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Enrichment of Lysobacter in a long-term organically managed agricultural field with low soilborne disease incidence.

Disease-suppressive soils, in which soilborne pathogens are naturally suppressed, offer a promising model for sustainable crop protection, particularly in organic farming systems where chemical disease control options are limited. Although disease suppression in these soils is considered to rely on biological control, the underlying mechanisms remain poorly understood. In this study, we investigated soil from a long-term organically managed field in Shiga Prefecture, Japan, where soilborne disease incidence has remained consistently low, to identify bacterial community features potentially associated with this field. The 16S rRNA gene amplicon sequencing indicated that this soil harbored a bacterial community distinct from those of nearby agricultural soils. Following the application of organic compounds, the genus Lysobacter, a taxon with known antagonistic activity against plant pathogens, was markedly enriched in response to proteinaceous organic inputs. This enrichment was consistent across sampling times and specific to certain proteinaceous organic inputs, whereas minimal effects were observed on chitin, N-acetyl-d-glucosamine, or cysteine. Broader soil surveys indicated that Lysobacter enrichment was not strictly associated with whether soils had been managed under organic or conventional farming practices. Stepwise multiple regression analysis identified 10 co-occurring bacterial genera that were strongly associated with Lysobacter abundance. These findings highlight condition-dependent Lysobacter enrichment as a characteristic microbial response to proteinaceous organic amendments in this low-disease-incidence field and provide microbial insights that may inform microbiome-based strategies for sustainable soil management.

Lysobacter

Acetylcholine signaling regulates osmotic stress adaptation in the phytopathogen Dickeya solani.

Plants impose strong selective pressures that shape both the composition and functional potential of plant microbiomes. The adaptation of plant-associated bacteria to their hosts relies on an extensive repertoire of signal transduction systems that sense plant-derived molecules and dynamically adjust bacterial physiology and metabolism within the holobiont. These signals include key plant signaling compounds that regulate processes essential for plant-microbe interactions. Among them, acetylcholine is emerging as an important signaling molecule in both plants and bacteria. Here, we demonstrate that acetylcholine regulates the expression of the osmotic stress response betIBA gene cluster in the important phytopathogen Dickeya solani, where it plays an important role in osmoprotection. We show that the TetR-family transcriptional regulator associated with this pathway, BetIDs, recognizes acetylcholine as well as choline and trimethylamine. These three ligands differentially induce betIBA transcription in a manner that correlates with their binding affinities. Ligand binding does not affect BetIDs binding to the bet promoter or its oligomeric state. Instead, it induces pronounced changes in the secondary structure of BetIDs, with the magnitude of these conformational changes being ligand-dependent. We further show that quorum sensing modulates osmotic stress tolerance in D. solani by regulating the expression of the Bet pathway. The Bet system is required for the full virulence of D. solani, particularly in chemically complex plant tissues. Phylogenetic analyses reveal that the BetIBA system is widely distributed among plant-associated Pseudomonadota, collectively supporting its importance for bacterial survival and adaptation in plant-related environments.

Osmotic Pressure

Quantifying the aromatic amino acid metabolome: UPLC-MS/MS analysis of aromatic amino acids and their host and co-metabolites in plasma.

Aromatic amino acids (AAAs), tryptophan, phenylalanine, and tyrosine along with their pathway metabolites have been implicated in the pathogenesis of diseases ranging from cardiovascular, neurological, inflammatory, and cancer diseases, among others. As such, the measurement of the primary AAAs, their host pathway metabolites, and microbiome derived co-metabolites in blood can provide a sensitive reflection of systemic health. The aim of the study was to develop a method for the quantification of 17 metabolites, the three AAAs and various of their metabolites in plasma using a high-throughput ultra performance liquid chromatography tandem mass spectrometry (UPLC-MS/MS) method. The method demonstrated a dynamic range (1 to 16,700 ng/mL), with detection limits (LOD) as low as 0.05 ng/mL. Quantification limits ranged from 3 to 5019 ng/mL (LLOQ) and up to 16,700 ng/mL (ULOQ). Recovery at LQC, MQC, and HQC was satisfactory and consistent across most metabolites, with significant matrix effects observed only for 4-ethylphenol sulfate. Furthermore, intra and inter-day accuracy and precision met all acceptance criteria at all quality control concentrations for most of the metabolites. Measurement of NIST SRM 1950 showcased the method's accuracy for most of the metabolites. Finally, the method was applied on the analysis of plasma samples from 55 individuals (13 males and 42 females) providing information on AAAs and their pathway metabolites relevant concentrations in human plasma.

Amino Acids, Aromatic

Faecal Microbiota Transplantation Reduces Lesion Severity and Medication Use in Canine Atopic Dermatitis: A Randomised, Placebo-Controlled, Double-Blinded Clinical Trial.

BACKGROUND: Faecal microbiota transplantation (FMT) is an established therapy for gastrointestinal disease, yet its role in canine atopic dermatitis (cAD) remains unclear. HYPOTHESIS/OBJECTIVES: We hypothesised that adjunctive FMT improves clinical severity and reduces symptomatic medication use in dogs with cAD. The objective was to evaluate efficacy and safety versus placebo. ANIMALS: Forty-six client-owned dogs with naturally occurring cAD were enrolled from a referral hospital population; 40 completed the study (FMT n = 20, placebo n = 20). MATERIALS AND METHODS: Prospective, randomised, placebo-controlled, double-blinded clinical trial. Dogs received daily oral lyophilised FMT capsules for 90 days plus three monthly rectal FMT administrations (Day [D]0, D30, D60) or placebo capsules with sham handling. Concomitant symptomatic therapies were permitted. Outcomes included Canine Atopic Dermatitis Extent and Severity Index, fourth iteration (CADESI-04), pruritus Visual Analog Scale (PVAS), Medication Score (D0-90) and Owner Global Assessment of Treatment Efficacy (OGATE, D90). RESULTS: CADESI-04 scores were lower with FMT at month (M) 2 (7 ± 6 vs. 16 ± 12; p = 0.006) and month 3 (8 ± 6 vs. 15 ± 12; p = 0.020). Sustained responders (≥ 50% CADESI-04 improvement at M2 and M3) were more frequent with FMT (35% vs. 5%; p = 0.044). In the FMT group, the medication scores were lower at M2 (16 ± 10 vs. 23 ± 11; p = 0.033) and M3 (13 ± 10 vs. 24 ± 15; p = 0.007) compared to placebo. PVAS decreased in both groups without between-group differences. OGATE favoured FMT (p = 0.028). FMT was well tolerated. CONCLUSIONS AND CLINICAL RELEVANCE: Adjunctive FMT reduced lesion severity and medication requirements, supporting its use as a safe microbiome-based add-on therapy in cAD.

Animals