Journal of Basic Microbiology最新文献

Tuber indicum, an ectomycorrhizal fungus endemic to southwestern China, typically forms brûlés, which underlying microbial and edaphic dynamics remain poorly understood. In this study, we investigated bacterial community composition associated with T. indicum ascocarps and soils in- and outside the brûlé at two natural sites (LB and BZL). Soil properties were analyzed to evaluate the correlation between the bacterial community and the soil properties. LB soils show higher pH, calcium, organic matter, total nitrogen, and available phosphorus, whereas BZL soils were enriched in iron and manganese. These factors significantly shaped the microbial communities, as shown by canonical correspondence analysis. Proteobacteria dominated all samples and positively correlated with organic matter, manganese, and pH, indicating potential roles in brûlé formation. Verrucomicrobia showed positive correlations with potassium, calcium, and magnesium. Site-specific enrichment patterns suggested that soil mineral composition exerts selective pressure on microbial assembly. Notably, Bradyrhizobium elkanii and other beneficial taxa such as Bacillus, Ensifer, and Pseudomonas were differentially distributed in ascocarps and adjacent soils, implying their potential involvement in truffle symbiosis and fruiting body development. This study elucidates the interactions between soil physicochemical properties and microbial communities, offering novel ecological insights into the mechanisms underlying T. indicum fruiting body formation.

Non-Basmati aromatic rice varieties of Indian landrace are preferred for their distinctive aroma and superior grain quality, yet they generally exhibit lower yield potential. Rhizosphere microbial activities play a crucial role in plant performance under organic nutrient management. A 3-year field experiment was conducted in Indo-Gangetic alluvial soil to evaluate whether microbial ecological diversity or functional attributes exert a stronger impact on the yield and aroma of six indigenous non-basmati aromatic rice varieties, along with one non-aromatic check. A total of 140 bacterial cultures, 20 from the rhizosphere of each variety, were characterized for carbon source utilization, stress resistance, and antibiotic resistance, and grouped by hierarchical clustering to estimate diversity. The correlation between the diversity indices and grain yield and aroma score was weak or negative. In contrast, microbial population size, nitrogen fixation, and nutrient-solubilizing capacity showed strong and positive correlation with grain yield and aroma intensity. Principal component analysis clearly distinguished functional traits from ecological diversity indices. Among the tested varieties, Kalojeera rhizosphere had the highest microbial functional activity (57%, 105%, 26%, and 33% higher N fixation and P, K, and Zn solubilization, respectively, than Dudheswar) and grain yield, while Dudheswar had comparatively lower functional capacities. The results clearly demonstrate that microbial functional capacity, rather than species diversity, is the primary determining factor for crop productivity and grain quality under organic farming. Strategies for the selection of aromatic rice varieties harboring rhizosphere microbial functional activities and promoting efficient nutrient cycling could help sustainable aromatic rice production.

Bacillus thuringiensis is the most widely used microbial bioinsecticide; however, only a few strains possess additional traits such as plant growth promotion and biocontrol potential. This study characterized 25 B. thuringiensis isolates obtained from soil and infected insect cadavers to identify multifunctional strains with insecticidal and plant growth-promoting (PGP) properties. Microscopic examination revealed diverse parasporal crystal morphologies, while 16S rRNA sequencing confirmed their identity with 99%–100% similarity to reference strains. Enzymatic profiling showed protease activity in 24 strains and lipase activity in 21 strains, whereas all isolates produced lecithinase and chitinase. All strains produced indole-3-acetic acid (11.22–31.87 µg mL⁻¹) and ammonia (26.74–77.68 µg mL⁻¹), while phosphate solubilization and siderophore production were observed in 21 and 11 strains, respectively. Bioassays against Spodoptera frugiperda identified five highly virulent strains causing more than 90% larval mortality. Among these, NBAIR Bt25 showed the highest efficacy, causing 92% mortality within 96 h with an LC₅₀ of 39.75 µg mL⁻¹. PCR analysis revealed that NBAIR Bt25 carries multiple pesticidal genes (cry1A, cry1D, cry1E, cry1I, cry2A, and vip3A). Paper towel and glasshouse assays demonstrated that strain NBAIR Bt25 significantly enhanced shoot growth and secondary root development. Overall, NBAIR Bt25 emerged as a promising multifunctional strain with strong insecticidal activity, plant growth-promoting ability, and biocontrol potential, making it a suitable candidate for sustainable pest management and climate-smart agriculture.

Ginger (Zingiber officinale Roscoe) is an economically and medicinally important spice crop, but its cultivation is severely affected by soft rot disease. In the present study, Fusarium solani (F. solani) associated with ginger soft rot was isolated, identified, and used as the target pathogen for antifungal evaluation. Diseased ginger rhizomes were collected from Gangapur village, Bahraich, Uttar Pradesh, India. The pathogen was isolated on potato dextrose agar (PDA), characterized morphologically and microscopically, and confirmed as F. solani through ITS sequencing and phylogenetic analysis. The antifungal potential of Trachyspermum ammi (T. ammi) essential oil was then evaluated against F. solani under in vitro conditions and supported by in silico analysis. The essential oil showed strong activity with a minimum inhibitory concentration (MIC) of 0.20 µL/mL and a minimum cidal concentration (MCC) of 0.60 µL/mL. The minimum killing time (MKT) of pure oil was 40 s, while the oil at its MCC required 24 h. Antifungal toxicity persisted at high inoculum density and remained stable after heating to 80°C and autoclaving. Molecular docking of F. solani cutinase indicated strongest binding for thymol, followed by p-cymene and γ-terpinene. These findings highlight the potential of T. ammi essential oil as an eco-friendly antifungal agent for managing F. solani-associated ginger soft rot.

