SynBio

Chondroitin is a glycosaminoglycan that has gained widespread use in nutraceuticals and pharmaceuticals, mainly for treating osteoarthritis. Traditionally, it has been extracted from animal cartilage but recently, biotechnological processes have emerged as a commercial alternative to avoid the risk of viral or prion contamination and offer a vegan-friendly source. Typically, these methods involve producing the chondroitin backbone using pathogenic bacteria and then modifying it enzymatically through the action of sulfotransferases. Despite the challenges of expressing active sulfotransferases in bacteria, the use of eukaryotic microorganisms is still limited to a few works using Pichia pastoris. To create a safer and efficient biotechnological platform, we constructed a biosynthetic pathway for chondroitin production in S. cerevisiae as a proof-of-concept. Up to 125 mg/L and 200 mg/L of intracellular and extracellular chondroitin were produced, respectively. Furthermore, as genome-scale models are valuable tools for identifying novel targets for metabolic engineering, a stoichiometric model of chondroitin-producing S. cerevisiae was developed and used in optimization algorithms. Our research yielded several novel targets, such as uridine diphosphate (UDP)-N-acetylglucosamine pyrophosphorylase (QRI1), glucosamine-6-phosphate acetyltransferase (GNA1), or N-acetylglucosamine-phosphate mutase (PCM1) overexpression, that might enhance chondroitin production and guide future experimental research to develop more efficient host organisms for the biotechnological production process. Full article

Pseudomonas chlororaphis ATCC 9446 is a non-pathogenic bacterium associated with the rhizosphere. It is commonly used as a biocontrol agent against agricultural pests. This organism can grow on a variety of carbon sources, has a robust secondary metabolism, and produces secondary metabolites with antimicrobial properties. This makes it an alternative host organism for synthetic biology applications. However, as a novel host there is a need for well-characterized molecular tools that allow fine control of gene expression and exploration of its metabolic potential. In this work we developed and characterized expression vectors for P. chlororaphis. We used two different promoters: the exogenously induced lac-IPTG promoter, and LuxR-C6-AHL, which we evaluated for its auto-inducible capacities, as well as using an external addition of C6-AHL. The expression response of these vectors to the inducer concentration was characterized by detecting a reporter fluorescent protein (YFP: yellow fluorescent protein). Furthermore, the violacein production operon was evaluated as a model heterologous pathway. We tested violacein production in shake flasks and a 3 L fermenter, showing that P. chlororaphis possesses a vigorous aromatic amino acid metabolism and was able to produce 1 g/L of violacein in a simple batch reactor experiment with minimal medium using only glucose as the carbon source. We compared the experimental results with the predictions of a modified genome scale model. The presented results show the potential of P. chlororaphis as a novel host organism for synthetic biology applications. Full article

Type II polyketide synthase (PKS) systems are a rich source of structurally diverse polycyclic aromatic compounds with clinically relevant antibiotic and chemotherapeutic properties. The enzymes responsible for synthesizing the polyketide core, known collectively as the minimal cassette, hold potential for applications in synthetic biology. The minimal cassette provides polyketides of different chain lengths, which interact with other enzymes that are responsible for the varied cyclization patterns. Additionally, the type II PKS enzyme clusters offer a wide repertoire of tailoring enzymes for oxidations, glycosylations, cyclizations, and rearrangements. This review begins with the variety of chemical space accessible with type II PKS systems including the recently discovered highly reducing variants that produce polyalkenes instead of the archetypical polyketide motif. The main discussion analyzes the previous approaches with an emphasis on further research that is needed to characterize the minimal cassette enzymes in vitro. Finally, the potential type II PKS systems hold the potential to offer new tools in biocatalysis and synthetic biology, particularly in the production of novel antibiotics and biofuels. Full article

Removal of fixed nitrogen compounds such as ammonium and nitrite from wastewater is of critical importance for balancing the nitrogen cycle and protecting aquatic environments from eutrophication. ANaerobic AMMonium OXidising (ANAMMOX) bacteria have recently been employed for fixed nitrogen removal purposes in wastewater treatment processes. These specialised bacteria convert ammonium and nitrite into nitrogen gas anaerobically, thereby reducing the amount of energy required for aeration in conventional wastewater treatment processes. However, slow growth rates of ANAMMOX remain a major obstacle towards their widespread use in industrial wastewater treatment processes. Thus, a pangenome-scale, constraint-based metabolic model, iRB399, of ANAMMOX bacteria has been developed to design strategies for accelerating their growth. The main metabolic limitation was identified in the energy metabolism of these bacteria, concerning the production of ATP. The extremely low efficiency of the electron transport chain combined with very high growth-associated maintenance energy is likely to be responsible for the slow growth of ANAMMOX. However, different ANAMMOX species were found to conserve energy using a variety of different redox couples, and the modelling simulations revealed their comparative advantages under different growth conditions. iRB399 also identified dispensable catabolic reactions that have demonstrably beneficial effects on enhancing the growth rates of ANAMMOX bacteria. Thus, the pangenome-scale model will not only help identify and overcome metabolic limitations of ANNAMOX bacteria, but also provide a valuable resource for designing efficient ANNAMOX-based wastewater treatment processes. Full article

