Search Results (8)

Diversified agricultural practices reconfigure agroecosystem services by modifying fertilization, tillage intensities, and cropping patterns, altering soil properties and microbial assemblages. However, microbial communities, as critical bioindicators of soil health and productivity, respond to agricultural disturbances, and the effects of multiple practices on productivity-associated indicator species require further validation. Using 16S and ITS amplicon sequencing, this study employed a field experiment to investigate the effects of agricultural practices on soil properties, maize productivity, and microbial communities under two fertilization treatments. Within each treatment, we assessed correlations between indicator species associated with cropping–tillage practices and soil productivity. Results showed that fertilization significantly altered soil properties, increased maize grain yield by 23.9%, and reshaped bacterial and fungal community structures, increasing bacterial richness by 23% but reducing fungal richness and Shannon index by 15% and 20%, respectively. Furthermore, cropping–tillage practices significantly affected microbial communities and grain yields in both fertilized and unfertilized treatments despite a slight influence on soil properties. Distinct sets of bacterial and fungal indicator species were identified for each fertilization treatment: unfertilized soils harbored 21 dominant bacterial indicator species (e.g., Bacillus, Rhizobium, Streptomyces) and 8 fungal indicators (e.g., Cryptococcus, Gibberella, Tetracladium); fertilized soils contained 24 dominant bacterial indicators (e.g., Fusobacterium, Clostridium, Lactobacillus) and 6 fungal indicators (e.g., Gibberella, Cladosporium, Mortierella). Notably, abundances of specific indicator genera (e.g., bacteria: Bacteroides, Gemmatirosa, Iamia, Lysobacter, Prevotella, Staphylococcus, Sutterella; fungi: Glomus, Fusicolla in unfertilized soil; bacteria: Dinghuibacter, Haliangium, Kribbella, Rhodomicrobium, Terrimonas; fungi: Pulvinula in fertilized soil) correlated positively with grain yields. These findings demonstrate that fertilization reshapes the composition of microbial indicator species significantly associated with maize productivity. Tailored microbial indicator assemblages specific to distinct fertilization strategies are therefore essential for evaluating crop productivity and assessing agricultural practice impacts. Consequently, monitoring these indicator species enables rapid assessment of soil fertility changes, offering guidance for fertilization management. Full article

Soil health reflects the sustained capacity of soil to function as a vital living ecosystem, ensuring support for all forms of life. The evaluation of soil health relies heavily on physicochemical indicators. However, it remains unclear whether and how microbial traits are related to soil health in soil with long-term organic manure amendment. This study aims to examine how detrimental and beneficial microbial traits change with soil health based on physicochemical indicators. This research measures the effects of 9-year manure supplementation on soil health using multiomics techniques. We found that, compared to 100% chemical fertilizers, the soil health index increased by 5.2%, 19.3%, and 72.6% with 25%, 50%, and 100% organic fertilizer amendments, respectively. Correspondingly, the abundance of beneficial microorganisms, including Actinomadura, Actinoplanes, Aeromicrobium, Agromyces, Azospira, Cryobacterium, Dactylosporangium, Devosia, Hyphomicrobium, Kribbella, and Lentzea, increased progressively, while the abundance of the pathogenic fungus Fusarium decreased with the organic manure application rate. In addition, the application of organic manure significantly increased the concentrations of soil metabolites, such as sugars (raffinose, trehalose, maltose, and maltotriose) and lithocholic acid, which promoted plant growth and soil aggregation. Moreover, the abundances of pathogens and beneficial microorganisms and the concentrations of beneficial soil metabolites were significantly correlated with the soil health index based on physicochemical indicators. We conclude that organic fertilizer can enhance soil health by promoting the increase in beneficial microorganisms while suppressing detrimental microorganisms, which can serve as potential indicators for assessing soil health. In agricultural production, substituting 25–50% of chemical fertilizers with organic fertilizers significantly helps improve soil health and promotes crop growth. Full article

