Current Microbiology最新文献

An actinomycete, designated strain H11422^T, was isolated from sediment collected from Mahu Lake, Sichuan Province, P.R. China, and characterized by a polyphasic taxonomic approach. Strain H11422^T, based on the 16 S rRNA gene sequence analysis, exhibited the highest similarities to Pseudonocardia acidicola K10HN5^T (98.5%), Pseudonocardia bannensis YIM63101^T (97.9%), Pseudonocardia nigra ATK03^T (97.8%) and Pseudonocardia saturnea IMSNU 20,052^T (97.7%). Phylogenetic analysis based on the 16 S rRNA gene sequence placed strain H11422^T into the genus Pseudonocardia, where it formed a subclade with Pseudonocardia acidicola K10HN5^T. Genomic comparison with the closest type strain revealed average nucleotide identity (ANI) value of 84.8%, average amino acid identity (AAI) value of 81.6%, and digital DNA-DNA hybridization (dDDH) value of 28.9%, all significantly below the accepted species delineation thresholds. The whole-cell hydrolysates of strain H11422^T were composed of meso-diaminopimelic acid (meso-DAP) as the diagnostic diamino acid, and arabinose, galactose, glucose and ribose as the major sugars. Mycolic acids were not present. The only menaquinone was determined to be MK-8(H₄). The phospholipid profile included diphosphatidylglycerol, phosphatidylethanolamine, phosphatidylglycerol, phosphatidylinositol, three unidentified phospholipids, two unidentified aminophospholipids and two unidentified lipids. The predominant fatty acid was iso-C_16:0. Based on this comprehensive taxonomic evidence, strain H11422^T represents a novel species within the genus Pseudonocardia, for which the name Pseudonocardia mahuensis sp. nov. is proposed. The type strain is H11422^T (= JCM 34850^T = CICC 25117^T).

Melanins are complex pigments generated when fungi, animals, plants, and bacteria oxidatively polymerize phenolic/indolic chemicals. Throughout history, this ubiquitous pigment has been utilized in various industrial applications attributed to its many qualities and uses across numerous sectors. This study focuses on the extraction and characterization of the melanin pigment of the rare Indian fungus Trichomerium bhatii NFCCI 4305. Potato dextrose broth was used for submerged fermentation of the pure fungal culture, and further, the black pigment was recovered from the biomass via alkali-acid treatment and then, purified. Through the use of UV spectroscopy, FTIR analysis, thermogravimetric analysis, and several physicochemical studies, the black pigment obtained was identified as "melanin". Elemental analysis suggests that the pigment may actually be eumelanin. The purified melanin exhibited significant biological activities. Antimicrobial assays showed MIC values of 62.5 µg/mL for Raoultella planticola, 125 µg/mL for Escherichia coli, Staphylococcus aureus, Bacillus subtilis and Candida albicansi and 250 µg/mL for Pseudomonas aeruginosa MTCC 2453. Antioxidant activity assessed using the DPPH radical-scavenging assay demonstrated a dose-dependent response (20-100 µg/mL) with an IC₅₀ of 4.35 µg/mL. Cytotoxicity analysis revealed only a mild, dose-dependent decrease in cell viability (56% to 40% across 5-320 µg/mL), indicating good biocompatibility. T. bhatii NFCCI 4305 melanin's encouraging biological activity points to possible industrial uses for it. This is the first study that we are aware of those reports and describes melanin pigment from the Trichomerium genus.

