Salinipostins A–K, Long-Chain Bicyclic Phosphotriesters as a Potent and Selective Antimalarial Chemotype

Despite significant advances in antimalarial chemotherapy over the past 30 years, development of resistance to frontline drugs remains a significant challenge that limits efforts to eradicate the disease. We now report the discovery of a new class of antimalarials, salinipostins A–K, with low nanomolar potencies and high selectivity indices against mammalian cells (salinipostin A: <i>Plasmodium falciparum</i> EC₅₀ 50 nM, HEK293T cytotoxicity EC₅₀ > 50 μM). These compounds were isolated from a marine-derived <i>Salinospora</i> sp. bacterium and contain a bicyclic phosphotriester core structure, which is a rare motif among natural products. This scaffold differs significantly from the structures of known antimalarial compounds and represents a new lead structure for the development of therapeutic targets in malaria. Examination of the growth stage specificity of salinipostin A indicates that it exhibits growth stage-specific effects that differ from compounds that inhibit heme polymerization, while resistance selection experiments were unable to identify parasite populations that exhibited significant resistance against this compound class

Total Synthesis of Glycinocins A–C

The glycinocins are a class of calcium-dependent, acidic cyclolipopeptide antibiotics structurally related to the clinically approved daptomycin. Herein, we describe a divergent total synthesis of glycinocins A–C, which differ in the structure of a branched α,β-unsaturated fatty acyl moiety. The three natural products exhibited calcium-dependent antimicrobial activity against Staphylococcus aureus and Bacillus subtilis with MICs ranging from 5.5 to 17 μM

Phylogenetic Relationships of Taxa Related to FI-1004.

<p>The evolutionary history was inferred using the Neighbor-Joining method. <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0035398#pone.0035398-Saitou1" target="_blank">[50]</a> The bootstrap consensus tree inferred from 1000 replicates is taken to represent the evolutionary history of the taxa analyzed. <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0035398#pone.0035398-Felsenstein1" target="_blank">[49]</a> Branches corresponding to partitions reproduced in less than 50% bootstrap replicates are collapsed. The percentage of replicate trees in which the associated taxa clustered together in the bootstrap test (1000 replicates) are shown next to the branches. <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0035398#pone.0035398-Felsenstein1" target="_blank">[49]</a> The tree is drawn to scale, with branch lengths in the same units as those of the evolutionary distances used to infer the phylogenetic tree. The evolutionary distances were computed using the Maximum Composite Likelihood method <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0035398#pone.0035398-Tamura2" target="_blank">[51]</a> and are in the units of the number of base substitutions per site. The analysis involved 24 nucleotide sequences. All positions containing gaps and missing data were eliminated. There were a total of 1353 positions in the final dataset. Evolutionary analyses were conducted in MEGA5. <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0035398#pone.0035398-Tamura1" target="_blank">[30]</a> The sequence of <i>Brevibacterium linens</i> DSM 20425^T was used as an outgroup.</p

Sloth Hair as a Novel Source of Fungi with Potent Anti-Parasitic, Anti-Cancer and Anti-Bacterial Bioactivity

<div><p>The extraordinary biological diversity of tropical forests harbors a rich chemical diversity with enormous potential as a source of novel bioactive compounds. Of particular interest are new environments for microbial discovery. Sloths – arboreal mammals commonly found in the lowland forests of Panama – carry a wide variety of micro- and macro-organisms on their coarse outer hair. Here we report for the first time the isolation of diverse and bioactive strains of fungi from sloth hair, and their taxonomic placement. Eighty-four isolates of fungi were obtained in culture from the surface of hair that was collected from living three-toed sloths (<i>Bradypus variegatus</i>, Bradypodidae) in Soberanía National Park, Republic of Panama. Phylogenetic analyses revealed a diverse group of Ascomycota belonging to 28 distinct operational taxonomic units (OTUs), several of which are divergent from previously known taxa. Seventy-four isolates were cultivated in liquid broth and crude extracts were tested for bioactivity <i>in vitro</i>. We found a broad range of activities against strains of the parasites that cause malaria (<i>Plasmodium falciparum</i>) and Chagas disease (<i>Trypanosoma cruzi</i>), and against the human breast cancer cell line MCF-7. Fifty fungal extracts were tested for antibacterial activity in a new antibiotic profile screen called BioMAP; of these, 20 were active against at least one bacterial strain, and one had an unusual pattern of bioactivity against Gram-negative bacteria that suggests a potentially new mode of action. Together our results reveal the importance of exploring novel environments for bioactive fungi, and demonstrate for the first time the taxonomic composition and bioactivity of fungi from sloth hair.</p></div

Molecular Phylogenetic Analysis by Maximum Likelihood for all Isolated, Culturable Strains of Bacteria Isolated from Fish Intestines.