The glutamate ionotropic kainate receptors, encoded by the GRIK gene family, are composed of four subunits and function as ligand-activated ion channels. They play a critical role in regulating synaptic transmission and various synaptic receptors’ processes, as well as in the pathophysiology of schizophrenia. However, their functions and mechanisms of action need to be better understood and are worthy of exploration. To further understand the exact role of the kainate receptors in vitro, we generated kainate-receptor-knockout (KO) isogenic SH-SY5Y cell lines using the CRISPR/Cas9-mediated gene editing method. We conducted RNA sequencing (RNA-seq) to determine the differentially expressed genes (DEGs) in the isogenic edited cells and used rhodamine-phalloidin staining to quantitate filamentous actin (F-actin) in differentiated edited cells. The RNA-seq and the Gene Ontology enrichment analysis revealed that the genetic deletion of the GRIK1, GRIK2, and GRIK4 genes disturbed multiple genes involved in numerous signal pathways, including a converging pathway related to the synaptic membrane. An enrichment analysis of gene–disease associations indicated that DEGs in the edited cell lines were associated with several neuropsychiatric disorders, especially schizophrenia. In the morphology study, fluorescent images show that less F-actin was expressed in differentiated SH-SY5Y cells with GRIK1, GRIK2, or GRIK4 deficiency than wild-type cells. Our data indicate that kainate receptor deficiency might disturb synaptic-membrane-associated genes, and elucidating these genes should shed some light on the pathophysiology of schizophrenia. Furthermore, the transcriptomic profiles for kainate receptor deficiency of SH-SY5Y cells contribute to emerging evidence for the novel mechanisms underlying the effect of kainate receptors and the pathophysiology of schizophrenia. In addition, our data suggest that kainate-receptor-mediated F-actin remodeling may be a candidate mechanism underlying schizophrenia. Full article

A number of antifungal drugs are based on polyene macrolides that cause severe side effects. Most of these compounds contain a single aminodeoxysugar, D-mycosamine. Toxicity can be reduced by increasing the extent of glycosylation. The aromatic heptaene 67-121C and two analogues of the degenerate heptaene nystatin have a second sugar attached to the C4′ hydroxyl of mycosamine. Another nystatin analogue has L-digitoxose as a second sugar attached to C35 on the macrolactone ring. The pentaene selvamicin has 4-O-methyl-L-digitoxose at C27, the equivalent position. To assist the production of new antifungals by synthetic biology, we explore further the utility of three classes of polyene glycosyltransferase: extending glycosyltransferases that form disaccharide-containing polyenes, glycosyltransferases that add the L-digitoxose sugars of nystatin A3 and selvamicin, and mycosaminyltransferases that add the primary aminodeoxysugar. In addition, we combine enzymatic hyperglycosylation with a known chemical method for adding sugars to the C3′ amino group of mycosamine. This was used to convert the disaccharide-containing 67-121C heptaene to forms containing branched trisaccharide or tetrasaccharide chains. These analogues are of interest for testing as anti-Leishmania drugs. Full article

Carbazoles are key scaffolds of either antimicrobial/antiviral alkaloid natural products or therapeutics. As such, access to structurally diverse indole-containing carbazoles has attracted considerable attention. In this report, a pilot study is described using biotransformation to provide carbazoles that contain various acyl substituents. The biotransformation system contains the thiamine-diphosphate (ThDP)-dependent enzyme NzsH, the FabH-like 3-ketoacyl-ACP synthase NzsJ, and the aromatase/cyclase NzsI, encoded in the biosynthetic gene cluster (nzs) of the bacterial carbazole alkaloid natural product named neocarazostatin A. The utilization of a range of acyl-SNACs (synthetic acyl-thioester analogues of the native substrate) together with indole-3-pyruvate and pyruvate in the designed biotransformation system allows production of carbazole derivatives. Our results demonstrate that this three-enzyme system displays a considerable substrate profile toward acyl donors for production of carbazoles with different acyl substituents. Finally, two more enzymes were included in the biotransformation system: the tryptophan synthase stand-alone β-subunit variant, PfTrpB, generated from directed evolution in the literature, and a commercially available L-amino acid oxidase (LAAO). The addition of these two enzymes allows the transformation to start with indole building blocks to provide carbazoles with modifications in the indole ring system. Full article

