International Microbiology最新文献

Selenium, an essential micronutrient that cannot be endogenously synthesized by mammals, requires exogenous dietary supplementation. Lactic acid bacteria can biotransform sodium selenite (Na₂SeO₃) into bioavailable selenium nanoparticles (SeNPs), creating multifunctional selenium-enriched forages. This study systematically assessed the synergy of SeNPs and Pediococcus acidilactici in alfalfa silage through four treatments: control (CK), P. acidilactici alone (LP), Na₂SeO₃ alone (Se), and combined treatment (LPSe). After 30 days of ensiling, fermentation quality, microbial community, and aerobic stability were determined. The results revealed that LPSe silage exhibited decreased pH, butyric acid, and binding protein contents compared with CK, while its organic selenium content (1.64 mg/kg DM) was Significantly higher than that of LP Silage. 16S rRNA sequencing showed increased abundance of Pediococcus and Lactobacillus in LPSe Silage with Simplified bacterial community structure. After 7 days of aerobic exposure, CK Silage showed rapid pH and ammonia Nitrogen increase, whereas LPSe Silage had 28.24% longer aerobic stability than CK and 11.50% longer than LP. These results demonstrate LPSe as the optimal treatment for alfalfa silage.

Oleaginous fungi, as a vital part of the microbiota in naturally diverse ecosystems, represent a reservoir for biomass-based lipid production. The challenge is the selection of promising strains with cost-effective operation for multiple applications. In the current study, 12 fungal strains were isolated and screened for their oleaginicity. All strains were fermented and accumulated over 20% lipids in their cell dry weight (CDW). After the preliminary screening, one strain was genetically identified as Gongronella butleri HMA-10 due to its maximum biomass (15.8 ± 0.8 g/L) and lipid (40.6 ± 1.7%) yields. Moreover, the HMA-10 was subjected to optimization of various parameters with the help of response surface methodology (RSM) for maximum lipid accumulation. The selected strain was fermented on fructose associated with a combination of sodium nitrite and yeast extract, exhibiting optimum nutritional conditions with a C/N ratio of (40:1). Cultivation conditions (4 days, 27.5 ℃, and pH of 7.0) resulted in the highest CDW and lipid content. Scaling up of HMA-10 in bioreactor fermentation under optimized conditions significantly induced biomass and lipid content (19.5 g/L and 53%), compared with shake flask fermentation (15.8 ± 0.8 g/L and 40.6 ± 1.7%), respectively. Fatty acid (FA) profile was confirmed by gas chromatography (GC) analysis, and the results revealed that oleic acid (OA) was the predominant (46.91%), while palmitic acid (PA), linoleic acid (LA), and γ-linolenic acid (GLA) were found in significant quantities (21.13, 9.67, and 8.06%), respectively. This study employed for the first time G. butleri HMA-10 as a promising candidate for high lipid accumulation with a potential second-generation biodiesel production in large-scale industrialization.

In this study, the biocontrol and plant growth-promoting properties of Pseudomonas chlororaphis VUPF5 were comprehensively evaluated using a series of in vitro biochemical assays. The strain showed strong enzymatic activities, such as the production of cellulase and protease, which contribute to nutrient recycling and degradation of pathogenic fungal structures. In addition, the ability to solubilize phosphate, produce siderophores, HCN, and indole-3-acetic acid (IAA) underscores its versatile potential to promote plant health and control pathogens through both direct and indirect mechanisms. To improve the viability and efficiency of the VUPF5 strain under environmental stress, it was encapsulated with a composite matrix of sodium alginate and soy protein isolate (SPI). Structural characterization by XRD, FTIR, and SEM confirmed the formation of a stable, biocompatible microcapsule with high encapsulation efficiency (approx. 84%) and controlled release over 55 days. These capsules protected the bacteria from environmental fluctuations while allowing their gradual release, ensuring sustained bioactivity in the soil. Greenhouse trials with pistachio seedlings infected with Phytophthora drechsleri showed that plants treated with microcapsules had an 87% disease control rate, outperforming both the free bacterial suspension and control groups. Interestingly, even empty capsules showed moderate protection, likely due to the bioactive nature of SPI, suggesting an additive effect in strengthening plant defenses. Overall, VUPF5 is a promising dual-function bioinoculant that improves plant growth and disease control. Encapsulation enhances its survival, release, and contribution to plant resistance, thus supporting sustainable agriculture.

