The myxobacterial compounds spirangien a and spirangien M522 are potent inhibitors of IL-8 expression

Myxobacteria: biology and bioactive secondary metabolites

Myxobacteria are Gram-negative eubacteria and they thrive in a variety of habitats including soil rich in organic matter, rotting wood, animal dung and marine environment. Myxobacteria are a promising source of new compounds associated with diverse bioactive spectrum and unique mode of action. The genome information of myxobacteria has revealed many orphan biosynthetic pathways indicating that these bacteria can be the source of several novel natural products. In this review, we highlight the biology of myxobacteria with emphasis on their habitat, life cycle, isolation methods and enlist all the bioactive secondary metabolites purified till date and their mode of action.

Myxobacteria as a Source of New Bioactive Compounds: A Perspective Study

Myxobacteria are unicellular, Gram-negative, soil-dwelling, gliding bacteria that belong to class δ-proteobacteria and order Myxococcales. They grow and proliferate by transverse fission under normal conditions, but form fruiting bodies which contain myxospores during unfavorable conditions. In view of the escalating problem of antibiotic resistance among disease-causing pathogens, it becomes mandatory to search for new antibiotics effective against such pathogens from natural sources. Among the different approaches, Myxobacteria, having a rich armor of secondary metabolites, preferably derivatives of polyketide synthases (PKSs) along with non-ribosomal peptide synthases (NRPSs) and their hybrids, are currently being explored as producers of new antibiotics. The Myxobacterial species are functionally characterized to assess their ability to produce antibacterial, antifungal, anticancer, antimalarial, immunosuppressive, cytotoxic and antioxidative bioactive compounds. In our study, we have found their compounds to be effective against a wide range of pathogens associated with the concurrence of different infectious diseases.

Chemistry and biology of spiroacetals from myxobacteria

This review details the isolation, biosynthesis, biological activity and synthesis of spiroacetals from the myxobacterium Sorangium cellulosum. The strategies utilised to access the challenging structures and stereochemistry of these natural products are highlighted.

Antiviral Compounds from Myxobacteria

Viral infections including human immunodeficiency virus (HIV), cytomegalovirus (CMV), hepatitis B virus (HBV), and hepatitis C virus (HCV) pose an ongoing threat to human health due to the lack of effective therapeutic agents. The re-emergence of old viral diseases such as the recent Ebola outbreaks in West Africa represents a global public health issue. Drug resistance and toxicity to target cells are the major challenges for the current antiviral agents. Therefore, there is a need for identifying agents with novel modes of action and improved efficacy. Viral-based illnesses are further aggravated by co-infections, such as an HIV patient co-infected with HBV or HCV. The drugs used to treat or manage HIV tend to increase the pathogenesis of HBV and HCV. Hence, novel antiviral drug candidates should ideally have broad-spectrum activity and no negative drug-drug interactions. Myxobacteria are in the focus of this review since they produce numerous structurally and functionally unique bioactive compounds, which have only recently been screened for antiviral effects. This research has already led to some interesting findings, including the discovery of several candidate compounds with broad-spectrum antiviral activity. The present review looks at myxobacteria-derived antiviral secondary metabolites.

Myxobacterial natural products: An under-valued source of products for drug discovery for neurological disorders

Age-related disorders impose noticeable financial and emotional burdens on society. This impact is becoming more prevalent with the increasing incidence of neurodegenerative diseases and is causing critical concerns for treatment of patients worldwide. Parkinson's disease, Alzheimer's disease, multiple sclerosis and motor neuron disease are the most prevalent and the most expensive to treat neurodegenerative diseases globally. Therefore, exploring effective therapies to overcome these disorders is a necessity. Natural products and their derivatives have increasingly attracted attention in drug discovery programs that have identified microorganisms which produce a large range of metabolites with bioactive properties. Myxobacteria, a group of Gram-negative bacteria with large genome size, produce a wide range of secondary metabolites with significant chemical structures and a variety of biological effects. They are potent natural product producers. In this review paper, we attempt to overview some secondary metabolites synthesized by myxobacteria with neuroprotective activity through known mechanisms including production of polyunsaturated fatty acids, reduction of apoptosis, immunomodulation, stress reduction of endoplasmic reticulum, stabilization of microtubules, enzyme inhibition and serotonin receptor modulation.

Antibiotics from Gram-negative bacteria: a comprehensive overview and selected biosynthetic highlights

Covering: up to 2017The overwhelming majority of antibiotics in clinical use originate from Gram-positive Actinobacteria. In recent years, however, Gram-negative bacteria have become increasingly recognised as a rich yet underexplored source of novel antimicrobials, with the potential to combat the looming health threat posed by antibiotic resistance. In this article, we have compiled a comprehensive list of natural products with antimicrobial activity from Gram-negative bacteria, including information on their biosynthetic origin(s) and molecular target(s), where known. We also provide a detailed discussion of several unusual pathways for antibiotic biosynthesis in Gram-negative bacteria, serving to highlight the exceptional biocatalytic repertoire of this group of microorganisms.

Natural products from myxobacteria: novel metabolites and bioactivities

Covering: 2011-July 2016Myxobacteria are a rich source for structurally diverse secondary metabolites with intriguing biological activities. Here we report on new natural products that were isolated from myxobacteria in the period of 2011 to July 2016. Some examples of recent advances on modes-of-action are also summarised along with a more detailed overview on five compound classes currently assessed in preclinical studies.

Screening of small molecules affecting mammalian P-body assembly uncovers links with diverse intracellular processes and organelle physiology

Processing bodies (P-bodies) are cytoplasmatic mRNP granules containing non-translating mRNAs and proteins from the mRNA decay and silencing machineries. The mechanism of P-body assembly has been typically addressed by depleting P-body components. Here we apply a complementary approach and establish an automated cell-based assay platform to screen for molecules affecting P-body assembly. From a unique library of compounds derived from myxobacteria, 30 specifically inhibited P-body assembly. Gephyronic acid A (GA), a eukaryotic protein synthesis inhibitor, showed the strongest effect. GA also inhibited, under stress conditions, phosphorylation of eIF2α and stress granule formation. Other hits uncovered interesting novel links between P-body assembly, lipid metabolism, and internal organelle physiology. The obtained results provide a chemical toolbox to manipulate P-body assembly and function.

Identification of myxobacteria-derived HIV inhibitors by a high-throughput two-step infectivity assay

Background

Drug-resistance and therapy failure due to drug-drug interactions are the main challenges in current treatment against Human Immunodeficiency Virus (HIV) infection. As such, there is a continuous need for the development of new and more potent anti-HIV drugs. Here we established a high-throughput screen based on the highly permissive TZM-bl cell line to identify novel HIV inhibitors. The assay allows discriminating compounds acting on early and/or late steps of the HIV replication cycle.

Results

The platform was used to screen a unique library of secondary metabolites derived from myxobacteria. Several hits with good anti-HIV profiles were identified. Five of the initial hits were tested for their antiviral potency. Four myxobacterial compounds, sulfangolid C, soraphen F, epothilon D and spirangien B, showed EC₅₀ values in the nM range with SI > 15. Interestingly, we found a high amount of overlapping hits compared with a previous screen for Hepatitis C Virus (HCV) using the same library.

Conclusion

The unique structures and mode-of-actions of these natural compounds make myxobacteria an attractive source of chemicals for the development of broad-spectrum antivirals. Further biological and structural studies of our initial hits might help recognize smaller drug-like derivatives that in turn could be synthesized and further optimized.