Microbiology spectrum最新文献

Bacteroides thetaiotaomicron (B. theta) dominates the gut microbiome of most mammals. This strictly anaerobic gut symbiont colonizes the mucus layer of host intestinal epithelial cells in both healthy and diseased conditions. Reduced neuronal and vagal afferent innervation observed in germ-free mice was found to be normalized by colonization with B. theta. In addition to deficits in gut innervation, germ-free mice have been reported to have reduced neuronal number and neurotransmitter levels in the brain. Here, we investigated the hallmarks of Alzheimer's disease (AD) in the brain of germ-free mice compared to mice mono-colonized with B. theta. We analyzed the number of mature neurons, neurotransmitter transporters, amyloid precursor protein processing, and inflammatory status in three brain regions: the hippocampus, prefrontal cortex (PFC), and cerebellum. The hippocampus and the PFC are regions thought to be highly susceptible to pathogenesis, whereas the cerebellum is thought to be only mildly affected. Interestingly, secretion of neuroprotective sAPPα decreased in hippocampus and remained unchanged in PFC, while levels were increased in the cerebellum in response to bacterial colonization. In addition, the number of presynaptic boutons increased in the hippocampus but remained unaffected in the cerebellum.

Importance: The gut microbiome has been reported to not only contribute to diseases of the gastrointestinal tract but also to interfere with and potentially even initiate diseases of other organ systems, such as the brain. Interference with the gut microbiome has been shown to elicit cognitive changes, for example, in rodent models of AD. Colonization with the common gut microbe B. theta not only affected the brain per se in our study but also showed specific brain region-dependent effects related to AD. This implies that evaluating the impact the microbiome might have on brain disorders needs a much more detailed investigation in the future with spatial and also potentially time resolution.

Woody ornamentals are integral to urban landscapes and play important roles in habitat restoration and ecological conservation, yet their national and international trade facilitates the spread of plant diseases with significant ecological and economic consequences. Vascular streak dieback (VSD) recently emerged on woody ornamentals in the United States and was found to be associated with the fungal pathogen Ceratobasidium sp. (Csp), but little is known about its genomic diversity and associated microbial communities. We thus applied metagenomic sequencing to 106 symptomatic samples that had tested positive for Csp and had been collected from 34 woody ornamental species in seven states. Taxonomic profiling identified Csp as the only putative pathogen of which we recovered 17 high-quality draft genomes. Phylogenomic and pangenome analyses revealed that U.S. Csp isolates form a tight genetic cluster, distinct in gene content from C. theobromae, a pathogen of cacao, avocado, and cassava in Southeast Asia. Comparative analyses highlighted gene content differences, including candidate effectors and secondary metabolite clusters, which may underlie host interactions and offer diagnostic targets. These findings provide the first genomic insights into the U.S. Csp population, suggest the recent introduction of a single genetic lineage with a broad host range, and establish a framework for improved detection, monitoring, and management of VSD in woody ornamentals.

Importance: Identification of the pathogen that causes an emerging disease, be it of humans, animals, or plants, is a prerequisite to develop effective treatment and/or management practices and to try to control the disease outbreak to prevent further pathogen spread. Vascular streak dieback (VSD) is an emerging disease of ornamental bushes and trees in the United States. Identification of the pathogen has been hindered by the difficulty in growing the fungal pathogen found to be associated with diseased plants in pure culture. Here, we succeeded in sequencing the DNA of the likely pathogen directly from plant tissue or from the fungal mass growing out of collected plant tissue. The sequences were assembled into genomes, which allowed us to precisely identify the pathogen, compare it to related pathogens of other plants, and predict how it causes disease. These results can now be used to inform management and control of VSD.

