Human Pathogen Research Articles

Cutaneous Prototheca wickerhamii infection identified with the matrix-assisted laser desorption/ionization time-of flight mass spectrometry after protein extraction protocol for filamentous fungi isolates from a facial discharge of a 66-year-old female patient in Korea: a case report

Prototheca wickerhamii is an achlorophyllic algae that rarely acts as an opportunistic pathogen in humans. We report the case of a 66-year-old female patient with a history of diabetes mellitus who presented with a pus-like discharge from face, facial redness, and swelling. The patient was admitted to the emergency room with worsening facial pain. Gram staining from pus-like discharge revealed yeast like features; however, an isolated colony on a blood agar plate was not identified using VITEK 2 (Biomerieux) or matrix-assisted laser desorption/ionization time-of flight mass spectrometry (MALDI-TOF) using VITEK®MS (Biomerieux). Lactophenol cotton blue staining of the colony revealed characteristic sporangia and endospore features. After performing the protein extraction procedure for filamentous fungi (mold) isolates using ethanol and formic acid, MALDI-TOF MS identified the colony as Prototheca wickerhamii, with 99.9% confidence. This case indicates that Prototheca spp. require specialized sample preparation steps, such as the ethanol/formic acid extraction procedure, for identification using MALDI-TOF MS.

The alphavirus determinants of intercellular long extension formation.

The alphavirus chikungunya virus (CHIKV) is a serious human pathogen that can cause large-scale epidemics characterized by fever and joint pain and often resulting in chronic arthritis. Infection by alphaviruses including CHIKV and the closely related Semliki Forest virus (SFV) can induce the formation of filopodia-like intercellular long extensions (ILEs). ILEs emanate from an infected cell, stably attach to a neighboring cell, and mediate cell-to-cell viral transmission that is resistant to neutralizing antibodies. However, our mechanistic understanding of ILE formation is limited, and the potential contribution of ILEs to CHIKV virulence or human CHIKV infection is unknown. Here, we used well-characterized virus mutants and monoclonal antibodies with known epitopes to dissect the virus requirements for ILE formation. Our results showed that both the viral E2 and E1 envelope proteins were required for ILE formation, while viral proteins 6K and transframe, and cytoplasmic nucleocapsid formation were dispensable. A subset of CHIKV monoclonal antibodies reduced ILE formation by masking specific regions particularly on the E2 A domain. Studies of the viral proteins from different CHIKV strains showed that ILE formation is conserved across the four major CHIKV lineages. Sera from convalescent human CHIKV patients inhibited ILE formation in cell culture, providing the first evidence for ILE inhibitory antibody production during human CHIKV infections.IMPORTANCEChikungunya virus (CHIKV) infections can cause severe fever and long-lasting joint pain in humans. CHIKV is disseminated by mosquitoes and is now found world-wide, including in the Americas, Asia, and Africa. In cultured cells, CHIKV can induce the formation of long intercellular extensions that can transmit virus to another cell. However, our understanding of the formation of extensions and their importance in human CHIKV infection is limited. We here identified viral protein requirements for extension formation. We demonstrated that specific monoclonal antibodies against the virus envelope proteins or sera from human CHIKV patients can inhibit extension formation. Our data highlight the importance of evaluation of extension formation in the context of human CHIKV infection.

The healthy human gut can take it all: vancomycin-variable, linezolid-resistant strains and specific bacteriocin-species interplay in Enterococcus spp.

