SIDERITE: Unveiling hidden siderophore diversity in the chemical space through digital exploration

Deciphering the δ-Lactam Formation and lron-Reducing Activity of Spinactins from Saccharopolyspora spinosa

The cyclic structure of non-ribosomal peptides (NRPs) is critical for enhancing their stability and bioactivity, which highlights the importance of exploring NRP cyclization enzymes for natural product discovery. Thioesterases (TEs) are crucial enzymes that catalyze the formation of various lactams, including macrolactams, β-lactams, and γ-lactams; however, their potential to produce other lactam types remains largely unexplored. In this study, we identified spinactin A (1) and novel derivatives, spinactin B-E (2-5), from Saccharopolyspora spinosa NRRL 18395 and characterized the biosynthetic enzymes involved, particularly a unique TE SncF, responsible for δ-lactam formation. Remarkably, compound 1 exhibited lower cytotoxicity and superior iron-reducing activity than United States Food and Drug Administration (FDA)-approved iron chelators deferiprone (DFP) and deferoxamine (DFO), indicating its potential for treating iron overload disorders, especially in beta-propeller protein-associated neurodegeneration (BPAN) cells. These findings highlight TEs' roles in expanding the repertoire of δ-lactam-containing NRPs with therapeutic potential.

Regulation of drought stress on nutrient cycle and metabolism of rhizosphere microorganisms in desert riparian forest

Microbial communities in desert riparian forest ecosystems have developed unique adaptive strategies to thrive in harsh habitats shaped by prolonged exposure to abiotic stressors. However, the influence of drought stress on the functional and metabolic characteristics of soil rhizosphere microorganisms remains unknown. Therefore, this study aimed to investigate the effects of drought stress on soil biogeochemistry and metabolism and analyze the relationship between the biogeochemical cycle processes and network of differentially-expressed metabolites. Using metagenomics and metabolomics, this study explored the microbial functional cycle and differential metabolic pathways within desert riparian forests. The predominant biogeochemical cycles in the study area were the Carbon and Nitrogen cycles, comprising 78.90 % of C, N, Phosphorus, Sulfur and Iron cycles. Drought led to increased soil C fixation, reduced C degradation and methane metabolism, weakened denitrification, and decreased N fixation. Furthermore, drought can disrupt iron homeostasis and reduce its absorption. The differential metabolic pathways of drought stress include flavonoid biosynthesis, arachidonic acid metabolism, steroid hormone biosynthesis, and starch and sucrose degradation. Network analysis of functional genes and metabolism revealed a pronounced competitive relationship between the C cycle and metabolic network, whereas the Fe cycle and metabolic network promoted each other, optimizing resource utilization. Partial least squares analysis revealed that drought hindered the expression and metabolic processes and functional genes, whereas the rhizosphere environment facilitated metabolic expression and the functional genes. The rhizosphere effect primarily promoted metabolic processes indirectly through soil enzyme activities. The integrated multi-omics analysis further revealed that the effects of drought and the rhizosphere play a predominant role in shaping soil functional potential and the accumulation of metabolites. These insights deepen our comprehension of desert riparian forest ecosystems and offer strong support for the functionality of nutrient cycling and metabolite dynamics.

Discovery of thiazostatin D/E using UPLC-HR-MS2-based metabolomics and σ-factor engineering of Actinoplanes sp. SE50/110

As the natural producer of acarbose, Actinoplanes sp. SE50/110 has high industrial relevance. Like most Actinobacteria, the strain carries several more putative biosynthetic gene clusters (BGCs) to produce further natural products, which are to be discovered. Applying a metabolomics-guided approach, we tentatively identified five further compounds that are produced by the strain: watasemycin, thiazostatin, isopyochelin, pulicatin, and aerugine. A comparison of the genomic context allowed the identification of the putative BGC, which is highly similar to the watasemycin biosynthetic gene cluster of Streptomyces venezuelae. In addition to the identified molecules, a thiazostatin-like compound was found. Isolation and structure elucidation with 1D and 2D NMR and HRMS were applied. The fraction containing m/z 369.0929 [M + H]+ comprised two highly similar compounds identified as thiazostatin D and thiazostatin E. The compounds possessed the same phenol-thiazole-thiazole molecular scaffold as the previously reported thiazostatin and watasemycin and have anti-proliferative activity against the breast adenocarcinoma cell line MCF7 and human melanoma cell line A2058, while no activity again the non-malignant immortalized fibroblast cell line MRC-5 was observed. We further showed that the manipulation of global transcriptional regulators, with sigH (ACSP50_0507) and anti-anti-σ factor coding ACSP50_0284 as an example, enabled the production manipulation of the 2-hydroxyphenylthiazoline family molecules. While the manipulation of sigH enabled the shift in the peak intensities between the five products of this pathway, ACSP50_0284 manipulation prevented their production. The production of a highly polar compound with m/z 462.1643 [M + H]+ and calculated elemental composition C19H27NO12 was activated under the ACSP50_0284 expression and is exclusively produced by the engineered strain.

Unearthing the soil-bacteria nexus to enhance potassium bioavailability for global sustainable agriculture: A mechanistic preview

Established as a plant macronutrient, potassium (K) substantially bestows plant growth and thus, global food production. It is absorbed by plants as potassium cation (K+) from soil solution, which is enriched through slow-release from soil minerals or addition of soluble fertilizers. Contribution of bioavailable K+ from soil is usually insignificant (< 2 %), although the earth's crust is rich in K-bearing minerals. However, K is fixed largely in interlayer spaces of K-bearing minerals, which can be released by K-solubilizing bacteria (KSB) such as Bacillus, Pseudomonas, Enterobacter, and Acidithiobacillus. The underlying mechanisms of K dissolution by KSB include acidolysis, ion exchange reactions, chelation, complexolysis, and release of various organic and inorganic acids such as citric, oxalic, acetic, gluconic, and tartaric acids. These acids cause disintegration of K-bearing minerals and bring K+ into soil solution that becomes available to the plants. Current literature review updates the scientific information about microbial species, factors, and mechanisms governing the bio-intrusion of K-bearing minerals. Moreover, it explores the potential of KSB not only for K-solubilization but also to enhance bioavailability of phosphorus, nitrogen, and micronutrients, as well as its other beneficial impact on plant growth. Thus, in the context of sustainable agricultural production and global food security, utilization of KSB may facilitate plant nutrient availability, conserve natural resources, and reduce environmental impacts caused by chemical fertilizers.

Exploring the Biological Pathways of Siderophores and Their Multidisciplinary Applications: A Comprehensive Review

Siderophores are a class of small molecules renowned for their high iron binding capacity, essential for all life forms requiring iron. This article provides a detailed review of the diverse classifications, and biosynthetic pathways of siderophores, with a particular emphasis on siderophores synthesized via nonribosomal peptide synthetase (NRPS) and non-NRPS pathways. We further explore the secretion mechanisms of siderophores in microbes and plants, and their role in regulating bioavailable iron levels. Beyond biological functions, the applications of siderophores in medicine, agriculture, and environmental sciences are extensively discussed. These applications include biological pest control, disease treatment, ecological pollution remediation, and heavy metal ion removal. Through a comprehensive analysis of the chemical properties and biological activities of siderophores, this paper demonstrates their wide prospects in scientific research and practical applications, while also highlighting current research gaps and potential future directions.