Extremophiles最新文献

Bdelloid rotifers are major components of zooplankton worldwide and have been reported in glacier ice in both Northern and Southern Hemispheres. Curiously, no reports of psychrophilic bdelloids have surfaced in North America despite exhaustive surveys of other ice-dwelling invertebrates, e.g., glacier ice worms. This distribution gap may be partially explained by a predator-prey relationship between these two animals, but the current study suggests that ice worms and bdelloids can co-inhabit at least some glacial ecosystems over geological time. Here we report the first ice-inhabiting bdelloid rotifer from North America, collected from the northern aspect of Mt. Deception, WA, USA. Nuclear and mitochondrial genotyping identified sister-species relationships within a clade of Nordic ice-dwelling bdelloids, and close evolutionary relationships with Antarctic/New Zealand specimens. Intrapopulation genetic divergences suggest that bdelloids arrived in North America near the onset of the Pleistocene (2.58 myr BP), but their circumpolar dispersal capabilities and robustness (e.g., freeze-thaw tolerance, ability to propagate at elevated temperatures and under extreme laboratory conditions) cannot rule out multiple transoceanic dispersal events throughout the Quaternary.

Natural polysaccharides from microorganisms have various biological activities. However, those from psychrophiles with immunomodulatory properties have rarely been found. In this study, an immunoactive exopolysaccharide was extracted from Antarctic Pseudoalteromonas sp. LP6-12-2 (EPS1-1), which isolated using DEAE-Sepharose Fast Flow, Sephadex G-75, and Sephadex G-100. EPS1-1, with a molecular weight 23.47 kDa, was composed of mannose, glucose, galactose, glucosamine, and galactosamine in the ratio of 83.1:7.2:4.3:4.2:1.2. Furthermore, EPS1-1 was found to have a main chain composed of α-D-Manp (1→2) and side chains composed of α-D-Manp (1→6) by FT-IR, methylation, and NMR analyses. Besides, through the Congo red test and I₂-KI reaction analyses, it was revealed that EPS1-1 lacked triple-helix structure and had more branches. Additionally, EPS1-1 could significantly advance the proliferation, phagocytosis, acid phosphatase activity, and cytokines production of macrophage cells. Data suggested EPS1-1 demonstrated potential as an immunomodulator for functional food or pharmaceutical development.

Natranaerobius thermophilus is an obligately anaerobic, halophilic alkalithermophilic microorganism that was isolated from the sediment of Lake Fazda of the Wadi An Natrun, Egypt. It can grow optimally at 3.3-3.9 M Na⁺, 53℃ and pH 9.5 (measured at 55℃). N. thermophilus has several properties that distinguish it from other halophilic anaerobes; it is simultaneously adapted to alkaline pH and high temperature and adopts a combined salt-in-compatible solute strategy for osmoadaptation, accumulating glycine betaine, proline and potassium in its cytoplasm. The F₁F₀-ATPase of N. thermophilus is Na⁺-coupled and functions primarily as a Na⁺ pump, expelling Na⁺ from the cytoplasm at the expense of ATP. N. thermophilus has a large cohort of electrogenic Na⁺(K⁺)/ H⁺ antiporters for cytoplasm acidification and has an acidic proteome. This minireview discusses the phylogeny and metabolism of N. thermophilus. Adaptive mechanisms employed by N. thermophilus to combat multiple extreme growth conditions will be presented.

