identifying-amino-acid-overproducers-using-rare-codon-rich-markers

Identifying Amino Acid Overproducers Using Rare-Codon-Rich Markers

To satisfy the ever-growing market for amino acids, high-performance production strains are needed. The amino acid overproducers are conventionally ...

effects-desmodium-caudatum-on-gastrointestinal-hormones-intestinal

Effects of <i>Desmodium caudatum </i> on Gastrointestinal Hormones and Intestinal Flora in Rats with Gastritis

In order to preliminarily explore the effects of Desmodium caudatum on gastritis and intestinal flora in rats, a chronic gastritis rat model was ...

beijing institute of technology

The Traditional Chinese Medicine Hospital of Beichuan Qiang Autonomous County

The carbon and energy needed for bioconversion processes face trade-offs between cell reproduction and chemical synthesis. In most processes, microbial cells containing overexpressed pathway enzymes were accumulated in exponential phase before the productions of value-added chemicals dominate the carbon and energy fluxes in stationary phase. The pathway enzymes need to be continuously supplied to compensate their degradation, but the promoters driving their overexpressions are downregulated under stationary phase or stressed conditions. In this study, the gadA promoter enabled stress-resistant and growth phase-independent isobutanol production up to 10-28 g l. To investigate the activation mechanism of gadA promoter and its potential in metabolic engineering, an in vitro transcription system was established. Results showed that gadA promoter could be transcribed efficiently under environments that inhibit the transcription of ribosomal promoters, while under moderate to rapid growth conditions, the large majority of new cellular transcripts are ribosomal. This differential transcription relies on the accumulation of environmental glutamate and/or the loss of supercoiling. These results implied that the gadA promoter could be functional or even dominate the cellular transcription under an exceedingly wide range of physiological conditions. Therefore, the gadA promoter is a novel candidate for driving pathway enzyme overexpressions under not only exponential phase but also stationary phase and stressed conditions, which is important for achieving efficient biofuel production.

Biofuel production with a stress-resistant and growth phase-independent promoter: mechanism revealed by in vitro transcription assays.

The translation of rare codons relies on their corresponding rare tRNAs, which could not be fully charged under amino acid starvation. Theoretically, disrupted or retarded translation caused by the lack of charged rare tRNAs can be partially restored by feeding or intracellular synthesis of the corresponding amino acids. Inspired by this assumption, we develop a screening or selection system for obtaining overproducers of a target amino acid by replacing its common codons with the corresponding synonymous rare alternative in the coding sequence of selected reporter proteins or antibiotic-resistant markers. Results show that integration of rare codons can inhibit gene translations in a frequency-dependent manner. As a proof-of-concept, Escherichia coli strains overproducing L-leucine, L-arginine or L-serine are successfully selected from random mutation libraries. The system is also applied to Corynebacterium glutamicum to screen out L-arginine overproducers. This strategy sheds new light on obtaining and understanding amino acid overproduction strains.

Utilization of rare codon-rich markers for screening amino acid overproducers.

Nanozymes with excellent enzyme-mimicking catalytic property are playing an increasingly significant role in tumor diagnosis and therapy. Fe-metal organic framework nanoparticles (MIL-101(Fe) NPs) are prepared as nanozymes to generate reactive oxygen species (ROS) and induce cancer cell death by catalyzing endogenous substances in tumor microenvironment. Abundant stimuli-responsive hydroxyl radicals (·OH) are accelerated to generate in the presence of microwave irradiation, realizing microwave enhancing dynamic therapy (MEDT). Moreover, MIL-101(Fe) NPs possess biodegradability and bioresponsibility, which exhibit favourable properties of metabolism and non-toxic accumulation comparing with inorganic nanozymes. Fluorescent gold nanoclusters (BSA-Au NCs) are rapidly coupled with the surface of MIL-101(Fe) NPs to obtain MIL-101(Fe)@BSA-AuNCs NPs. MIL-101(Fe)@BSA-AuNCs NPs with magnetic resonance imaging (MRI) and fluorescent imaging (FI) not only image accurately for the site of tumor, but also monitor dynamic distribution process of MIL-101(Fe) in vivo. The signal intensity of FI and MRI reaches maximum at 1 h in the liver and 5 h in the tumor. Ionic liquid (IL) is also loaded into MIL-101(Fe)@BSA-AuNCs NPs as microwave sensitive reagents for microwave thermal therapy (MTT). This work synthesizes the nanozymes that possess degradability, microwave sensitivity and dual-mode imaging to achieve the combination of MTT and MEDT against tumor. Experiment result in vivo confirms that the kill rate of tumor is up to 96.65%, showing an outstanding anti-tumor efficacy.

ArticleTotal : 2	Year
Publication title Cited by 5	2019
Publication title Cited by 1	2024

Article	Year
Biofuel production with a stress-resistant and growth phase-independent promoter: mechanism revealed by in vitro transcription assays. Applied microbiology and biotechnology\| PubMed ID: 29442168	2018
Utilization of rare codon-rich markers for screening amino acid overproducers. Nature communications\| PubMed ID: 30190534	2018
Multifunctional iron-based Metal-Organic framework as biodegradable nanozyme for microwave enhancing dynamic therapy. Biomaterials\| PubMed ID: 31174065	2019

Xiaoyan Ma

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