International Microbiology最新文献

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.

Produced water (PW), a major by-product of the petrochemical industry, contains a complex mixture of contaminants that limit its reuse and pose environmental risks if discharged untreated. Numerous treatment technologies have been developed to remediate this water, with bioremediation standing out as one of the most promising novel approaches. One such bioremediation method is through the application of cyanobacteria, which are able to remove pollutants such as heavy metals from produced water, although the mechanism by which the pollutants are removed is still unknown. In this study, a well-characterized cyanobacterium, Synechococcus elongatus, was used as a model organism to establish a proof of concept for identifying genes responsive to PW exposure and heavy metal stress. RNA sequencing was performed to analyze transcriptomic changes in S. elongatus grown in BG-11 (control) and exposed to 3 mg/mL of iron (heavy metal (HM)) or 25% v/v PW in BG-11. Differential expression analysis revealed that 11 and 67 genes were ≥ fivefold upregulated, and 337 and 27 genes were ≥ fivefold downregulated under HM and PW exposure, respectively, compared to the control. Among the over-expressed genes, the plasma membrane transporter, nitrate ABC transporter permease, was identified, suggesting its important role in the bioremediation process of heavy metals from wastewater. These findings provide foundational insights into stress-responsive gene networks in cyanobacteria and inform future bioengineering strategies for enhancing bioremediation capabilities in S. elongatus and related strains.

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.

The global aquaculture industry, particularly the farming of Pacific white shrimp (Litopenaeus vannamei), faces significant economic challenges due to infectious diseases, with Vibrio spp. being a primary causative agent of vibriosis. The widespread and often indiscriminate use of antibiotics in aquaculture has led to an alarming increase in antimicrobial resistance (AMR) among Vibrio strains, rendering conventional treatments increasingly ineffective. This study aimed to characterize the phenotypic antibiotic resistance profiles and the presence of associated resistance genes in Vibrio spp. isolates obtained from diseased L. vannamei. Our findings reveal a high prevalence of multidrug-resistant (MDR) Vibrio spp., exhibiting resistance to several commonly used antibiotics, including ampicillin, amoxicillin, doxycycline, tetracycline, erythromycin, azithromycin, dalacin (clindamycin), and cefpodoxime. Molecular analysis identified a high frequency of resistance genes such as Carb, SHV, tetA, floR, sulI, sulII, sulIII, and gryA. Notably, despite widespread phenotypic resistance to ampicillin, the Amp, the amp gene was consistently absent, suggesting alternative or intrinsic resistance mechanisms. A unique and highly unusual finding was the detection of a mecA-homologous gene in Vibrio isolate V28, whose genus identity was confirmed by 16S rRNA sequencing. The pervasive nature of AMR in these Vibrio isolates underscores the urgent need for sustainable alternative strategies, such as bacteriophage therapy. This characterization provides critical foundational data essential for the future development of such targeted interventions.

Garlic (Allium sativum L.) is a high-value horticultural crop whose bulbs provide a unique ecological niche for specialized endophytic microbiota. Despite their potential as microbial reservoirs for plant health and biocontrol, these endophytes remain poorly studied, particularly within clove meristems. This study investigated the cultivable endophytic communities from clove meristems of ten Mexican garlic varieties. A total of 119 bacterial isolates, belonging to 14 genera, and 38 fungal isolates, grouped into 2 genera, were obtained. The bacteria exhibited key functional traits, including nutrient solubilization, nitrogen fixation, and hydrolytic enzyme production, with most strains significantly promoting the growth of garlic explants. In contrast, the isolated fungi (Fusarium and Penicillium) proved pathogenic. In antagonism assays, Paenibacillus sp. MP10 and Rhodococcus sp. MP3 showed high inhibition (65.38-94.74%) against the tested fungal strains. In garlic germination assays, Pseudomonas sp. 1JPC and Enterobacter sp. 2AMTX, 2APTE, and 4AMTX increased root length 2-fourfold, root number 3-fourfold, and fresh weight approximately onefold. In maize bioassays, Phytobacter sp. 5AMCH94, Pseudomonas sp. 1APCY, and Paenibacillus sp. H1 enhanced seedling area by 20-60%, seedling length by 10-30%, root number by 30-140%, and dry weight by 40-50%. Furthermore, 16S rRNA sequencing revealed that inoculation with Paenibacillus sp. H1 increased endophytic bacterial diversity and the relative abundance of Comamonadaceae and Lactobacillaceae. These findings highlight the value of garlic meristems as reservoirs for microbial bioinoculant development and the recovery of conserved varieties.

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.

Chronic hyperglycemia in diabetic patients promotes Staphylococcus aureus colonization and biofilm formation, contributing to persistent infection and poor wound healing in diabetic foot ulcers (DFUs). Biofilms hinder antibiotic penetration and promote resistance, highlighting the need for targeted anti-biofilm strategies. In this study, domain antibody-displaying M13 phages were developed to selectively target S. aureus biofilms. Among the selected clones, A7-displayed phage showed the strongest binding to S. aureus based on indirect ELISA and exhibited potent, dose-dependent inhibition of biofilm formation without affecting bacterial viability. This non-bactericidal, anti-virulence effect was associated with a significant reduction in staphyloxanthin production, a pigment linked to oxidative stress resistance. Quantitative RT-PCR analysis further revealed that A7 and C1 downregulated the expression of icaA, a key gene involved in biofilm matrix synthesis. Despite its efficacy, checkerboard synergy testing showed that combining A7-displayed phage with ampicillin resulted in an antagonistic interaction (FICI > 4), suggesting that A7 is most effective as a standalone anti-biofilm agent. Target identification using far-western blotting and MS/MS analysis revealed that A7 binds specifically to a cadmium-transporting ATPase, and molecular docking analysis showed A7 interaction with the C-terminal helical domain of CadA, potentially affecting cadmium efflux and oxidative stress homeostasis. This disruption may underlie the observed biofilm inhibition. These findings establish A7-displayed phage as a promising, non-cytotoxic biotherapeutic targeting S. aureus biofilms, offering a novel strategy for DFU management and other chronic infections where conventional antibiotics fall short.