Extremophiles最新文献

A novel alkaliphilic sulfate-reducing bacterium, strain M08but^T, was isolated from a salsa lake of terrestrial mud volcano (Taman Peninsula, Russia). Cells were rod-shaped, motile and Gram-stain-negative. The temperature range for growth was 15-42 °C (optimum at 30 °C). The pH range for growth was 7.0-11.0, with an optimum at pH 8.5-9.0 Strain M08but^T used sulfate, thiosulfate, sulfite, dimethyl sulfoxide and arsenate as electron acceptors. Acetate, formate, butyrate, fumarate, succinate, glycerol and pyruvate were utilized as electron donors with sulfate. Fermentative growth was observed with fumarate, pyruvate, crotonate. Strain M08but^T grew chemolithoautotrophically with H₂ and CO₂. The G + C content of the genomic DNA was 60.1%. The fatty acid profile of strain M08but^T was characterized by the presence of anteiso-C_15:0 as the major component (68.8%). The closest phylogenetic relative of strain M08but^T was Desulfatitalea tepidiphila (the order Desulfobacterales) with 96.3% 16S rRNA gene sequence similarity. Based on the phenotypic, genotypic and phylogenetic characteristics of the isolate, strain M08but^T is considered to represent a novel species of the genus Desulfatitalea, with proposed name Desulfatitalea alkaliphila sp. nov. The type strain of Desulfatitalea alkaliphila is M08but^T (= KCTC 25382^T = VKM B-3560^T = DSM 113909^T = JCM 39202^T = UQM 41473^T).

Salt tolerance is an important property of duplex-specific nuclease (DSN). DSN with high salt tolerance can be more widely used in genetic engineering, especially in the production of nucleic acid drugs. To improve the salt tolerance of DSN, we selected five DNA-binding domains from extremophilic organisms, which have been shown the ability to improve salt tolerance of DNA polymerases and nucleases. The experimental results demonstrated that the fusion protein TK-DSN produced by fusing a N-terminal DNA-binding domain, which comprised two HhH (helix-hairpin-helix) motifs domain from an extremely halotolerant bacterium Thioalkalivibrio sp. K90mix, has a significantly improved salt tolerance. TK-DSN can tolerate the concentration of NaCl up to 800 mM; in addition, the ability of digesting DNA was also enhanced during in vitro transcription and RNA purification. This strategy provides the method for the personalized customization of biological tool enzymes for different applications.

An acid-active exo/endo-chitinase; comprising a GH18 catalytic domain and substrate insertion domain; originating from the thermophilic filamentous fungus Rasamsonia emersonii, was expressed in Pichia pastoris. In silico analysis including phylogenetic analysis, and recombinant production, purification, biochemical characterisation, and industrial application testing, was carried out. The expressed protein was identified by SDS-PAGE as a smear from 56.3 to 125.1 kDa, which sharpens into bands at 46.0 kDa, 48.4 kDa and a smear above 60 kDa when treated with PNGase F. The acid-active chitinase was primarily a chitobiosidase but displayed some endo-chitinase and acetyl-glucosamidase activity. The enzyme was optimally active at 50 °C, and markedly low pH of 2.8. As far as the authors are aware, this is the lowest pH optima reported for any fungal chitinase. The acid-active chitinase likely plays a role in chitin degradation for cell uptake in its native environment, perhaps in conjunction with a chitin deacetylase. Comparative studies with other R. emersonii chitinases indicate that they may play a synergistic role in this. The acid-active chitinase displayed some efficacy against non-treated substrates; fungal chitin and chitin from shrimp. Thus, it may be suited to industrial chitin hydrolysis reactions for extraction of glucosamine and chitobiose at low pH.