Enterococcus spp. are opportunistic human pathogens colonizing the human gut and a significant reservoir for the continuous adaptation of hospital clones. However, studies on the features of enterococci species co-colonizing healthy individuals are scarce. We investigated the prevalence, antibiotic resistance, and bacteriocin profiles of Enterococcus species in fecal samples from healthy adults in Portugal using culture-based methods, WGS, and bacteriocin inhibition assays. Results were compared with data from a 2001 study in the same region. Enterococcus spp. (n = 315; 24% MDR) were recovered from all volunteers. Enterococcus lactis was the prevalent species (75%), followed by Enterococcus faecalis (65%) and Enterococcus faecium (47%). E. lactis prevalence increased 2.5-fold since 2001. Linezolid resistance genes (optrA/poxtA) were detected in E. faecium and Enterococcus thailandicus isolates, while a vancomycin-variable E. faecium was also identified. Virulence and plasmid profiles were diverse across species, with evidence of exchange of virulence markers and plasmid replicons between E. faecium and E. lactis. Bacteriocin gene repertoires were extensive and species-specific. Higher numbers of bacteriocin genes were associated with stronger inhibition profiles, and 25% of E. faecium and E. lactis isolates were capable of inhibiting relevant VRE clones. This study unveils the co-occurrence and ecological dynamics of Enterococcus species in the healthy human gut, reinforcing its role as a reservoir for key antibiotic resistance genes and potentially pathogenic strains. The shift toward E. lactis prevalence and the detection of linezolid resistance genes in healthy individuals underscore the need for ongoing surveillance of the gut microbiome to guide public health strategies and antibiotic stewardship efforts.IMPORTANCEThis study highlights the role of Enterococcus species in the healthy human gut, revealing important insights into their prevalence and antibiotic resistance. It emphasizes that the human gut serves as a significant reservoir for antibiotic-resistant strains and shows a notable increase and prevalence of Enterococcus lactis, which has been underappreciated due to identification challenges. The research also underscores the bacteriocins' role in microbial competition, where commensal strains inhibit clinical VRE, potentially aiding the restoration of the gut microbiota, after antibiotic treatment. The findings accentuate the need for ongoing surveillance to track changes in gut bacteria, especially with the emergence of resistance genes to last resort antibiotics. Such monitoring is crucial for shaping public health strategies and managing the growing threat of antibiotic-resistant infections. Profiling bacteriocins at the species and strain level can identify ecological adaptation factors and inform strategies to target high-risk clones.

Farm-to-fork changes in poultry microbiomes and resistomes in Maputo City, Mozambique.

While chicken eggs and meat are a critical protein source in low-income settings, antibiotics are routinely fed to chickens with consequences for selection of antimicrobial resistance. Evaluating how poultry gut bacterial communities, including potential human pathogens and high-risk antimicrobial resistance genes, differ from farm to market could help identify where to target interventions to minimize transmission risks to human populations. In this study in Maputo City, Mozambique, we found compositional differences between commercial and local chicken breeds at production and market sites. We also found that while all potentially pathogenic bacteria and many high-risk antimicrobial resistance genes persisted from production and market through processing, some resistance genes were detected on carcass samples only after processing, suggesting human or environmental contamination is occurring within markets. Overall, our findings indicate that open-air markets may represent a critical juncture for human exposures to pathogens and antimicrobial resistance genes from poultry and poultry products.

Antimicrobial activity of iron-depriving pyoverdines against human opportunistic pathogens

The global rise of antibiotic resistance calls for new drugs against bacterial pathogens. A common approach is to search for natural compounds deployed by microbes to inhibit competitors. Here, we show that the iron-chelating pyoverdines, siderophores produced by environmental Pseudomonas spp., have strong antibacterial properties by inducing iron starvation and growth arrest in pathogens. A screen of 320 natural Pseudomonas isolates used against 12 human pathogens uncovered several pyoverdines with particularly high antibacterial properties and distinct chemical characteristics. The most potent pyoverdine effectively reduced growth of the pathogens Acinetobacter baumannii, Klebsiella pneumoniae, and Staphylococcus aureus in a concentration- and iron-dependent manner. Pyoverdine increased survival of infected Galleria mellonella host larvae and showed low toxicity for the host, mammalian cell lines, and erythrocytes. Furthermore, experimental evolution of pathogens combined with whole-genome sequencing revealed limited resistance evolution compared to an antibiotic. Thus, pyoverdines from environmental strains have the potential to become a new class of sustainable antibacterials against specific human pathogens.

Understanding Bacterial Resistance to Heavy Metals and Nanoparticles: Mechanisms, Implications, and Challenges.