This study aimed to produce secondary metabolites (SM) through the co-cultivation of Trichotomospora caesia AC-1134 and Streptoverticillium sp. AC-1375 and to evaluate their antioxidant properties. The fermentation was carried out on GYM, ISP, LB, and YGGS agar media. The radical scavenging activity of metabolites was studied using the ABTS and DPPH assays. The metabolites produced by the bacteria were identified with gas chromatography coupled with mass spectrometry (GC-MS). The GC-MS analysis revealed 39 and 28 compounds for the ethyl acetate and chloroform extracts, respectively. The compounds identified were grouped into the following classes: ketones, aldehydes, fatty acids, phthalate esters, ergot alkaloids, fatty amides, amides, esters, glycol ethers, ethers, etc. The DPPH radical scavenging activity of ethyl acetate and chloroform extracts ranged from 12.06 to 31.40% and 6.24 to 19.29%, respectively. The ABTS radical scavenging potential of the ethyl acetate and chloroform extracts ranged from 7.30 to 58.58% and 5.29 to 22.32%, respectively. The ethyl acetate extracts showed better free radical scavenging properties compared to the chloroform extracts. Co-cultivation of the two bacterial strains increased the diversity of the secondary metabolites produced. Microbial co-cultivation could be employed as an alternative to conventional monoculture techniques due to its ability to stimulate the production of additional metabolites that cannot be produced by single microbial strains.

Microalgae are valuable sources of biotechnological products for industrial applications. The increasing interest in microalgal biomass has also highlighted its ability to release extracellular byproducts, including enzymes of industrial relevance, into the culture medium. This study evaluated the combined effects of CO₂ availability, nitrogen levels, light color, and light intensity on the growth and extracellular amylolytic and lipase activities of Chlorella sorokiniana using a Taguchi L₄ experimental design. Cell growth and lipase activity were favored under purple light and moderate light intensity at low CO₂ supplementation, whereas amylolytic activity was enhanced under purple light combined with increased CO₂ availability and lower light intensity. Overall, light color emerged as the main factor influencing both growth and extracellular enzyme production, followed by CO₂ concentration and light intensity. These findings demonstrate the potential of controlling light and carbon supplies to modulate microalgal growth and extracellular enzyme activity, supporting the development of integrated and sustainable microalgal bioprocesses.

Biofilm formation provides probiotics with a natural barrier against harsh conditions and increases their bioavailability. The dynamic culture system could effectively promote probiotic biofilm formation. In view of the excellent probiotic properties and biofilm-forming ability of Bifidobacterium adolescentis BL-8, a dynamic culture system for this strain was constructed in this study and utilized to carry out in-depth mechanistic and potential application research. The results showed that innovatively establishing this system with physical-biological synergies for B. adolescentis BL-8, using oat bran as the carrier, achieved a 46.6% increase in the biofilm-forming rate and reduced the formation time by 12 h. This enhancement was attributed to carrier-strain interactions that this system strengthened bacterial initial aggregation during reversible adhesion through electrostatic/hydrophilic force regulation. Transcriptome analysis during irreversible adhesion and growth maturation phase further discovered that this system controls two-component signaling systems to boost nitrogen assimilation and c-di-GMP pathways to suppress flagella assembly, collectively promoting bacterial growth and morphological transitions. Dynamic cultivation also regulated the quorum-sensing system, prolonged biofilm growth, and stimulated extracellular polymeric substance synthesis. These modulations reinforced the biofilm's structural integrity, enabling increased bacterial resistance to freeze-drying and gastrointestinal stress and the storage time of the freeze-dried probiotic powder. This dynamic culture system with physical-biological synergies effectively promoted B. adolescentis BL-8 biofilm formation through enhanced initial adhesion, bacterial proliferation and morphological transformations, and prolonged biofilm formation, exhibiting great potential for applications. This study provides an important theoretical basis and new insights for the development of probiotic biofilm-modulation technology and its industrial applications.

Biofilms, complex microbial communities embedded in extracellular polymeric substances (EPS), pose significant challenges across medical, industrial and environmental sectors due to their enhanced resistance to antibiotics and chemical agents. Traditional treatments often fail to combat biofilm-associated infections, leading to increased healthcare costs and mortality rates. This comprehensive review explores the potential of natural anti-biofilm agents derived from plants, microorganisms, marine organisms and other natural sources as alternative strategies. Plant-derived compounds, microbial products and marine bioactive substances exhibit promising anti-biofilm properties through various mechanisms, including inhibition of microbial adhesion, quorum sensing (QS) interference and EPS disruption. The review highlights the efficacy of these agents in both in vitro and in vivo studies and discusses their potential applications in industries such as medicine, food processing and water treatment. Despite the promising results, challenges such as standardization, biocompatibility and environmental impact remain. Future research should focus on optimizing these natural agents and exploring synergistic combinations to enhance their efficacy. This review underscores the importance of sustainable and interdisciplinary approaches in developing effective, eco-friendly anti-biofilm strategies for diverse applications.

