Fems Microbiology Letters最新文献

Hemolytic proteins are a major group of virulence factors in pathogenic Aeromonas hydrophila. Six genes encoding presumable hemolytic proteins were revealed from the genome of virulent A. hydrophila (vAh) that caused severe disease in channel catfish. The aim of this study was to assess the contribution of these hemolytic proteins to the virulence of this bacterium. Genes coding for following six proteins were investigated: aerolysin (Arl), 21-kDa hemolysin (Hly1), thermostable hemolysin (Hly2), phospholipase/lecithinase-related hemolysin (Hly3), membrane-associated hemolysin III (Hly4), and cytolysin-associated hemolysin (Hly5). Individual genes were deleted from the bacterium using CRISPR-Cas9 mediated methods. Assessment showed that deletion of Arl gene (Δarl) completely abolished hemolytic activity of this mutant while Δhly1-Δhly5 mutants had the same activity as the wild vAh. Extracellular proteins (ECPs) of the Δarl mutant caused significantly (p < 0.01) less cell death in vitro with viability increased by approximately 20%, compared to the wild vAh. ECPs of mutants Δhly1-Δhly5 remained the same cell toxicity as the wild vAh. A second deletion of hly5 from the Δarl mutant further lowered the cell toxicity of the ECP of the mutant (Δarl + Δhly5). Assays in vivo showed that both Δarl and Δhly5 mutants caused less fish mortality with reduction of 57% and 16%, respectively, compared to the wild vAh; the Δarl + Δhly5 mutant caused the least mortality with approximately 87% of reduction; and other mutants had the same virulence as the wild vAh. Analyses of SDS-PAGE (sodium dodecyl sulfate-polyacrylamide gel electrophoresis) and Western blotting evidently indicate that both Arl and Hly5 proteins formed hexamer-like stable structures post secretion from the bacterium. Arl and Hly5 apparently had synergistic action in cytotoxicity and causing disease and were the major virulence factors among the six hemolytic proteins analyzed in this study.

Bacterial transcription terminator, Rho is an RNA (Ribonucleic Acid)-dependent ATPase that terminates transcription. Several structures of pretermination complexes of the Rho-transcription elongation complex (EC) revealed a static picture of components of the EC that come close to the nascent RNA-bound Rho, where many of the residues of EC reside ≤10 Å from the Rho residues. However, the in vitro-formed Rho-EC complexes do not reveal the in vivo Rho-EC dynamic interaction patterns during the termination process. Here we report synthetic defect analyses of various combinations of the mutations in RNAP β, β' and ω-subunits, NusA, NusG, and Rho proteins to delineate the functional network of this process. Several mutations in the β-flap and β'-Zn-finger and -Clamp helices domains of RNAP are synthetically defective in the presence of Rho mutants indicating functional involvement of these domains. Mutations in the NusA RNA-binding domains were synthetically defective with the Rho mutants suggesting its involvement. Our genetic analyses also revealed functional antagonisms between the ω-subunit of RNAP and the NusG-CTD (c-terminal domain) during termination. We concluded that the regions surrounding the RNA exit channel, the RNA-binding domains of NusA, the RNAP ω-subunit, and NusG-CTD constitute a functional network with Rho just before the onset of in vivo Rho-dependent termination.

Entomophagy, the practice of consuming insects, is a global tradition. In Mexico, one of the most notable and widely consumed insects is the larva of Aegiale hesperiaris. This insect feeds on the leaves of various Agave species with high polysaccharide content, suggesting their potential role as prebiotics for the intestinal microbiota, particularly lactic acid bacteria (LAB). LAB are recognized for their use as probiotics in foods due to their health-promoting capabilities. In this study, LAB from the intestinal microbiota of A. hesperiaris larvae were isolated and characterized, utilizing 16S rRNA gene identification. The analysis revealed three bacterial species from the Lactobacillaceae family, indicating a close symbiotic relationship with the insect. This suggests a significant impact on carbohydrate and protein metabolism, vitamin synthesis, and amino acid production, contributing to the high nutritional value of this edible insect. The study provides insights into the bacteria within the digestive tract of A. hesperiaris larvae and their role in enhancing the nutritional value of this edible insect. Additionally, it establishes a foundation for future research on the ecological roles and potential biotechnological benefits of these bacteria in the food industry and the development of therapies for various conditions and diseases.

