Extremophiles最新文献

Halophilic microorganisms from extreme environments are increasingly recognized as promising sources of industrial enzymes and antimicrobial compounds. However, many saline ecosystems remain unexplored. In this study, the bacteriological profile of the extreme salt lake of Arzew (Oran, Algeria) was investigated for the first time. Twenty-nine halophilic bacterial strains were isolated from five saline soil samples around the lake and were preliminarily screened for the production of nine industrially relevant enzymes and antimicrobial activities. The enzymatic screening revealed that 69% of the isolates showed single or combined hydrolytic activities, with gelatinase, protease, inulinase, and lipase activities being the most prevalent. The antimicrobial screening showed significant activity against Gram-positive pathogens, Aspergillus niger, Fusarium sp., and Phytophthora infestans. Four of the most potent strains were selected for further phenotypic and molecular characterization. Based on 16S rRNA gene sequencing, the results showed that three isolates belonged to the genus Streptomyces and one representative isolate to the Nocardiopsis genus. Both phylotypes demonstrated tolerance to wide ranges of salt, pH, and temperature. Notably, isolate O61 displayed a distinct phylogenetic position, suggesting its potential affiliation as a novel Streptomyces species. These results provide a baseline microbial resource discovery from an underexplored Algerian hypersaline environment and highlight promising candidates for future detailed characterization for biotechnological applications.

The rise of multidrug-resistant (MDR) strains of Mycobacterium tuberculosis (M. tb) has driven the search for new antimycobacterial agents. Our study focused on isolation and characterization of actinomycetes from the hypersaline Tso-Kar Salt lake in Ladakh, India, to explore their antibacterial potential. We isolated 145 bacterial isolates from various soil, salt and water samples and found 23 actinomycete isolates effective against Mycobacterium smegmatis through cross-streak screening. Molecular identification confirmed that these isolates belonged to 14 genera of actinomycetes. Out of 23 extracts from these isolates, 15 ethyl acetate organic extracts exhibited strong antimycobacterial activities against M. smegmatis, M. tb H37Ra, and M. tb H37Rv, with MIC values between 125 and 31.25 µg/mL. Importantly, all 15 extracts demonstrated bactericidal activities at their respective MICs against M. tb H37Rv. The other 8 extracts displayed comparatively weaker MIC and MBC ranging 500-250 µg/mL and 1000-500 µg/mL respectively. These extracts were equally effective against drug-resistant and drug-susceptible M. tb clinical isolates. Furthermore, they showed broad antibacterial activity against both gram-positive and gram-negative bacteria, with MICs ranging from 500 to 31.25 µg/mL. The GC-MS analysis of the potent extracts revealed that a wide range of compounds including Phenolics, Peptides, Ergot alkaloids and their derivates may have contributed to anti-mycobacterial activity. The genetic diversity and significant antimicrobial properties of these actinomycetes from extreme environments highlight their potential for developing new antituberculosis and general antibiotic agents, particularly against MDR infections.

The gene (SSO1457) encoding a L-glutamate dehydrogenase (GDH) homolog from the thermoacidophilic archaeon Saccharolobus solfataricus P2 was overexpressed in Escherichia coli. At a substrate concentration of 50 mM, the enzyme (SSO1457) produced exhibited much higher specific activity toward L-norvaline than L-glutamate at temperatures between 55 and 75°C, whereas the enzyme showed higher activity for L-glutamate than L-norvaline at 85°C. The crystal structures of both NAD⁺/2-oxovalerate-bound and NAD⁺/2-oxoglutarate-bound SSO1457 were determined. Comparison of the two structures showed that the positioning of the substrate molecules and the surrounding residues is nearly identical in the two complexes. In the 2-oxoglutarate-bound structure, the C5-carboxylate group of 2-oxoglutarate is hydrogen-bonded with the side chains of Lys72, Arg188, and Ser351, as observed in other GDHs. By contrast, in the 2-oxovalerate-bound structure, the C01, C02, and C03 atoms of 2-oxovalerate are anchored via hydrophobic interactions to the side chains of Met93 and Val348. Site-directed mutagenesis shows that the side chain of Met93 mainly mediates the reactivity of SSO1457 towards L-norvaline and contributes to high specific activities for L-norvaline.

The Atacama Desert, one of the most extreme environments on our planet, harbors a plethora of unique microbial communities adapted to the harsh conditions of the habitat. In this study, strain ATCH4^T, a novel Gram-stain-negative, curved rod-shaped bacterium, was isolated from the Llamara salt pan, located in the Atacama Desert in the north of Chile. ATCH4^T was capable of growth within a range of 3-12% (w/v) NaCl, 4-40 °C, and pH 6-9. Comparative 16S rRNA analysis placed the strain within the genus Idiomarina, with its closest related type species being I. loihiensis, I. ramblicola, and I. abyssalis. Genomic analysis revealed the presence of several genes linked to halophilicity as well as unique metabolic pathways, including the ability to synthesize C5 and C10-C20 isoprenoids, which may contribute to the isolate's survival in hypersaline conditions. The observed isoprenoid biosynthesis pathways suggest potential applications in various biotechnological fields, including the production of biofuels, pharmaceuticals, and other valuable chemicals. Levels of DNA-DNA relatedness, average nucleotide identity, and several phenotypic and chemotaxonomic markers clearly indicate that strain ATCH4^T represents a novel species of the genus Idiomarina, for which the designation Idiomarina aminovorans sp. nov. (type strain ATCH4^T = DSM 114475 = LMG 32710) is proposed.

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.