Plants of the genus Terminalia have been widely used in traditional medicine for the treatment of multiple ailments, including infectious diseases. Previously, our group performed metabolomic analyses using liquid chromatography-mass spectrometry of various Terminalia spp. and highlighted several phytochemicals (particularly flavonoids) that may contribute to the antibacterial activities of those species. Herein, we screen 15 flavonoids found in Terminalia spp. against antibiotic-resistant and antibiotic-sensitive strains of Escherichia coli, Klebsiella pneumoniae, and Staphylococcus aureus. Orientin, hispidulin, vitexin, rutin, fisetin, and isoorientin inhibited the growth of both methicillin- and β-lactam-resistant pathogens, producing MIC values ranging from 250 to 62.5 µg/mL. Orientin and isoorientin were the most effective at restricting the growth of methicillin-resistant and β-lactamase pathogens, with MIC values of 125 µg/mL against E. coli and extended-spectrum β-lactamase E. coli and 62.5 µg/mL against S. aureus. In combination with selected conventional antibiotics, some flavonoids potentiated the antimicrobial activity of selected conventional antibiotics. A total of 4 synergistic, 4 additive, and 22 non-interactive interactions were identified. The toxicity of the flavonoids was examined using Artemia franciscana nauplii lethality assays. With the exception of fisetin, genistein, and gossypetin, the flavonoids were non-toxic. Orientin and isoorientin were assessed for their potential to inhibit efflux pumps and demonstrated notable efflux pump inhibitory activity at four different concentrations: 125.0, 62.5, 31.25, and 15.26 µg/mL. The results obtained suggest that these flavonoids could serve as a valuable tool in combating antibiotic resistance.

Importance: Bacteria are becoming resistant to many types of antibiotics. This study has identified plant phytochemicals known as flavonoids, which were found to be capable of inhibiting the growth of numerous bacterial pathogens. Evidence is shown which reveals that the compounds are capable of blocking bacterial efflux pumps, which demonstrate that the flavonoids may be valuable compounds in the design of new antibiotic drugs.

Corn silk extract (CSE), a traditional medicinal food rich in polysaccharides, flavonoids, and saponins, has been used as a natural antihypertensive agent, but its mechanism remains unclear. This study aimed to evaluate whether CSE can lower blood pressure through gut microbiota modulation. Spontaneously hypertensive rats received oral CSE for 4 weeks, followed by a 4-week drug-free observation. The treatment significantly reduced blood pressure, increased microbial diversity, decreased the Firmicutes/Bacteroidetes ratio, and enriched beneficial genera, such as Akkermansia and Lactobacillus. These changes were accompanied by reduced serum lipopolysaccharide and pro-inflammatory cytokines, elevated nitric oxide (NO) levels, and restored endothelial function. Permutational multivariate analysis of variance (PERMANOVA) and correlation analyses showed that microbiota and inflammatory markers were more strongly associated with blood pressure improvements than urinary indices. Structural equation modeling suggested a potential mechanistic pathway involving gut microbiota-inflammation-NO regulation. Importantly, fecal microbiota transplantation using post-treatment donor samples reproduced the antihypertensive and anti-inflammatory effects, confirming the microbiota's critical mediating role. These findings provide the first experimental evidence that CSE functions as a prebiotic to improve gut microbial balance and vascular health, offering a promising natural strategy for microbiota-targeted blood pressure control.

Importance: This study identifies corn silk extract (CSE) as a novel plant-derived prebiotic with antihypertensive effects mediated through gut microbiota modulation. Using a spontaneously hypertensive rat model, we demonstrated that CSE reshapes gut microbial composition, enhances microbial diversity, and promotes beneficial genera while reducing systemic inflammation and restoring nitric oxide (NO)-mediated vascular function. Importantly, fecal microbiota transplantation confirmed the causal role of gut microbiota in mediating these effects. These findings highlight a gut microbiota-inflammation-NO axis as a key pathway through which CSE regulates blood pressure. As a safe, accessible, and food-compatible intervention, CSE represents a promising strategy for non-pharmacological blood pressure management and broadens the application scope of prebiotics in cardiovascular health.

