Frontiers in Microbiology最新文献

Objective: This study aimed to investigate the potential relation between the retarded growth of skeletal muscle (SM) and dysbiosis of gut microbiota (GM) in children with asthma, and to explore the potential action mechanisms of traditional pediatric massage (TPM) from the perspective of regulating GM and short-chain fatty acids (SCFAs) production by using an adolescent rat model of asthma.

Methods: Male Sprague-Dawley rats aged 3weeks were divided randomly into the 5 groups (n=6~7) of control, ovalbumin (OVA), OVA + TPM, OVA + methylprednisolone sodium succinate (MP) and OVA + SCFAs. Pulmonary function (PF) was detected by whole body plethysmograph, including enhanced pause and minute ventilation. Airway allergic inflammation (AAI) status was assessed by concentrations of OVA-specific immunoglobulin E in plasma, interleukin (IL)-4 and IL-1β in bronchoalveolar lavage fluid via ELISA assay. SM mass was assessed by using cross-sectional areas of diaphragm muscle and gastrocnemius via hematoxylin and eosin staining. GM and SCFAs production were detected by 16S rDNA sequencing and GC-MS, respectively. The protein and gene expressions of free fatty acid receptor 2 in SM were detected by using immunohistochemical staining and qRT-PCR, respectively. qRT-PCR was used to detect other relative gene expressions that were closely related with SM mass. The activity of insulin-like growth factor-1 (IGF-1)/protein kinase B (PKB/AKT) pathway in SM was detected by western blotting test.

Results: OVA exposure caused obvious AAI and poor PF in adolescent rats. OVA-exposed adolescent rats had a retarded growth of SM mass and inhibited activity of IGF-1/AKT pathway, which was related with GM dysbiosis, reduced SCFAs production and FFAR2 expressions in SM. TPM efficiently enhanced the SM mass, along with alleviating AAI and improving PF. TPM activated IGF-1/AKT pathway in SM, which was closely related with correcting GM dysbiosis, enhanced SCFAs production and FFAR2 expressions.

Conclusion: The retarded growth of SM mass and inhibition of IGF-1/AKT pathway existed in OVA-exposed adolescent rats, which was related with GM dysbiosis, reduced SCFAs production and FFAR2 expressions in SM. TPM efficiently enhanced the SM mass, at least, partially via regulating GM, enhancing SCFAs production and activating FFAR2-IGF-1/AKT pathway.

Introduction: Post-translational modifications of proteins provide cellular physiology with a broad range of adaptability to the external environment flexibly and rapidly. In the case of the protozoan parasite Giardia lamblia, the study of these modifications has gained relevance in recent years, mainly focusing on methylation and deacetylation of proteins. This study investigates the significance of acetylation in this protozoan parasite.

Methods: This study explores the role of acetylation in G. lamblia through a combination of immunofluorescence assays, manipulation of acetyltransferase enzymes, and the use of garcinol, an acetylation inhibitor, during the growth phase.

Results: The acetylation of histone marks H3K9 and H3K27 occurs during growth and is followed by deacetylation during encystation. Transfections modifying acetyltransferase activity induced a latent cellular state, underscoring the importance of protein acetylation for parasite survival. Garcinol treatment during growth caused significant morphological changes, including plasma membrane blebbing and apoptotic-like bodies. Immunofluorescence revealed these bodies contained α-tubulin/acetylated α-tubulin and reactive oxygen species. Flow cytometry and Annexin V staining indicated early apoptosis within 24 hours of treatment. Additionally, garcinol led to the deacetylation of H3K9 and H3K27, with redistribution of tubulin and acetylated tubulin from microtubules to the cytosol. Significantly, garcinol prevented parasite recrudescence after treatment withdrawal.

Discussion: These results demonstrate that acetylation is essential for trophozoite survival and highlight the natural histone acetyltransferase inhibitor garcinol as a potential candidate for drug development against giardiasis, considering its giardicidal activity.

Introduction: Microbial contamination remains a vital challenge across the food production chain, particularly due to mycotoxins-secondary metabolites produced by several genera of fungi such as Aspergillus, Fusarium, Alternaria, and Penicillium. These toxins, including aflatoxins, fumonisins, ochratoxins, and trichothecenes (nivalenol, deoxynivalenol, T2, HT-2). These contaminants pose severe risks to human and animal health, with their potential to produce a variety of different toxic effects. Notably, up to 50% of global cereal production is affected by mycotoxin contamination, leading to significant economic losses. Current research focuses on innovative technologies to mitigate mycotoxins, with cold atmospheric pressure plasma emerging as a promising decontamination method.

Method: This systematic review aimed at describing recent advances in the application of cold atmospheric plasma for the decontamination of toxigenic fungi and mycotoxins.