Incorporation of plant residues in soil affects microbial community structure and ecological function, which can improve soil fertility. It is reported that substrate qualities could regulate microbial keystone taxa and their interactions, wielding an important effect on nutrient cycling in ecosystems, such as soil labile phosphorus (P) transformation. However, there is little understanding of the specific microbial mechanisms governing P’s availability in acidic soils following the incorporation of plant residues of various qualities. In this 210-day incubation experiment, two high-quality residues of pumpkin stover and mango branch and one low-quality residue of rice straw, different in terms of their labile carbon (C) content and carbon/phosphorus ratio (C/P), were separately mixed with an acidic soil. The aim was to investigate how the residues affected the community composition, keystone species, and interaction patterns of soil bacteria and fungi, and how these microbial characteristics altered soil P mineralization and immobilization processes, along with P availability. The results showed that adding high-quality pumpkin stover significantly increased the soil’s available P content (AP), microbial biomass P content (MBP), and acid phosphatase activity (ACP), by 63.7%, 86.7%, and 171.7% compared to the control with no plant residue addition, respectively. This was explained by both the high abundance of dominant bacteria (Kribbella) and the positive interactions among fungal keystone species. Adding mango branch and rice straw induced cooperation within fungal communities while resulting in lower bacterial abundances, thereby increasing AP, MBP, and ACP less than the addition of pumpkin stover. Moreover, the labile C of plant residues played a dominant role in soil P transformation and determined the P availability of the acidic soil. Therefore, it may be suitable to incorporate high-quality plant residues with high labile C and low C/P into acidic soils in order to improve microbial communities and enhance P availability. Full article

The synthesis of betalain using microorganisms is an innovative developmental technology, and the excavation of microorganisms closely related to betalain can provide certain theoretical and technical support to this technology. In this study, the characteristics of soil microbial community structures and their functions in the rhizospheres of white-fleshed dragon fruit (Hylocereus undatus) and red-fleshed dragon fruit (Hylocereus polyrhizus) were analyzed. The results show that the soil bacterial and fungal compositions in the rhizospheres were shaped differently between H. undatus and H. polyrhizus. Bacterial genera such as Kribbella and TM7a were the unique dominant soil bacterial genera in the rhizospheres of H. undatus, whereas Bradyrhizobium was the unique dominant soil bacterial genus in the rhizospheres of H. polyrhizus. Additionally, Myrothecium was the unique dominant soil fungal genus in the rhizospheres of H. polyrhizus, whereas Apiotrichum and Arachniotus were the unique dominant soil fungal genera in the rhizospheres of H. undatus. Moreover, TM7a, Novibacillus, Cupriavidus, Mesorhizobium, Trechispora, Madurella, Cercophora, and Polyschema were significantly enriched in the rhizospheres of H. undatus, whereas Penicillium, Blastobotrys, Phialemonium, Marasmius, and Pseudogymnoascus were significantly enriched in the rhizospheres of H. polyrhizus. Furthermore, the relative abundances of Ascomycota and Penicillium were significantly higher in the rhizospheres of H. polyrhizus than in those of H. undatus. Full article

Minor genera actinomycetes are considered a promising source of new secondary metabolites. The strain Kribbella sp. CA-293567 produces sandramycin and kribbellichelins A & B In this work, we describe the complete genome sequencing of this strain and the in silico identification of biosynthetic gene clusters (BGCs), focusing on the pathways encoding sandramycin and kribbellichelins A–B. We also present a comparative analysis of the biosynthetic potential of 38 publicly available genomes from Kribbella strains. Full article

