Dalma Kovacs

Due to their diverse phytochemical composition, medicinal plants belonging to the families Amaryllidaceae, Lamiaceae, and Myrtaceae possess antimicrobial and antioxidant properties. In this study, six ethanolic extracts of Allium ursinum, Allium sativum, Allium cepa, Salvia rosmarinus, Ocimum basilicum, and Syzygium aromaticum were analyzed by HS-SPME GC-MS and HPLC. Their chemical composition was evaluated and compared by chemometrics and their biological activity determined by an antimicrobial assay. A total of 72 compounds was detected (terpenoids, phenolic derivatives, fatty acids, and phytosterols). In Allium species, phytosterols were mainly abundant, whereas O. basilicum extracts were characterized by high contents of linalool and S. rosmarinus by 2-hydroxychalcone and 4-hydroxybutanoic acid lactone. Principal component analysis distinguished chemically species-specific chemical profiles, whilst the HPLC evaluation resulted in the highest quercetin content in S. rosmarinus extracts, which also displayed the best antibacterial effect against Staphylococcus aureus. Despite the observed correlation between the quercetin content and antibacterial activity, no definitive relation could be established without biological replicates, MIC evaluation, and tests with isolated compounds.

Background and Objectives: Polyethylene (PE) mulching enhances crop productivity through microclimate optimization but introduces synthetic polymer-derived compounds into agricultural soils. Despite widespread use, biochemical and microbial impacts of PE mulch emissions remain poorly understood. This study investigated the impact of PE mulch emissions on soil metabolomes and microbial communities during field pea (Pisum sativum L.) cultivation. Methods: A 75-day field experiment compared PE-mulched and non-mulched soils across five temporal sampling points (T0–T4). Headspace solid-phase microextraction coupled with gas chromatography–mass spectrometry was used to identify PE-derived organic compounds in mulched soils. Microbial community structure was assessed through the phospholipids derived fatty acids (PLFA) approach, whereas mass spectrometric untargeted metabolomics was used to characterize the soil biochemical profiles. Results: Analysis identified 18 PE-derived organic compounds (n-alkanes, phthalates, and additives) in the mulched soils. PE mulching significantly increased bacterial abundance (anaerobic bacteria, actinomycetes, and aerobic bacteria) but suppressed all functional fungal guilds, particularly saprotrophic fungi (30% reduction) and arbuscular mycorrhizal symbionts. PE-derived organic compounds were associated primarily with the first RDA axis (RDA1), which alone explained 44.6% of the metabolome variance. These compounds presented strong positive correlations with organic nitrogen compounds and lipids and negative correlations with benzenoids and nucleotides. Pathway analysis revealed perturbations in energy metabolism, lipid metabolism, and xenobiotic degradation pathways. Conclusions: PE mulch emissions differentially shift soil microbial communities and metabolic networks, with bacterial proliferation contrasting with fungal suppression. These findings highlight the complex trade-offs between agronomic benefits and soil biological impacts, emphasizing the need for sustainable mulching alternatives.

Background: Soil mulching is a widely adopted agricultural practice known to regulate soil microclimate and enhance crop productivity; yet the biochemical mechanisms by which intact plastic and biodegradable mulch films influence soil nitrogen (N) cycling at the metabolic pathway level remain largely unexplored. Understanding these nitrogen transformation pathways is critical for assessing the long-term impacts of mulching materials on soil microbial communities, soil health, and sustainable agricultural management. This study focuses on the biochemical effects of intact mulch film application on soil N metabolism. Methods: N cycle-related soil metabolites were profiled using GC–MS/MS and MALDI TOF/TOF MS and then integrated with multivariate statistical modelling and pathway-level metabolic network perturbation analysis to compare conventional plastic and biodegradable plastic mulch film application against unmulched controls. Results: A panel of 62 KEGG-annotated N-cycle metabolites was profiled, and material-dependent metabolome separation was confirmed by OPLS-DA (R2Y 0.893–0.956; Q2 0.546–0.786). Both mulching materials significantly perturbed soil N-metabolite pools but differed in terms of pathway identity, magnitude, and directionality. Conventional plastic mulching caused the greatest disruption—near-complete suppression of N-storage and stress-adaptation pools (NES of −1.16; impact score of 10.01) and severe impairment of aspartate-centred metabolism—with L-aspartate identified as a critical stoichiometric hub. Biodegradable mulching material imposed a distinct profile dominated by inhibition of branched-chain amino acid catabolism and lysine degradation, with L-pipecolate as a treatment-specific critical impact node. Conclusions: These findings support that mulching material choice is a primary determinant of soil N-cycling biochemistry. The observed metabolite-level perturbations are suggestive of potential consequences for nitrogen retention. Though this inference is based on metabolite pool size differences and network topology metrics rather than directly measured process rates, it should therefore be interpreted with appropriate caution.