Results and discussion: Cold atmospheric plasma offers a sustainable and cost effective solution to preserve food quality while inactivating toxigenic fungi and degrading mycotoxins. Through the generation of reactive oxygen and nitrogen species, cold plasma disrupts fungal cell integrity, hinders spore germination, and inhibits toxin biosynthesis. Additionally, cold atmospheric plasma-driven degradation of mycotoxins involves structural modifications, breaking key molecular bonds that reduce toxicity. The effectiveness of cold plasma depends on operational parameters and the specific characteristics of the treated food, with notable efficacy in degrading aflatoxin B₁ and deoxynivalenol by converting them into less toxic substances and inhibiting their spores and DNA responsible for their biosynthesis. While the data demonstrates that cold atmospheric plasma has minimal impact on food composition, further research is needed to fully assess the nature of the degradation products of mycotoxins, its influence on food quality attributes and to optimize application strategies for different products.

The YhaJ transcription factor responds to dinitrophenol (DNT) and its metabolic products. The YhaJ-involving cells have been exploited for whole-cell biosensors of soil-buried landmines. Such biosensors would decrease the damage to personnel who approach landmine fields. By the structure determination of the DNA-binding domain (DBD) of YhaJ and the structure-guided mutagenesis, we found that the mutation increasing the DNA binding affinity decreases the signal leakage in the absence of an effector, resulting in a significant enhancement of the response ratio for the DNT metabolite detection. The decrease in signal leakage explains the LysR-type transcriptional regulators' (LTTRs') unique mechanism of signal absence repression by choosing between two different activation binding sites. We showed that the biosensor performance enhancement by the decrease in signal leakage could combine with the previous signal-enhancing mutations. The novel mechanism of performance enhancement of YhaJ shed light on bacterial transcription regulation and the optimization of biosensors that involve the large family of LTTRs.

Streptococcus pneumoniae capsular polysaccharide (CPS) is a crucial virulence factor for this pathogenic bacterium and is partially under transcriptional control. In this study, we used electrophoretic mobility shift assays and DNA enzyme footprinting to identified the hypothetical protein SPD_0410 as a negative regulator of cps locus. Our results showed that the D39Δspd0410 mutant strain exhibited significantly elevated CPS levels compared to the parental strain D39s. SPD_0410 directly binds at two specific sites on the cps promoter. The regulatory effect of SPD_0410 on CPS was weakened after the mutation of specific binding sites in the promoter. RNAseq analysis revealed that the deletion of spd0410 led to alterations in glucose metabolism. However, the altered glucose levels appeared to eliminate the regulation of CPS synthesis by SPD_0410. Deleting the spd0410 gene resulted in higher invasion and phagocytic resistance of bacteria and in vivo mouse experiments confirmed that D39Δspd0410 caused more severe systemic disease than the parental strain D39s. Our results indicated that SPD_0410 negatively regulates the synthesis of S. pneumoniae capsules and can directly alter pneumococcal virulence.

Colonization by multidrug-resistant (MDR) bacteria and related bloodstream infections (BSI) are associated with a high rate of mortality in patients with hematological malignancies after intensive chemotherapy and allogeneic stem cell transplantation (allo-SCT). In this retrospective study, we analyzed the outcomes of patients colonized with MDR bacteria (primarily carbapenem-resistant klebsiella pneumoniae, KPC), before allo-SCT. We also investigated the feasibility and safety of an antimicrobial de-escalating approach in these patients. Since 2021, 106 patients have been undergoing allo-SCT in our department, and 34 (32%) of them were colonized by MDR bacteria before allo-SCT. In the pre-engraftment period, 84% received an empiric antibiotic therapy (EAT) active against MDR bacteria and 16% were treated with a conventional EAT. The MDR translocation rate was null, and the overall de-escalation rate was 79%, with 75% in patients with fever of unknown origin (FUO). Among the cohort of patients with MDR-positive rectal swabs just before allo-SCT (n = 18), the de-escalation rate was 100%. The all-cause mortality rates at 30 and 100 days for the whole MDR patient population were 6% (2/34) and 12% (4/34), respectively. Day +30 infection-related mortality rate was 3%. In this study, we confirm the safety of the de-escalation approach in patients with previous MDR infection after allo-SCT. This could reduce the exposure time to EAT antibiotics, reducing the selective pressure.

The gut microbiota actually shares the host's physical space and affects the host's physiological functions and health indicators through a complex network of interactions with the host. However, its role as a determinant of host health and disease is often underestimated. With the emergence of new technologies including next-generation sequencing (NGS) and advanced techniques such as microbial community sequencing, people have begun to explore the interaction mechanisms between microorganisms and hosts at various omics levels such as genomics, transcriptomics, metabolomics, and proteomics. With the enrichment of multi-omics integrated analysis methods based on the microbiome, an increasing number of complex statistical analysis methods have also been proposed. In this review, we summarized the multi-omics research analysis methods currently used to study the interaction between the microbiome and the host. We analyzed the advantages and limitations of various methods and briefly introduced their application progress.