Antimicrobial resistance is a global health problem as it contributes to high mortality rates in several infectious diseases. To address this issue, engineered nanoparticles/nano-formulations of antibiotics have emerged as a promising strategy. Nanoparticles are typically defined as materials with dimensions up to 100nm and are made of different materials such as inorganic particles, lipids, polymers, etc. They are widely dispersed in the environment through various consumer products, and their clinical applications are diverse, ranging from contrast agents in imaging to carriers for gene and drug delivery. Nanoparticles can also act as antimicrobial agents either on their own or in combination with traditional antibiotics to produce synergistic effects, earning them the label of "next-generation therapeutics." They have also shown great effectiveness against multidrug-resistant pathogens responsible for nosocomial infections. However, overexposure or prolonged exposure to sublethal doses of nanoparticles can promote the development of resistance in human pathogens. The resistance can arise from various factors such as genetic mutation, horizontal gene transfer, production of reactive oxygen species, changes in the outer membrane of bacteria, efflux-induced resistance, cross-resistance from intrinsic antibiotic resistance determinants, plasmid-mediated resistance, and many more. Continuous exposure to nanoparticles can also transform an antibiotic-susceptible bacterial pathogen into multidrug resistance. Considering all these, the current review focuses on the mode of action of different heavy metals and nanoparticles and possible mechanisms through which bacteria attain resistance towards these heavy metals and nanoparticles.

Emerging Aeromonas spp. infections in Europe: characterization of human clinical isolates from German patients

Bacteria of the genus Aeromonas are widely distributed in water bodies around the world. Some Aeromonas species have been identified as human pathogens causing intestinal and a variety of extraintestinal infections. In Germany, information on diseases caused by Aeromonas is rare, because Aeromonas infections are not notifiable in Germany. To address this information gap and gain better insights, a successful collaboration with human medical diagnostic laboratories within Germany was established and several Aeromonas isolates from diseased patients were sent to the Aeromonas laboratory of the German Federal Institute for Risk Assessment. 52 clinical Aeromonas isolates, of which anonymized patients’ data were available, were selected for further characterization by MALDI-TOF MS, biochemical testing, and whole genome sequencing (WGS). Nearly half of the isolates were from patients older than 60 years, whereas only four isolates were from patients aged up to 10 years. 30 isolates originated from stools of patients with diarrhea/(gastro-)enteritis and 22 strains were from patients with diverse extraintestinal infections, such as wound infection, septicemia, bursitis, abscesses, cholangitis, urinary tract infections, and pneumonia. Taxonomical identification revealed following predominant species: A. veronii biovar sobria (18 isolates), A. caviae (17 isolates), and A. hydrophila (nine isolates). Two A. salmonicida isolates and one isolate each of A. dhakensis, A. bestiarum, and A. encheleia were also identified. Three closely related intestinal isolates could not be assigned to a recognized Aeromonas species. The clustering of strains based on virulence factor profile resulted in a grouping that closely resembles the clustering of the phylogenetic tree suggesting that the profiles are specific for each species. Our study on clinical Aeromonas isolates characterizes for the first time human pathogenic strains isolated in Germany. These bacteria are important microorganisms within the One Health context because of their ubiquitous presence in the environment and as a cause of opportunistic infections in humans and animals. Infections caused by Aeromonas bacteria show a seasonality with increased infection rates in warmer periods. In view of climate change, Aeromonas bacteria are regarded as emerging pathogens and research is required to determine the reservoirs in One Health sources from which human infections may arise.

A gut-derived Streptococcus salivarius produces the novel nisin variant designated nisin G and inhibits Fusobacterium nucleatum in a model of the human distal colon microbiome.

