Microbiological research最新文献

This review provides a comprehensive analysis of the intricate architecture of bacterial sensing systems, with a focus on signal transduction mechanisms and their critical roles in microbial physiology. It highlights quorum sensing (QS), quorum quenching (QQ), and quorum sensing interference (QSI) as fundamental processes driving bacterial communication, influencing gene expression, biofilm formation, and interspecies interactions. The analysis explores the importance of diffusible signal factors (DSFs) and secondary messengers such as cAMP and c-di-GMP in modulating microbial behaviors. Additionally, cross-kingdom signaling, where bacterial signals impact host-pathogen dynamics and ecological balance, is systematically reviewed. This review introduces "signalomics", an novel interdisciplinary framework integrating genomics, proteomics, and metabolomics to offer a holistic framework for understanding microbial communication and evolution. These findings hold significant implications for various domains, including food preservation, agriculture, and human health.

Listeria (L.) monocytogenes can survive for extended periods in the food producing environment. Here, biofilms possibly provide a niche for long-term survival due to their protective nature against environmental fluctuations and disinfectants. This study examined the behaviour of a L. monocytogenes ST121 isolate in a multispecies biofilm composed of Pseudomonas (P.) fragi, Brochothrix (B.) thermosphacta, and Carnobacterium (C.) maltaromaticum, previously isolated from a meat processing facility. The composition of the biofilm community and matrix, and transcriptional activity were analysed. L. monocytogenes colonised the multispecies biofilm, accounting for 6.4 % of all total biofilm cells after six hours. Transcriptomic analysis revealed 127 significantly up-regulated L. monocytogenes genes compared to the inoculum, including motility, chemotaxis, iron, and protein transport related genes. When comparing the differentially expressed transcripts within the multispecies biofilm with and without L. monocytogenes, only a cadmium/zinc exporting ATPase gene in C. maltaromaticum was significantly upregulated, while the other 9313 genes in the biofilm community showed no significant differential expression. We further monitored biofilm development over time (6, 24 hours and 7 days). P. fragi remained the dominant species, while L. monocytogenes was able to survive in the multispecies biofilm accounting for 2.4 % of total biofilm cells after 7 days, without any significant changes in its abundance. The presence of L. monocytogenes did neither alter the biofilm community nor its matrix composition (amount of extracellular DNA, carbohydrates, and protein). Our data indicate that L. monocytogenes resides in multispecies biofilms, potentially increasing survival against cleaning and disinfection in food processing environments, supporting persistence.

Ehrlichia chaffeensis is an obligatory intracellular bacterium that infects monocytes and macrophages and causes human monocytic ehrlichiosis. Ehrlichia translocated factor-3 (Etf-3) is a type IV secretion system effector that binds host-cell ferritin light chain and induces ferritinophagy, thus increasing cellular labile iron pool for Ehrlichia proliferation. To further characterize roles of Etf-3 in Ehrlichia infection, we produced immune libraries of Etf-3-specific nanobodies (Nbs). Based on distinct complementarity-determining region 3 sequences, we identified 16 and 15 families of anti-Etf-3 Nbs that could specifically bind the N- and C-terminal halves of Etf-3, respectively. Transfection with plasmids encoding the anti-Etf-3 Nbs N48 and N51, but not N59, significantly inhibited E. chaffeensis infection in HEK293 cells. All three Nbs colocalized with Etf-3-GFP in co-transfected RF/6A cells, but N48 and N51 had significantly higher binding affinities for recombinant Etf-3. Etf-3-GFP transfection-induced ferritinophagy and endogenous ferritin degradation was abrogated in HEK293 cells co-transfected with N48 or N51, but not with N59. To efficiently express Nbs in the infected host-cell cytoplasm, lipid nanoparticles-encapsulated mRNAs (LNP-mRNAs) encoding N48, N51, or N59 were created for delivery into cells or mice. Incubation of HEK293 cells or inoculation of mice with LNP-mRNA-N48 or LNP-mRNA-N51 significantly inhibited E. chaffeensis infection compared to those with LNP-mRNA-N59 or without LNP-mRNA. Our results demonstrate that Etf-3-specific Nbs delivered via LNP-mRNAs can inhibit Etf-3 functions and Ehrlichia infection.

Mounting evidence indicates that gut microbial metabolites are central hubs linking the gut microbiota to atherosclerosis (AS). Gut microbiota enriched with pathobiont bacteria responsible for producing metabolites like trimethylamine N-oxide and phenylacetylglutamine are related to an increased risk of cardiovascular events. Furthermore, gut microbiota enriched with bacteria responsible for producing short-chain fatty acids, indole, and its derivatives, such as indole-3-propionic acid, have demonstrated AS-protective effects. This study described AS-related gut microbial composition and how microbial metabolites affect AS. Summary findings revealed gut microbiota and their metabolites-targeted diets could benefit AS treatment. In conclusion, dietary interventions centered on the gut microbiota represent a promising strategy for AS treatment, and understanding diet-microbiota interactions could potentially be devoted to developing novel anti-AS therapies.

