New prodrugs and analogs of the phenazine 5,10-dioxide natural products iodinin and myxin promote selective cytotoxicity towards human acute myeloid leukemia cells

Design of the Smallest Intramolecular Singlet Fission Chromophore with the Fastest Singlet Fission

We designed an intramolecular singlet fission (iSF) chromophore, pyrazino[2,3-g]quinoxaline-1,4,6,9-tetraoxide. Appropriate substitutions into anthracene enhance the tetraradical character, so that the molecule accommodates a pair of triplet excitons in its lowest singlet excited state. Our simulation showed a 16 fs fast iSF of the design, which is a new record. The design also sets a new record of small size iSF chromophore and high exciton density. The design can be synthesized by oxidizing the tertiary N centers of the existent pyrazino[2,3-g]quinoxaline.

Type Strains of Entomopathogenic Nematode-Symbiotic Bacterium Species, Xenorhabdus szentirmaii (EMC) and X. budapestensis (EMA), Are Exceptional Sources of Non-Ribosomal Templated, Large-Target-Spectral, Thermotolerant-Antimicrobial Peptides (by Both), and Iodinin (by EMC)

Antimicrobial multidrug resistance (MDR) is a global challenge, not only for public health, but also for sustainable agriculture. Antibiotics used in humans should be ruled out for use in veterinary or agricultural settings. Applying antimicrobial peptide (AMP) molecules, produced by soil-born organisms for protecting (soil-born) plants, seems a preferable alternative. The natural role of peptide-antimicrobials, produced by the prokaryotic partner of entomopathogenic-nematode/bacterium (EPN/EPB) symbiotic associations, is to sustain monoxenic conditions for the EPB in the gut of the semi-anabiotic infective dauer juvenile (IJ) EPN. They keep pathobiome conditions balanced for the EPN/EPB complex in polyxenic (soil, vanquished insect cadaver) niches. Xenorhabdus szentirmaii DSM16338(T) (EMC), and X. budapestensis DSM16342(T) (EMA), are the respective natural symbionts of EPN species Steinernema rarum and S. bicornutum. We identified and characterized both of these 15 years ago. The functional annotation of the draft genome of EMC revealed 71 genes encoding non-ribosomal peptide synthases, and polyketide synthases. The large spatial Xenorhabdus AMP (fabclavine), was discovered in EMA, and its biosynthetic pathway in EMC. The AMPs produced by EMA and EMC are promising candidates for controlling MDR prokaryotic and eukaryotic pathogens (bacteria, oomycetes, fungi, protozoa). EMC releases large quantity of iodinin (1,6-dihydroxyphenazine 5,10-dioxide) in a water-soluble form into the media, where it condenses to form spectacular water-insoluble, macroscopic crystals. This review evaluates the scientific impact of international research on EMA and EMC.

Biosynthesis, regulation, and engineering of natural products from Lysobacter

Covering: up to August 2021Lysobacter is a genus of Gram-negative bacteria that was classified in 1987. Several Lysobacter species are emerging as new biocontrol agents for crop protection in agriculture. Lysobacter are prolific producers of new bioactive natural products that are largely underexplored. So far, several classes of structurally interesting and biologically active natural products have been isolated from Lysobacter. This article reviews the progress in Lysobacter natural product research over the past ten years, including molecular mechanisms for biosynthesis, regulation and mode of action, genome mining of cryptic biosynthetic gene clusters, and metabolic engineering using synthetic biology tools.

Monooxygenase LaPhzX is Involved in Self-Resistance Mechanisms during the Biosynthesis of N-Oxide Phenazine Myxin

Self-resistance genes are deployed by many microbial producers of bioactive natural products to avoid self-toxicity. Myxin, a di-N-oxide phenazine produced by Lysobacter antibioticus OH13, is toxic to many microorganisms and tumor cells. Here, we uncovered a self-defense strategy featuring the antibiotic biosynthesis monooxygenase (ABM) family protein LaPhzX for myxin degradation. The gene LaPhzX is located in the myxin biosynthetic gene cluster (LaPhz), and its deletion resulted in bacterial mutants that are more sensitive to myxin. In addition, the LaPhzX mutants showed increased myxin accumulation and reduction of its derivative, compound 4, compared to the wild-type strain. Meanwhile, in vitro biochemical assays demonstrated that LaPhzX significantly degraded myxin in the presence of nicotinamide adenine dinucleotide phosphate (NADPH), nicotinamide adenine dinucleotide (NADH), flavin mononucleotide (FMN), and flavin adenine dinucleotide (FAD). In addition, heterologous expression of LaPhzX in Xanthomonas oryzae pv. oryzae and Escherichia coli increased their resistance to myxin. Overall, our work illustrates a monooxygenase-mediated self-resistance mechanism for phenazine antibiotic biosynthesis.