Letters in Applied Microbiology最新文献

Environmental microbes have been linked to both beneficial and harmful effects on the lungs in relation to asthma. The aim of our study was to characterize the bacterial microbiome in lung samples from a mouse model of asthma exposed to titanium dioxide (TiO2) particles, and the effect of OM-85 Broncho-Vaxom®, a bacterial lysate on lung microbiome in mice. The mice were divided randomly into four groups of 6-8 mice per group. To identify the microbial communities in lung samples the upper right lung of all groups, we amplified and sequenced the rRNA gene regions from bacterial DNA (16S). The amplified 16S region was sequenced using the Roche-454 Life Sciences Titanium pyrosequencing platform. In the OVA + TiO2 + OM-85 group, airway hyperresponsiveness and inflammatory cells in bronchoalveolar lavage fluid (BALF) decreased compared to the OVA + TiO2 group. Inflammatory cytokine levels were lower in the OVA + TiO2 + OM-85 group. Certain bacteria, and Collinsella aerofaciens, decreased in the OVA + TiO2 + OM-85 group, while Neisseria perflava and Fusobacterium periodonticum increased. Lactic acid bacteria groups decreased in the OVA + TiO2 + OM-85 group. TiO2 particles exposure changed lung microbial taxa, and modified by a bacterial lysate, suggesting that a probiotic can be helpful in reducing exacerbation of airway disease exposed to air pollutants.

Bacillus thuringiensis RZ2MS9, a plant growth-promoting rhizobacterium isolated from the rhizosphere of guarana plants, has shown significant growth enhancement in both soybean and maize crops. To explore its full potential, we investigated RZ2MS9's entomopathogenic properties against Lepidoptera and Coleoptera larvae in vitro, and against Hemiptera populations in both in vitro and field conditions. The strain was evaluated for insecticidal crystal proteins, which were found in cuboid and spherical forms. Comparative genomic analysis revealed that while RZ2MS9 did not share significant pesticidal protein genes with B. thuringiensis HD1, it has unique genes related to plant growth promotion and nutrient acquisition. RZ2MS9 also exhibited chitinolytic activity, linked to the presence of the chitosanase coding gene (chP). Under laboratory conditions, the larvae mortality under RZ2MS9 treatment was 90% for sugarcane borer (Diatraea saccharalis), 92.5% for old-world cotton bollworm (Helicoverpa armigera), 30% for Agrotis ipsilon, and 87.5% for Anthonomus grandis. In addition, RZ2MS9 caused severe wing deformities in 40% of Spodoptera frugiperda moths and repelled Piezodorus guildinii from its food source. In field trials, soybean plants inoculated with RZ2MS9 exhibited significative increased length. P. guildinii was more prevalent in the inoculated plants, while the incidence of Euchistus heros remained unchanged.

Arbuscular mycorrhizal fungi (AMF) are known to enhance the accumulation of bioactive compounds with medicinal properties in plants. However, the potential cytotoxic effects of extracts from mycorrhizal plants on peripheral blood mononuclear cells (PBMC) remain unexplored. Therefore, this study aimed to verify the cytotoxic potential of foliar extract from Hymenaea martiana Hayne seedlings, either associated or not associated with AMF on PBMC. A greenhouse experiment was conducted with two treatments: a control group (without AMF) and a group inoculated with Acaulospora longula Spain and N.C. Schenck. After 148 days, leaves were collected to prepare aqueous extracts, and cytotoxicity of the extracts was assessed using the MTT (3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2H-tetrazolium bromide) assay. Additionally, the antioxidant potential and the content of soluble carbohydrates, flavonoids, flavonols, flavonones, dihydroflavonols, and saponins were assessed. Hymenaea martiana seedlings associated with A. longula exhibited a more than 50% increase in the accumulation of phenolic compounds compared to the control. However, no toxicity was detected for PBMC under any of the conditions evaluated. This study provides the first evidence of the effect of mycorrhizal plant extracts on human blood cells, highlighting their potential safety for medicinal and cosmetic applications.