As the human population grows, so does the demand for higher agricultural yields. As a result, agricultural intensification practices are increasing while soil health is often declining. Integrating the benefits of microorganisms into agricultural management systems can reduce the need for external resource inputs. One particular group of plant symbionts that can help plants to acquire additional nutrients and promote plant growth are arbuscular mycorrhizal fungi (AMF). The application of AMF in agricultural practice has been hampered by the variability in the success of mycorrhizal inoculation and the lack of consistency in different fields. Here, we tested whether it is possible to predict mycorrhizal inoculation success based on soil health and productivity. We hypothesized higher inoculation success on fields with poor soil health because in such fields, mycorrhiza can improve nutrient uptake and biotic resistance to pathogens. We calculated a soil health index by aggregating six biotic and abiotic variables from 54 maize fields and tested its correlation with the mycorrhizal growth response (MGR). The MGR was linked to soil health and significantly higher in less healthy soils and less productive fields. This implies that soil inoculation with AMF has most potential in fields with poor soil health and low productivity. Based on these findings, we propose a soil health framework that highlights the potential benefits of AMF field inoculation.

Antibiotic resistance and the persistence of sessile cells within biofilms complicate the eradication of biofilm-related infections using conventional antibiotics. This highlights the necessity for alternate therapy methods. The objective of this study was to investigate the biofilm destruction activity of α-tocopherol against Staphylococcus aureus, Proteus mirabilis, and Pseudomonas aeruginosa on polystyrene. α-Tocopherol showed significant biofilm destruction activity on the pre-formed biofilms of S. aureus (45%-46%), Pr. mirabilis (42%-54%), and Ps. aeruginosa (28%). Resazurin assay showed that α-tocopherol disrupted all bacterial biofilms without interfering with their cell viability. Scanning electron microscope images showed lower bacterial cell count and less compacted cell aggregates on polystyrene surfaces after treatment with α-tocopherol. This study demonstrated the biofilm destruction activity of α-tocopherol against S. aureus, Pr. mirabilis, and Ps. aeruginosa. α-Tocopherol could potentially be used to decrease biofilm-associated infections of these bacteria.

The genus Pantoea of the Erwinaceae is a genetically and metabolically diverse group whose representatives span a broad range of clinical and nonclinical environments. We sought to develop a culturing medium to facilitate the identification of Pantoea from environmental samples, and to distinguish its members from other closely related Gram-negative genera. We developed a semiselective differential medium, Pantoea Differential Medium (PDM), which contains crystal violet, sodium citrate, tryptone, as well as protease peptone. The efficacy of the medium was evaluated by assessing the growth and phenotype of 42 bacterial strains, including 18 strains of Pantoea along with other representatives of the Enterobacterales. All Pantoea strains, as well as Kosakonia sp. and Duffyella gerundensis formed orange-yellow pigmented colonies on the medium, while all other representative members of the Enterobacterales evaluated formed purple to pink colonies. The medium was also used to distinguish Pantoea from other bacteria in mixed cultures from environmental samples, with 44 of the 48 orange-yellow colonies being identified as members of Pantoea. PDM provides a means for rapidly identifying members of Pantoea from environmental samples, and differentiating them from many of the closely related members of the Erwiniaceae.