Biotechnology and artificial intelligence have sparked a revolution in dentistry, with a focus on restoring natural tissue functions. This transformation has given rise to bioactive materials, inspired by biomimetics, aimed at replicating the processes found in nature. As synthetic biology advances, there is a heightened focus on signaling systems crucial for bio-based diagnostics and therapeutics. Dentistry now harnesses synthetic proteins for tissue regeneration and dental material enhancement. A current research priority is bacterial biofilm inhibition, vital for dental health. Given the role of Streptococcus mutans in dental caries, the development of synthetic antimicrobial peptides targeting this bacterium is underway. The balance of dental enamel between demineralization and remineralization impacts caries formation. Factors such as the presence of hydroxyapatite and salivary peptides influence enamel health. Recent studies have spotlighted salivary protein-inspired peptides for enhanced remineralization. In the realm of bone regeneration, synthetic proteins like bone morphogenetic proteins (BMP) have been spotlighted, earning FDA approval. Research is currently delving into peptides such as cementum protein 1 peptide (CEMP-1-p1) and parathyroid hormone variants like PTH (1-34), underscoring their potential in advancing dental and bone health. Full article

To assist in the speed and accuracy of designing brick-based DNA nanostructures, we introduce a lightweight software suite 3DNA that can be used to generate complex structures. Currently, implementation of this fabrication strategy involves working with generalized, typically commercial CAD software, ad-hoc sequence-generating scripts, and visualization software, which must often be integrated together with an experimental lab setup for handling the hundreds or thousands of constituent DNA sequences. 3DNA encapsulates the solutions to these challenges in one package by providing a customized, easy-to-use molecular canvas and back-end functionality to assist in both visualization and sequence design. The primary motivation behind this software is enabling broader use of the brick-based method for constructing rigid, 3D DNA-based nanostructures, first introduced in 2012. 3DNA is developed to provide a streamlined, real-time workflow for designing and implementing this type of 3D nanostructure by integrating different visualization and design modules. Due to its cross-platform nature, it can be used on the most popular desktop environments, i.e., Windows, Mac OS X, and various flavors of Linux. 3DNA utilizes toolbar-based navigation to create a user-friendly GUI and includes a customized feature to analyze the constituent DNA sequences. Finally, the oligonucleotide sequences themselves can either be created on the fly by a random sequence generator, or selected from a pre-existing set of sequences making up a larger molecular canvas. Full article

Actinobacteria from the genus Streptomyces feature complex primary and secondary metabolism, developmental cycle, and ability to produce a variety of natural products. These soil bacteria are major producers of antibiotics and other bioactive compounds and have been extensively investigated due to the medical and industrial relevance of Streptomyces-derived secondary metabolites. However, the genetic toolbox for Streptomyces engineering as well as yield optimization strategies for the production of relevant metabolites are limited. On the one hand, the genetic potential of these organisms has not been fully utilized due to many “silent” or poorly expressed biosynthetic gene clusters, whose activation depends on environmental stimuli and nutrient availability. On the other hand, these GC-rich Gram-positive bacteria are difficult to manipulate, and traditional genetic manipulation strategies are time-consuming and have low efficiency. Recent studies of Streptomyces metabolism and genomes provided new insights into possibilities to overcome these challenges. In this review, advances and approaches for Streptomyces manipulations and secondary metabolite production optimization are discussed. Special focus is given to understanding the interplay between primary and secondary metabolism in Streptomyces and the supply of nitrogen-containing compounds into secondary metabolism. Existing strategies to manipulate cellular metabolism in Streptomyces are reviewed. Full article