Fusobacterium nucleatum is a human pathogen associated with intestinal conditions including colorectal cancer. Screening for gut-derived strains that exhibit anti-F. nucleatum activity in vitro revealed Streptococcus salivarius DPC6487 as a strain of interest. Whole-genome sequencing of S. salivarius DPC6487 identified a nisin operon with a novel structural variant designated nisin G. The structural nisin G peptide differs from the prototypical nisin A with respect to seven amino acids (Ile4Tyr, Ala15Val, Gly18Ala, Asn20His, Met21Leu, His27Asn, and His31Ile), including differences that have not previously been associated with a natural nisin variant. The nisin G gene cluster consists of nsgGEFABTCPRK with transposases encoded between the nisin G structural gene (nsgA) and nsgF, notably lacking an equivalent to the nisI immunity determinant. S. salivarius DPC6487 exhibited a narrower spectrum of activity in vitro compared to the nisin A-producing Lactococcus lactis NZ9700. Nisin G-producing S. salivarius DPC6487 demonstrated the ability to control F. nucleatum DSM15643 in an ex vivo model colonic environment while exerting minimal impact on the surrounding microbiota. The production of this bacteriocin by a gut-derived S. salivarius, its narrow-spectrum activity, and its anti-F. nucleatum activity in a model colonic environment indicates that this strain merits further attention with a view to harnessing its probiotic potential.IMPORTANCEFusobacterium nucleatum is a human pathogen associated with intestinal conditions, including colorectal cancer, making it a potentially important therapeutic target. Bacteriocin-producing probiotic bacteria demonstrate the potential to target disease-associated taxa in situ in the gut. A gut-derived strain Streptococcus salivarius DPC6487 was found to demonstrate anti-F. nucleatum activity, which was attributable to a gene encoding a novel nisin variant designated nisin G. Nisin G-producing S. salivarius DPC6487 demonstrated the ability to control an infection of F. nucleatum in a simulated model of the human distal colon while exerting minimal impact on the surrounding microbiota. Here, we describe this nisin variant produced by S. salivarius, a species that is frequently a focus for probiotic development. The production of nisin G by a gut-derived S. salivarius, its narrow-spectrum activity against F. nucleatum, and its anti-F. nucleatum activity in a model colonic environment warrants further research to determine its probiotic-related applications.

Small mammals in a biodiversity hotspot harbor viruses of emergence risk

Abstract Metagenomic sequencing has transformed the understanding of viral diversity in wildlife and the potential threats these viruses pose to human health. Despite this progress, such sequencing studies often have lacked systematic and ecologically informed sampling, thereby likely missing many potential human pathogens and the drivers behind their ecology, evolution and emergence. We conducted an extensive search for viruses in the lungs, spleens, and guts of 1,688 mammals from 38 species across 428 sites in Yunnan Province, China—a hotspot for zoonoses emergence. We identified 162 mammalian viruses, including 102 new ones and 24 posing potential risks to humans due to their relationships with known human pathogens associated with serious diseases or their ability to cross major host species barriers. Our findings offer an in-depth view of virus organotropism, cross-host associations, host sharing patterns, and the ecological factors influencing viral evolution, all of which are critical for anticipating and mitigating future zoonotic outbreaks.

Evolution of two metabolic genes involved in nucleotide and amino acid metabolism in Pseudomonas aeruginosa.

Pseudomonas aeruginosa is an opportunistic human pathogen causing various severe infections. Understanding genetic mechanisms of its metabolic versatility aids in developing novel antibacterial drugs and therapeutic strategies to address multidrug-resistant P. aeruginosa infections. The metabolism of nucleotides and amino acids contributes to the cycle of two key biological macromolecules in the genetic central dogma. Guanine deaminase (GuaD) catalyzes the deamination of guanine to produce xanthine to maintain the homeostasis of the nucleotide pool, and transporters specific to BCAAs (termed as BraT) import BCAAs to keep its intracellular availability level. However, little is known about the evolution of GuaD and BraT in P. aeruginosa population. Here, two copies turned out to be widespread in P. aeruginosa population for each of GuaD and BraT. The phylogenic analysis demonstrated that GuaD1 and BraB were inherited from the ancestor of Pseudomonas, while GuaD2 and BraZ were additionally acquired via evolutionary events in the ancestors of P. aeruginosa. The functional divergence of two copies was supported by different distribution patterns of dN/dS ratios, divergent expression levels, differentially co-expressed genes, and their functional enrichment modules with few intersections. Besides, some co-expressed genes with known functions are involved in infecting hosts, forming biofilm and resisting antibiotic treatment. Taken together, functional divergence following copy number increase and differentiation of co-expression networks might confer greater metabolic potential to P. aeruginosa, especially in response to host immune responses and antibiotic treatments in clinical settings.

