Hepatocyte-specific Selenoi deficiency predisposes mice to hepatic steatosis and obesity.

Selenoprotein I (Selenoi) is highly expressed in liver and plays a key role in lipid metabolism as a phosphatidylethanolamine (PE) synthase. However, the precise function of Selenoi in the liver remains elusive. In the study, we generated hepatocyte-specific Selenoi conditional knockout (cKO) mice on a high-fat diet to identify the physiological function of Selenoi. The cKO group exhibited a significant increase in body weight, with a 15.6% and 13.7% increase in fat accumulation in white adipose tissue (WAT) and the liver, respectively. Downregulation of the lipolysis-related protein (p-Hsl) and upregulation of the adipogenesis-related protein (Fasn) were observed in the liver of cKO mice. The cKO group also showed decreased oxygen consumption (VO2), carbon dioxide production (VCO2), and energy expenditure (p < .05). Moreover, various metabolites of the steroid hormone synthesis pathway were affected in the liver of cKO mice. A potential cascade of Selenoi-phosphatidylethanolamine-steroid hormone synthesis might serve as a core mechanism that links hepatocyte-specific Selenoi cKO to biochemical and molecular reactions. In conclusion, we revealed that Selenoi inhibits body fat accumulation and hepatic steatosis and elevates energy consumption; this protein could also be considered a therapeutic target for such related diseases.

CAVE: a cloud-based platform for analysis and visualization of metabolic pathways.

Flux balance analysis (FBA) is an important method for calculating optimal pathways to produce industrially important chemicals in genome-scale metabolic models (GEMs). However, for biologists, the requirement of coding skills poses a significant obstacle to using FBA for pathway analysis and engineering target identification. Additionally, a time-consuming manual drawing process is often needed to illustrate the mass flow in an FBA-calculated pathway, making it challenging to detect errors or discover interesting metabolic features. To solve this problem, we developed CAVE, a cloud-based platform for the integrated calculation, visualization, examination and correction of metabolic pathways. CAVE can analyze and visualize pathways for over 100 published GEMs or user-uploaded GEMs, allowing for quicker examination and identification of special metabolic features in a particular GEM. Additionally, CAVE offers model modification functions, such as gene/reaction removal or addition, making it easy for users to correct errors found in pathway analysis and obtain more reliable pathways. With a focus on the design and analysis of optimal pathways for biochemicals, CAVE complements existing visualization tools based on manually drawn global maps and can be applied to a broader range of organisms for rational metabolic engineering. CAVE is available at https://cave.biodesign.ac.cn/.

Benchmarking of long-read sequencing, assemblers and polishers for yeast genome.

BACKGROUND: The long reads of the third-generation sequencing significantly benefit the quality of the de novo genome assembly. However, its relatively high single-base error rate has been criticized. Currently, sequencing accuracy and throughput continue to improve, and many advanced tools are constantly emerging. PacBio HiFi sequencing and Oxford Nanopore Technologies (ONT) PromethION are two up-to-date platforms with low error rates and ultralong high-throughput reads. Therefore, it is urgently needed to select the appropriate sequencing platforms, depths and genome assembly tools for high-quality genomes in the era of explosive data production. METHODS: We performed 455 (7 assemblers with 4 polishing pipelines or without polishing on 13 subsets with different depths) and 88 (4 assemblers with or without polishing on 11 subsets with different depths) de novo assemblies of Yeast S288C on high-coverage ONT and HiFi datasets, respectively. The assembly quality was evaluated by Quality Assessment Tool (QUAST), Benchmarking Universal Single-Copy Orthologs (BUSCO) and the newly proposed Comprehensive_score (C_score). In addition, we applied four preferable pipelines to assemble the genome of nonreference yeast strains. RESULTS: The assembler plays an essential role in genome construction, especially for low-depth datasets. For ONT datasets, Flye is superior to other tools through C_score evaluation. Polishing by Pilon and Medaka improve accuracy and continuity of the preassemblies, respectively, and their combination pipeline worked well in most quality metrics. For HiFi datasets, Flye and NextDenovo performed better than other tools, and polishing is also necessary. Enough data depth is required for high-quality genome construction by ONT (>80X) and HiFi (>20X) datasets.

Tri©DB: an integrated platform of knowledgebase and reporting system for cancer precision medicine.

