Current Microbiology最新文献

The microbial communities inhabiting the root zone of plants play a crucial role in their development,. However, the interaction between root-associated microbial populations and soil physicochemical properties, including changes in fungal biodiversity, remains an area of ongoing investigation. Despite extensive research, the effects of tobacco mosaic virus (TMV) infection on Nicotiana benthamiana are still inadequately understood, particularly with regard to its long-term impacts and physiological responses. We used amplicon sequencing to examine the succession of fungal communities in the root-associated soils of plants from both diseased (YTD) and healthy (YTW) soil groups after TMV inoculation and to determine their potential impact on plant health. In the YTW soil group, we determined the relationship between fungal communities and TMV resistance and observed a more intricate fungal network structure compared with that found in YTD. Over time, fungal communities became predominant and included beneficial fungi, such as Penicillium, Mortierella, and Cladosporium, and the common pathogenic fungus Fusarium. Our findings indicate that TMV resistance in healthy plants may be mediated not only by beneficial fungi but also by specific fungal taxa conventionally classified as pathogens, potentially through activation of systemic acquired resistance pathways. Moreover, TMV inoculation of Nicotiana benthamiana altered the physicochemical properties of the root-associated soil, with significant variations in available phosphorus, nitrate nitrogen, total nitrogen, and soil organic carbon under different soil conditions. These results enhance our understanding of fungal microbial resistance to TMV, suggesting that more complex microbial communities or soil-associated rhizosphere microbes enriched in beneficial fungi are more conducive to enhancing plant resistance to TMV, which could enhance tobacco yield and serve as a reference for biological control strategies.

Leptospirosis, also known as "rat-urine disease", is a neglected zoonotic and waterborne disease that is caused by Leptospira spp. This disease is transmitted by direct and indirect exposure to the urine and stool of infected animals. The current estimate has highlighted that leptospirosis has caused at least one million cases and 60,000 deaths, with high endemicity in tropical regions. With climate change, urbanisation, and increasing human-animal interaction, the threat of leptospirosis and other zoonotic diseases will continue to emerge. Investing in multidisciplinary research, technology, and global collaboration is critical to anticipate, detect, and respond effectively to these evolving threats.

Research on prokaryotes living in geothermal ecosystems have broadened our understanding of their compositions and response to extreme environmental stresses, especially for plankton bacterial communities in hot spring water. However, the comprehensive exploration of microbial diversity, assemblages, and interactions in geothermal spring mats in Africa, particularly in Rwanda, remain underexplored. This study explored the bacterial and eukaryotic communities' biodiversity, assemblages, and interactions within microbial mats from the Bugarama hot pool (BHP; 40-47 °C) and Gisenyi hot springs (GHS; 58-71.4 °C) in Rwanda, using high-throughput sequencing of the 16S rRNA gene and 18S rRNA gene, complemented by null and neutral community models and physicochemical analytical methods. Interestingly, the bacterial Shannon, Evenness, and Simpson indices were significantly different (P < 0.05) among geothermal spring mats. In BHP and GHS, the abundances of Chloroflexota, Proteobacteria, Firmicutes, and Acidobacteriota were significantly higher in BHP (P < 0.05) than in GHS, whereas Cyanobacteria, Bacteroidota, Planctomycetota, Verrucomicrobiota, and Spirochaetota were significantly more abundant in GHS (P < 0.01). Conversely, Chloroplastida, Mucoromycota, Arthropoda, and Cryptomycota were significantly more prevalent in BHP (P < 0.05), while the SAR supergroup, Ascomycota, Nematoda, and Amoebozoa dominated in GHS (P < 0.05). Through null and neutral modeling, stochastic processes exerted greater influence on bacterial and eukaryotic community assembly in fine-scale variations within geothermal spring mats. Despite this stochastic predominance, abiotic environmental factors (deterministic processes) such as temperature, pH, salinity (EC and TDS), and nitrate cannot be entirely ruled out. Moreover, Co-occurrence network analysis (|r|> 0.7, P < 0.05) revealed more complex and stable microbial interactions at higher temperatures (GHS). These findings highlight the rich underexplored microbial diversity and interactions in Rwandan geothermal spring mats through metagenomic analysis, shedding light on ecological processes and dynamics in extreme environments. Despite being ignored in metagenomic studies, eukaryotic communities highlight novel temperature-tolerant taxa: Echinamoeba and Tubulinea in phylum Amoebozoa, Monhysterida in phylum Nematoda, and Novel_Clade_Gran-5 in phylum Cercozoa, which are both pathogens and fierce predators thriving in geothermal habitats.

Classical swine fever virus (CSFV) remains a major threat to the swine industry, causing severe economic losses in endemic regions. However, the limited use of conserved non-structural genes in molecular surveillance contains the understanding of viral evolution. This study aimed to evaluate the NS5B gene as a phylogenetic marker to elucidate the genetic diversity of circulating CSFV strains in India. A total of 870 clinical and tissue samples collected during a nationwide surveillance program (December 2023-2024) were screened using NS5B-specific RT-PCR, of which 43 (4.95%) samples tested positive for CSFV. Phylogenetic analysis involving 43 field-derived NS5B sequences and 66 reference sequences revealed a distinct lineage, PV820729, within genotype 1.1. Multi-locus comparison of NS5B, partial E2 (PX233330), and 5' UTR (PX237204) regions confirmed its genetic distinctness from known sub-genotypes, supported by pairwise nucleotide identities of 97.3% (recent Indian strains), 84-85% (older ones), 94.8-95.8% (E2), and 95.7-96.2% (5' UTR). Bayesian molecular clock analysis (GTR + G + I/UCLD/GMRF) estimated the mean tMRCA at 1837.9 (95% HPD: 1710.5-1926.9), aligning with previous E2- and whole-genome-based studies. SNP profiling across the NS5B region identified 133 substitutions, primarily C→T and A→G transitions, reflecting ongoing evolutionary activity within this conserved locus. Collectively, the results support the identification of a candidate novel sub-genotype, provisionally designated 1.1d, and emphasize the value of NS5B-based phylogenetic surveillance for monitoring CSFV evolution and informing control strategies in India.

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.