The results of a single-crystal structure determination when in CIF format can now be validated routinely by automatic procedures. In this way, many errors in published papers can be avoided. The validation software generates a set of ALERTS detailing issues to be addressed by the experimenter, author, referee and publication journal. Validation was pioneered by the IUCr journal Acta Crystallographica Section C and is currently standard procedure for structures submitted for publication in all IUCr journals. The implementation of validation procedures by other journals is in progress. This paper describes the concepts of validation and the classes of checks that are carried out by the program PLATON as part of the IUCr checkCIF facility. PLATON validation can be run at any stage of the structure refinement, independent of the structure determination package used, and is recommended for use as a routine tool during or at least at the completion of every structure determination. Two examples are discussed where proper validation procedures could have avoided the publication of incorrect structures that had serious consequences for the chemistry involved.

/pdf/single-crystal-structure-validation-with-the-program-platon-2pdiuo25f2.pdf

Single-crystal structure validation with the program PLATON

Chemistry and biochemistry of 4-hydroxynonenal, malonaldehyde and related aldehydes.

https://pubs.rsc.org/en/content/articlepdf/2019/NP/C8NP00092A

Marine natural products.

Physiological and ecological constraints play key roles in the evolution of plant growth patterns, especially in relation to defenses against herbivores. Phenotypic and life history theories are unified within the growth-differentiation balance (GDB) framework, forming an integrated system of theories explaining and predicting patterns of plant defense and competitive interactions in ecological and evolutionary time. Plant activity at the cellular level can be classified as growth (cell division and enlargement) of differentiation (chemical and morphological changes leading to cell maturation and specialization). The GDB hypothesis of plant defense is premised upon a physiological trade-off between growth and differentiation processes. The trade-off between growth and defense exists because secondary metabolism and structural reinforcement are physiologically constrained in dividing and enlarging cells, and because they divert resources from the production of new leaf area. Hence the dilemma of plants: Th...

https://www.jstor.org/stable/pdfplus/2830650.pdf

The dilemma of plants: To grow or defend.

Advances in flavonoid research since 1992.

thus the discovery of a major new group of thesebacteria in marine sediments suggests that the ocean repre-sents an overlooked habitat from which to isolate theseimportant microorganisms. Given thatthe rate of discovery ofnew biologically active compounds from common soil actino-mycetes has been falling,

https://www.onlinelibrary.wiley.com/doi/pdf/10.1002/anie.200390115

Salinosporamide A: a highly cytotoxic proteasome inhibitor from a novel microbial source, a marine bacterium of the new genus salinospora.

Natural products are both a fundamental source of new chemical diversity and an integral component of today's pharmaceutical compendium. Yet interest in natural-product drug discovery has waned, in part owing to diminishing returns from traditional resources such as soil bacteria. The oceans cover 70% of the Earth's surface and harbor most of the planet's biodiversity. Although marine plants and invertebrates have received considerable attention as a resource for natural-product discovery, the microbiological component of this diversity remains relatively unexplored. Recent studies have revealed that select groups of marine actinomycetes are a robust source of new natural products. Members of the genus Salinispora have proven to be a particularly rich source of new chemical structures, including the potent proteasome inhibitor salinosporamide A, and other distinct groups are yielding new classes of terpenoids, amino acid–derived metabolites and polyene macrolides. The continued development of improved cultivation methods and technologies for accessing deep-sea environments promises to provide access to this significant new source of chemical diversity.

Developing a new resource for drug discovery: marine actinomycete bacteria

Herbivory has a profound effect on seaweeds in both temperate and tropical communities (11, 17, 21, 33, 43, 47, 80, 124). This is especially true on coral reefs where 60-97% (11, 42) of the total seaweed production may be removed by herbivores. To persist in marine communities, seaweeds must escape, deter, or tolerate herbivory. The ecological and evolutionary importance of spatial and temporal escapes has been extensively studied for seaweeds and adequately reviewed in the recent literature (33, 45, 47, 71, 80). The ability of seaweeds to tolerate herbivory has received limited attention. On coral reefs, rapidly growing filamentous algae are heavily grazed, but the algae quickly replace these losses and appear to be dependent upon herbivores to prevent their habitat from being overgrown by larger but less herbivoretolerant species (11, 71). Additionally, several seaweeds have spores or vegetative portions that can withstand gut passage; in some cases this significantly increases the growth rates of the newly settled spores (6, 122). These types of seaweeds may be considered herbivore tolerant. Although numerous seaweed characteristics can deter some herbivores, the effects of morphology and chemistry have been studied most thoroughly. The

Marine Plant-Herbivore Interactions: The Ecology of Chemical Defense

A major taxon of obligate marine bacteria within the order Actinomycetales has been discovered from ocean sediments. Populations of these bacteria (designated MAR 1) are persistent and widespread, spanning at least three distinct ocean systems. In this study, 212 actinomycete isolates possessing MAR 1 morphologies were examined and all but two displayed an obligate requirement of seawater for growth. Forty-five of these isolates, representing all observed seawater-requiring morphotypes, were partially sequenced and found to share characteristic small-subunit rRNA signature nucleotides between positions 207 and 468 (Escherichia coli numbering). Phylogenetic characterization of seven representative isolates based on almost complete sequences of genes encoding 16S rRNA (16S ribosomal DNA) yielded a monophyletic clade within the family Micromonosporaceae and suggests novelty at the genus level. This is the first evidence for the existence of widespread populations of obligate marine actinomycetes. Organic extracts from cultured members of this new group exhibit remarkable biological activity, suggesting that they represent a prolific resource for biotechnological applications.

Widespread and persistent populations of a major new marine actinomycete taxon in ocean sediments.

Recent fermentation studies have identified actinomycetes of the marine-dwelling genus Salinispora as prolific natural product producers. To further evaluate their biosynthetic potential, we sequenced the 5,183,331-bp S. tropica CNB-440 circular genome and analyzed all identifiable secondary natural product gene clusters. Our analysis shows that S. tropica dedicates a large percentage of its genome (≈9.9%) to natural product assembly, which is greater than previous Streptomyces genome sequences as well as other natural product-producing actinomycetes. The S. tropica genome features polyketide synthase systems of every known formally classified family, nonribosomal peptide synthetases, and several hybrid clusters. Although a few clusters appear to encode molecules previously identified in Streptomyces species, the majority of the 17 biosynthetic loci are novel. Specific chemical information about putative and observed natural product molecules is presented and discussed. In addition, our bioinformatic analysis not only was critical for the structure elucidation of the polyene macrolactam salinilactam A, but its structural analysis aided the genome assembly of the highly repetitive slm loci. This study firmly establishes the genus Salinispora as a rich source of drug-like molecules and importantly reveals the powerful interplay between genomic analysis and traditional natural product isolation studies.

/pdf/genome-sequencing-reveals-complex-secondary-metabolome-in-56zhchh870.pdf

William Fenical

Papers

Salinosporamide A: a highly cytotoxic proteasome inhibitor from a novel microbial source, a marine bacterium of the new genus salinospora.

Developing a new resource for drug discovery: marine actinomycete bacteria

Marine Plant-Herbivore Interactions: The Ecology of Chemical Defense

Widespread and persistent populations of a major new marine actinomycete taxon in ocean sediments.

Genome sequencing reveals complex secondary metabolome in the marine actinomycete Salinispora tropica