BACKGROUND: With the development of cancer precision medicine, a huge amount of high-dimensional cancer information has rapidly accumulated regarding gene alterations, diseases, therapeutic interventions and various annotations. The information is highly fragmented across multiple different sources, making it highly challenging to effectively utilize and exchange the information. Therefore, it is essential to create a resource platform containing well-aggregated, carefully mined, and easily accessible data for effective knowledge sharing. METHODS: In this study, we have developed "Consensus Cancer Core" (Tri©DB), a new integrative cancer precision medicine knowledgebase and reporting system by mining and harmonizing multifaceted cancer data sources, and presenting them in a centralized platform with enhanced functionalities for accessibility, annotation and analysis. RESULTS: The knowledgebase provides the currently most comprehensive information on cancer precision medicine covering more than 40 annotation entities, many of which are novel and have never been explored previously. Tri©DB offers several unique features: (i) harmonizing the cancer-related information from more than 30 data sources into one integrative platform for easy access; (ii) utilizing a variety of data analysis and graphical tools for enhanced user interaction with the high-dimensional data; (iii) containing a newly developed reporting system for automated annotation and therapy matching for external patient genomic data. Benchmark test indicated that Tri©DB is able to annotate 46% more treatments than two officially recognized resources, oncoKB and MCG. Tri©DB was further shown to have achieved 94.9% concordance with administered treatments in a real clinical trial. CONCLUSIONS: The novel features and rich functionalities of the new platform will facilitate full access to cancer precision medicine data in one single platform and accommodate the needs of a broad range of researchers not only in translational medicine, but also in basic biomedical research. We believe that it will help to promote knowledge sharing in cancer precision medicine. Tri©DB is freely available at www.biomeddb.org , and is hosted on a cutting-edge technology architecture supporting all major browsers and mobile handsets.

An Integrative Analysis Framework for Identifying the Prognostic Markers from Multidimensional RNA Data of Clear Cell Renal Cell Carcinoma.

The altered regulatory status of long noncoding RNA (lncRNA), miRNA, and mRNA and their interactions play critical roles in tumor proliferation, metastasis, and progression, which ultimately influence cancer prognosis. However, there are limited studies of comprehensive identification of prognostic biomarkers from combined data sets of the three RNA types in the highly metastatic clear cell renal cell carcinoma (ccRCC). The current study employed an integrative analysis framework of functional genomics approaches and machine learning methods to the lncRNA, miRNA, and mRNA data and identified 16 RNAs (3 lncRNAs, 6 miRNAs, and 7 mRNAs) of prognostic value, with 9 of them novel. A 16 RNA-based score was established for prognosis prediction of ccRCC with significance (P < 0.0001). The area under the curve for the score model was 0.868 to 0.870 in the training cohort and 0.714 to 0.778 in the validation cohort. Construction of the lncRNA-miRNA-mRNA interaction network showed that the downstream mRNAs and upstream lncRNAs in the network initiated from the miRNA or lncRNA markers exhibit significant enrichment in functional classifications associated with cancer metastasis, proliferation, progression, or prognosis. The functional analysis provided clear support for the role of the RNA biomarkers in predicting cancer prognosis. This study provides promising biomarkers for predicting prognosis of ccRCC using multidimensional RNA data, and these findings are expected to facilitate potential clinical applications of the biomarkers.

Transcription factor DegU-mediated multi-pathway regulation on lichenysin biosynthesis in Bacillus licheniformis.

Lichenysin, producted by Bacillus licheniformis, is an important cyclic lipopeptide biosurfactant, which has potential applications in oil exploitation, drug development, biological control of agriculture and bioremediation. While studies are lacking on metabolism regulation of lichenysin biosynthesis, which limits metabolic engineering and large-scale production of lichenysin. In this study, the yield of lichenysin was improved obviously by 13.6 folds to 2.18 ± 0.03 g/L in degU deletion strain (WX02△degU) compared with the wild-type strain (WX02) and completely inhibited in degU overexpressed strain (WX02/pHY-degU). We further proved that DegU, a transcription factor plays a significant role in multicellular behavior, is a key negative regulator of lichenysin synthesis lchA operon. But interestingly, lichenysin yield was still inhibited by overexpressing DegU in the promoter-substituted strain (WX02-PP43lch), in which promoter of lchA operon cannot be controlled by DegU. Thus, through 13C-metabolic flux analysis, we found that deletion of degU also enhanced glucose uptake, branched chain amino acid synthesis, and fatty acid synthesis, while decrease acetoin synthesis, which is beneficial for the supply of lichenysin precursors. Further experiments demonstrate that DegU regulates these pathways by binding to the promoter regions of related genes. Overall, we systematically investigated the multi-pathway regulation network mediated by DegU on lichenysin biosynthesis, which not only contributes to the further metabolic engineering for lichenysin high-production, but sheds light on studies of transcription factor regulation.