Non-tuberculous Mycobacteria (NTM) are found extensively in various environments, yet most are non-pathogenic. Only a limited number of these organisms can cause various infections, including those affecting the lungs, skin, and central nervous system, particularly when the host's autoimmune function is compromised. Among these, Non-tuberculous Mycobacteria Pulmonary Diseases (NTM-PD) are the most prevalent. Currently, there is a lack of effective treatments and preventive measures for NTM infections. This article aims to deepen the comprehension of the pathogenic mechanisms linked to NTM and to formulate new intervention strategies by synthesizing current research and detailing the different tactics used by NTM to avoid elimination by the host's immune response. These intricate mechanisms not only affect the innate immune response but also successfully oppose the adaptive immune response, establishing persistent infections within the host. This includes effects on the functions of macrophages, neutrophils, dendritic cells, and T lymphocytes, as well as modulation of cytokine production. The article particularly emphasizes the survival strategies of NTM within macrophages, such as inhibiting phagosome maturation and acidification, resisting intracellular killing mechanisms, and interfering with autophagy and cell death pathways. This review aims to deepen the understanding of NTM's immune evasion mechanisms, thereby facilitating efforts to inhibit its proliferation and spread within the host, ultimately providing new methods and strategies for NTM-related treatments.

Reactive oxygen and nitrogen species (RONS) are emerging as a novel antibacterial strategy to combat the alarming increase in antimicrobial resistance (AMR). RONS can inhibit bacterial growth through reactions with cellular molecules, compromising vital biological functions and leading to cell death. While their mechanisms of action have been studied, many remain unclear, especially in biologically relevant environments. In this study, we exposed Gram-positive and Gram-negative bacteria to varying RONS ratios, mimicking what microbes may naturally encounter. A ratio in favour of RNS induced membrane depolarization and pore formation, resulting in an irreversible bactericidal effect. By contrast, ROS predominance caused membrane permeabilization and necrotic-like responses, leading to biofilm formation. Furthermore, bacterial cells exposed to more RNS than ROS activated metabolic processes associated with anaerobic respiration, DNA & cell wall/membrane repair, and cell signalling. Our findings suggest that the combination of ROS and RNS can be an effective alternative to inhibit bacteria, but only under higher RNS levels, as ROS dominance might foster bacterial tolerance, which in the context of AMR could have devastating consequences.

Folate is an essential nutrient for nearly all organisms. While the physiological function and mechanism aspects of folate have been extensively and deeply investigated in Eukarya, related researches in Bacteria remains poorly understood. In this study, we focus on physiological functions of folate in Lactiplantibacillus plantarum by employing a combination of genetics, biochemistry and microscopy approaches. Deletion of the genes folE, folP, or both folE and folK in the folate biosynthesis pathway generated the mutant strains ΔfolE, ΔfolP, and ΔfolKE, respectively. Folate production in ΔfolE, ΔfolKE, and ΔfolP decreased to 51 %, 32 %, and 74 % of the wild-type level, respectively. Simultaneous deletion folE and folK distinctly extended the glutamate tail of folate. These mutants exhibited severely impaired growth capacity under normal conditions. Notably, only ΔfolP cells precipitated in liquid culture. All mutant strains displayed increased cell length, with the extent of elongation correlating to intracellular folate levels. It is noticed that DNA content was increased along with the cell size in deletion mutants. Additionally, 12 % of ΔfolKE cells and 4 % of ΔfolP cells exhibited abnormal lysis, characterized by granular cytoplasm. These findings provide significant insights into the physiological roles of folate in Bacteria.

Intercropping is emerging as a sustainable strategy to manage soil-borne diseases, yet the underlying mechanisms remain largely elusive. Here, we investigated how intercropping chrysanthemum (Chrysanthemum morifolium) with ginger (Zingiber officinale) suppressed Fusarium wilt and influenced the associated rhizo-microbiome. Chrysanthemum plants in intercropping systems exhibited a marked reduction in wilt severity and greater biomass compared to those grown in monoculture. In contrast, soil sterilization intensified wilt severity and abrogated the benefits of intercropping, highlighting the critical role of soil microbiota. 16S rRNA gene amplicon analysis revealed that intercropping significantly changed the composition and structure of rhizo-bacterial communities, particularly enriching Burkholderia species, which were closely associated with plant growth and disease resistance. Further investigation demonstrated that ginger root exudates, including sinapyl alcohol and 6-gingerol, greatly promoted the proliferation and colonization of Burkholderia sp. in chrysanthemum rhizosphere, conferring the enhanced disease suppression. Metabolomic profiling revealed that ginger root exudates stimulated the release of specific metabolites by chrysanthemum roots, which promoted the growth and biofilm formation of Burkholderia sp. Our findings uncovered the mechanism by which intercropping chrysanthemum with ginger plants modulated the rhizo-microbiome and thereby resulted in the enhanced disease suppression, offering insights into optimizing plant-microbe interactions for improving crop health and productivity.

The emergence and rapid dissemination of carbapenem-resistant hypervirulent Klebsiella pneumoniae (CR-hvKP) pose a serious threat to public health. Antibiotic treatment failure of K. pneumoniae infections has been largely attributed to acquisition of antibiotic resistance and bacterial biofilm caused by the presence of antibiotic persisters. There is an urgent need for novel antimicrobial agents or therapy strategies to manage infections caused by these notorious pathogens. In this study, we screened a collection of compounds that can dissipate bacterial proton motive force (PMF) and intermediate metabolites that can suppress antibiotic tolerance, and identified an antifungal drug sulconazole which can act in combination with glucose or trehalose to exert strong antibacterial effect against starvation-induced CR-hvKP persisters. Investigation of underlying mechanisms showed that sulconazole alone caused dissipation of transmembrane PMF, and sulconazole used in combination with glucose or trehalose could significantly inhibit the efflux activity, reduce NADH and ATP levels, and cause intracellular accumulation of reactive oxygen species (ROS) in CR-hvKP persisters, eventually resulting in bacterial cell death. These findings suggest that the sulconazole and glucose/trehalose combination is highly effective in eradicating multidrug-resistant and hypervirulent K. pneumoniae persisters, and may be used in development of a feasible strategy for treatment of chronic and recurrent K. pneumoniae infections.