<p>The evolutionary history was inferred by using the Maximum Likelihood method based on the Kimura 2-parameter model. <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0035398#pone.0035398-Kimura1" target="_blank">[48]</a> The bootstrap consensus tree inferred from 2000 replicates is taken to represent the evolutionary history of the taxa analyzed. <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0035398#pone.0035398-Felsenstein1" target="_blank">[49]</a> Branches corresponding to partitions reproduced in less than 50% bootstrap replicates are collapsed. The percentage of replicate trees in which the associated taxa clustered together in the bootstrap test (2000 replicates) are shown next to the branches. <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0035398#pone.0035398-Felsenstein1" target="_blank">[49]</a> Initial tree(s) for the heuristic search were obtained automatically as follows. When the number of common sites was <100 or less than one fourth of the total number of sites, the maximum parsimony method was used; otherwise BIONJ method with MCL distance matrix was used. A discrete Gamma distribution was used to model evolutionary rate differences among sites (5 categories (+<i>G</i>, parameter = 0.4869)). The rate variation model allowed for some sites to be evolutionarily invariable ([+<i>I</i>], 38.9340% sites). The tree is drawn to scale, with branch lengths measured in the number of substitutions per site. The analysis involved 53 nucleotide sequences. All positions containing gaps and missing data were eliminated. There were a total of 1244 positions in the final dataset. Evolutionary analyses were conducted in MEGA5. <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0035398#pone.0035398-Tamura1" target="_blank">[30]</a> Strains identified as psychrophilic bacteria in NCBI denoted with blue diamonds. Strains whose closest published NCBI relatives are uncultured clones denoted with open triangles.</p

Sebastenoic Acid (1) MICs Against Bacterial Panel.

<p>Sebastenoic Acid (1) MICs Against Bacterial Panel.</p

Chemical Structure for Sebastenoic Acid.

<p>a, b and c are subunits found using 2D NMR methods. HMBC correlations depicted by solid arrows, COSY correlations depicted by bold lines, NOESY correlations depicted by dashed arrows.</p

Fish Origins and Taxonomy, Microbial Isolates, and NCBI Closest Relatives.

<p>Fish Origins and Taxonomy, Microbial Isolates, and NCBI Closest Relatives.</p

Bioactivities of Fish Microbiome Isolates.

<p>A = Actinobacteria, F = Firmicutes, α = Alphaproteobacteria, γ = Gammaproteobacteria, (−) = Gram-negative, (+) = Gram-positive. Check mark indicates activity in growth inhibition assay.</p

Bioactivity of fungi from sloth hair isolated on potato dextrose agar (PDA) or malt extract agar (2%; MEA) against a range of Gram-positive and Gram-negative bacteria in the BioMAP assay [30].

<p>Fungi with particularly potent bioactivity were selected for further study and are marked with an asterisk (*). Fungal extracts causing full cell death are marked ‘A’ and those causing partial cell death are marked ‘WA’.</p><p>B. sub  =  Bacillus subtilis 168; E. fae  =  Enterococcus faecium ATCC 6569; L. iva  =  Listeria ivanovii BAA-139; S. epi  =  Staphylococcus epidermis ATCC 14990; S. au  =  Staphylococcus aureus ATCC 29213; MRSA  =  Methicillin Resistant Staphylococcus aureus BAA-44; Y. pse  =  Yersinia pseudotuberculosis IP2666 pIBI; P. aer  =  Pseudomonas aeruginosa ATCC 27835; S. typ  =  Salmonella typhimerium LT2; V. chol  =  Vibrio cholerae O1 (biotype El Tor A1552); E. coli  =  Escherichia coli K12 (BW 25113); A. baum  =  Acinetobacteria baumanii NCIMB 12457; E. aero  =  Enterobacter aerogenes ATCC 35029; O. ant  =  Ochrobactrum anthropi ATCC 49687; P. alc  =  Providencia alcallifaciens ATCC 9886.</p