Multilevel metabolic engineering of Bacillus licheniformis for de novo biosynthesis of 2-phenylethanol.

Due to its pleasant rose-like scent, 2-phenylethanol (2-PE) has been widely used in the fields of cosmetics and food. Microbial production of 2-PE offers a natural and sustainable production process. However, the current bioprocesses for de novo production of 2-PE suffer from low titer, yield, and productivity. In this work, a multilevel metabolic engineering strategy was employed for the high-level production of 2-PE. Firstly, the native alcohol dehydrogenase YugJ was identified and characterized for 2-PE production via genome mining and gene function analysis. Subsequently, the redirection of carbon flux into 2-PE biosynthesis by combining optimization of Ehrlich pathway, central metabolic pathway, and phenylpyruvate pathway enabled the production of 2-PE to a titer of 1.81 g/L. Specifically, AroK and AroD were identified as the rate-limiting enzymes of 2-PE production through transcription and metabolite analyses, and overexpression of aroK and aroD efficiently boosted 2-PE synthesis. The precursor competing pathways were blocked by eliminating byproduct formation pathways and modulating the glucose transport system. Under the optimal condition, the engineered strain PE23 produced 6.24 g/L of 2-PE with a yield and productivity of 0.14 g/g glucose and 0.13 g/L/h, respectively, using a complex medium in shake flasks. This work achieves the highest titer, yield, and productivity of 2-PE from glucose via the phenylpyruvate pathway. This study provides a promising platform that might be widely useful for improving the production of aromatic-derived chemicals.

Deciphering Molecular Mechanism Underlying Self-Flocculation of Zymomonas mobilis for Robust Production.

Zymomonas mobilis metabolizes sugar anaerobically through the Entner-Doudoroff pathway with less ATP generated for lower biomass accumulation to direct more sugar for product formation with improved yield, making it a suitable host to be engineered as microbial cell factories for producing bulk commodities with major costs from feedstock consumption. Self-flocculation of the bacterial cells presents many advantages, such as enhanced tolerance to environmental stresses, a prerequisite for achieving high product titers by using concentrated substrates. ZM401, a self-flocculating mutant developed from ZM4, the unicellular model strain of Z. mobilis, was employed in this work to explore the molecular mechanism underlying this self-flocculating phenotype. Comparative studies between ZM401 and ZM4 indicate that a frameshift caused by a single nucleotide deletion in the poly-T tract of ZMO1082 fused the putative gene with the open reading frame of ZMO1083, encoding the catalytic subunit BcsA of the bacterial cellulose synthase to catalyze cellulose biosynthesis. Furthermore, the single nucleotide polymorphism mutation in the open reading frame of ZMO1055, encoding a bifunctional GGDEF-EAL protein with apparent diguanylate cyclase/phosphodiesterase activities, resulted in the Ala526Val substitution, which consequently compromised in vivo specific phosphodiesterase activity for the degradation of cyclic diguanylic acid, leading to intracellular accumulation of the signaling molecule to activate cellulose biosynthesis. These discoveries are significant for engineering other unicellular strains from Z. mobilis with the self-flocculating phenotype for robust production. IMPORTANCE Stress tolerance is a prerequisite for microbial cell factories to be robust in production, particularly for biorefinery of lignocellulosic biomass to produce biofuels, bioenergy, and bio-based chemicals for sustainable socioeconomic development, since various inhibitors are released during the pretreatment to destroy the recalcitrant lignin-carbohydrate complex for sugar production through enzymatic hydrolysis of the cellulose component, and their detoxification is too costly for producing bulk commodities. Although tolerance to individual stress has been intensively studied, the progress seems less significant since microbial cells are inevitably suffering from multiple stresses simultaneously under production conditions. When self-flocculating, microbial cells are more tolerant to multiple stresses through the general stress response due to enhanced quorum sensing associated with the morphological change for physiological and metabolic advantages. Therefore, elucidation of the molecular mechanism underlying such a self-flocculating phenotype is significant for engineering microbial cells with the unique multicellular morphology through rational design to boost their production performance.