The genus Bacillus features species with remarkable plant growth-promoting traits (PGPTs) and is widely recognized for its biotechnological potential in sustainable agriculture. Among them, Bacillus paramycoides has recently attracted attention for its versatility in green synthesis of biopolymers, metal-based nanoparticles, and inhibition fungal phytopathogens; however, its PGPTs remain poorly underexplored. In this study, an integrated genomic and physiological approach was applied to B. paramycoides RZ3MS14, isolated from the guarana rhizosphere in Amazonian rainforest, to explore and correlate its potential PGPTs through in vitro and in vivo assays. The genome of B. paramycoides RZ3MS14 harbors genes related to N/P/Fe mobilization, bacillibactin synthesis, exopolysaccharides and biofilm formation, plant signaling, stress tolerance, biocontrol, and antibiotic resistance. Functional validation through in vitro assays, confirmed the strain's ability to solubilize phosphate, mineralize phytate, and produce siderophores, auxins, exopolysaccharides, and biofilm. These findings point diverse plant-growth promoting (PGP) traits that contributed to significant improvements in sugarcane growth and root architecture in the greenhouse. Specifically, root dry mass, shoot dry mass, root length, root surface area, and root volume increased by 225.92%, 520.89%, 231.47%, 242.25%, and 252.92%, respectively. Bacillus paramycoides RZ3MS14 exhibited a low antagonistic effect against the phytopathogenic fungi Fusarium verticillioides and Ceratocystis paradoxa. In contrast, microbial volatiles defined synergistic interactions with beneficial fungi Trichoderma afroharzianum and Purpureocillium lilacinum. This is the first study to unveil the PGP attributes of B. paramycoides, underscoring RZ3MS14's potential as a sugarcane bioinput and providing insights into its combined application with other microorganisms.

The WHO fungal priority pathogen list (FPPL), introduced in 2022, highlights 19 fungal species posing major public health risks. This systematic review evaluates the diversity and distribution of FPPL species in Indonesia, a tropical country favorable to fungal growth. Following Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines, we searched PubMed, Scopus, Google Scholar, and Indonesian databases (2000-2025), identifying 79 eligible studies from 825 records. These covered clinical and environmental samples across 18 of 34 provinces. Medium-priority species were most frequent (n = 70), followed by critical (n = 32) and high-priority (n = 6). Fusarium spp. dominated plant-related samples, while Candida spp. were prevalent in clinical settings. Critical-priority pathogens such as Aspergillus fumigatus, Candida tropicalis, and Cryptococcus neoformans were reported in multiple contexts. West and East Java showed the highest species diversity (17 each), likely reflecting better surveillance. Gaps remain for Candidozyma auris, Candida parapsilosis, Cryptococcus gattii, some Mucorales, and eumycetoma agents. Frequent detection of pathogenic fungi in both environmental and clinical underscores substantial health threats. Strengthened surveillance, diagnostics, and a One Health approach are essential. Limitations include uneven geographic coverage and methodological variation, which may underestimate the true burden in Indonesia.

Pectobacterium brasiliense 1692 (Pbr1692) is a necrotrophic pathogen that infects many crops such as potatoes and ornamental plants and derives nutrients from degraded plant tissue. Previous studies have identified Pbr1692 genes required for ecological fitness and virulence, however there is a lack of information on nutrient utilization in Pbr1692. Carbon source utilization profiling in Pbr1692 could provide a platform to decipher its metabolic flexibility and adaptation. This study assessed the nutrient utilization of Pbr1692 in different carbon sources, using Biolog Phenotypic Microarray (PM). An array of carbon sources utilized by Pbr1692 were identified, 32 carbohydrates and 8 carboxylic acids were among the preferred carbon nutrients utilized by Pbr1692. The PM results also revealed that the citric acid cycle, amino acid metabolism, and pentose phosphate metabolic pathways might be used to produce energy for Pbr1692. In addition, growth of Pbr1692 cells in minimal medium supplemented with citric acid, glucose, and aspartic acid retained the typical rod shape, suggesting that nutrient variation did not influence Pbr1692 cell morphology adaptation. This study provides an understanding on the adaptation of Pbr1692 and lays a foundation for understanding carbon metabolism of Pbr1692.

Onychomycosis is a common nail disorder typically caused by dermatophytes, with Candida species and non-dermatophytic molds being less frequent agents. Nakaseomyces glabratus (formerly Candida glabrata) is a rare cause of nail infections, notable for its intrinsic resistance to azoles and diagnostic challenges. We report a case of chronic nail discoloration, thickening, and fragility initially misdiagnosed as psoriasis. Microscopy and culture, followed by selective medium analysis, confirmed N. glabratus infection. This case emphasizes the importance of considering uncommon yeast species and highlights both the need for accurate identification to guide therapy and the possible misdiagnosis with other pathologies. Awareness and proper diagnostic approaches are essential for timely and effective management of such rare fungal nail infections.