Two novel aerobic, rod-shaped, motile bacterial strains, designated as strains sgz302251^T and sgz5001026^T, were both isolated from paddy soils. 16S rRNA gene sequences analysis revealed that strain sgz302251^T exhibited 98.3% similarity with its closest reference strain Paenibacillus vietnamensis N4^T, while strain sgz5001026^T had the highest similarity of 97.5% to Ectobacillus polymachus KACC 18242^T. The average nucleotide identity (ANI) and digital DNA-DNA hybridization (dDDH) values between strains sgz302251^T, sgz5001026^T and their closest reference strains were 86.0% and 21.2%, 84.9% and 22.9%, respectively. The genomic DNA G + C contents of sgz302251^T and sgz5001026^T were 63.4% and 68.8%, respectively. Strain sgz302251^T grew at 20-37 °C (optimum 30 °C), pH 5.0-9.0 (optimum 6.5-7.5) and tolerated 0-1.0% NaCl (optimum 0.5%, w/v), while strain sgz5001026^T grew at 4-45 °C (optimum 37 °C), pH 5.0-9.0 (optimum 6.0) and 0-0.5% NaCl (optimum 0%). The quinone in both strains was MK-7 and major polar lipids were diphosphatidylglycerol (DPG), phosphatidylethanolamine (PE) and phosphatidylglycerol (PG). The main fatty acids (> 5%) of strain sgz302251^T were anteiso-C_15:0, anteiso-C_17:0, and C_16:0, whereas strain sgz5001026^T included anteiso-C_15:0, iso-C_15:0, iso-C_16:0 and iso-C_14:0. Based on the above evidence, the proposed names of the two novel species are Paenibacillus praedii sp. nov. (type strain sgz302251^T = MCCC 1K09633^T = KCTC 43808^T), Ectobacillus soli sp. nov. (type strain sgz5001026^T = MCCC 1K09373^T = KCTC 25903^T), respectively.

A Gram-stain-negative, non-motile and yellowish-orange colored bacterium, designated as Alg-005^T, was isolated from decomposing pelagic Sargassum biomass stranded off the coast of Barbados. The 16S rRNA gene analysis revealed that the strain Alg-005^T closely relates to Chryseobacterium daecheongense DSM 15,235^T (99.1%) and C. defluvii DSM 14,219^T (98.7%). Subsequently, genome-based analysis was performed to assess the evolutionary relatedness of strain Alg-005^T via determination of the overall genomic relatedness indices (OGRI) values, dDDH (digital DNA-DNA hybridization), ANI (average nucleotide identity), orthoANI (orthologous average nucleotide identity) and AAI (average amino acid identity). The dDDH, ANI, orthoANI and AAI values between the genome sequences of the strain Alg-005^T and its closest relative C. daecheongense DSM 15,235^T were recorded as 33.3%, 87.1%, 87.4% and 91.5%, respectively. These OGRI values were well below the recommended cut-off values (dDDH < 70%, ANI < 95-96%, orthoANI < 95-96% and AAI < 95%) for delineation of a novel bacterial species. The unique cellular fatty acids of the strain Alg-005^T compared to C. daecheongense DSM 15,235^T were identified as C14:0, iso-C14:0 3-OH, iso-C16:0, C16:1 ω7c/C16:1 ω6c, iso-C17:1 ω5c, iso-C17:1 ω7c, iso-C17:1 ω12c, C18:0 and C18:1 ω7c. The distinct phenotypic characteristics of the strain Alg-005^T compared to C. daecheongense DSM 15,235^T include, the utilization of D-galactose, L-histidine, α-ketoglutaric acid, L-maleic acid, D-maltose, propionic acid, quinic acid and D-salicin. Therefore, the strain Alg-005^T represents a novel species of genus Chryseobacterium, for which the name Chryseobacterium barbadense sp. nov. is proposed. The type strain is Alg-005^T (= DSM 117339^T = LMG 33495^T).