The microbiota within the guts of insects plays beneficial roles for their hosts, such as facilitating digestion and extracting energy from their diet. The African palm weevil (APW) lives within and feeds on the high lignin-containing trunk of palm trees; therefore, their guts could harbour a large community of lignin-degrading microbes. In this study, we aimed to explore the bacterial community within the gut of the APW larvae, specifically with respect to the potential for lignin degradation in various gut segments as a first step to determining the viability of mining bacterial lignin-degrading enzymes for the bioconversion of lignocellulosic biomass to biofuels and biomaterials. Bacterial metagenomic DNA was extracted from the foregut, midgut, and hindgut of larvae of the APW, and the V3-V4 hypervariable region of the 16S rRNA gene was sequenced using the Illumina MiSeq platform. The generated data were analysed and taxonomically classified to identify the different bacterial phylotypes within the gut community cumulatively and per gut segment. We then determined the presence, diversity, and abundance of bacteria associated with lignin degradation within each larval gut compartment as a basis for suggesting the gut segment(s) where lignin degradation occurs the most. All sequences were classified and belonged to the bacterial kingdom. Firmicutes (54.3%) and Proteobacteria (42.5%) were the most dominant phyla within the gut, followed distantly by Bacteroidota (1.7%) and Actinobacteriota (1.4%). Enterococcus, Levilactobacillus, Lactococcus, Shimwellia, Megasphaera, Klebsiella, Pectinatus, Salmonella, Lelliotia, and Enterobacter constituted the most abundant genera found across all gut segments. The foregut and midgut had many similar genera, whilst the hindgut appeared unique. Overall, 29.5% of total gut bacteria comprising 21 genera were lignin degraders found predominantly in the Firmicutes and Proteobacteria phyla (56.8 and 39.5%, respectively), then moderately in Actinobacteriota (2.5%) and Bacteroidota (1.1%). The most abundant ligninolytic genera were Levilactobacillus (46.4%), Klebsiella (22.9%), Enterobacter (10.7%), Lactiplantibacillus (5.9%), Citrobacter (2.2%), Corynebacterium (1.8%), Paucilactobacillus (1.8%), Serratia (1.5%), Bacteroides (1.1%), and Leucobacter (1.0%) found in different amounts in different gut compartments. The foregut had the most diverse and highest abundance of lignin-degrading phylotypes, and we present reasons that point to the foregut as the main location for the depolymerization of lignin in the APW larval gut.

The utilization of chemical pesticides recovers 30%-40% of food losses. However, their application has also triggered a series of problems, including food safety, environmental pollution, pesticide resistance, and incidents of poisoning. Consequently, green pesticides are increasingly seen as viable alternatives to their chemical counterparts. Among these, Plant Growth-Promoting Rhizobacteria (PGPR), which are found within plant rhizosphere, stand out for their capacity to stimulate plant growth. Recently, we isolated a strain, BN, with broad-spectrum antimicrobial activity from the rhizosphere of Lilium brownii. Identification revealed that this strain belongs to the species Bacillus velezensis and exhibits significant inhibitory effects against various fungal plant pathogens. The complete genome sequence of B. velezensis BN consists of a circular chromosome with a length of 3,929,791 bp, includes 3,747 protein-coding genes, 81 small RNAs, 27 rRNAs, and 86 tRNAs. Genomic analysis revealed that 29% of the genes are directly involved in plant growth, while 70% of the genes are indirectly involved. In addition, 12 putative biosynthetic gene clusters were identified, responsible for the synthesis of secondary metabolites, such as non-ribosomal peptides, lanthipeptides, polyketides, siderophores, and terpenes. These findings provide a scientific basis for the development of efficient antimicrobial agents and the construction of biopesticide production platforms in chassis cells.

Dental caries has been one of the most prevalent diseases globally over the last few decades, threatening human oral and general health. The most critical aspect in caries control is to inhibit the dominant cariogenic bacteria Streptococcus mutans (S. mutans). Sulforaphane (SFN), a compound found in a wide range of cruciferous plants, has demonstrated bacteriostatic activities against various pathogenic bacteria. The objective of the present study was to investigate the effects of SFN on S. mutans though both in vitro and in vivo experiment. The minimum inhibitory concentration (MIC) against S. mutans was determined at 256 μg/mL. The growth of S. mutans and the biofilm formation were inhibited by SFN in a dose-dependent manner through suppressing the synthesis of extracellular polysaccharide (EPS) and acid production, as well as decreasing the acid tolerance. Meanwhile, SFN significantly weakened the cariogenic properties of S. mutans at sub-inhibitory concentrations, which were further illustrated by quantitative real-time PCR (qRT-PCR). Moreover, SFN were found to inhibit quorum sensing (QS) by downregulate comCDE system in S. mutans. Further investigation using a rat caries model displayed a prominent caries control in the SFN-treated group with no observed toxicity. The notable results demonstrated in this study highlight the potential of SFN as a natural substitute for current anti-caries agents, while also providing valuable insights into the potential applications of SFN in caries control.