Project description:Background. Transforming waste and non-food materials into bulk biofuels and chemicals represents a major stride in creating a sustainable bioindustry, optimizing the use of resources while reducing environmental footprints. Yet, despite these advancements, the production of high-value natural products often continues to rely on first-generation substrates, underscoring the intricate processes and specific requirements of their biosynthesis. This is also true for Streptomyces lividans, a renowned host organism celebrated for its capacity to produce and uncover a wide array of natural products, attributed to its genetic versatility and potent secondary metabolism. Given this context, it becomes imperative to assess and optimize this microorganism for the synthesis of natural products specifically from waste and non-food substrates. Results. We metabolically engineered S. lividans TK24 to heterologously produce the ribosomally synthesized and post-translationally modified peptide, bottromycin, as well as the polyketide, pamamycin. The modified strains successfully produced these compounds using waste and non-food model substrates like protocatechuate (derived from lignin), 4-hydroxybenzoate (sourced from plastic waste), and mannitol (from seaweed). Comprehensive transcriptomic and metabolomic analyses offered insights into how these substrates influenced the cellular metabolism of S. lividans. When evaluating production efficiency, S. lividans showcased remarkable tolerance, especially in a fed-batch process using a mineral medium containing the toxic aromatic 4-hydroxybenzoate, leading to enhanced and highly selective bottromycin production. Additionally, it generated a unique spectrum of pamamycins when cultured in mannitol-rich seaweed extract without the need for added nutrients. Conclusion. Our study showcases the successful production of high-value natural products using varied waste and non-food raw materials, thereby circumventing the reliance on costly, food-competing resources. S. lividans exhibited remarkable adaptability and resilience across these diverse substrates. When cultured on aromatic compounds, it displayed a distinct array of intracellular CoA esters, presenting promising avenues for polyketide production. Future research could focus on enhancing S. lividans' substrate utilization pathways to more efficiently process the intricate mixtures commonly found in waste and non-food sources.
Project description:Abstract: The Army is replacing traditional munitions with insensitive munitions (IM) resistant to accidental detonation. Although the parent IM compound nitroguanidine (NQ) is generally not acutely toxic at concentrations >1000 mg/L in aquatic exposures, products formed by intensive UV-degradation resulted in of multiple-order of magnitude increase in toxicity. A methylated congener of NQ, 1-methyl-3-nitroguanidine (MeNQ), is also being assessed for potential use in IM explosive formulations and consequently was here investigated for UV-degradation hazard and bioaccumulation potential. While up to 716 mg/L parent MeNQ caused no significant mortality or effects on growth in in larval P. promelas in 7-d exposures, the same concentration of MeNQ subjected to UV-treatment resulted in 85% mortality. The UV-treatment degraded only 3.3% of the MeNQ (5,800 mg/L stock, UV-treated for 6h at UV 12x > sunlight), indicating that MeNQ degradation products have potentially high potency. The parent MeNQ exposure decreased transcriptional expression of genes within the significantly enriched insulin metabolic pathway suggesting antagonism of bioenergetics pathways which compliments observed, although non-significant, decreases in body weights. Transcriptional expression in the UV-degraded MeNQ exposures resulted in significant enrichment of pathways and functions related to cell cycle, but also erythrocyte function related to O2/CO2 exchange. These functions likely represent the mechanistic source(s) of increased toxicity observed in the UV-degraded MeNQ exposures, which are distinct from previously observed mechanisms underlying increased UV-degraded NQ toxicity in fish.
Project description:The production of lignocellulosic-derived biofuels is a highly promising source of alternative energy, but it has been constrained by the lack of a microbial platform capable to efficiently degrade this recalcitrant material and cope with by-products that can be toxic to cells. Species that naturally grow in environments where carbon is mainly available as lignin are promising for finding new ways of removing the lignin that protects cellulose for improved conversion of lignin to fuel precursors.