Halorubrum salinarum RHB-CT, an archaeon known for its extreme halophilic, neutrophilic, and mesophilic characteristics, was studied for its carotenoids' potential as singlet oxygen antioxidants. This resilient organism thrives optimally at pH 7, 45°C temperature, and 25%-30% salinity. Optimization revealed that pH 7, 30°C temperature, and 25% salinity enhanced carotenoid production, likely due to oxidative stress and slower growth at lower temperatures, which in turn stimulate secondary metabolism. Carotenoids identified were haloxanthin (38%), bacterioruberin (BRB) (20%), monoanhydro-bacterioruberin (MABR) (20%), and one unidentified compound (23%). A 40 µM crude extract showed the highest singlet oxygen antioxidant activity at 19.68%, comparable to butylated hydroxyanisole and butylated hydroxytoluene.

Rice leaves harbor a diverse agriculturally important bacteriome. Using different dilutions and media, 20 bacterial isolates were obtained from the diseased and healthy leaves of two rice cultivars (cv. BPT-5204 and cv. Tetep). Later, the taxonomy was deduced based on the 16S rDNA sequences, which revealed 17 bacterial species belonging to 13 genera. The antifungal activity of 17 bacteria was tested against Rhizoctonia solani, which showed that Bacillus cereus, Stenotrophomonas maltophilia, and Acinetobacter lwoffii exhibited the mycelial inhibition of 65.18%, 61.85%, and 61.85%, respectively. Further, six selected bacteria (treatments: T1-T6) in three different methods of inoculation (methods: M1-M3) were tested on-field against sheath blight (ShB) for two consecutive Kharif seasons (2022 and 2023). The two-season data indicated a statistically insignificant effect of methods on the % disease index (PDI) (40.51-42.47), whereas different bacteria treatments (T1-T6) showed a significant impact on PDI (29.15-52.08). S. maltophilia isolated from the diseased BPT-5204 was superior to all other strains in reducing the PDI (29.15). We successfully isolated and functionally characterized 17 bacteria from the artificially diseased contrasting genotypes. This study demonstrated that rice lesions naturally harbor a diverse bacterium with antifungal effects that can be used to develop non-chemical-based disease management strategies.

Mycoplasma amphoriforme is an emerging respiratory pathogen for which little is known about the population structure or transmission dynamics. In this study, we developed the first multilocus sequence typing (MLST) scheme for M. amphoriforme and applied it to a previous genomic data set. The genomes of seven M. amphoriforme isolates from the UK and Denmark were sequenced and used to develop the MLST scheme based on loci used for previous Mycoplasma MLST schemes. The resulting MLST scheme consisted of four loci (gyrB, atpG, uvrA, and rpoB) and was applied to 20 previously sequenced genomes obtained from the UK and France/Tunisia. From the 27 sequences examined, 13 sequence types were identified. A phylogenetic tree of concatenated sequences showed a comparable topology to a previously described tree based on whole genome data. Additionally, the MLST scheme corroborated the previous suggestion of possible healthcare-associated transmission of M. amphoriforme between two separate patients. The MLST scheme gave a population structure analysis comparable to previous whole-genome-based analyses.

Human milk has a low microbial biomass with a microbiome dominated by typical skin and oral taxa, raising concerns about contamination during sample collection. However, to date, no study has directly compared samples collected with and without aseptic technique, leaving questions related to potential contamination within the field. To address this, we compared the microbiota of hand-expressed milk samples collected from 23 mothers before and after cleansing of the hands and breast. Metataxonomic analysis showed that taxonomic profiles were largely unaffected by cleansing, with only Rothia mucilaginosa significantly more abundant in non-aseptically collected samples (P = 0.007). Although aseptically and non-aseptically collected samples were taxonomically similar, there was a higher level of bacterial richness (P = 0.003) and evenness (Shannon diversity, P = 0.0002) in non-aseptically collected samples, suggesting that multiple low-abundance taxa are introduced via skin contamination. These findings support the use of aseptic collection methods to minimize external contamination and accurately assess milk microbial diversity. Importantly, they also suggest that common skin and oral taxa detected in human milk are likely true members of the mammary microbiome.