The long-term sustainability of food production and the usage of agricultural land are seriously threatened by soil salinization. To combat the salinization, the salt-tolerant cyanobacteria can be a potent candidate. However, it is not yet clear how these microbes work to remediate saline soil. Salinity is a global problem, mainly caused by higher evaporation rate, low rainfall, seawater intrusion into freshwater, overuse of chemical fertilizers, etc. This study examined the effect of various salt concentrations on Desertifilum salkalinema SSAU 7 (SSAU 7), which is isolated from the river Ganges, Prayagraj, India. This study examined the tolerance of microbes by analysing the chlorophyll-a, carotenoid, carbohydrate, and photosynthetic activity. It also includes the activity of trehalose and antioxidants, for the mechanism involved in the tolerance and providing new insights that will help the development of cyanobacteria bio-stimulants capable of ameliorating the adverse effects of salinity. The findings revealed that the strain SSAU 7 has the ability to survive up to 20 gL^-1 salt concentrations efficiently. The study showed that the halotolerant cyanobacterium can not only survive at high salt concentration but also it can help in Cicer arietinum (chickpea) plant growth by secreting Indole acetic acid. With increased germination percentage of seed, stem, and root length, SSAU 7 clearly had a good impact on plant growth. These results highlight how cyanobacteria enormously combat salt stress efficiently and can also promote the production of crops while reducing the negative impact of agrochemicals on the environment.

Heavy metals (HM) exhibit a dual effect on fungal growth and development, displaying both toxicity and stimulatory properties. At low concentrations, HM can enhance fungal biomass, colony growth, sporulation, nucleic acid synthesis, gene expression, and toxin production. Given that membrane lipids and cytosolic biomolecules (storage lipids, carbohydrates, and polyols) serve as crucial indicators of fungal vitality under both optimal and stress conditions, we hypothesized that growth-stimulating HM exposure would alter their composition, revealing stress responses. Specifically, this study investigated the impact of growth-stimulating zinc concentrations (resulting in a 50-60% increase in biomass) on the membrane and storage lipid profiles, as well as the cytosolic osmolyte profiles, of the soil filamentous fungi Clonostachys farinosa, Fusarium equiseti, Trichoderma asperellum, and Trichoderma harzianum. All fungi exhibited a hormetic response to zinc, evidenced by increased biomass and stimulated sporulation. Zinc altered the composition of both membrane lipids and intracellular biomolecules. Specifically, we observed a consistent decrease in membrane sterol content, an increase in the unsaturation of membrane phospholipid fatty acids, and a reduction in storage triacylglycerides across all species. Mannitol dominated the carbohydrate and polyol profiles, and its proportion increased in the presence of zinc ions, while trehalose levels remained unchanged or decreased. These collective findings suggest a predominantly hormetic, rather than a stress-induced, response to zinc exposure.

Antibiotic resistance poses a major threat to global health. This study focuses on Streptomyces, a genus of Actinobacteria known for antibiotic production. We aimed to investigate the antimicrobial activity and metabolic profile of Streptomyces sp. strains isolated from the unexplored regions of Khouribga province, Morocco, to discover new potential treatments. Forty isolates of Actinobacteria were subjected to a preliminary antimicrobial screening, using double-layer and cross-dragging methods against a variety of microorganisms. The most active isolates were characterized by various techniques, followed by fermentation and extraction with organic solvents. The antimicrobial activity of the extracts obtained was then assessed by disk diffusion against multidrug-resistant (MDR) bacteria and phytopathogenic fungi. The isolate E4-10 showed promising antimicrobial activity against MDR strains such as E. coli 23I2341, Enterococcus 23I2357, S. aureus 23K1625, and S. saprophyticus 23I2352, as well as phytopathogenic fungi like Aspergillus niger, Penicillium sp., and C. albicans ATCC 60193. GC-MS analysis revealed 18 bioactive compounds, including 2 major components: S-Methyl methanethiosulfonate (15.41%), and 5-oxopyrrolidine-3-carboxylic acid (21.44%). Furthermore, a computational study was investigated (Density Functional Theory (DFT), ADMET, and molecular docking) to analyze the 2 compounds, the results show that the chosen compounds possess promising structural and reactive properties, effectively interacting with proteins in S. aureus, E. coli, and Fusarium sp. Their binding to specific proteins affects membrane fluidity and permeability, while their compliance with pharmacokinetic criteria underscores their therapeutic potential as candidates for further research in treating bacterial and fungal infection.

To combat the issue of pathogenic infections, the current work successfully synthesized a nanocomposite, which is based on the aqueous extract of Alkanna tinctoria (ATE) and silver-zinc oxide nanoparticles (ATE@Ag-ZnO NPs), using a green technique. Analytical methods were used to characterize the synthesized nanocomposite to verify its size, shape, distribution, surface charge, and crystallinity. The resulting nanocomposite created permanent colloidal nano-solutions, demonstrated excellent dispersion, and appeared at the nanoscale. The antimicrobial, antifungal, and antibiofilm characteristics of the ATE@Ag-ZnO nanocomposite were assessed. For every studied microbial strain, the ATE@Ag-ZnO nanocomposite's minimum inhibitory concentration (MIC) was determined. The encouraging findings showed that the MIC range of ATE@Ag-ZnO against all strains was 250-31.25 µg/mL. It demonstrated promise against S. epidermidis and A. calcoaceticus, with a MIC of 31.25 µg/mL. Furthermore, with inhibition zones of 22.0, 20.0, and 15.0 mm, respectively, the ATE@Ag-ZnO nanocomposite demonstrated antibacterial efficacy against gram-positive bacteria A. calcoaceticus, S. epidermidis, and C. tropicalis at 250 µg/mL. The highest percentage of inhibition (91.44%) was seen in S. aureus treated with 250 µg/mL ATE@Ag-ZnO nanocomposite, followed by A. calcoaceticus (68.83%) and C. albicans (64.81%). In conclusion, we successfully created the green synthesized ATE@Ag-ZnO nanocomposite, which demonstrated promising antibacterial, antifungal, and antibiofilm agents against some pathogenic microbes.

