Function of the loading module in CorI and of the O-methyltransferase CorH in vinyl carbamate biosynthesis of the antibiotic corallopyronin A

Methyl carbamates of phosphatidylethanolamines and phosphatidylserines reveal bacterial contamination in mitochondrial lipid extracts of mouse embryonic fibroblasts

The occurrence of methyl carbamates of phosphatidylethanolamines and phosphatidylserines in the lipid extract of mitochondria obtained from mouse embryonic fibroblasts was ascertained by hydrophilic interaction liquid chromatography with electrospray ionization single and multi-stage mass spectrometry, performed using sinergically a high resolution (quadrupole-Orbitrap) and a low resolution (linear ion trap) spectrometer. Two possible routes to the synthesis of methyl carbamates of phospholipids were postulated and evaluated: (i) a chemical transformation involving phosgene, occurring as a photooxidation by-product in the chloroform used for lipid extraction, and methanol, also used for the latter; (ii) an enzymatic methoxycarbonylation reaction due to an accidental bacterial contamination, that was unveiled subsequently on the murine mitochondrial sample. A specific lipid extraction performed on a couple of standard phosphatidyl-ethanolamines/-serines, based on purposely photo-oxidized chloroform and deuterated methanol, indicated route (i) as negligible in the specific case, thus highlighting the enzymatic route related to bacterial contamination as the most likely source of methyl carbamates. The unambiguous recognition of the latter might represent the starting point toward a better understanding of their generation in biological systems and a minimization of their occurrence when an artefactual formation is ascertained.

Corallopyronin A: antimicrobial discovery to preclinical development

Covering: August 1984 up to January 2022Worldwide, increasing morbidity and mortality due to antibiotic-resistant microbial infections has been observed. Therefore, better prevention and control of infectious diseases, as well as appropriate use of approved antibacterial drugs are crucial. There is also an urgent need for the continuous development and supply of novel antibiotics. Thus, identifying new antibiotics and their further development is once again a priority of natural product research. The antibiotic corallopyronin A was discovered in the 1980s in the culture broth of the Myxobacterium Corallococcus coralloides and serves, in the context of this review, as a show case for the development of a naturally occurring antibiotic compound. The review demonstrates how a hard to obtain, barely water soluble and unstable compound such as corallopyronin A can be developed making use of sophisticated production and formulation approaches. Corallopyronin A is a bacterial DNA-dependent RNA polymerase inhibitor with a new target site and one of the few representatives of this class currently in preclinical development. Efficacy against Gram-positive and Gram-negative pathogens, e.g., Chlamydia trachomatis, Orientia tsutsugamushi, Staphylococcus aureus, and Wolbachia has been demonstrated. Due to its highly effective in vivo depletion of Wolbachia, which are essential endobacteria of most filarial nematode species, and its robust macrofilaricidal efficacy, corallopyronin A was selected as a preclinical candidate for the treatment of human filarial infections. This review highlights the discovery and production optimization approaches for corallopyronin A, as well as, recent preclinical efficacy results demonstrating a robust macrofilaricidal effect of the anti-Wolbachia candidate, and the solid formulation strategy which enhances the stability as well as the bioavailability of corallopyronin A.

Heterologous production of myxobacterial α-pyrone antibiotics in Myxococcus xanthus

Myxopyronins (MXN) and corallopyronins (COR) are structurally related α-pyrone antibiotics from myxobacteria that represent a highly promising compound class for the development of broad-spectrum antibacterial therapeutic agents. Their ability to inhibit RNA polymerase through interaction with the "switch region", a novel target, distant from previously characterized RNA polymerase inhibitors (e.g. rifampicin), makes them particularly promising candidates for further research. To improve compound supply for further investigation of MXN, COR and novel derivatives of these antibacterial agents, establishment of an efficient and versatile microbial production platform for myxobacterial α-pyrone antibiotics is highly desirable. Here we describe design, construction and expression of a heterologous production and engineering platforms for MXN and COR to facilitate rational structure design and yield improvement approaches in the myxobacterial host strain Myxococcus xanthus DK1622. Optimization of the cultivation medium yielded significantly higher production titers of MXN A at around 41-fold increase and COR A at around 25-fold increase, compared to the standard CTT medium.

Biosynthesis of polyketides by trans-AT polyketide synthases

This review discusses the biosynthesis of natural products that are generated bytrans-AT polyketide synthases, a family of catalytically versatile enzymes that represents one of the major group of proteins involved in the production of bioactive polyketides.

Antibiotics from myxobacteria

Covering: up to the end of 2013. Myxobacteria produce a vast range of structurally diverse natural products with prominent biological activities. Here, we provide a detailed description and judge the potential of all antibiotically active myxobacterial compounds as lead structures, pointing out their particularities and, if known, their mode of action. Thus, the review provides an overview of the potential of specific compounds, suitable for future investigations and possible clinical applications.