Endophytes of Panax ginseng are symbiotic microbes colonizing internal tissues asymptomatically, forming a core component of the ginseng microecosystem through co-evolution. This review summarizes recent progress on ginseng endophytes, covering community diversity, ecological functions, and application prospects. Culturable endophytic fungi span over 40 genera, dominated by Ascomycota, while endophytic bacteria mainly belong to Firmicutes, Proteobacteria and Actinobacteria. Research methodologies have advanced from culture-based isolation to high-throughput amplicon sequencing and ASV-based profiling. Functionally, approximately 78% of culturable isolates produce indole-3-acetic acid, and strains with phosphate-solubilizing, nitrogen-fixing and siderophore-secreting activities are widely identified. For biocontrol, Paenibacillus and Burkholderia strains show broad-spectrum antagonism against 5–8 common ginseng pathogens, with Bacillus strains achieving 61.45%–80% mycelial inhibition. Over 10 endophytic species can synthesize ginsenosides or convert common ginsenosides into rare monomers like Rg2, Rb3, and compound K, with some elicitor strains increasing total ginsenoside contents in adventitious roots up to fourfold. Ginseng endophytes show great potential as microbial fertilizers and biocontrol agents for sustainable ginseng cultivation, biocatalysts for rare ginsenosides production, and sources of novel bioactive lead compounds for drug discovery. Current challenges, including the abundance of unculturable microbiota, unclear host-microbe interactions, and inconsistent field efficacy are discussed, along with future research directions.

Country bean (Lablab purpureus L.) is an economically significant legume vegetable in Bangladesh, but its production is threatened by a new disease, web blight caused by Rhizoctonia solani. This study presented a comprehensive analysis of the pathogen's epidemiology, genetic diversity, physiology, host resistance, and chemical control strategies. Field surveys in six upazilas of Gazipur district revealed high disease prevalence (50%–80%), with incidence and severity ranging from 59%–92% to 38%–52%, respectively, peaking in October-November. Thirty isolates of R. solani were collected, and molecular characterization of four representative isolates identified AG-1 IA, AG-1 ID, and AG-5, indicating preliminary genetic variability among representative isolates. The detection of AG-1 ID and AG-5 is the first report on country bean. Optimal fungal growth occurred at 25°C–30°C and pH 7.0–9.0, with peptone, L-arginine, sodium nitrate, sorbitol, mannitol, and galactose as preferred nutrient sources. Maximum virulence, as measured by disease incidence, severity, and lesion development, was observed at 30°C. The pathogen exhibited a broad host range, infecting crops across Fabaceae, Poaceae, and Solanaceae. Screening of 94 country bean genotypes revealed a general lack of resistance, with most exhibiting moderate to high susceptibility. Among tested fungicides, Autostin 50 WG (carbendazim) and Nativo 75 WG (tebuconazole + trifloxystrobin) showed complete inhibition of mycelial growth in vitro. In planta application significantly reduced disease severity, achieving 83%–85% protection in preventive and 77%–81% in curative treatments, with efficacy lasting up to 15 days. These findings offer a novel insight into the web blight pathosystem in country bean, supporting the development of effective disease management strategies.

Rhizosphere microbes are vital for plant growth. Dark septate endophytes (DSE) can enhance host plant adaptability and regulate microbial communities, showing promise for yam soil remediation. This study examined how single and mixed inoculations of eight DSE strains affect yam rhizosphere carbon metabolism. Results showed that rhizosphere microbes preferred carbohydrate and amino acid carbon sources. Single inoculations exhibited relatively high overall metabolic activity, whereas mixed inoculations demonstrated distinct advantages in the utilization of specific carbon sources, such as carbohydrates. Key discriminators were phenolic acid, carboxylic acid, and carbohydrate utilization. Different strains enhanced specific pathways: Pe and Fu improved amine metabolism; Ac and Zo excelled in carbohydrate use; Pl boosted polymer metabolism. Changes in carbon metabolism correlated with soil properties: polymer and amine use with pH and SOC; carbohydrate use with AP; phenolic and carboxylic acid use with AN. Soil properties were also altered strain-specifically. The Pe strain emerged as the prime candidate for mitigating yam continuous cropping obstacles by synergistically improving both carbon metabolism and soil quality. These findings aid in developing biofertilizers and rhizosphere remediation strategies.

Ustiloxins are toxic cyclic peptides produced by the rice false smut fungus Ustilaginoidea virens. False smut disease turns rice grains into yellow-orange spores later turned into greenish-black smut balls, significantly reducing yield and grain quality. Due to their hydrophilic nature ustiloxins leach from spore balls and contaminate paddy soil, water, and rice products. They block eukaryotic cell division by binding tubulin and inhibit microtubule polymerization. This review provides information on advances in ustiloxin biology and control. It summarizes ribosomally synthesized and post-translationally modified peptides (RiPPs) biosynthesis and recent insights into pathway genes, regulatory networks including target of rapamycin (TOR) signaling, and comparative fungal genomics. Environmental occurrence is reviewed with emphasis on persistence in soil, water and translocation into rice grains. Ecotoxicological evidence is consolidated, spanning phytotoxicity, effects on beneficial microbes, aquatic organisms, and mammalian toxicity supported by in vivo and mechanistic studies. Progress in detection is outlined with improved LC–MS/MS, immunoassays, and emerging biosensors for field diagnostics. Management strategies are evaluated, including resistant cultivars, disease forecasting, fungicidal and biological controls, and post-harvest detoxification via enzymatic and physical approaches. A dedicated risk assessment discusses human dietary exposure, regulatory status, and the need for maximum limits. The review concludes by highlighting research priorities such as multi-omics, spread modeling, and biotechnological interventions, to close key knowledge gaps and enable effective monitoring and mitigation toward an ustiloxin-free rice agroecosystem.