Aerobic composting of livestock manure concentrates heavy metals like cadmium (Cd), elevating environmental risks after land application. This study screened composite microbial strains for simultaneous promotion of compost maturation and Cd passivation, exploring their mechanisms on the composting process, microbial community succession, and Cd speciation transformation. Three Cd-resistant strains-Enterobacter hormaechei (LB3), Enterobacter cloacae (LB4), and Bacillus velezensis (J-1-2)-were isolated from chicken manure, formulated into two composite inoculants (T1: LB3 + LB4; T2: LB3 + LB4 + J-1-2), and compared with an uninoculated control (CK) during composting. Maturity parameters, Cd species distribution, and microbial community dynamics were monitored. Results showed composite inoculants significantly improved composting: T1 extended the thermophilic phase and enhanced organic matter degradation; T2 achieved optimal nitrogen retention, with the highest NO₃^--N (1504 mg/kg, representing a 13.51% increase compared to CK) and lowest NH₄⁺-N (153 mg/kg, a 23.12% reduction compared to CK). Microbial community analysis revealed Ace/Chao1 indices in T1/T2 were 1.5-1.8 times higher than CK in the heating phase, while the Shannon index at maturity was 10.13% and 22.40% higher, respectively. T2 had the highest Cd passivation efficiency (66.7%), with exchangeable Cd decreasing from 27 to 9%. Inoculants promoted composting and Cd immobilization via microbial community modulation and adsorption-complexation mediated by key genera (e.g., Thauera), providing an effective strategy for safe reuse of livestock manure and heavy metal pollution mitigation.

Plant growth-promoting bacteria (PGPB) play a vital role in enhancing crop productivity by improving nutrient availability, phytohormone production, and stress tolerance. While the individual effects of PGPB and organic matter on plant growth are well-documented, their combined influence remains less explored. This research aimed to investigate the effects of certain plant growth-promoting bacteria belonging to different genera on the growth of Corn when organic matter was added to the soil. Plant growth-promoting properties were measured using conventional methods, and the highest phosphate solubility (42.46 mg/L) and auxin production (3.36 mg/L) were observed in isolate Bacillus 2MDP-10, while the highest release of potassium was measured in isolate Azotobacter 3MDP-4 (6.73 mg/L). A greenhouse experiment was conducted using a factorial, completely randomized design. Results indicated that all measured growth parameters, including fresh and dry weight of roots and shoots, plant height, stem diameter, and chlorophyll index, were significantly higher in inoculated treatments compared to the non-inoculated treatment (negative control). Ensifer sp. 3MDP-1 improved Corn growth more effectively than the positive control. This isolate resulted in a 2.8-fold increase in shoot dry weight, a 2.4-fold increase in root dry weight, a 29% increase in plant height, and a 2.4-fold increase in chlorophyll index relative to the negative control. Our results demonstrated that the addition of organic matter in the form of manure significantly enhanced all measured parameters; however, no significant interaction was observed between manure addition and bacterial inoculation, except for root dry weight and nitrogen percentage. It is likely that bacterial colonization in the rhizosphere and the utilization of carbon released by the roots are key factors responsible for this response.

Streptomyces spp. are widely recognized for their capacity to produce bioactive secondary metabolites, including plant growth regulators such as indole-3-acetic acid (IAA), which have promising applications in sustainable agriculture. Streptomyces californicus represents a relatively unexplored species in terms of auxin biosynthesis. This study aimed to evaluate and optimize IAA production by S. californicus CLV91, assessing its potential as a biostimulant. The isolate CLV91 was identified via whole-genome sequencing and cultivated in ISP2 medium under standard and optimized conditions. IAA quantification was performed using the Salkowski colorimetric method. The impact of culture conditions on auxin synthesis was assessed, and plant growth promotion assays were conducted using Phaseolus vulgaris seeds. Under standard conditions, S. californicus CLV91 synthesized 550 µg mL⁻¹ of IAA, and supplementation with 0.2 g L⁻¹ L-tryptophan increased production by 55.42%, reaching 816 ± 17.26 µg mL⁻¹. Despite the enhanced production, combining all optimized variables led to a reduction in auxin levels, suggesting metabolic stress under cumulative conditions. In plant assays, CLV91-derived auxin significantly increased root elongation, with a maximum effect of 62.7% at 20 µg mL⁻¹. These findings demonstrate the potential of S. californicus CLV91 as a microbial source of auxins for use in biostimulant formulations, supporting its further investigation for field-scale applications in sustainable crop management.