Four extremely halophilic archaeal strains (ZJ2^T, BND6^T, DT87^T, and YPL30^T) were isolated from marine environments and a salt mine in China. The 16S rRNA and rpoB' gene sequence similarities among strains ZJ2^T, BND6^T, DT87^T, YPL30^T and the current species of Natrinema were 93.2-99.3% and 89.2-95.8%, respectively. Both phylogenetic and phylogenomic analyses revealed that strains ZJ2^T, BND6^T, DT87^T, and YPL30^T cluster with the Natrinema members. The overall genome-related indexes (ANI, isDDH, and AAI) among these four strains and the current species of genus Natrinema were 70-88%, 22-43% and 75-89%, respectively, clearly below the threshold values for species boundary. Strains ZJ2^T, BND6^T, DT87^T, and YPL30^T could be distinguished from the related species according to differential phenotypic characteristics. The major polar lipids of the four strains were phosphatidic acid (PA), phosphatidylglycerol (PG), phosphatidylglycerol phosphate methyl ester (PGP-Me), sulfated mannosyl glucosyl diether (S-DGD-1), and disulfated mannosyl glucosyl diether (S₂-DGD). The phenotypic, chemotaxonomic, phylogenetic and phylogenomic features indicated that strains ZJ2^T (= CGMCC 1.18786 ^T = JCM 34918 ^T), BND6^T (= CGMCC 1.18777 ^T = JCM 34909 ^T), DT87^T (= CGMCC 1.18921 ^T = JCM 35420 ^T), and YPL30^T (= CGMCC 1.15337 ^T = JCM 31113 ^T) represent four novel species of the genus Natrinema, for which the names, Natrinema caseinilyticum sp. nov., Natrinema gelatinilyticum sp. nov., Natrinema marinum sp. nov., and Natrinema zhouii sp. nov., are proposed.

Droplet digital PCR (ddPCR) is being increasingly adopted for gene detection and quantification because of its higher sensitivity and specificity. According to previous observations and our laboratory data, it is essential to use endogenous reference genes (RGs) when investigating gene expression at the mRNA level under salt stress. This study aimed to select and validate suitable RGs for gene expression under salt stress using ddPCR. Six candidate RGs were selected based on the tandem mass tag (TMT)-labeled quantitative proteomics of Alkalicoccus halolimnae at four salinities. The expression stability of these candidate genes was evaluated using statistical algorithms (geNorm, NormFinder, BestKeeper and RefFinder). There was a small fluctuation in the cycle threshold (Ct) value and copy number of the pdp gene. Its expression stability was ranked in the vanguard of all algorithms and was the most suitable RG for quantification of expression by both qPCR and ddPCR of A. halolimnae under salt stress. Single RG pdp and RG combinations were used to normalize the expression of ectA, ectB, ectC and ectD under four salinities. The present study constitutes the first systematic analysis of endogenous RG selection for halophiles responding to salt stress. This work provides a valuable theory and an approach reference of internal control identification for ddPCR-based stress response models.

Three novel filamentous halophilic archaea, strains DFN5^T, RDMS1, and QDMS1, were isolated from the coastal saline soil samples of the intertidal zones located in different regions of Jiangsu Province, China. The colonies of these strains were pinkish-white due to the presence of white spores. These three strains are extremely halophilic and grew optimally at 35-37 °C and pH 7.0-7.5. Based on 16S rRNA and rpoB' gene analysis, strains DFN5^T, RDMS1, and QDMS1 gathered together in phylogenetic trees and then clustered with the current species of the genus Halocatena showing 96.9-97.4% and 82.2-82.5% similarities, respectively. Both the 16S rRNA gene-based and rpoB' gene-based phylogenies were fully supported by the phylogenomic analysis, and the overall genome-related indexes indicated that strains DFN5^T, RDMS1, and QDMS1 should be a novel species of the genus Halocatena. Genome mining revealed that there are considerable differences in the genes related to β-carotene synthesis among these three strains and the current species of Halocatena. The major polar lipids of strains DFN5^T, RDMS1, and QDMS1 are PA, PG, PGP-Me, S-TGD-1, TGD-1, and TGD-2. The minor polar lipids, S-DGD-1, DGD-1, S₂-DGD, and S-TeGD may be detected. According to the phenotypic characteristics, phylogenetic analysis, genomic and chemotaxonomic features, strains DFN5^T (= CGMCC 1.19401 ^T = JCM 35422 ^T), RDMS1 (= CGMCC 1.19411) and QDMS1 (= CGMCC 1.19410) were classified as a novel species of the genus Halocatena with the proposed name, Halocatena marina sp. nov. This is the first report of the description of a novel filamentous haloarchaeon isolated from marine intertidal zones.

