, the biodiversity of endolithic microbial colonisations are only partly understood. In this study, we used a combination of molecular community metabarcoding using the 16S rRNA gene, light microscopy, CT-scan analysis, and Raman spectroscopy to describe gypsum endolithic communities in 2 sites-southern Poland and northern Israel. The obtained results have shown that despite different geographical areas, climatic conditions, and also physical features of colonized gypsum outcrops, both of these sites have remarkably similar microbial and pigment compositions. Cyanobacteria dominate both of the gypsum habitats, followed by Chloroflexi and Pseudomonadota. Among cyanobacteria, Thermosynechococcaceae were more abundant in Israel while Chroococcidiopsidaceae in Poland. Interestingly, no Gloeobacteraceae sequences have been found in Poland, only in Israel. Some of the obtained 16S rRNA gene sequences of cyanobacteria matched previously detected sequences from endolithic communities in various substrates and geographical regions, supporting the hypothesis of global metacommunity, but more data are still needed. Using Raman spectroscopy, cyanobacterial UV-screening pigments-scytonemin and gloeocapsin have been detected alongside carotenoids, chlorophyll a and melanin. These pigments can serve as potential biomarkers for basic taxonomic identification of cyanobacteria. Overall, this study provides more insight into the diversity of cyanobacterial endolithic colonisations in gypsum across different areas.

The heterotrophic cultivation of extremophilic archaea still heavily relies on complex media. However, complex media are associated with unknown composition, high batch-to-batch variability, potential inhibiting and interfering components, as well as regulatory challenges, hampering advancements of extremophilic archaea in genetic engineering and bioprocessing. For Metallosphaera sedula, a widely studied organism for biomining and bioremediation and a potential production host for archaeal ether lipids, efforts to find defined cultivation conditions have still been unsuccessful. This study describes the development of a novel chemically defined growth medium for M. sedula. Initial experiments with commonly used complex casein-derived media sources deciphered Casamino Acids as the most suitable foundation for further development. The imitation of the amino acid composition of Casamino Acids in basal Brock medium delivered the first chemically defined medium. We could further simplify the medium to 5 amino acids based on the respective specific substrate uptake rates. This first defined cultivation medium for M. sedula allows advanced genetic engineering and more controlled bioprocess development approaches for this highly interesting archaeon.

3' → 5' exoribonucleases play a critical role in many aspects of RNA metabolism. RNase R, PNPase, and RNase II are the major contributors to RNA processing, maturation, and quality control in bacteria. Bacteria don't seem to have dedicated RNA degradation machineries to process different classes of RNAs. Under different environmental and physiological conditions, their roles can be redundant and sometimes overlapping. Here, I discuss why PNPase and RNase R may have switched their physiological roles in some bacterial species to adapt to environmental conditions, despite being biochemically distinct exoribonucleases.

The extremophile bacterium Deinococcus radiodurans is characterized by its ability to survive and sustain its activity at high levels of radiation and is considered an organism that might survive in extraterrestrial environments. In the present work, we studied the combined effects of temperature and chlorine-containing salts, with focus on perchlorate salts which have been detected at high concentrations in Martian regolith, on D. radiodurans activity (CO₂ production rates) and viability after incubation in liquid cultures for up to 30 days. Reduced CO₂ production capacity and viability was observed at high perchlorate concentrations (up to 10% w/v) during incubation at 0 or 25 °C. Both the metabolic activity and viability were reduced as the perchlorate and chloride salt concentration increased and temperature decreased, and an interactive effect of temperature and salt concentration on the metabolic activity was found. These results indicate the ability of D. radiodurans to remain metabolically active and survive in low temperature environments rich in perchlorate.

Carotenoids are a diverse group of pigments known for their broad range of biological functions and applications. This study delves into multifaceted potential of carotenoids extracted from Haloferax larsenii NCIM 5678 previously isolated from Pachpadra Salt Lake in Rajasthan, India. H. larsenii NCIM 5678 was able to grow up to OD₆₀₀ 1.77 ± 0.03 with carotenoid concentration, 3.3 ± 0.03 µg/ml. The spectrophotometric analysis of carotenoid extract indicated the presence of three-fingered peak (460, 490 and 520 nm) which is a characteristic feature of bacterioruberin and its derivatives. The bacterioruberin was purified using silica gel column chromatography and thin layer chromatography. The carotenoid extract showed 12.3 ± 0.09 mm zone of growth inhibition with a minimum inhibitory concentration 546 ng/ml against indicator strain, H. larsenii HA4. The percentage antioxidant activity of carotenoid was found to be 84% which was higher as compared to commercially available ascorbic acid (56.74%). Thus, carotenoid extract from H. larsenii NCIM 5678 possesses unique attributes with compelling evidence of antimicrobial and antioxidant potential for the development of novel pharmaceuticals and nutraceuticals.

