Engineering Microbiology最新文献

The signal transduction system of microorganisms helps them adapt to changes in their complex living environment. Two-component system (TCS) is a representative signal transduction system that plays a crucial role in regulating cellular communication and secondary metabolism. In Gram-negative bacteria, an unorthodox TCS consisting of histidine kinase protein GacS (initially called LemA) and response regulatory protein GacA is widespread. It mainly regulates various physiological activities and behaviors of bacteria, such as quorum sensing, secondary metabolism, biofilm formation and motility, through the Gac/Rsm (Regulator of secondary metabolism) signaling cascade pathway. The global regulatory ability of GacS/GacA in cell physiological activities makes it a potential research entry point for developing natural products and addressing antibiotic resistance. In this review, we summarize the progress of research on GacS/GacA from various perspectives, including the reaction mechanism, related regulatory pathways, main functions and GacS/GacA-mediated applications. Hopefully, this review will facilitate further research on GacS/GacA and promote its application in regulating secondary metabolism and as a therapeutic target.

Microbial natural products (NPs) and their derivates have been widely used in health care and agriculture during the past few decades. Although large-scale bacterial or fungal (meta)genomic mining has revealed the tremendous biosynthetic potentials to produce novel small molecules, there remains a lack of universal approaches to link NP biosynthetic gene clusters (BGCs) to their associated products at a large scale and speed. In the last ten years, a series of emerging technologies have been established alongside the developments in synthetic biology to engineer cryptic metabolite BGCs and edit host genomes. Diverse computational tools, such as antiSMASH and PRISM, have also been simultaneously developed to rapidly identify BGCs and predict the chemical structures of their products. This review discusses the recent developments and trends pertaining to the accelerated discovery of microbial NPs driven by a wide variety of next-generation synthetic biology approaches, with an emphasis on the in situ activation of silent BGCs at scale, the direct cloning or refactoring of BGCs of interest for heterologous expression, and the synthetic-bioinformatic natural products (syn-BNP) approach for the guided rapid access of bioactive non-ribosomal peptides.

Cellulose degradation results from the synergistic effect of different enzymes, but which enzyme is involved in the initial stage of cellulose degradation is still not well understood. Cellobiohydrolase 2 (CBH2) attached to the conidial surface is possibly associated with the initial stage. However, its specific mechanism is still incompletely known. This study explored the potential role of CBH2 in initiating cellulose degradation using a constitutive overexpression strategy. First, the CBH2-overexpression Trichoderma reesei strains Qgc2–5 and Qrc2–40 were constructed using the constitutive promoters Pgpd1 and PrpS30, respectively. It was found that cbh2 was expressed at a high level under the glucose conditions and was significantly higher than that of the parental strain QM9414 at the early stage of 29 h when cellulose was used as the carbon source. Particularly, the constitutive overexpression of cbh2 caused the strong expression of major cellulase-encoding genes (cbh1, eg1, and eg2) and the rapid decomposition of cellulosic material. Meanwhile, the scanning electron microscope showed that the groove-like structure of the cellulose surface was eroded seriously owing to CBH2 overexpression, which caused the cellulose surface to be smooth. These results showed that the overexpression of CHB2 caused the major cellulase enzymes to be expressed and contributed to cellulose degradation, showing the potential role of CBH2 in the initial stage of the cellulose hydrolytic process.

Essential oil (EO) has significant antifungal activity. However, there is limited information on the mechanism of the synergistic antifungal effect of the effective components of EO against fungi. In the present study, molecular electrostatic potential and molecular docking were used for the first time to investigate the synergistic antifungal mechanism of eugenol and citral small molecule (C_EC) against Penicillium roqueforti. The results showed that the C_EC treatment made the activity of β-(1,3)-glucan synthase (GS) and chitin synthase (CS) decreas by 20.2% and 11.1%, respectively, and the contents of which decreased by 85.0% and 27.9%, respectively compared with the control group. Molecular docking revealed that C_EC small molecules could bind to GS and CS through different amino acid residues, inhibiting their activity and synthesis. The C_EC can combine with tryptophan, tyrosine, and phenylalanine in the cell membrane, causing damage to the cell membrane. The binding sites between small molecules and amino acids were mainly around the OH group. In addition, C_EC affected the energy metabolism system and inhibited the glycolysis pathway. Simultaneously, C_EC treatment reduced the ergosterol content in the cell membrane by 58.2% compared with the control group. Finally, changes in β-galactosidase, metal ion leakage, and relative conductivity confirmed the destruction of the cell membrane, which resulted in the leakage of cell contents. The above results showed that C_EC can kill P. roqueforti by inhibiting energy metabolism and destroying the integrity of the cell membrane.