Differential analysis of ergosterol function in response to high salt and sugar stress in Zygosaccharomyces rouxii.

Zygosaccharomyces rouxii is an osmotolerant and halotolerant yeast that can participate in fermentation. To understand the mechanisms of salt and sugar tolerance, the transcription levels of Z. rouxii M 2013310 under 180 g/L NaCl stress and 600 g/L glucose stress were measured. The transcriptome analysis showed that 2227 differentially expressed genes (DEGs) were identified under 180 g/L NaCl stress, 1530 DEGs were identified under 600 g/L glucose stress, and 1278 DEGs were identified under both stress conditions. Then, KEGG enrichment analyses of these genes indicated that 53.3% of the upregulated genes were involved in the ergosterol synthesis pathway. Subsequently, quantitative PCR was used to verify the results, which showed that the genes of the ergosterol synthesis pathway were significantly upregulated under 180 g/L NaCl stress. Finally, further quantitative testing of ergosterol and spotting assays revealed that Z. rouxii M 2013310 increased the amount of ergosterol in response to high salt stress. These results highlighted the functional differences in ergosterol under sugar stress and salt stress, which contributes to our understanding of the tolerance mechanisms of salt and sugar in Z. rouxii.

The potential use of Zymomonas mobilis for the food industry.

Zymomonas mobilis is a gram-negative facultative anaerobic spore, which is generally recognized as a safe. As a promising ethanologenic organism for large-scale bio-ethanol production, Z. mobilis has also shown a good application prospect in food processing and food additive synthesis for its unique physiological characteristics and excellent industrial characteristics. It not only has obvious advantages in food processing and becomes the biorefinery chassis cell for food additives, but also has a certain healthcare effect on human health. Until to now, most of the research is still in theory and laboratory scale, and further research is also needed to achieve industrial production. This review summarized the physiological characteristics and advantages of Z. mobilis in food industry for the first time and further expounds its research status in food industry from three aspects of food additive synthesis, fermentation applications, and prebiotic efficacy, it will provide a theoretical basis for its development and applications in food industry. This review also discussed the shortcomings of its practical applications in the current food industry, and explored other ways to broaden the applications of Z. mobilis in the food industry, to promote its applications in food processing.

Potential applications of Zymomonas mobilis in food industry summarized for the first time.Research status of Z. mobilis in food additive synthesis, fermentation applications, and probiotics are discussed in details.Future research perspectives of Z. mobilis in food industry further proposed.

Evolutionary and reverse engineering in Saccharomyces cerevisiae reveals a Pdr1p mutation-dependent mechanism for 2-phenylethanol tolerance.

BACKGROUND: 2-Phenylethanol (2-PE), a higher alcohol with a rose-like odor, inhibits growth of the producer strains. However, the limited knowledge regarding 2-PE tolerance mechanisms renders our current knowledge base insufficient to inform rational design. RESULTS: To improve the growth phenotype of Saccharomyces cerevisiae under a high 2-PE concentration, adaptive laboratory evolution (ALE) was used to generate an evolved 19-2 strain. Under 2-PE stress, its OD600 and growth rate increased by 86% and 22% than that of the parental strain, respectively. Through whole genome sequencing and reverse engineering, transcription factor Pdr1p mutation (C862R) was revealed as one of the main causes for increased 2-PE tolerance. Under 2-PE stress condition, Pdr1p mutation increased unsaturated fatty acid/saturated fatty acid ratio by 42%, and decreased cell membrane damage by 81%. Using STRING website, we identified Pdr1p interacted with some proteins, which were associated with intracellular ergosterol content, reactive oxygen species (ROS), and the ATP-binding cassette transporter. Also, the results of transcriptional analysis of genes encoded these proteins confirmed that Pdr1p mutation induced the expression of these genes. Compared with those of the reference strain, the ergosterol content of the PDR1_862 strain increased by 72%-101%, and the intracellular ROS concentration decreased by 38% under 2-PE stress. Furthermore, the Pdr1p mutation also increased the production of 2-PE (11% higher). CONCLUSIONS: In the present work, we have demonstrated the use of ALE as a powerful tool to improve yeast tolerance to 2-PE. Based on the reverse engineering, transcriptional and physiological analysis, we concluded that Pdr1p mutation significantly enhanced the 2-PE tolerance of yeast by regulating the fatty acid proportion, intracellular ergosterol and ROS. It provides new insights on Pdr1p mediated 2-PE tolerance, which could help in the design of more robust yeasts for natural 2-PE synthesis.