Hyperthermophilic archaean Methanocaldococcus sp. FS406-22 (hereafter FS406) is a hydrogenotrophic methanogen isolated from a deep-sea hydrothermal vent. To better understand the energetic requirements of hydrogen oxidation under extreme conditions, the thermodynamic characterization of FS406 incubations is necessary and notably underexplored. In this work, we quantified the bioenergetics of FS406 incubations at a range of temperatures (65, 76, and 85 ℃) and hydrogen concentrations (1.1, 1.4, and 2.1 mm). The biomass yields (C-mol of biomass per mol of H₂ consumed) ranged from 0.02 to 0.19. Growth rates ranged from 0.4 to 1.5 h^-1. Gibbs energies of incubation based on macrochemical equations of cell growth ranged from $-198$ kJ/C-mol to $-1840$ kJ/C-mol. Enthalpies of incubation determined from calorimetric measurements ranged from $-4150$ kJ/C-mol to $-36333$ kJ/C-mol. FS406 growth rates were most comparable to hyperthermophilic methanogen Methanocaldococcus jannaschii. Maintenance energy calculations from the thermodynamic parameters of FS406 and previously determined heterotrophic methanogen data revealed that temperature is a primary determinant rather than an electron donor. This work provides new insights into the thermodynamic underpinnings of a hyperthermophilic hydrothermal vent methanogen and helps to better constrain the energetic requirements of life in extreme environments.

The present study investigates the low temperature tolerance strategies of thermophilic bacterium Anoxybacillus rupiensis TPH1, which grows optimally at 55 °C , by subjecting it to a temperature down-shift of 10 °C (45 °C) for 4 and 6 h followed by studying its growth, morphophysiological, molecular and proteomic responses. Results suggested that although TPH1 experienced increased growth inhibition, ROS production, protein oxidation and membrane disruption after 4 h of incubation at 45 °C yet maintained its DNA integrity and cellular structure through the increased expression of DNA damage repair and cell envelop synthesizing proteins and also progressively alleviated growth inhibition by 20% within two hours i.e., 6 h, by inducing the expression of antioxidative enzymes, production of unsaturated fatty acids, capsular and released exopolysaccharides and forming biofilm along with chemotaxis proteins. Conclusively, the adaptation of Anoxybacillus rupiensis TPH1 to lower temperature is mainly mediated by the synthesis of large numbers of defense proteins and exopolysaccharide rich biofilm formation.

This study characterized cultivable fungi present in sediments obtained from Boeckella Lake, Hope Bay, in the north-east of the Antarctic Peninsula, and evaluated their production of enzymes and biosurfactants of potential industrial interest. A total of 116 fungal isolates were obtained, which were classified into 16 genera within the phyla Ascomycota, Basidiomycota and Mortierellomycota, in rank. The most abundant genera of filamentous fungi included Pseudogymnoascus, Pseudeurotium and Antarctomyces; for yeasts, Thelebolales and Naganishia taxa were dominant. Overall, the lake sediments exhibited high fungal diversity and moderate richness and dominance. The enzymes esterase, cellulase and protease were the most abundantly produced by these fungi. Ramgea cf. ozimecii, Holtermanniella wattica, Leucosporidium creatinivorum, Leucosporidium sp., Mrakia blollopis, Naganishia sp. and Phenoliferia sp. displayed enzymatic index > 2. Fourteen isolates of filamentous fungi demonstrated an Emulsification Index 24% (EI_24%) ≥ 50%; among them, three isolates of A. psychrotrophicus showed an EI_24% > 80%. Boeckella Lake itself is in the process of drying out due to the impact of regional climate change, and may be lost completely in approaching decades, therefore hosts a threatened community of cultivable fungi that produce important biomolecules with potential application in biotechnological processes.