Microbial fermentation has contributed to 80% of global amino acid production. The key to microbial fermentation is to obtain fermentation strains with high performance to produce target amino acids with a high yield. These strains are primarily derived from screening enormous mutant libraries. Therefore, a high-throughput, rapid, accurate, and universal screening strategy for amino acid overproducers has become a guarantee for obtaining optional amino acid overproducers. In recent years, the rapid development of various novel screening strategies has been witnessed. However, proper analysis and discussion of these innovative technologies are lacking. Here we systematically reviewed recent advances in screening strategies: the auxotrophic-based strategy, the biosensor-based strategy, and the latest translation-based screening strategy. The design principle, application scope, working efficiency, screening accuracy, and universality of these strategies were discussed in detail. The potential for screening nonstandard amino acid overproducers was also analyzed. Guidance for the improvement of future screening strategies is provided in this review, which could expedite the reconstruction of amino acid overproducers and help promote the fermentation industry to reduce cost, increase yield, and improve quality.

Cyclodipeptides are diverse chemical scaffolds that show a broad range of bioactivities relevant for medicine, agriculture, chemical catalysis, and material sciences. Cyclodipeptides can be synthesized enzymatically through two unrelated enzyme families, non-ribosomal peptide synthetases (NRPS) and cyclodipeptide synthases (CDPSs). The chemical diversity of cyclodipeptides is derived from the two amino acid side chains and the modification of those side-chains by cyclodipeptide tailoring enzymes. While a large spectrum of chemical diversity is already known today, additional chemical space - and as such potential new bioactivities - could be accessed by exploring yet undiscovered NRPS and CDPS gene clusters as well as via engineering. Further, to exploit cyclodipeptides for applications, the low yield of natural biosynthesis needs to be overcome. In this review we summarize current knowledge on NRPS and CDPS-based cyclodipeptide biosynthesis, engineering approaches to further diversity the natural chemical diversity as well as strategies for high-yield production of cyclodipeptides, including a discussion of how advancements in synthetic biology and metabolic engineering can accelerate the translational potential of cyclodipeptides.

In recent decades, third-generation (3G) biofuels have become a more attractive method of fuel production, as algae cultivation does not infringe on resources needed for food production. Additionally, algae can adapt to different environments, has high photosynthetic efficiency (CO₂ fixation), and has a high potential for carbohydrate accumulation. The prevalence of algae worldwide demonstrates its ability to adapt to different environments and climates, proving its biodiversity and versatility. Algae can be grown in wastewater, seawater, and even sewage, thus ensuring a lower water footprint and greater energy efficiency during algal biomass production. Because of this, the optimization of 3G ethanol production appears to be an excellent alternative to mitigate environmental impacts and increase energy and food security. This critical review presents (i) the stages of cultivation and processing of micro and macroalgae; (ii) the selection of yeasts (through engineering and/or bioprospecting) to produce ethanol from these biomasses; (iii) the potential of seawater-based facilities to reduce water footprint; and (iv) the mass and energy balances of 3G ethanol production in the world energy matrix. This article is, above all, a brainstorm on the environmental viability of algae bioethanol.

Predicting biodiversity and dynamics of complex communities is a fundamental challenge in ecology. Leveraging bacterial microcosms with well-controlled laboratory conditions, Hu et al. recently performed a direct test of theory predicting that two community-level parameters (i.e., species pool size and inter-species interaction strength) dictate transitions between three dynamical phases: stable full coexistence, stable partial coexistence, and persistent fluctuations. Generally, communities experience species extinctions before they lose stability as either of the two parameters increases.

Diterpenes, or diterpenoids, are the most abundant and diverse subgroup of terpenoids, the largest family of secondary metabolites. Most diterpenes possess broad biological activities including anti-inflammatory, antiviral, anti-tumoral, antimicrobial, anticancer, antifungal, antidiabetic, cardiovascular protective, and phytohormone activities. As such, diterpenes have wide applications in medicine (e.g., the anticancer drug Taxol and the antibiotic pleuromutilin), agriculture (especially as phytohormones such as gibberellins), personal care (e.g., the fragrance sclareol) and food (e.g., steviol glucosides as low-calorie sweeteners) industries. Diterpenes are biosynthesized in a common route with various diterpene synthases and decoration enzymes like cytochrome P450 oxidases, glycosidases, and acyltransferases. Recent advances in DNA sequencing and synthesis, omics analysis, synthetic biology, and metabolic engineering have enabled efficient production of diterpenes in several chassis hosts like Escherichia coli, Saccharomyces cerevisiae, Yarrowia lipolytica, Rhodosporidium toruloides, and Fusarium fujikuroi. This review summarizes the recently discovered diterpenes, their related enzymes and biosynthetic pathways, particularly highlighting the microbial synthesis of high-value diterpenes directly from inexpensive carbon sources (e.g., sugars). The high titers (>4 g/L) achieved mean that some of these endeavors are reaching or close to commercialization. As such, we envisage a bright future in translating microbial synthesis of diterpenes into commercialization.

The microbiome is an essential component of ecological systems and is comprised of a diverse array of microbes. Over the past decades, the accumulated observational evidence reveals a close correlation between the microbiome and human health and disease. Many groups are now manipulating individual microbial strains, species and the community as a whole to gain a mechanistic understanding of the functions of the microbiome. Here, we discuss three major approaches for introducing DNA to engineer model bacteria and isolated undomesticated bacteria, including transformation, transduction, and conjugation. We provide an overview of these approaches and describe the advantages and limitations of each method. In addition, we highlight examples of human microbiome engineering using these approaches. Finally, we provide perspectives for the future of microbiome engineering.