Marinoquinolones and Marinobactoic Acid: Antimicrobial and Cytotoxic ortho-Dialkylbenzene-Class Metabolites Produced by a Marine Obligate Gammaproteobacterium of the Genus Marinobacterium

Marine natural products

Covering: January to the end of December 2022This review covers the literature published in 2022 for marine natural products (MNPs), with 645 citations (633 for the period January to December 2022) referring to compounds isolated from marine microorganisms and phytoplankton, green, brown and red algae, sponges, cnidarians, bryozoans, molluscs, tunicates, echinoderms, the submerged parts of mangroves and other intertidal plants. The emphasis is on new compounds (1417 in 384 papers for 2022), together with the relevant biological activities, source organisms and country of origin. Pertinent reviews, biosynthetic studies, first syntheses, and syntheses that led to the revision of structures or stereochemistries, have been included. An analysis of NP structure class diversity in relation to biota source and biome is discussed.

Phenotypic and genotypic characterization of Marinobacterium weihaiense sp. nov. and Marinobacterium marinum sp. nov., isolated from marine sediment, and genomic properties of the genus Marinobacterium

In this study, two novel bacterial strains were isolated from coastal sediment of Weihai, China. The two strains were Gram-stain-negative and facultatively aerobic, designated 3-1745T and A346T. Based on phenotypic, genetic and phylogenetic properties, strains 3-1745T and A346T represent two novel species of the genus Marinobacterium. The results of genome analysis revealed many central carbohydrate metabolism pathways such as gluconeogenesis, pyruvate oxidation, tricyclic acid cycle, pentose phosphate pathway and PRPP biosynthesis in the genus Marinobacterium. The ability of strains 3-1745T and A346T to utilize volatile fatty acids was experimentally confirmed. Polyhydroxyalkanoate synthases (PhaA, PhaB and PhaC) for the synthesis of polyhydroxyalkanoates were prevalent in the genus Marinobacterium. Multiple BGCs (biosynthetic gene clusters) including betalactone, ectoine, ranthipeptide, redox-cofactor, RiPPs (ribosomally synthesized post-translationally modified peptides) and T3PKS (polyketide synthases) in the genome of the genus Marinobacterium were found. Additional genome analyses suggested that the genus Marinobacterium contained diverse potential mechanisms of salt tolerance and mainly utilized oligosaccharides. This is the first report on broad genomic analyses of the genus Marinobacterium with the description of two novel species and potential ecological and biotechnological implications.

Development of a drug discovery approach from microbes with a special focus on isolation sources and taxonomy

After the successful discoveries of numerous antibiotics from microorganisms, frequent reisolation of known compounds becomes an obstacle in further development of new drugs from natural products. Exploration of biological sources that can provide novel scaffolds is thus an urgent matter in drug lead screening. As an alternative source to the conventionally used soil microorganisms, we selected endophytic actinomycetes, marine actinomycetes, and actinomycetes in tropical areas for investigation and found an array of new bioactive compounds. Furthermore, based on the analysis of the distribution pattern of biosynthetic gene clusters in bacteria together with available genomic data, we speculated that biosynthetic gene clusters for secondary metabolites are specific to each genus. Based on this assumption, we investigated actinomycetal and marine bacterial genera from which no compounds have been reported, which led to the discovery of a variety of skeletally novel bioactive compounds. These findings suggest that consideration of environmental factor and taxonomic position is critically effective in the selection of potential strains producing structurally unique compounds.

Bulbiferamide, an Antitrypanosomal Hexapeptide Cyclized via an N-Acylindole Linkage from a Marine Obligate Microbulbifer

UV absorption spectroscopy-guided fractionation of the culture extract of a marine obligate bacterium of the genus Microbulbifer yielded a novel cyclic hexapeptide, bulbiferamide (1). NMR spectroscopic and mass spectrometric analyses revealed the structure of 1 to be a cyclic tetrapeptide appending a ureido-bridged two amino acid unit. Notably, Trp is a junction residue, forming on one hand a very rare N-aminoacylated indole linkage for cyclization and on the other hand connecting the ureido-containing tail structure, which is an unprecedented way of configuring peptides. The component amino acids were determined to be l by the advanced Marfey's method. Compound 1 displayed growth inhibitory activity against Trypanosoma cruzi epimastigotes with an IC₅₀ value of 4.1 μM, comparable to the currently approved drug benznidazole, while it was not cytotoxic to P388 murine leukemia cells at 100 μM.