The regulatory mechanisms underlying ploidy dynamics in cyanobacteria under phosphorus (P) limitation remain poorly understood. In this study, we investigated the impact of phosphate deprivation on the polyploidy of Synechocystis sp. PCC 6803 through integrated approaches combining spectrofluorometry, flow cytometry, comparative transcriptomics, Pho regulon prediction, and enzymatic activity assays. Our results revealed a significant reduction in genomic DNA content (P < 0.01) during cultivation in phosphate-free BG11 medium, with average genome copy numbers decreasing from 24.34 ± 0.27 in standard BG11 to 6.18 ± 0.25 under P-depleted conditions (P < 0.01). Transcriptomic analysis demonstrated marked upregulation of genes associated with two-component signaling systems, ABC transporters, and nucleotide metabolism, while DNA replication, homologous recombination, and mismatch repair pathways were significantly downregulated (P < 0.05). Concurrently, alkaline phosphatase activity exhibited a substantial increase (P < 0.01), suggesting enhanced phosphate mobilization. These findings collectively indicated that genome copy number in Synechocystis sp. PCC 6803 was dynamically regulated through the coordinated interplay between DNA replication suppression and degradation activation in response to phosphorus availability. This work provides novel insights into the molecular basis of ploidy regulation in cyanobacteria and offers valuable implications for understanding analogous mechanisms in chloroplasts.

Maize, groundnut, and sorghum are important staple crops in several countries, but are prone to mycotoxin contamination. In the tropics and subtropics, Aspergillus flavus frequently contaminates those crops with aflatoxins and, sometimes, with cyclopiazonic acid (CPA). However, some genotypes cannot produce one or both toxins. In various countries, atoxigenic isolates of A. flavus are formulated into biocontrol products for field use to outcompete aflatoxin producers. The products effectively limit aflatoxin but their utility to reduce CPA remains unexplored. The abilities of four atoxigenic isolates (AF-) from Burkina Faso to control CPA by an isolate with high capacity to produce aflatoxins (AF+) and CPA was tested in co-inoculations at varying ratios (100+, 75+/25-, 50+/50-, 25+/75-, 100-), under simulated abiotic stress conditions. Experiments were conducted on 2% sorghum-based media at 0.95 and 0.90 water activity (aw), at 30°C and 37°C, for 12 days. CPA was quantified using liquid chromatography tandem mass spectroscopy. CPA concentrations gradually decreased as the proportion of atoxigenic isolates increased, with effectiveness varying depending on the environmental conditions.

Yersinia enterocolitica is one of the most important foodborne pathogens with significant impact on public health. It can be divided into six biotypes and approximately 60 O-serotypes, with O:3, O:9, O:8, and O:5,27 being predominantly associated with human yersiniosis. We present a two-group quadruplex real-time quantitative PCR (RT‒qPCR) for the patho-serotyping of Y. enterocolitica. The design of primers and probes within group 1 was based on sero-specific genes within the O antigen gene cluster, and those within group 2 were selected from the virulence markers and the restriction modification system to distinguish O:5,27 from O:5. The specificity was tested using reference strains, and was confirmed by a comparison with those obtained by a previous multiplex PCR. The limit of detection is 0.1 ng, or 104 copies μl-1 of genomic DNA, and the standard curves exhibited high linearity and correlation coefficients, demonstrating our assay's robustness. Among the 81 isolates used to evaluate the reproducibility, the results for 76 were consistent between the two approaches, indicating that the sensitivity of our RT‒qPCR is 100%, and the positive predictive value is 94%. Our assay can serve as a tool for identifying sources of Y. enterocolitica contamination and for epidemiological monitoring of this bacterium.