Current needs in finding new antibiotics against emerging multidrug-resistant superbugs are pushing the scientific community into coming back to Nature for the discovery of novel active structures. Recently, a survey of halophilic actinomyectes from saline substrates of El Saladar del Margen, in the Cúllar-Baza depression (Granada, Spain), led us to the isolation and identification of 108 strains from the rhizosphere of the endemic plant Limonium majus. Evaluation of the potential of these strains to produce new anti-infective agents against superbug pathogens was performed through fermentation in 10 different culture media using an OSMAC approach and assessment of the antibacterial and antifungal properties of their acetone extracts. The study allowed the isolation of two novel antibiotic compounds, kribbellichelin A (1) and B (2), along with the known metabolites sandramycin (3), coproporphyrin III (4), and kribelloside C (5) from a bioassay-guided fractionation of scaled-up active extracts of the Kribbella sp. CA-293567 strain. The structures of the new molecules were elucidated by ESI-qTOF-MS/MS, 1D and 2D NMR, and Marfey’s analysis for the determination of the absolute configuration of their amino acid residues. Compounds 1–3 and 5 were assayed against a panel of relevant antibiotic-resistant pathogenic strains and evaluated for cytotoxicity versus the human hepatoma cell line HepG2 (ATCC HB-8065). Kribbellichelins A (1) and B (2) showed antimicrobial activity versus Candida albicans ATCC-64124, weak potency against Acinetobacter baumannii MB-5973 and Pseudomonas aeruginosa MB-5919, and an atypical dose-dependent concentration profile against Aspergillus fumigatus ATCC-46645. Sandramycin (3) confirmed previously reported excellent growth inhibition activity against MRSA MB-5393 but also presented clear antifungal activity against C. albicans ATCC-64124 and A. fumigatus ATCC-46645 associated with lower cytotoxicity observed in HepG2, whereas Kribelloside C (5) displayed high antifungal activity only against A. fumigatus ATCC-46645. Herein, we describe the processes followed for the isolation, structure elucidation, and potency evaluation of these two new active compounds against a panel of human pathogens as well as, for the first time, the characterization of the antifungal activities of sandramycin (3). Full article

In this paper, we report on the chemistry of the rare South African Actinomycete Kribbella speibonae strain SK5, a prolific producer of hydroxamate siderophores and their congeners. Two new analogues, dehydroxylated desferrioxamines, speibonoxamine 1 and desoxy-desferrioxamine D₁ 2, have been isolated, together with four known hydroxamates, desferrioxamine D₁ 3, desferrioxamine B 4, desoxy-nocardamine 5 and nocardamine 6, and a diketopiperazine (DKP) 7. The structures of 1–7 were characterized by the analysis of HRESIMS and 1D and 2D NMR data, as well as by comparison with the relevant literature. Three new dehydroxy desferrioxamine derivatives 8–10 were tentatively identified in the molecular network of K. speibonae strain SK5 extracts, and structures were proposed based on their MS/MS fragmentation patterns. A plausible spb biosynthetic pathway was proposed. To the best of our knowledge, this is the first report of the isolation of desferrioxamines from the actinobacterial genus Kribbella. Full article

The present study was conducted to examine the influence of a pathogen Sclerotinia sclerotiorum (Lib.) de Bary on the actinobacterial community associated with the soybean roots. A total of 70 endophytic actinobacteria were isolated from the surface-sterilized roots of either healthy or diseased soybeans, and they were distributed under 14 genera. Some rare genera, including Rhodococcus, Kribbella, Glycomyces, Saccharothrix, Streptosporangium and Cellulosimicrobium, were endemic to the diseased samples, and the actinobacterial community was more diverse in the diseased samples compared with that in the heathy samples. Culture-independent analysis of root-associated actinobacterial community using the high-throughput sequencing approach also showed similar results. Four Streptomyces strains that were significantly abundant in the diseased samples exhibited strong antagonistic activity with the inhibition percentage of 54.1–87.6%. A bioactivity-guided approach was then employed to isolate and determine the chemical identity of antifungal constituents derived from the four strains. One new maremycin analogue, together with eight known compounds, were detected. All compounds showed significantly antifungal activity against S. sclerotiorum with the 50% inhibition (EC₅₀) values of 49.14–0.21 mg/L. The higher actinobacterial diversity and more antifungal strains associated with roots of diseased plants indicate a possible role of the root-associated actinobacteria in natural defense against phytopathogens. Furthermore, these results also suggest that the root of diseased plant may be a potential reservoir of actinobacteria producing new agroactive compounds. Full article