Combination Therapy for Cryptosporidiosis in Immunocompromised Patients: A Systematic Review

Cryptosporidium sp. is a pathogen that causes gastroenteritis and may increase mortality and morbidity in immunocompromised patients. Cryptosporidium became widely recognized as a human pathogen. Diarrhea is a common problem in AIDS patients and about 30%–60% of patients in developed countries and 90% in developing countries experience diarrhea. This study was conducted using a systematic review design. Two articles with cohort design and two with case report design were selected based on the eligibility criteria. Three of these studies used a combination of nitazoxanide with azithromycin as an intervention, one in cohort design and two in case report design. One cohort study used a nitazoxanide and fluoroquinolone combination as an intervention. 54 samples participated in this study were post kidney transplantation patients and one sample was with acute lymphoblastic leukemia (ALL). Nitazoxanide and fluoroquinolone combination is a better therapy for cryptosporidiosis in immunocompromised patients compared to nitazoxanide and azithromycin combination. The(OR) for stool clearance was significantly lower with nitazoxanide alone compared to that of nitazoxanide and fluoroquinolone (OR: 0.65, 95% CI: 0.34, 0.92, P= 0.01), and the OR for diarrhea stopped was significantly lower with nitazoxanide alone compared to that of nitazoxanide and fluoroquinolone (OR: 0.45, 95% CI: 0.21, 0.81, P= 0.004). The OR for stool clearance was lower with nitazoxanide and azithromycin than monotherapy (OR 0.27, 95% CI: 0.01, 5.77), but P=0.24, which means not statistically significant.

Draft genome sequence of a non-human primate-derived isolate of Candida parapsilosis.

Candida parapsilosis is a common human commensal and opportunistic fungal pathogen that is also found in non-human primates (NHPs). Here, we report the first draft sequence of C. parapsilosis NCYC 4418, a fecal isolate from an adult cynomolgus macaque.

Unveiling the Potency: Synthesis and Assessment of Antimicrobial Potential of Some Bis(indolyl)methane Derivatives

Background: The urgent need for new antimicrobial compounds arises from the growing threat of multidrug-resistant human pathogens responsible for infectious diseases. The indole moiety, a prevalent heterocyclic ring system found in nature, is a key structural element in many pharmaceutical agents due to its wide range of biological activities. Bis(in-dolyl)methanes, in particular, have emerged as promising candidates for antibacterial activ-ity. Aim: This study aimed to evaluate the antibacterial activity of nine bis(indolyl)methane derivatives against a range of pathogenic bacterial strains responsible for various human diseases. Methods: The compounds were synthesized using a solvent-free method, and their antibac-terial activity was evaluated using the disk diffusion assay. The minimum inhibitory con-centration (MIC) of the active compounds identified in the disk diffusion assay was deter-mined by the microtiter broth dilution method in 96-well microtiter plates. Bacterial strains in the mid-log phase of growth were utilized. Bacterial suspensions equivalent to 0.5 McFar-land standards were prepared by suspending the bacterial inoculum in sterile water. A work-ing concentration of 100 μg/mL was achieved by diluting the test compounds in 100% DMSO. Results: The antimicrobial activity of nine synthetic compounds was evaluated against nine medically significant pathogenic strains. These include Pseudomonas aeruginosa, Bacillus cereus, and Shigella flexneri, known for producing toxins that cause acute foodborne ill-nesses, as well as Escherichia coli K12 and Enterococcus faecalis, which can disrupt the intestinal barrier in immunocompromised individuals. The results suggest that these com-pounds have the potential to be effective antimicrobial agents. Conclusion: Our findings demonstrate the promising antimicrobial activity of the synthe-sized compounds, with 1-ethyl-3-((1-ethyl-1H-indol-3-yl)(phenyl)methyl)-1H-indole emerging as the most potent, significantly inhibiting most tested bacterial strains. These results highlight the potential for developing novel compounds for antibacterial treatment.

