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PubMed2025

CRISPR-based gene knockout in the model haloarchaeon Haloferax mediterranei.

Halophilic archaea, a specialized group of extremophiles that inhabit hypersaline environments, exhibit distinctive physiological and metabolic features. Traditional genetic manipulation of these organisms, predominantly reliant on homologous recombination techniques, suffers from limitations such as complex procedures and extended timelines, which hinder functional genomics research and the development of practical applications. This study established a CRISPR (Clustered Regularly Interspaced Short Palindromic Repeats)-mediated gene knockout system in the model halophilic archaeon Haloferax mediterranei. A polyethylene glycol (PEG)-mediated transformation method was used to deliver a plasmid carrying a mini-CRISPR array into H. mediterranei. The crtB gene, involved in pigment synthesis, was successfully knocked out, demonstrating the feasibility of CRISPR-based editing in H. mediterranei. To further validate the reliability and targeting accuracy of the system, the hlyR4 gene, encoding an extracellular serine protease, was also disrupted. The CRISPR-mediated gene knockout efficiency for hlyR4 reached 27%, significantly higher than the approximately 3% efficiency achieved with conventional homologous recombination. The establishment of this CRISPR-based gene knockout system provides a more efficient genetic tool for H. mediterranei and lays a new experimental foundation for exploiting microbial resources from extreme environments. In this study, H. mediterranei was selected as the model organism for haloarchaea. For the first time, we successfully constructed a CRISPR-based gene knockout system in a model halophilic archaeon. This system provides a solution for CRISPR-based gene knockout tools, which are currently unavailable in model halophilic archaea, and offers an effective tool for functional genomics studies in extremophiles.

Haloferax mediterranei↗

PubMed2026

Rhodococcus folensis sp. nov., an orange-red-pigmented bacterium from mining soil.

Mining-impacted environments represent chemically complex ecosystems that may harbor metabolically versatile and pigment-producing microorganisms. During a survey of pigment-producing bacteria from abandoned mining soil in Trabzon, Türkiye, a red-pigmented strain, designated FMA22T, was isolated and characterized using a polyphasic taxonomic approach. 16 S rRNA gene sequence analysis placed the strain within the genus Rhodococcus, showing the highest similarity to R. corynebacterioides DSM 20,151T (99.57%), R. kroppenstedtii DSM 44908ᵀ (99.06%) and R. trifolii T8T (98.96%). The strain was Gram-stain-positive, aerobic and non-motile, and grew at 4-40 °C. Polar lipids included phosphatidylethanolamine, diphosphatidylglycerol, phosphatidylinositol, phosphatidylinositol mannoside, phosphatidylcholine, five unidentified glycolipids, four unidentified lipids, one unidentified phospholipid and one unidentified phosphoglycolipid; MK-8(H2) was the major respiratory quinone. Major fatty acids were C18:1 ω9c, summed feature 3 (C16:1 ω7c/C16:1 ω6c) and C16:0. ANI and dDDH values with the closest relatives were below 76.8% and 20.5%, respectively. The draft genome (4.23 Mb; 67.2 mol% G + C; 4,106 CDSs) harbors a terpene-associated carotenoid cluster containing crtB, crtI and crtY. The orange-red pigment (λmax = 475 nm) showed antioxidant activity (DPPH SC₅₀ = 5.38 mg mL⁻¹; FRAP = 4.34 µmol TE g⁻¹) and weak but measurable HIV-1 reverse transcriptase inhibition (IC₅₀ = 22 mg mL⁻¹). These data support the proposal of Rhodococcus folensis sp. nov., with FMA22ᵀ (= LMG 34144ᵀ = DSM 120048ᵀ) as the type strain.

Soil Microbiology↗

PubMed2026

Isolation and Characterization of a Naturally Occurring Brevundimonas vesicularis Strain Exhibiting High Phytoene Accumulation.

Phytoene, a colorless precursor of carotenoids, has attracted increasing attention because of its favorable bioavailability, antioxidant activity, and potential applications in functional foods, nutraceuticals, and animal nutrition. However, its industrial utilization remains limited by low natural abundance and the dependence of current production strategies on genetic engineering or metabolic pathway manipulation. In this study, we identified and characterized a naturally occurring Brevundimonas vesicularis strain (Bv-xms2024) exhibiting pronounced phytoene accumulation without genetic modification. The strain was comprehensively characterized using morphological, biochemical, molecular, genomic, metabolomic, and transcriptional analyses. Quantitative LC-MS/MS analysis demonstrated that Bv-xms2024 accumulated phytoene to 420.42 ± 98.11 μg/g dry biomass after 96 h of cultivation, substantially exceeding the levels of downstream carotenoids, including β-carotene and astaxanthin. Optimization of cultivation parameters identified 25 °C, pH 7.0, and 96 h as the optimal conditions for phytoene accumulation, while serial passaging confirmed stable production over 20 generations. Genome annotation identified the carotenoid biosynthetic gene repertoire, while RT-qPCR analysis revealed a temporal shift from early upregulation of crtE and crtB to later upregulation of downstream pathway genes, consistent with the observed phytoene-dominant carotenoid profile. Short-term tolerance evaluations in mice and chickens revealed no observable adverse effects under the tested conditions. Collectively, these findings identify Bv-xms2024 as a promising natural microbial resource for phytoene production and provide a basis for further process development and strain-level safety evaluation.

Brevundimonas vesicularis↗