Project description:Microarrays have become established tools for describing microbial systems, however the assessment of expression profiles for environmental microbial communities still presents unique challenges. Notably, the concentration of particular transcripts are likely very dilute relative to the pool of total RNA, and PCR-based amplification strategies are vulnerable to amplification biases and the appropriate primer selection. Thus, we apply a signal amplification approach, rather than template amplification, to analyze the expression of selected lignin-degrading enzymes in soil. Controls in the form of known amplicons and cDNA from Phanerochaete chrysosporium were included and mixed with the soil cDNA both before and after the signal amplification in order to assess the dynamic range of the microarray. We demonstrate that restored prairie soil expresses a diverse range of lignin-degrading enzymes following incubation with lignin substrate, while farmed agricultural soil does not. The mixed additions of control cDNA with soil cDNA indicate that the mixed biomass in the soil does interfere with low abundance transcript changes, nevertheless our microarray approach consistently reports the most robust signals. Keywords: comparative analysis, microbial ecology, soil microbial communities We used lignin degradation as a model process to demonstrate the use of an oligonucleotide microarray for directly detecting gene expression in soil communities using signal amplification instead of template amplification to avoid the introduction of PCR bias. In the current study, we analyzed mRNA isolated from two distinct soil microbial communities and demonstrate our ability to detect the expression of a small subset of lignin degrading genes following exposure to a lignitic substrate. We also included purified control amplicons and mixed target experiments with pure P. chrysosporium genomic cDNA to determine the level of interference from soil biomass on target hybridization.
Project description:Lignin is a biopolymer found in plant cell walls that accounts for 30% of the organic carbon in the biosphere. White-rot fungi (WRF) are considered the most efficient organisms at degrading lignin in Nature. While lignin depolymerization by WRF has been exhaustively studied, the possibility that WRF are able to utilize lignin as a carbon source is still a matter of controversy. Here we employ 13C-labeling and systems biology approaches to demonstrate that two WRF, Trametes versicolor and Gelatoporia subvermispora, funnel lignin-derived aromatic compounds into central carbon metabolism via intracellular catabolic pathways. These results provide insights into global carbon cycling in soil ecosystems, and furthermore establishes a foundation for employing WRF in simultaneous lignin depolymerization and bioconversion to bioproducts – a key step towards enabling a sustainable bioeconomy.
Project description:Drought is a major environmental constraint affecting physiological, biochemical and molecular changes of crops, causing loss in crop productivities. Understanding the molecular mechanisms of drought tolerance is important for crop biotechnology. Here, we report that the rice (Oryza sativa) homeodomain-leucine zipper class IV transcription factor gene, Rice outermost cell-specific gene 10 (Roc10), improves drought tolerance and grain yield by increasing lignin accumulation in ground tissues of rice plants. Overexpression of Roc10 significantly enhanced drought tolerance of transgenic rice plants at the vegetative stages of growth with highly effective photosystem and reduction of water loss rate as compared with non-transgenic control and RNAi plants. More importantly, Roc10 overexpression plants had higher drought tolerance at the reproductive stage of growth with higher grain yield over controls under field-drought conditions. We identified downstream and putative target genes of Roc10 by using RNA-seq and ChIP-seq data of rice shoots. Roc10 overexpression elevated the expression levels of lignin biosynthetic genes in shoots with a concomitant increase in accumulation of lignin. The overexpression and RNAi lines showed opposite patterns of lignin accumulation. The Roc10 is mainly expressed in the outer cell layers including epidermis and vasculature of shoots that coincides with areas of increased lignification. Furthermore, the Roc10 was found to directly bind to the promoter of PEROXIDASEN/PEROXIDASE38, a key gene in lignin biosynthesis. Together, our findings suggested that the Roc10 confers drought stress tolerance by enhancing lignin biosynthesis in ground tissues of rice plants.
Project description:Drought is a major environmental constraint affecting physiological, biochemical and molecular changes of crops, causing loss in crop productivities. Understanding the molecular mechanisms of drought tolerance is important for crop biotechnology. Here, we report that the rice (Oryza sativa) homeodomain-leucine zipper class IV transcription factor gene, Rice outermost cell-specific gene 10 (Roc10), improves drought tolerance and grain yield by increasing lignin accumulation in ground tissues of rice plants. Overexpression of Roc10 significantly enhanced drought tolerance of transgenic rice plants at the vegetative stages of growth with highly effective photosystem and reduction of water loss rate as compared with non-transgenic control and RNAi plants. More importantly, Roc10 overexpression plants had higher drought tolerance at the reproductive stage of growth with higher grain yield over controls under field-drought conditions. We identified downstream and putative target genes of Roc10 by using RNA-seq and ChIP-seq data of rice shoots. Roc10 overexpression elevated the expression levels of lignin biosynthetic genes in shoots with a concomitant increase in accumulation of lignin. The overexpression and RNAi lines showed opposite patterns of lignin accumulation. The Roc10 is mainly expressed in the outer cell layers including epidermis and vasculature of shoots that coincides with areas of increased lignification. Furthermore, the Roc10 was found to directly bind to the promoter of PEROXIDASEN/PEROXIDASE38, a key gene in lignin biosynthesis. Together, our findings suggested that the Roc10 confers drought stress tolerance by enhancing lignin biosynthesis in ground tissues of rice plants.