ISOLATION, BIOCHEMICAL CHARACTERIZATION AND ANTIBIOTIC SENSITIVITY OF LACTOBACILLI IN QUAIL DROPPINGS

Background: Probiotics are microorganisms which are when given in a specific amount, have favorable effects on the host health. Objectives: The current study was conducted on quail’s droppings, which were collected from the various sailing points within district Dera Ismail Khan. The core aim of this field study was to isolate the Lactobacillus species from the droppings to identify and characterize them. Methods: Three species (lactobacillus brevis, lactobacillus salivarius and lactobacillus fermentum) were isolated on the basis of biochemical tests. Results: Lactobacillus salivarius was found more tolerant at pH 2 as compared to the other two species of lactobacillus, likewise at pH 3 lactobacillus brevis showed maximum growth, which was significantly higher than other species of lactobacillus. Similarly, all the three species of lactobacillus showed higher growth on 0.5 % ox gall as compared to the 1 % ox gall. Likewise antibiotic sensitivity testing of lactobacillus species shown sensitivity to erythromycin except L. fermentum and all three were resistance to tetracycline, kanamycin, ciprofloxacin and gentamycin. Conclusion: It is concluded that lactobacillus species have huge benefits like their tolerance to low pH and their growth on bile salts. Their use in diets will not only balance the gut microflora but also will inhibit the growth of pathogens in humans, animals and poultry species, as described by different studies which are conducted on above mentioned species.

Structural characterization of the full-length Hantaan virus polymerase.

Hantaviridae are a family of segmented negative-sense RNA viruses that contains important human and animal pathogens. Hantaviridae contain a viral RNA-dependent RNA polymerase that replicates and transcribes the viral genome. Here we establish the expression and purification polymerase from the Old World Hantaan virus and characterise the structure using Cryo-EM. We determine a series of structures at resolutions between 2.7 and 3.3 Å of RNA free polymerase comprising the core, core and endonuclease, and a full-length polymerase. The full-length polymerase structure depicts the location of the cap binding and C-terminal domains which are arranged in a conformation that is incompatible with transcription and in a novel conformation not observed in previous conformations of cap-snatching viral polymerases. We further describe structures with 5' vRNA promoter in the presence and absence of a nucleotide triphosphate. The nucleotide bound structure mimics a replication pre-initiation complex and the nucleotide stabilises the motif E in a conformation distinct from those previously observed. We observe motif E in four distinct conformations including β-sheet, two helical arrangements, and nucleotide primed arrangement. The insights gained here guide future mechanistic studies of both the transcription and replication activities of the hantavirus polymerase and for the development of therapeutic targets.

The gE/gI complex is necessary for kinesin-1 recruitment during alphaherpesvirus egress from neurons.

Alphaherpesviruses include important human and veterinary pathogens that share a unique propensity to establish life-long latent infections in the peripheral nervous system. Upon reactivation, these viruses navigate back to body surfaces and transmit to new hosts. In this study, we demonstrate that the virus gE/gI-US9p membrane complex routes virus particles down this complex neuronal egress pathway by coordinating their association with multiple kinesin microtubule motors.

H3K4 Methylation and Demethylation in Fungal Pathogens: The Epigenetic Toolbox for Survival and Adaptation in the Host

Pathogenic fungi represent a diverse group of eukaryotic microorganisms that significantly impact human health and agriculture. In recent years, the role of epigenetic modifications, particularly histone modifications, in fungal pathobiology has emerged as a prominent area of interest. Among these modifications, methylation of histone H3 at lysine-4 (H3K4) has garnered considerable attention for its implications in regulating gene expression associated with diverse cellular processes. A body of literature has uncovered the pivotal roles of H3K4 methylation in multiple biological processes crucial for pathogenic adaptation in a wide range of fungal pathogens of humans and food crops. This review delves into the recent advancements in understanding the impact of H3K4 methylation/demethylation on fungal pathogenesis. We explore the roles of H3K4 methylation in various cellular processes, including fungal morphogenesis and development, genome stability and DNA repair, metabolic adaptation, cell wall maintenance, biofilm formation, antifungal drug resistance, and virulence. We also discuss the conservation of H3K4 methylation regulators and their potential as therapeutic targets to prevent fungal diseases. Collectively, this review underscores the intricate links between H3K4 methylation, fungal pathogenesis, and potential avenues for novel antifungal strategies.