In this study, we report the draft genome sequence of strain A2. The genome size was 3.8 Mbp, the GC content was 67.4%, and it was predicted to contain 3520 protein-coding genes, 62 tRNA genes, 8 rRNA genes, and 4 snRNA genes. Phylogenetic analysis of the 16S rRNA gene in different databases suggests that strain A2 belongs to Halomonas salifodinae. Also, Multilocus Sequence Typing analysis confirms that A2 is closely related to H. salifodinae. Phylogenomic of the core genes and comparative genomic analysis using the Average Nucleotide Identity, digital DNA-DNA Hybridization, Average Amino acid Identity, the Percentage of Conserved Proteins values indicators, and the Genome Taxonomy Database indicates that strain A2 is identified as H. salifodinae and suggest that this species has a closer phylogenetic relationship with the genus Bisbaumannia than with Halomonas. The pangenomic analysis of A2 against 100 reference genomes of described Halomonas and another related genus shows 136,122 genes that comprise the pangenome with 317 core genes, 3457 shell genes, 132,332 accessory genome genes, and 691 unique genes. A2 has 261 signature genes that it shares only with Bisbaumannia and Halomonas salifodinae. For strain A2 we found 29 genes for secretion systems, 23 genes for Na⁺ and K⁺ ion transport, 6 Biosynthetic Gene Clusters groups, a total of 12 genomic islands, an 8.2 kb gene prophage region, 15 regions associated with CRISPR and one CAS-TypeIF cas gene cluster region, 12 genes of biotechnological importance, 38 unique genes essential for adaptability and biotechnological relevance, as well as, 35 genes for the synthesis of compatible solutes. Comparative genomics analysis shows that strain A2 has multiple unique genetic features that could be useful for biotechnological applications. The result of this study places the species Halomonas salifodinae in a very close relationship with the genus Bisbaumannia than with Halomonas, so its reclassification to the genus Bisbaumannia is proposed for future validation.

We aimed to investigate the phosphate solubilization by filamentous fungi isolated from Antarctic lichen and sediment. The results yielded a total of 80 strains, 9 of which were positive for phosphate solubilization in solid NBRIP medium. Cladosporium sp. 1EM.P1 and Penicillium steckii 5Y.P4 showed the largest halos, indicating their potential in phosphate solubilization. Cladosporium sp. 1EM.P1 was the most efficient phosphorus (P) solubilizer with maximum P levels of 106.14 mg/L at 15 °C and 80.89 mg/L at 25 °C. This strain also showed solubilization activity at 0.5 M NaCl with P levels of 127.93 mg/L. At pH 8.0, the P content was 137.93 mg/L, and glucose was the best carbon source (P 146.55 mg/L). Moreover, the isolated fungus showed activity only with tricalcium phosphate as an inorganic phosphate source. During the solubilization process, Cladosporium sp. 1EM.P1 released formic, malic, and succinic acids by the 15th day of incubation (P 208.99 mg/L). These findings indicate that Cladosporium sp. 1EM.P1 from Antarctic sediment has the potential to solubilize phosphate and thus unveils new possibilities for the agricultural sector, aimed to reducing reliance on chemical fertilizers.

Extracellular proteases produced by haloarchaea, termed halolysins, possess potential applications in diverse fields including food fermentation and bio-remediation. In this study, an extracellular protease encoding gene, hly32^PRR32, from Halostella sp. PRR32 isolated from a salt mine in Anhui, China, was identified and expressed in Escherichia coli. The expressed protein MBP-Hly32 was purified and biochemically characterized. The results indicate that Hly32 belongs to the S8 family of serine proteases (halolysin). A BLAST search on NCBI reveals that Hly32 has an amino acid sequence identity of 68.87% with serine protease Hly176B from Haloarchaeobius sp. FL176. MBP-Hly32 contains a catalytic triad of Asp¹⁵⁹-His¹⁹⁸-Ser³⁵⁰ and two C-terminal extensions which are crucial for its activity. The optimal conditions for its enzyme activity are 50 °C, pH 8.0, and 4.0 M NaCl. Under these conditions, the K_m, V_max and K_cat for the MBP-Hly32 were determined to be 2.34 mM, 935.50 U·mg^-1 and 1472.40 s^-1, respectively. Metal ions and organic reagents affect its activity differently from the typical halolysins; for example, Ca²⁺, which enhances the activity of other halolysin enzymes, has no effect on MBP-Hly32. Furthermore, the activity of Hly32 was inhibited by the presence of PMSF, DTT, and EDTA. Furthermore, a three-dimensional structure prediction based on functional domains was obtained in this study which will facilitate modification and protein engineering halolysins to generate mutants with new physiological activities.