MicroRNAs (miRNAs) are small non-coding RNA molecules that play a fundamental role in the regulation of gene expression in humans. There has been a growing interest in investigating the interactions between human miRNAs and viruses to better understand the underlying mechanisms of the immune response and viral pathogenesis. The Ilheus virus, an arbovirus transmitted by mosquitoes, is known to cause disease in humans, with symptoms ranging from mild fever to severe neurological complications. This scientific article aims to explore the potential role of human miRNAs in their association with the genome of the Ilheus virus. Previous research has indicated that miRNAs can affect viral replication and the host’s immune response, playing a critical role in modulating the virus–host interaction. Here, we will investigate the possible interactions between specific human miRNAs and regions of the Ilheus virus genome, focusing on identifying miRNAs that may impact viral replication or the host’s immune response. A search for potential human miRNAs associated with the viral genome of ILHV was conducted through database searches such as miRBase. For the elucidation of targets regulated by these miRNAs, the TargetScan program was adopted. Functional enrichment analysis, inferring the function of genes regulated by miRNAs, was provided by the DAVID software. To elucidate the secondary structure, tools hosted in the RNAFold repositories were employed. In summary, our research has identified miRNAs linked to crucial sections of the Ilheus virus genome. These miRNAs can potentially regulate genes associated with neurological and immune functions. This highlights the intricate interplay between human miRNAs and the Ilheus virus genome, suggesting a pivotal role for these molecules in the host’s response to viral infections. Full article

Serine integrases are emerging as one of the most powerful biological tools for biotechnology. Over the past decade, many research papers have been published on the use of serine integrases in synthetic biology. In this review, we aim to systematically summarize the various studies ranging from structure and the catalytic mechanism to genetic design and interdisciplinary applications. First, we introduce the classification, structure, and catalytic model of serine integrases. Second, we present a timeline with milestones that describes the representative achievements. Then, we summarize the applications of serine integrases in genome engineering, genetic design, and DNA assembly. Finally, we discuss the potential of serine integrases for advancing interdisciplinary research. We anticipate that serine integrases will be further expanded as a versatile genetic toolbox for synthetic biology applications. Full article

Even more than 60 years after its introduction into the clinic, cyclophosphamide (CP), which belongs to the group of alkylating cytostatics, is indispensable for the treatment of cancer. This is despite the fact that its exact mechanism of action was unknown until a few years ago, and therefore, all attempts to improve the effectiveness of CP failed. The reason for not knowing the mechanism of action was the uncritical transfer of the chemical processes that lead to the formation of the actual alkylating CP metabolite phosphoreamide mustard (PAM) in vitro to in vivo conditions. In vitro—e.g., in cell culture experiments—PAM is formed by β-elimination of acrolein from the pharmacologically active CP metabolite aldophosphamide (ALD). In vivo, on the other hand, it is formed by enzymatic cleavage of ALD by phosphodiesterases (PDE) with the formation of 3-hydroxypropanal (HPA). The discovery of HPA as a cyclophosphamide metabolite, together with the discovery that HPA is a proapoptotic aldehyde and the discovery that the cell death event in therapy with CP is DNA-alkylation-initiated p53-controlled apoptosis, led to the formulation of a mechanism of action of CP and other oxazaphosphorine cytostatics (OX). This mechanism of action is presented here and is confirmed by newly developed CP-like compounds with lower toxicity and an order of magnitude better effectiveness. Full article

In bacterial communities, quorum sensing (QS) is a process mediated via chemical signalling that individuals use to coordinate their collective phenotypes. It is closely associated with pathogenic traits such as virulence factor production and antibiotic resistance. In their natural habitats, bacteria live in small niches, forming intricate consortia, where the role of QS is little understood. This work aims to construct a tuneable, trackable, and reconfigurable model bacterial community for studying QS. To this end, three Escherichia coli fluorescent reporter strains were constructed based on the paradigm LuxI/LuxR QS system. The strains recreate the three major aspects of QS response: sensing (S), autoinducer production (P), and regulation (R). We found that the response of the S strain as a function of the N-(3-oxohexanoyl)-L-homoserine lactone (OHHL) concentration did not saturate and exhibited a concentration-dependent response (in the range 10⁻⁷ to 10⁻⁴ M). The P strain produced OHHL and showed the ability to activate the S response, while the R strain showed the ability to attenuate the response due to the expression of the lactonase AiiA. Monitoring the fluorescent signals of the strains permits tracking the activation and attenuation activities of the LuxI/LuxR QS system. Future studies can now also benefit from this straightforward subcloning strategy to study other QS systems. Full article

