Extremophiles最新文献

L-asparaginase (ASNase, E.C. 3.5.1.1) catalyzes the deamination of L-asparagine to L-aspartic acid and ammonia and is widely used in medicine to treat acute lymphocytic leukemia. It also has significant applications in the food industry by inhibiting acrylamide formation. In this study, we characterized a thermostable ASNase from the hyper thermophilic strain, Pyrococcus yayanosii CH1. The recombinant enzyme (PyASNase) exhibited maximal activity at pH 8.0 and 85 °C. Moreover, PyASNase demonstrated promising thermostability across temperatures ranging from 70 to 95 °C. The kinetic parameters of PyASNase for L-asparagine were a K_m of 6.3 mM, a k_cat of 1989s^-1, and a k_cat/K_m of 315.7 mM^-1 s^-1. Treating potato samples with 10 U/mL of PyASNase at 85 °C for merely 10 min reduced the acrylamide content in the final product by 82.5%, demonstrating a high efficiency and significant advantage of PyASNase in acrylamide inhibition.

Hydrometallurgical bioprocesses for base metal recovery in environmentally friendly electronic device waste (e-waste) recycling are typically studied under neutral pH conditions to avoid competition between metals and hydrogen ions. However, metal leachate is generally strongly acidic, thus necessitating a neutralisation process in the application of these bioprocesses to e-waste recycling. To solve this pH disparity, we focused on acid-tolerant bacteria for metal recovery under strongly acidic conditions. Four acid-tolerant bacterial strains were isolated from neutral pH environments to recover base metals from simulated waste metal leachate (pH 1.5, containing 100 or 1000 mg L^-1 of Co, Cu, Li, Mn, and Ni) without neutralisation. The laboratory setting for sequential metal recovery was established using these strains and a reported metal-adsorbing bacterium, Micrococcus luteus JCM1464. The metal species were successfully recovered from 100 mg L^-1 metal mixtures at the following rates: Co (8.95%), Cu (21.23%), Li (5.49%), Mn (13.18%), and Ni (9.91%). From 1000 mg L^-1 metal mixtures, Co (7.23%), Cu (6.82%), Li (5.85%), Mn (7.64%), and Ni (7.52%) were recovered. These results indicated the amenability of acid-tolerant bacteria to environmentally friendly base metal recycling, contributing to the development of novel industrial application of the beneficial but unutilised bioresource comprising acid-tolerant bacteria.

We acquired and analyzed metagenome and 16S/18S rRNA gene amplicon data of green-colored microbial mats from two hot springs within the Onikobe geothermal region (Miyagi Prefecture, Japan). The two collection sites-Tamago and Warabi-were in proximity and had the same temperature (40 °C), but the Tamago site was connected to a nearby stream, whereas the Warabi site was isolated. Both the amplicon and metagenome data suggest the bacterial, especially cyanobacterial, dominance of the mats; other abundant groups include Chloroflexota, Pseudomonadota, Bacteroidota/Chlorobiota, and Deinococcota. At finer resolution, however, the taxonomic composition entirely differed between the mats. A total of 5 and 21 abundant bacterial 16S rRNA gene OTUs were identified for Tamago and Warabi, respectively; of these, 12 are putative chlorophyll- or rhodopsin-based phototrophs. The presence of phylogenetically diverse microbial eukaryotes was noted, with ciliates and amoebozoans being the most abundant eukaryote groups for Tamago and Warabi, respectively. Fifteen metagenome-assembled genomes (MAGs) were obtained, represented by 13 bacteria, one ciliate (mitochondrion), and one giant virus. A total of 15 novel taxa, including a new deeply branching Chlorobiota species, is noted from the amplicon and MAG data, highlighting the importance of environmental sequencing in uncovering hidden microorganisms.

Methanogenic archaea are chemolithotrophic prokaryotes that can reduce carbon dioxide with hydrogen gas to form methane. These microorganisms make a significant contribution to the global carbon cycle, with methanogenic archaea from anoxic environments estimated to contribute > 500 million tons of global methane annually. Archaeal methanogenesis is dependent on the methanofurans; aminomethylfuran containing coenzymes that act as the primary C₁ acceptor molecule during carbon dioxide fixation. Although the biosynthetic pathway to the methanofurans has been elucidated, structural adaptations which confer thermotolerance to Mfn enzymes from extremophilic archaea are yet to be investigated. Here we focus on the methanofuran biosynthetic enzyme MfnB, which catalyses the condensation of two molecules of glyceralde-3-phosphate to form 4‑(hydroxymethyl)-2-furancarboxaldehyde-phosphate. In this study, MfnB enzymes from the hyperthermophile Methanocaldococcus jannaschii and the mesophile Methanococcus maripaludis have been recombinantly overexpressed and purified to homogeneity. Thermal unfolding studies, together with steady-state kinetic assays, demonstrate thermoadaptation in the M. jannaschii enzyme. Molecular dynamics simulations have been used to provide a structural explanation for the observed properties. These reveal a greater number of side chain interactions in the M. jannaschii enzyme, which may confer protection from heating effects by enforcing spatial residue constraints.

The peptidoglycan of the hyperthermophile Thermotoga maritima contains an unusual D-lysine in addition to the typical D-alanine and D-glutamate. Previously, we identified the D-lysine and D-glutamate biosynthetic pathways of T. maritima. Additionally, we reported some multifunctional enzymes involved in amino acid metabolism. In the present study, we characterized the enzymatic properties of TM1744 (threonine aldolase) to probe both its potential multifunctionality and D-amino acid metabolizing activities. TM1744 displayed aldolase activity toward both L-allo-threonine and L-threonine, and exhibited higher activity toward L-threo-phenylserine. It did not function as an aldolase toward D-allo-threonine or D-threonine. Furthermore, TM1744 had racemase activity toward two amino acids, although its racemase activity was lower than its aldolase activity. TM1744 did not have other amino acid metabolizing activities. Therefore, TM1744 is a low-specificity L-threonine aldolase with limited racemase activity.

Lichens are dual organisms, with one major mycobiont and one major photobiont in each lichen symbiosis, which can survive extreme environmental conditions in the Arctic. However, the diversity and distribution of lichen photobionts in the Arctic remain poorly understood compared to their mycobiont partners. This study explored the diversity of lichen mycobionts and photobionts in 197 lichen samples collected from the Ny-Ålesund region (Svalbard, High Arctic). The nuclear ribosomal internal transcribed spacer (ITS) regions were sequenced and phylogenetic analyses were performed. The relationships between mycobionts and photobionts, as well as the association patterns, were also investigated. A total of 48 species of lichen mycobionts (16 families, nine orders) and 31 species/lineages of photobionts were identified. These 31 photobiont species belonged to one class (Trebouxiophyceae) and five genera, including 22 species of Trebouxia, five species of Asterochloris, two species of Chloroidium, one species of Symbiochloris, and one species of Coccomyxa. The results indicated that most analyzed lichen mycobionts could associate with multiple photobiont species, and the photobionts also exhibited a similar pattern. The results provided an important reference dataset for characterizing the diversity of lichen mycobionts and photobionts in the High Arctic region.

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.