Synthesis and Chemical Characterisation of Some Novel Substituted Flavone’s for It’s Anti Microbial Activity

The present study reports an experiment on some derivatives of 2-phenyl-chromen-4-one (flavone ring) have a proven inhibitory activity against a variety of human pathogens, including antibiotic-resistant Gram-positive and Gram-negative bacteria and antifungal activities screened against four human pathogenic bacteria and two phytopathogenic fungi. Flavanoid derivatives have been made through Algar– Flynn–Oyamada reaction from hydroxyacetophenones and aromatic-aldehydes. The structures of the synthesized compounds were elucidated by UV, IR and 1H NMR spectroscopic techniques, and elemental analysis. These compounds are potentially useful pharmacologically active compounds and are studied for biological activities like antibacterial and antifungal screens performed in vitro by the plate-hole diffusion method.

In vitro Antifungal Effects of Various Essential Oils against Aspergillus Crown Rot of Peanut

Synthetic fungicides that combat plant pathogenic fungi can enhance crop yields, ensuring stable crop production and market quality. However, the increase in the use of fungicides may cause to development of fungicide-resistant pathogen strains and the accumulation of fungicide residues in the food chain above safe limits. This situation underscores the need for improved fungal disease management through alternatives to synthetic fungicides. These alternatives include plant-derived compounds such as essential oils and extracts. Essential oils are known to be potent antifungal compounds against both human and plant pathogens. Aspergillus niger is a toxin-producing fungal disease agent that causes Aspergillus crown rot in peanuts. In this study, the antifungal activities of nine different essential oils from Foeniculum vulgare, Lippia citriodora, Origanum majorana, Origanum minutiflorum, Origanum onites, Origanum syriacum, Origanum vulgare, Salvia aramiensis and Thymus syriacus plants were evaluated against A. niger under in vitro conditions by using disc diffusion test. Among the nine essential oils tested, the highest antifungal activities were displayed by O. vulgare essential oil (with an inhibition zone diameter of 49.33 mm) which was followed by T. syriacus, O. onites, O. syriacum and O. minutiflorum essential oils (48.67, 47.00, 46.33 and 43.33 mm, respectively). The essential oils of F. vulgare, L. citriodora, and O. majorana showed relatively lower antifungal effects. The essential oil of S. aramiensis did not show antifungal effect against pathogen. The results indicated that plant essential oils could be valuable in promoting research aimed at developing new antifungal agent(s) for fungal disease management. However, further studies are needed to optimize the in vivo application conditions of essential oils against A. niger.

Biochar Reduced the Risks of Human Bacterial Pathogens in Soil via Disturbing Quorum Sensing Mediated by Persistent Free Radicals.

Biochar has great potential in reducing the abundance of antibiotic resistance genes (ARGs) and mobile genetic elements (MGEs) from soil. However, its efficiency in removing other biological pollutants, such as human bacterial pathogens (HBPs) and virulence factor genes (VFGs), is rarely studied. Herein, by pyrolyzing rice straw (RS) and pine wood (PW) at 350 and 700 °C, we prepared a series of biochar (RS350, RS700, PW350, and PW700) and investigated their impacts on the abundance and pathogenicity of HBPs. Compared with PW biochar, RS biochar effectively reduced the abundance of HBPs by 6.3-40.1%, as well as their pathogenicity, evidenced by an 8.2-10.1% reduction in the abundance of VFGs. Mechanistically, more persistent free radicals (PFRs) were formed in RS biochar than that of PW biochar during pyrolysis, and PFRs triggered the degradation of N-butyryl-l-homoserine lactone (C4-HSL) from 1.05 to 0.68 ng/kg, thereby disturbing the quorum sensing (QS) of HBPs. Once the QS was disturbed, the communications among HBPs were hindered, and their virulence factors were reduced, which ultimately lowered the abundance and pathogenicity of HBPs. Collectively, our study provides insights into the role of biochar in decreasing the risks of HBPs, which is significant in the development of biochar-based technologies for soil remediation.