Periodontitis, a chronic inflammatory oral condition triggered by bacteria, archaea, viruses, and eukaryotic organisms, is a well-known and widespread disease around the world. While there are effective treatments for periodontitis, there are also several shortcomings associated with its management, including limited treatment options, the risk of recurrence, and the high cost of treatment. Our goal is to develop a more efficient, systematic drug design for periodontitis before clinical trials. We work on systems drug discovery and design for periodontitis treatment via systems biology and deep learning methods. We first applied big database mining to build a candidate genome-wide genetic and epigenetic network (GWGEN), which includes a protein-protein interaction network (PPIN) and a gene regulatory network (GRN) for periodontitis and healthy control. Next, based on the unhealthy and healthy microarray data, we applied system identification and system order detection methods to remove false positives in candidate GWGENs to obtain real GWGENs for periodontitis and healthy control, respectively. After the real GWGENs were obtained, we picked out the core GWGENs based on how significant the proteins and genes were via the principal network projection (PNP) method. Finally, referring to the annotation of the Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways, we built up the core signaling pathways of periodontitis and healthy control. Consequently, we investigated the pathogenic mechanism of periodontitis by comparing their core signaling pathways. By checking up on the downstream core signaling pathway and the corresponding cellular dysfunctions of periodontitis, we identified the fos proto-oncogene, AP-1 Transcription Factor Subunit (FOS), TSC Complex Subunit 2 (TSC2), Forkhead Box O1 (FOXO1), and nuclear factor kappa-light chain enhancer of activated B cells (NF-$\mathsf{\kappa }$B) as significant biomarkers on which we could find candidate molecular drugs to target. To achieve our ultimate goal of designing a combination of molecular drugs for periodontitis treatment, a deep neural network (DNN)-based drug-target interaction (DTI) model was employed. The model is trained with the existing drug-target interaction databases for the prediction of candidate molecular drugs for significant biomarkers. Finally, we filter out brucine, disulfiram, verapamil, and PK-11195 as potential molecular drugs to be combined as a multiple-molecular drug to target the significant biomarkers based on drug design specifications, i.e., adequate drug regulation ability, high sensitivity, and low toxicity. In conclusion, we investigated the pathogenic mechanism of periodontitis by leveraging systems biology methods and thoroughly developed a therapeutic option for periodontitis treatment via the prediction of a DNN-based DTI model and drug design specifications. Full article

Rheumatoid arthritis (RA) is one of the most common autoimmune diseases, affecting 0.5% to 1% of the population. It could ultimately result in joint destruction, functional decline, work disability, and enhanced mortality. Cyclic citrullinated peptide antibodies (CCP Abs) are useful biomarkers for the early detection and diagnosis of RA. In this study, we used plant viral-based expression vectors that produce rapidly large quantities of CCP-specific monoclonal antibodies. Heavy and light chain genes of a CCP monoclonal antibody (CCP mAb) were cloned from the hybridoma cell (12G1) and introduced into two separate plant viral-based expression vectors, TMV and PVX. A cyclic citrullinated peptide monoclonal antibody was produced in Nicotiana benthamiana through an Agrobacterium-mediated transient expression system. The expression of CCP mAb in tobacco plants was confirmed by dot blot, western blot analysis, and enzyme-linked immunosorbent assays (ELISA). It was shown that tobacco plants could accumulate CCP mAbs up to 0.35% of total soluble protein. Accumulated CCP mAb from infiltrated leaves was purified by protein G affinity chromatography. Immunoblot assays and ELISA showed plant-produced CCP mAbs successfully bound to a synthetic CCP peptide antigen. This system provides a fast strategy for the production of pharmaceutical CCP mAbs in tobacco plants. Full article

Covering 2009–2022. Phenylnaphthacenoid polyketides have gained significant interest in recent years owing to their potent antibacterial and anticancer activities. Notably, more than 100 members of this class of natural products have been discovered from various Streptomyces species by different research groups including ours over the last 13 years. This review summarizes the current knowledge of the discovery, chemical diversity, and bioactivity of phenylnaphthacenoid polyketides. The current review also highlights the cell factory for phenylnaphthacenoid production: (1) native strains, (2) mutant strains, (3) heterologous expression, and (4) biocatalytic halogenations. Furthermore, current challenges and future opportunities are also presented as a guide for researchers to explore them more purposefully. Full article

Synthetic biology tools have become increasingly prevalent as we look to nature for biological approaches to complex problems. With an ever-growing global population, issues of food safety and security, as well as addressing pollution and striving for sustainability are of the utmost importance. In this review, we first highlight synthetic biology techniques such as directed evolution as a toolset for protein engineering and show direct applications for food safety and security. Moreover, we offer an introduction to creative approaches for biosensor design and development and spotlight a few innovative examples. Finally, we address biomanufacturing with direct applications, as well as biomanufacturing to improve natural processes. Full article