This study investigates soil volatilomics as an innovative approach to assessing the impact of land use on soil quality. This research addresses the critical need for sensitive diagnostic tools to distinguish subtle biochemical variations in soils influenced by different land use management practices. Soil samples were collected along a land use transect in Cluj County. Their volatile organic compounds were extracted by headspace solid-phase microextraction (HS–SPME) followed by a gas chromatography–mass spectrometry (GC–MS) analysis. A multivariate statistical method was used to differentiate the volatilome profile. Among the 106 detected compounds, oxygenated species dominated across all land uses, with the highest concentrations in forest soils (77%), followed by grasslands (71%) and agricultural soils (65%). Principal component analysis revealed distinct clustering patterns, with the first two components explaining 72.8% of the total variance (PC1: 41.7%, PC2: 31.1%). Supervised PLS-DA modeling demonstrated robust land use discrimination, achieving AUC values of 0.868 for agricultural versus forest comparisons and 0.810 for both forest versus grassland and grassland versus agricultural comparisons. The volatilome diversity analysis indicated that grasslands contained the highest number of distinct compounds (64), closely followed by forest soils (63), while agricultural soils showed reduced diversity (51). These key findings revealed distinct volatile signatures, with forest soils exhibiting the highest complexity and agricultural soils demonstrating a more homogeneous profile, whereas grassland soils presented high internal variability. These results underscore the potential of soil volatilome profiling as a sensitive indicator of the effects of land use on soil biochemical processes and support the utility of soil volatilomics in sustainable land management and ecosystem monitoring.

IntroductionLongan is a perennial crop and profitable export fruit well-suited to the Mekong Delta's climate and soils. Although soil deterioration in longan orchards has been studied, little research has addressed soil bacterial communities and their role in soil health. This study investigated the structure of soil bacterial communities and their associations with soil physicochemical properties in longan orchards.MethodsSoil samples were collected from longan orchards cultivated for 15 (N15), 20 (N20) and 30 years (N30) in Vinh Long Province, Vietnam. High-throughput sequencing of 16S rRNA amplicons was employed to assess bacterial diversity and community composition, followed by correlation analyses with soil properties.Results and DiscussionThe dominant bacterial phyla identified across sites included Acidobacteria, Proteobacteria, Chloroflexi, Actinobacteria, and Bacteriodota. Bacterial abundance in these soils was positively correlated with sand, pH, NO3- and phosphate solubilizing microorganisms, and negatively correlated with moisture, silt, clay, NH4+, exchangeable potassium and available manganese. Longan orchard soils from all three time periods (N15, N20, N30) had more microbial species in common, than in unique ways. However, time under cultivation was an important factor, with species diversity decreasing with age. The youngest orchards (N15) exhibited the highest number of soil bacterial diversity, followed by decreasing diversity as the orchards aged (N20) and lowest at 30 years (N30). Soil properties exhibited complex and interlinked relationships with soil bacterial phyla. Overall, long-term cultivation of longan orchard soil negatively impacted microbial diversity, potentially altering key properties of soil, hence underscoring the necessity for sustainable soil management to preserve soil health and production.