Transcriptomic profiling of nitrogen fixation and the role of NifA in Methylomicrobium buryatense 5GB1.

Methanotrophs capable of converting C1-based substrates play an important role in the global carbon cycle. As one of the essential macronutrient components in the medium, the uptake of nitrogen sources severely regulates the cell's metabolism. Although the feasibility of utilizing nitrogen gas (N2) by methanotrophs has been predicted, the mechanism remains unclear. Herein, the regulation of nitrogen fixation by an essential nitrogen-fixing regulator (NifA) was explored based on transcriptomic analyses of Methylomicrobium buryatense 5GB1. A deletion mutant of the nitrogen global regulator NifA was constructed, and the growth of M. buryatense 5GB1ΔnifA exhibited significant growth inhibition compared with wild-type strain after the depletion of nitrate source in the medium. Our transcriptome analyses elucidated that 22.0% of the genome was affected in expression by NifA in M. buryatense 5GB1. Besides genes associated with nitrogen assimilation such as nitrogenase structural genes, genes related to cofactor biosynthesis, electron transport, and post-transcriptional modification were significantly upregulated in the presence of NifA to enhance N2 fixation; other genes related to carbon metabolism, energy metabolism, membrane transport, and cell motility were strongly modulated by NifA to facilitate cell metabolisms. This study not only lays a comprehensive understanding of the physiological characteristics and nitrogen metabolism of methanotrophs, but also provides a potentially efficient strategy to achieve carbon and nitrogen co-utilization.Key points• N2 fixation ability of M. buryatense 5GB1 was demonstrated for the first time in experiments by regulating the supply of N2.• NifA positively regulates nif-related genes to facilitate the uptake of N2 in M. buryatense 5GB1.• NifA regulates a broad range of cellular functions beyond nif genes in M. buryatense 5GB1.

Rapamycin enhanced the production of 2-phenylethanol during whole-cell bioconversion by yeast.

2-Phenylethanol (2-PE), a higher alcohol with a rose-like odor, has been widely utilized in food, perfume, and beverages. Saccharomyces cerevisiae is one of the most promising microorganisms for the biosynthesis of natural 2-PE. However, the growth of S. cerevisiae is generally inhibited by 2-PE, which makes its production in yeast cell factories challenging. Here, the whole-cell bioconversion was used to avert growth inhibition, leading to an increase in the concentration and productivity of 2-PE. Moreover, rapamycin (Rap) addition further improved the efficiency of 2-PE synthesis. The concentration of 2-PE (2.20 g/L) was 1.68-fold higher than that in the absence of Rap during the whole-cell bioconversion by S. cerevisiae BY4741. RT-qPCR results showed that Rap addition increased the transcription of ARO9, ARO10, ADH2, GAP1, ARO80, GLN3, and GDH2. When the GLN3 was knocked out, the transcriptional levels of the genes were dramatically decreased, and the concentration of 2-PE significantly decreased to 0.21 g/L. The results indicated that Rap enhanced the flux of the Ehrlich pathway, and Gln3 exerted a central role in the regulation of Rap. Furthermore, commercial yeast (S. cerevisiae FY202001) was selected to verify the applicability of Rap. In the presence of Rap, 3.67 g/L 2-PE was obtained by whole-cell bioconversion in flask, which was increased by 9% than that in the absence of Rap. Finally, the 2-PE titer reached 4.93 g/L by whole-cell bioconversion in a 5 L bioreactor, with a yield of 84 mol% from L-phenylalanine and a productivity of 0.103 g/L h, which was far higher than that of the currently reported in S. cerevisiae. These findings provided a new idea for the efficient synthesis of 2-PE. KEY POINTS: • Whole-cell bioconversion was used to produce 2-PE. • The regulation of the Ehrlich pathway by Rap provides a theoretical basis for developing an effective yeast cell factory to produce 2-PE. • The 2-PE productivity of 0.103 g/L h is far higher than that of the currently reported in S. cerevisiae .

Curcumin: A review of experimental studies and mechanisms related to periodontitis treatment.

