Greenberg, I. | Search bioRxiv

bioRxiv2025

Effect of biogel C addition on biochar degradation and microbial activities

Biochar contributes to long-term soil carbon stabilization (C) by acting both as a stable carbon pool and as a sorbent for labile compounds. Biogels from roots and microbes are known to form persistent surface coatings with soil sorbents, where they host microbial hotspots. Yet research has mainly focused on their interactions with minerals. The interactive effects of biogels and biochar on soil carbon dynamics remain largely unexplored. This study aimed to assess the effects of biogel coatings on fresh and aged biochar, particularly under drought, with a focus on biochar degradation and microbial responses. We conducted a three-factorial soil incubation study to examine the effects of fresh and aged biochar, with or without biogel amendment, under two moisture levels (30% and 70% water holding capacity, WHC). Using 14C labelled biochar, we quantified biochar degradation and biochar- induced priming effects by measuring 14CO2respiration, microbial biomass carbon (MBC) and its 14C incorporation, hydrolytic and oxidative enzyme activities, and changes in biochar surface area. Mucilage strongly enhanced microbial incorporation of biochar-derived C, specifically from aged biochar under drought conditions, while the opposite effect was observed in soils amended with fresh biochar. This demonstrates the greater microbial accessibility of aged biochar surfaces and limited use of fresh biochar due to inaccessibility of the hydrophobic surfaces, and in consequence the preference for more easily accessible C sources. Additionally, mucilage significantly reduced the Michaelis Menten constant (Km) of {beta}-glucosidase by up to 58% in soils amended with aged biochar under drought. This indicates that under these conditions, the interaction of the aged biochar with the biogel may have created a unique habitat requiring specific enzyme systems with higher affinity. Our findings highlight the role of mucilage in regulating microbial surface access and thus the decomposition of biochar, particularly under moisture- limited conditions. The synergy between aged biochar and biogels provides a promising new perspective to further enhance biochar-based drought mitigation, specifically for managing microbial activity in drought-prone soils.

ecology↗

bioRxiv2022

Genomic alterations drive brain metastases formation in colorectal cancer: The role of IRS2

Colorectal cancer (CRC) is currently the fourth leading etiology of brain metastasis (BM). Yet, mechanisms supporting the formation of CRC BM are mostly unknown. In order to identify drivers that lead to tropism and adaptation of CRC cells to the brain environment, we analyzed an extensive genomic database, consisting of over 36,000 human CRC primary and metastasis samples. Several genomic alterations specific for BM were noted, among them increased prevalence of insulin receptor substrate 2 (IRS2) amplification, observed in 7.6% of BM, compared to only 2.9% of primary tumors or other metastatic sites (p<7E-05). This observation was validated by Immunohistochemistry studies of human clinical samples, showing increased expression of IRS2 protein in BM. IRS2 is a cytoplasmic adaptor mediating effects of insulin and IGF-1 receptors and is involved in more aggressive behavior of different cancer types. In order to study the ability of IRS2 to promote growth of CRC cells under brain microenvironment conditions, we employed an in vitro system consisting of cultured human astrocytes or their conditioned media. Indeed, IRS2-overexpressed CRC cells survived better and formed larger 3D spheres when grown in brain-mimicking conditions, while IRS2-silenced CRC cells showed a mirror image. Similarly, In vivo studies, using intracranial CRC BM mouse model, demonstrated that IRS2-overexpressed cells generated larger brain lesions, while silencing IRS2 dramatically decreased tumor outgrowth and extended survival. Transcriptomic analysis revealed enrichment of oxidative phosphorylation (OXPHOS) and Wnt/{beta}-catenin pathways by IRS2. Indeed, IRS2-expressing cells showed increased mitochondrial activity and glycolysis-independent viability. Furthermore, IRS2-expressing cells had increased {beta}-catenin transcriptional activity, and either {beta}-catenin inhibition or IRS2 inhibition in IRS2-expressing cells decreased their viability, {beta}-catenin transcriptional activity, and mitochondrial activity. These data suggest involvement of IRS2 in modulating OXPHOS through {beta}-catenin. Exploiting this mechanism as a potential vulnerability allowed us to develop novel treatment strategies against CRC BM. NT219 is a novel IRS1/2 inhibitor already being tested in clinical trials. Treatment of mice harboring CRC BM with NT219 and 5-flourouracil reduced tumor growth and prolonged mice survival. These data reveal, for the first time, the unique genomic profile of CRC BM and imply the IRS2 role in promoting CRC BM. These effects may be mediated, at least in part, by modulation of the {beta}-catenin and OXPHOS pathway. These findings may pave the way for clinical trials evaluation this novel IRS2-based strategy for the treatment of CRC BM. Accession no GSE203017 and here is the link: https://www.ncbi.nlm.nih.gov/geo/query/acc.cgi?acc=GSE203017

cancer biology↗