Four lakes in the same region of Aotearoa New Zealand were investigated to characterize sediment microbial communities and functions under contrasting environmental conditions. Two lakes, an acidic lake (Rototai) and a lake with elevated metals and nutrients (Killarney) were impacted by extreme stressors, while the lowland mesotrophic lake (Kaihoka East) and an alpine lake (Peel) were used as reference lakes. Using metabarcoding and metagenomics analysis, we profiled community composition, functional pathways, and resistance mechanisms in the lake sediments. Rototai contained high abundances of genes involved in sulfur cycling (assimilatory and dissimilatory sulfate reduction, sulfur oxidation) and acid tolerance (kdp potassium-transport system, ClcA antiporters). In contrast, Killarney had elevated abundances of genes involved in methanogenesis, however despite high metal concentrations, no enrichment of metal-resistance genes was detected. Kaihoka East contained the highest prokaryotic diversity and an elevated abundance of genes involved in nitrification. Although community taxonomic differences were modest across lakes, functional analyses revealed distinct metabolic adaptations. These findings highlight the utility of using metagenomic approaches to identify biogeochemical processes and stress-response strategies in lakes. Improved understanding of microbial functional diversity in surface sediments has implications for lake management, particularly in systems impacted by acidification, high nutrient loading, and metal contamination.

The identification and characterization of promoters and regulatory elements are commonly assessed using reporter genes. However, very few of these are available for haloarchaea. In this study, we describe the construction and validation of a reporter system for the haloarchaeon Haloferax volcanii based on a modified and stable version of the carotenoid biosynthesis enzyme phytoene synthase (PSY). This tool enables the analysis of a target gene expression through direct visualization of cell pigmentation and/or the extraction and quantification of carotenoid content. The modified crtB gene encoding PSY was cloned into the pTA963 vector under two regulatable promoters previously characterized in H. volcanii: PtnaA and Pxyl, inducible with tryptophan and xylose, respectively. The construct was introduced into and expressed in a non-pigmented H. volcanii strain (ΔcrtB) under varying inducer concentrations. For both promoters, a clear increase in pigmentation was visually observed in cultures and cell pellets with increasing inducer levels. These observations were corroborated by carotenoid extraction and quantification, as well as by Western blot analysis of PSY protein levels. This work presents a robust, easy-to-use, and versatile reporter system for investigating gene expression in H. volcanii, expanding the toolkit for genetic studies in haloarchaea.

Halophilic bacteria are recognized as a promising source of novel enzymes and biopolymers with various applications in biotechnology and the industry. In comparison with their mesophilic analogues, halophilic metabolites are stable under extreme conditions typically encountered in the industrial processes. In this study, the biotechnological potential of twenty strains of halophilic bacteria isolated from the Provadia salt deposit, Bulgaria was investigated for the first time. The strains were identified based on the sequencing of the 16S rRNA gene and were assigned to 13 different species falling in the Bacillota and Pseudomonadota phyla. The majority (90%) of them showed single or combined hydrolytic enzyme activity. Half of the strains (55%) were able to produce between three and eight extracellular hydrolytic enzymes-arabinase, cellulase, gelatinase, glucanase, L-glutaminase, pectinase, and xylanase. Ten strains were able to synthesise exopolysaccharides (EPS) in concentration between 32 and 227 μg/ml. The optimal EPS production kinetics (1.6 ± 0.15 g/l) by Virgibacillus halodenitrificans PSZ-34 was systematically investigated for the first time. Three strains also exhibited antimicrobial activity. The present study involved culture-dependant isolation of halophilic bacteria from the Provadia salt deposit and shed more light on their capability to synthesise hydrolytic enzymes and EPS with potential industrial exploitation.