Curcumin is the main active ingredient of turmeric, which has a wide range of pharmacological effects, including antitumor, antibacterial, anti-inflammatory, anti-oxidation, immune regulation, and so on. Periodontitis is a prevalent oral inflammatory disease caused by a variety of factors. In recent years, many studies have shown that curcumin has a potential role on the treatment of periodontitis. Curcumin has been used in research related to the treatment of periodontitis in the form of solution, chip, gel, and capsule. Combined with other periodontitis treatment methods, such as scaling and root planing (SRP) and photodynamic therapy (PDT), can enhance curcumin's efficacy in treating periodontitis. In addition to natural curcumin, chemically modified curcumin, such as 4-phenylaminocarbonyl bis-demethoxy curcumin (CMC 2.24) and 4-methoxycarbonyl curcumin (CMC 2.5), have also been used in animal models of periodontitis. Here, this paper reviews the research progress of curcumin on the treatment of periodontitis and its related mechanisms.

Synthetic counter-selection markers and their application in genetic modification of Synechococcus elongatus UTEX2973.

Due to its robustness to environmental stresses and fast growth, Synechococcus elongatus UTEX2973 is developed as a new model for researches on cyanobacterial molecular biology and biotechnology. However, systematic genetic modifications of S. elongatus UTEX2973 were hindered by the lack of effective genetic manipulation tools, especially available counter-selection markers. Here, six synthetic counter-selection markers (SCOMs) were assembled by fusing six toxin genes from either Escherichia coli or cyanobacteria with a theophylline-inducible promoter. The SCOMs containing SYNPCC7002_G0085 from Synechococcus sp. PCC7002 or mazF from E. coli were proved to be inducible by theophylline in S. elongatus UTEX2973. By using the mazF-based SCOM, the neutral locus 1 and 23 small regulatory RNAs were completely deleted from the genome of S. elongatus UTEX2973 after one round of selection with both kanamycin and theophylline. The genetic tools developed in this work will facilitate future researches on molecular genetics and synthetic biology in S. elongatus UTEX2973. KEY POINTS: • Two inducible counter-selection markers are lethal to S. elongatus UTEX2973. • The counter-selection marker benefits the gene targeting in S. elongatus UTEX2973. • Twentry-three small regulatory RNAs were fully deleted via the novel gene targeting method.

CRISPR-assisted multi-dimensional regulation for fine-tuning gene expression in Bacillus subtilis.

Fine-tuning of gene expression is crucial for protein expression and pathway construction, but it still faces formidable challenges due to the hierarchical gene regulation at multiple levels in a context-dependent manner. In this study, we defined the optimal targeting windows for CRISPRa and CRISPRi of the dCas9-α/ω system, and demonstrated that this system could act as a single master regulator to simultaneously activate and repress the expression of different genes by designing position-specific gRNAs. The application scope of dCas9-ω was further expanded by a newly developed CRISPR-assisted Oligonucleotide Annealing based Promoter Shuffling (OAPS) strategy, which could generate a high proportion of functional promoter mutants and facilitate the construction of effective promoter libraries in microorganisms with low transformation efficiency. Combing OAPS and dCas9-ω, the influences of promoter-based transcription, molecular chaperone-assisted protein folding and protease-mediated degradation on the expression of amylase BLA in Bacillus subtilis were systematically evaluated, and a 260-fold enhancement of BLA production was obtained. The success of the OAPS strategy and dCas9-ω for BLA production in this study thus demonstrated that it could serve as a powerful tool kit to regulate the expression of multiple genes multi-directionally and multi-dimensionally in bacteria.

Characterization and repurposing of the endogenous Type I-F CRISPR-Cas system of Zymomonas mobilis for genome engineering.

Application of CRISPR-based technologies in non-model microorganisms is currently very limited. Here, we reported efficient genome engineering of an important industrial microorganism, Zymomonas mobilis, by repurposing the endogenous Type I-F CRISPR-Cas system upon its functional characterization. This toolkit included a series of genome engineering plasmids, each carrying an artificial self-targeting CRISPR and a donor DNA for the recovery of recombinants. Through this toolkit, various genome engineering purposes were efficiently achieved, including knockout of ZMO0038 (100% efficiency), cas2/3 (100%), and a genomic fragment of >10 kb (50%), replacement of cas2/3 with mCherry gene (100%), in situ nucleotide substitution (100%) and His-tagging of ZMO0038 (100%), and multiplex gene deletion (18.75%) upon optimal donor size determination. Additionally, the Type I-F system was further applied for CRISPRi upon Cas2/3 depletion, which has been demonstrated to successfully silence the chromosomally integrated mCherry gene with its fluorescence intensity reduced by up to 88%. Moreover, we demonstrated that genome engineering efficiency could be improved under a restriction-modification (R-M) deficient background, suggesting the perturbance of genome editing by other co-existing DNA targeting modules such as the R-M system. This study might shed light on exploiting and improving CRISPR-Cas systems in other microorganisms for genome editing and metabolic engineering practices.