Mycoplasma hyopneumoniae (M. hyopneumoniae, Mhp), the primary causative agent of swine enzootic pneumonia, poses significant threats to the pork industry, challenging food safety and sustainable development of the livestock industry. Here, four protoberberine alkaloids-epiberberine, jatrorrhizine, berberine, and coptisine-were identified by screening multiple natural compounds, and their anti-Mhp activity was evaluated. All alkaloids exhibited potent inhibitory effects against the virulent Mhp strain ES-2, with minimum inhibitory concentrations from 8 to 32 µg/mL. Their bactericidal activities were time- and concentration-dependent. At the cellular level, all protoberberine alkaloids significantly enhanced infected cell viability, suppressed pro-inflammatory cytokine expression (TNF-α, IL-6, and IL-1β), and exhibited low cytotoxicity toward host cells. In a Chang Da binary cross-breeding pig infection model, jatrorrhizine markedly alleviated clinical symptoms, reduced pulmonary pathogen loads, and mitigated histopathological damage in lung tissues, with therapeutic efficacy comparable to that of florfenicol. Our findings demonstrated that protoberberine alkaloids possessed potent anti-Mhp activity, high safety profiles, and promising therapeutic potential.

Importance: Swine enzootic pneumonia, caused by Mycoplasma hyopneumoniae (M. hyopneumoniae), remains one of the most economically devastating respiratory diseases in the global swine industry. The emergence of antibiotic resistance in livestock highlights the urgent need for effective, safe, and sustainable alternatives. This study demonstrates that naturally derived protoberberine alkaloids exhibit potent antibacterial activity against M. hyopneumoniae while maintaining low host cytotoxicity and strong anti-inflammatory effects. Among them, jatrorrhizine showed remarkable therapeutic efficacy in infected pigs, comparable with that of florfenicol. These findings provide a scientific basis for developing protoberberine alkaloids as promising natural alternatives to conventional antibiotics for controlling M. hyopneumoniae infections, thereby contributing to improved animal health, reduced antimicrobial resistance, and sustainable swine production.

Mycobacterium avium is a major causative agent of nontuberculous mycobacterial pulmonary disease, which poses therapeutic challenges owing to its intrinsic drug resistance and the need for prolonged multidrug regimens. In this study, we identified two novel nucleoside analogs, MCCB-04-35 and MCCB-04-37, as potential therapeutic candidates against M. avium infection. Both compounds exhibited significant bacteriostatic activity in vitro and in infected macrophages, with minimal cytotoxicity. Time-kill kinetics and MIC assays confirmed their potent inhibitory effects, particularly against slow-growing mycobacteria. Checkerboard synergy testing revealed additive to synergistic interactions with clinically used antibiotics such as clarithromycin and ciprofloxacin. In a mouse model of chronic lung infection, both compounds significantly reduced pulmonary bacterial burden, inflammatory cytokine levels, and histopathological damage. Transcriptomic analysis of treated M. avium revealed the downregulation of key metabolic pathways, including oxidative phosphorylation and nitrogen metabolism, indicating disruption of intracellular energy homeostasis. These findings suggest that MCCB-04-35 and MCCB-04-37 exert antimicrobial effects through metabolic interference and may serve as effective therapeutic agents either alone or in combination for treating M. avium infections.IMPORTANCEPulmonary disease caused by Mycobacterium avium complex (MAC) is notoriously difficult to treat due to intrinsic antibiotic resistance and the need for prolonged multidrug therapy, often poorly tolerated with suboptimal outcomes. The identification of new therapeutic candidates with novel mechanisms of action is urgently needed. Here, we report two novel nucleoside analogs, MCCB-04-35 and MCCB-04-37, exhibiting strong anti-mycobacterial activity against M. avium both in vitro and in vivo, with minimal cytotoxicity. These compounds showed additive to synergistic effects when combined with existing antibiotics such as clarithromycin. In a mouse model of chronic lung infection, they significantly reduced bacterial burden, inflammation, and tissue damage. Transcriptomic profiling revealed downregulation of metabolic pathways essential for bacterial energy production, suggesting a unique mechanism of antimicrobial action. Our findings provide promising leads for the development of more effective treatments for MAC pulmonary disease, either as monotherapy or in combination with current drugs.