Urban expansion fragments once-contiguous forest patches, generating pronounced edge gradients that modulate soil physicochemical properties and biodiversity. We quantified how fragmentation reshaped the soil microbiome continuum and its implications for soil carbon storage in a temperate urban mixed deciduous forest. A total of 18 plots were considered in this study, with six plots for each fragment type. Intact interior forest (F), internal forest path fragment (IF), and external forest path fragment (EF) soils were sampled at 0–15, 15–30, and 30–45 cm depths and profiled through phospholipid-derived fatty acid (PLFA) chemotyping and amino sugar proxies for living microbiome and microbial-derived necromass assessment, respectively. Carbon fractionation was performed through the chemical oxidation method. Diversity indices (Shannon–Wiener, Pielou evenness, Margalef richness, and Simpson dominance) were calculated based on the determined fatty acids derived from the phospholipid fraction. The microbial biomass ranged from 85.1 to 214.6 nmol g−1 dry soil, with the surface layers of F exhibiting the highest values (p < 0.01). Shannon diversity declined systematically from F > IF > EF. The microbial necromass varied from 11.3 to 23.2 g⋅kg−1. Fragmentation intensified the stratification of carbon pools, with organic carbon decreasing by approximately 14% from F to EF. Our results show that EFs possess a declining microbiome continuum that weakens their carbon sequestration capacity in urban forests.

Despite the increasing recognition of the role of urban orchard ecosystems in sustainable urban development, the mechanistic understanding of how tree species soil biochemical heterogeneity drives microbial community assembly, the spatial patterns governing microbe-environment interactions, and their collective contributions to ecosystem multifunctionality remain poorly characterized. This study investigated how Prunus species and soil depth affect microbial biodiversity and metabolomic signatures in an urban orchard in Cluj-Napoca, Romania. Soil samples were collected from five fruit tree species (apricot, peach, plum, cherry, and sour cherry) across three depths (0–10, 10–20, and 20–30 cm), resulting in 225 samples. The microbial community structure was analyzed through phospholipid fatty acid (PLFA) profiling, whereas the soil metabolome was analyzed by mass spectrometry techniques, including gas chromatography–mass spectrometry (GC–MS/MS) and MALDI time-of-flight (TOF/TOF) MS, which identified 489 compounds across 18 chemical classes. The results revealed significant tree species-specific effects on soil microbial biodiversity, with bacterial biomarkers dominating and total microbial biomass varying among species. The soils related to apricot trees presented the highest microbial activity, particularly in the surface layers. Metabolomic analysis revealed 247 distinct KEGG-annotated metabolites, with sour cherry exhibiting unique organic acid profiles and cherry showing distinctive quinone accumulation. Depth stratification influenced both microbial communities and metabolite composition, reflecting oxygen gradients and substrate availability. These findings provide mechanistic insights into urban orchard soil biogeochemistry, suggesting that strategic species selection can harness tree species-soil microbe interactions to optimize urban soil ecosystem services and enhance urban biodiversity conservation.

Background: Land use change fundamentally alters soil microbial communities and biochemical processes, yet the integrated effects on rhizosphere microbiome–metabolome networks remained poorly understood. Objective: This study investigated land uses as forest, grassland and intermediary edge shape the rhizosphere biochemical networks of naturally grown Barbarea vulgaris. Methods: Rhizosphere soils of Barbarea vulgaris were analysed for microbial community structure abundance, and metabolomic profile applying phospholipid fatty acid (PLFA) profiling and mass spectrometric untargeted metabolomics (GC–MS/MS and MALDI–TOF/TOF MS). These were coupled with co–inertia analysis to assess microbiome–metabolome interactions. Results: Microbial community analysis revealed significant effects of land use on bacterial community structure (G+/G−, p < 0.001). Untargeted metabolomics identified 248 metabolites, of which 161 were mapped to KEGG pathways. Amino acids and derivatives (21.1%) followed by organic acids (16.8%) were the most representative among identified metabolites. Pathway enrichment analysis revealed coordinated reprogramming of central carbon and nitrogen metabolism across land use gradients, particularly in the amino acid metabolism, TCA cycle, and glycolysis/gluconeogenesis pathways. Microbiome–metabolome coupling analysis revealed distinct correlation patterns between microbial phenotypes and metabolite classes, with forest environments showing the strongest biochemical network integration (RV = 0.91). Edge habitats presented intermediate signatures, supporting their role as transitional zones with unique biochemical properties. Conclusions: The environmental context fundamentally shapes rhizosphere biochemical network organization through coordinated shifts in bacterial community structure and metabolic pathway activity. These habitat-specific metabolic signatures suggest that land use change triggers adaptive biochemical responses that may influence plant performance and ecosystem functioning across environmental gradients.