Caldicellulosiruptor species are proficient at solubilizing carbohydrates in lignocellulosic biomass through surface (S)-layer bound and secretomic glycoside hydrolases. Tāpirins, surface-associated, non-catalytic binding proteins in Caldicellulosiruptor species, bind tightly to microcrystalline cellulose, and likely play a key role in natural environments for scavenging scarce carbohydrates in hot springs. However, the question arises: If tāpirin concentration on Caldicellulosiruptor cell walls increased above native levels, would this offer any benefit to lignocellulose carbohydrate hydrolysis and, hence, biomass solubilization? This question was addressed by engineering the genes for tight-binding, non-native tāpirins into C. bescii. The engineered C. bescii strains bound more tightly to microcrystalline cellulose (Avicel) and biomass compared to the parent. However, tāpirin overexpression did not significantly improve solubilization or conversion for wheat straw or sugarcane bagasse. When incubated with poplar, the tāpirin-engineered strains increased solubilization by 10% compared to the parent, and corresponding acetate production, a measure of carbohydrate fermentation intensity, was 28% higher for the Calkr_0826 expression strain and 18.5% higher for the Calhy_0908 expression strain. These results show that enhanced binding to the substrate, beyond the native capability, did not improve C. bescii solubilization of plant biomass, but in some cases may improve conversion of released lignocellulose carbohydrates to fermentation products.

Xichú River is a Mexican river located in an environmental preservation area called Sierra Gorda Biosphere Reserve. Around it, there are tons of abandoned mine residues that represent a serious environmental issue. Sediment samples of Xichú River, visibly contaminated by flows of an acid mine drainage, were collected to study their prokaryotic diversity. The study was based on both cultural and non-cultural approaches. The analysis of total 16S rRNA gene by MiSEQ sequencing allowed to identify 182 Operational Taxonomic Units. The community was dominated by Pseudomonadota, Bacteroidota, "Desulfobacterota" and Acidobacteriota (27, 21, 19 and 16%, respectively). Different culture conditions were used focusing on the isolation of anaerobic bacteria, including sulfate-reducing bacteria (SRB) and arsenate-reducing bacteria (ARB). Finally, 16 strains were isolated. Among them, 12 were phylogenetically identified, with two strains being SRB, belonging to the genus Solidesulfovibrio ("Desulfobacterota"), while ten are ARB belonging to the genera Azospira (Pseudomonadota), Peribacillus (Bacillota), Raineyella and Propionicimonas (Actinomycetota). The isolate representative of Raineyella genus probably corresponds to a new species, which, besides arsenate, also reduces nitrate, nitrite, and fumarate.

A strain, 3EQS1, was isolated from a salt sample taken from Lake Qarun (Fayoum Province, Egypt). On the basis of physiological, biochemical, and phylogenetic analyses, the strain was classified as Chromohalobacter salexigens. By 72 h of growth at 25 °C, strain 3EQS1 produced large amounts (15.1 g L^-1) of exopolysaccharide (EPS) in a liquid mineral medium (initial pH 8.0) containing 10% sucrose and 10% NaCl. The EPS was precipitated from the cell-free culture medium with chilled ethanol and was purified by gel-permeation and anion-exchange chromatography. The molecular mass of the EPS was 0.9 × 10⁶ Da. Chemical analyses, Fourier transform infrared spectroscopy, and nuclear magnetic resonance spectroscopy showed that the EPS was a linear β-D-(2 → 6)-linked fructan (levan). In aqueous solution, the EPS tended to form supramolecular aggregates with a critical aggregation concentration of 240 µg mL^-1. The EPS had high emulsifying activity (E₂₄, %) against kerosene (31.2 ± 0.4%), sunflower oil (76.9 ± 1.3%), and crude oil (98.9 ± 0.8%), and it also had surfactant properties. A 0.1% (w/v) aqueous EPS solution reduced the surface tension of water by 11.9%. The levan of C. salexigens 3EQS1 may be useful in various biotechnological processes.

Lithopanspermia is defined as dispersal of living extremophiles from one planetary body to another, through life-bearing rocks ejected by meteor impacts. If lithopanspermia proves concrete, it should be viewed as an eco-evolutionary phenomenon. Biogeographic/microevolutionary models have been proposed as analogues for lithopanspermia dynamics; however, extremophile arrival on a planetary body is not the end of story. Here, we suggest that eco-evolutionary (environment + organismal microevolution) dynamics can lead to distinct macroevolutionary scenarios after extremophile arrival on a planetary body. Speciation would be the most important factor in interplanetary dynamics due to the possibly long time and distance between dispersive events, similar to long-distance dispersal dynamics on Earth. In previously uninhabited planets, persistence of extremophiles and descendants depends almost only on evolvability of extremophiles against abiotic filters. Considering a previously inhabited planet, ecological interactions at local or global scales could drive persistence (speciation/extinction) of extremophiles in the new habitat. Thus, we might expect high extinction rates if negative interactions are dominant, or, high speciation, if positive interactions occur, with extremophile lineages overpower (or not) the native biota. If interplanetary dispersal is possible, theories about the evolution of life may be universal, leading to a general eco-evolutionary model for life in the Universe.