Severe hydropericardium-hepatitis syndrome (HHS) caused by fowl adenovirus 4 (FAdV-4) significantly affects the global poultry industry. However, there is currently no convenient and sensitive platform available for the rapid screening of antiviral drugs and the detection of neutralizing antibodies. Here, we first established an improved reverse genetics system for FAdV-4 Y17215-1 strain and identified the optimal insertion site for expressing foreign genes (between the ORF19A and ORF4 genes). To obtain a quantifiable recombinant reporter FAdV-4, the HiBiT-tag reporter gene was inserted into this site, and recombinant FAdV-4 expressing the HiBiT gene (rFAdV-4-HiBiT) was successfully rescued. Further analysis showed that rFAdV-4-HiBiT had similar growth kinetics to the parental virus and retained luciferase activity and genetic stability after 10 rounds of serial passages. A proof-of-concept test confirmed that rFAdV-4-HiBiT can be used to rapidly quantify anti-FAdV-4 neutralizing antibodies in chicken serum samples and screen for antiviral agents, including antiviral drugs and proteins, based on the intensity of luciferase activity. Collectively, the HiBiT-tagged virus rFAdV-4-HiBiT provides a robust tool for the rapid detection of FAdV-4 and facilitates the development of novel therapeutics and vaccines for FAdV-4.

Importance: The epidemic spread of fowl adenovirus 4 (FAdV-4) presents significant challenges for the global poultry industry. However, there are currently few convenient and sensitive platforms available for antiviral drug screening and neutralizing antibody detection. In this study, we first established an improved reverse genetics system for the FAdV-4 and screened for the optimal insertion site for foreign genes between ORF19A and ORF4. Furthermore, the HiBiT gene was further inserted into this site, and rFAdV-4-HiBiT was successfully rescued. A luciferase-based FAdV-4 neutralizing antibody detection method has been successfully established, which can reduce detection time and greatly enhance the efficiency of neutralizing antibody testing. Furthermore, this system can serve as a more convenient screening platform for anti-FAdV-4 drugs. Collectively, rFAdV-4-HibiT represents an important tool with great potential for facilitating the development of novel therapeutics and vaccines for FAdV-4.

Leishmania spp., the causative agents of leishmaniasis, pose significant global health threats, with visceral leishmaniasis being the most severe and fatal form. The increasing drug resistance in the treatment of leishmaniasis emphasizes the urgent need for novel therapeutic approaches. One promising strategy involves targeting essential cellular mechanisms such as nutrient acquisition, particularly iron, which is critical for energy metabolism and signal transduction. Leishmania spp. cannot synthesize heme de novo and rely on host-derived iron and heme for survival and pathogenicity. Gallium [Ga(III)] is an iron [Fe(III)]-mimetic molecule that has emerged as a promising antimicrobial agent, offering a novel approach to combat infections, mainly by replacing Fe(III) in redox enzymes thereby disrupting essential metabolic pathways and impairing microbial viability. In this study, the antiparasitic activity of Ga (III)-protoporphyrin IX (GaPPIX) was tested against Leishmania major and Leishmania infantum, both in promastigotes and intracellular amastigotes. Our results demonstrate that GaPPIX inhibits the viability of both species, specifically targeting the enzymatic activity of cytochrome c oxidase, with a higher sensitivity observed in L. major. The inhibitory effect is reversed by hemin, suggesting specificity for Leishmania heme-dependent cellular processes and a possible cytostatic action. Moreover, we found that GaPPIX can effectively synergize with miltefosine. This feature, coupled with its minimal toxicity toward human cells, makes GaPPIX a good candidate to be potentially developed as a novel anti-Leismania agent.IMPORTANCEThis study is significant as it addresses a critical challenge in leishmaniasis management, namely, the increasing incidence of drug resistance and toxicity, compounded by the scarcity of effective therapeutic options. We demonstrate that GaPPIX, a heme-mimetic compound, exhibits potent antiparasitic activity against both Leishmania major and Leishmania infantum, while displaying minimal cytotoxicity toward human cells, underscoring its potential as a safe and targeted therapeutic candidate. Importantly, the ability of GaPPIX to synergize with the first-line drug miltefosine highlights its translational relevance in combination therapies, which are essential for overcoming resistance and improving treatment efficacy. Collectively, these findings advance GaPPIX as a promising approach for the development of innovative therapeutics against a neglected but globally significant disease.