Origins and features of pectate lyases and their applications in industry.

Pectate lyase treatment can be an alternative strategy of the chemical processing, which causes severe environmental pollution, and has been broadly studied and applied for diverse industrial applications including textile industry, beverage industry, pulp processing, pectic wastewater pretreatment, and oil extraction. This review gave a brief description of the origins, enzymatic characterizations, structure, and applications of pectate lyases (Pels). Most of the reported pectate lyases are originated from microorganisms with a small number of them from plants and animals. Due to the diverse environments that these microorganisms exist, Pels present diversified features, especially for the range of optimal pH and temperature. The diversified biochemical properties of Pels define their applications in different industries, and the applications of alkaline Pels on cotton bioscouring and ramie degumming in textile industry were focused in this review. This review also discussed the perspectives of the development and applications of Pels. KEY POINTS: • The first review on pectate lyase focusing on biotechnological applications. • Origins, features, structures, applications of pectate lyases reviewed. • Applications of alkaline Pels in textile industry demonstrated. • Perspectives on future development and applications of Pels discussed.

Identification and characterization of ethanol-inducible promoters of Zymomonas mobilis based on omics data and dual reporter-gene system.

Zymomonas mobilis is a model bacterial ethanologen and has been engineered to produce lignocellulosic biofuels and biochemicals such as 2,3-butanediol. We have previously identified promoters of different strengths using systems biology datasets and characterized them using the flow cytometry-based dual reporter-gene system. Here, we further demonstrated the capability of applying the dual reporter-gene system and omics datasets on discovering inducible promoters. Ten candidate ethanol-inducible promoters were identified through omics datasets mining and clustering. Using the dual reporter-gene system, these promoters were characterized under natural growth, ethanol stress, and ethanol-induced condition to investigate the transcriptional strength and ethanol inducibility. The results demonstrated that three promoters of P0405, P0435, and P0038 driving the expression of native genes of ZMO0405, ZMO0435, and ZMO0038, correspondingly, are potential ethanol-responsive promoters and may be growth related. This study not only identified and verified three ethanol-inducible promoters as biological parts, which can be used to synchronize the expression of heterologous pathway genes with the ethanol production process of Z. mobilis, but also demonstrated the power of combining omics datasets and dual reporter-gene system to identify biological parts for metabolic engineering and synthetic biology applications in Z. mobilis and related microorganisms.

Enhanced Biomass and Astaxanthin Production of Haematococcus pluvialis by a Cell Transformation Strategy with Optimized Initial Biomass Density.

: Astaxanthin from H. pluvialis is an antioxidant and presents a promising application in medicine for human health. The two-stage strategy has been widely adopted to produce astaxanthin by the Haematococcus industry and research community. However, cell death and low astaxanthin productivity have seriously affected the stability of astaxanthin production. This study aims to test the effect of cell transformation strategies on the production of astaxanthin from H. pluvialis and determine the optimal initial biomass density (IBD) in the red stage. The experimental design is divided into two parts, one is the vegetative growth experiment and the other is the stress experiment. The results indicated that: (1) the cell transformation strategy of H. pluvialis can effectively reduce cell death occurred in the red stage and significantly increase the biomass and astaxanthin production. (2) Compared with the control group, the cell mortality rate of the red stage in the treatment group was reduced by up to 81.6%, and the biomass and astaxanthin production was increased by 1.63 times and 2.1 times, respectively. (3) The optimal IBD was determined to be 0.5, and the highest astaxanthin content can reach 38.02 ± 2.40 mg·g-1. Thus, this work sought to give useful information that will lead to an improved understanding of the cost-effective method of cultivation of H. pluvialis for natural astaxanthin. This will be profitable for algal and medicine industry players.