E. Esquenazi - Academia.edu (original) (raw)

Papers by E. Esquenazi

Proceedings of the National Academy of Sciences, 2011

Sessile marine organisms are prolific sources of biologically active natural products. However, t... more Sessile marine organisms are prolific sources of biologically active natural products. However, these compounds are often found in highly variable amounts, with the abiotic and biotic factors governing their production remaining poorly understood. We present an approach that permits monitoring of in vivo natural product production and turnover using mass spectrometry and stable isotope ( 15 N) feeding with small cultures of various marine strains of the natural product-rich cyanobacterial genus Lyngbya. This temporal comparison of the amount of in vivo 15 N labeling of nitrogencontaining metabolites represents a direct way to discover and evaluate factors influencing natural product biosynthesis, as well as the timing of specific steps in metabolite assembly, and is a strong complement to more traditional in vitro studies. Relative quantification of 15 N labeling allowed the concurrent measurement of turnover rates of multiple natural products from small amounts of biomass. This technique also afforded the production of the neurotoxic jamaicamides to be more carefully studied, including an assessment of how jamaicamide turnover compares with filament growth rate and primary metabolism and provided new insights into the biosynthetic timing of jamaicamide A bromination. This approach should be valuable in determining how environmental factors affect secondary metabolite production, ultimately yielding insight into the energetic balance among growth, primary production, and secondary metabolism, and thus aid in the development of methods to improve compound yields for biomedical or biotechnological applications.

PLoS ONE, 2011

Filamentous marine cyanobacteria are extraordinarily rich sources of structurally novel, biomedic... more Filamentous marine cyanobacteria are extraordinarily rich sources of structurally novel, biomedically relevant natural products. To understand their biosynthetic origins as well as produce increased supplies and analog molecules, access to the clustered biosynthetic genes that encode for the assembly enzymes is necessary. Complicating these efforts is the universal presence of heterotrophic bacteria in the cell wall and sheath material of cyanobacteria obtained from the environment and those grown in uni-cyanobacterial culture. Moreover, the high similarity in genetic elements across disparate secondary metabolite biosynthetic pathways renders imprecise current gene cluster targeting strategies and contributes sequence complexity resulting in partial genome coverage. Thus, it was necessary to use a dual-method approach of single-cell genomic sequencing based on multiple displacement amplification (MDA) and metagenomic library screening. Here, we report the identification of the putative apratoxin. A biosynthetic gene cluster, a potent cancer cell cytotoxin with promise for medicinal applications. The roughly 58 kb biosynthetic gene cluster is composed of 12 open reading frames and has a type I modular mixed polyketide synthase/nonribosomal peptide synthetase (PKS/NRPS) organization and features loading and off-loading domain architecture never previously described. Moreover, this work represents the first successful isolation of a complete biosynthetic gene cluster from Lyngbya bouillonii, a tropical marine cyanobacterium renowned for its production of diverse bioactive secondary metabolites.

Journal of Proteomics, 2012

Many microbes can be cultured as single-species communities. Often, these colonies are controlled... more Many microbes can be cultured as single-species communities. Often, these colonies are controlled and maintained via the secretion of metabolites. Such metabolites have been an invaluable resource for the discovery of therapeutics (e.g. penicillin, taxol, rapamycin, epothilone). In this article, written for a special issue on imaging mass spectrometry, we show that MALDI-imaging mass spectrometry can be adapted to observe, in a spatial manner, the metabolic exchange patterns of a diverse array of microbes, including thermophilic and mesophilic fungi, cyanobacteria, marine and terrestrial actinobacteria, and pathogenic bacteria. Dependent on media conditions, on average and based on manual analysis, we observed 11.3 molecules associated with each microbial IMS experiment, which was split nearly 50:50 between secreted and colony-associated molecules. The spatial distributions of these metabolic exchange factors are related to the biological and ecological functions of the organisms. This work establishes that MALDI-based IMS can be used as a general tool to study a diverse array of microbes. Furthermore the article forwards the notion of the IMS platform as a window to discover previously unreported molecules by monitoring the metabolic exchange patterns of organisms when grown on agar substrates. This article is part of a Special Issue entitled: Mass Spectrometry Imaging.

Journal of Natural Products, 2011

b S Supporting Information C yanobacteria form a monophyletic bacterial phylum extraordinarily ri... more b S Supporting Information C yanobacteria form a monophyletic bacterial phylum extraordinarily rich in bioactive secondary metabolites. 1,2 A number of these metabolites are potent toxins associated with harmful algal blooms. 3 Ironically, many of these same bioactive molecules have simultaneously been discovered to have a variety of potential pharmaceutical applications. 2 In order to support and enhance the search for novel natural products, it is valuable to have proper understanding of the taxonomy of the secondary metabolite-producing cyanobacteria. 4 The traditional system of classifying cyanobacteria, which is based on phenotypical observations, has recently shown major incongruities with phylogenetic classifications where evolutionarily informative housekeeping genes are analyzed. 5,6 This is partly a result of significant morphological plasticity among cyanobacteria, even at the genus level. 7 Furthermore, cyanobacterial classification systems are largely founded on a relatively limited number of morphological characters, which often appear similar due to convergent evolution. 8 Thus, the recent inclusion of phylogenetic analysis in classification of these microorganisms has led to a more accurate taxonomic understanding of these cyanobacterial groups. 9,10 These developments have benefitted not only the field of taxonomy but also natural products drug discovery efforts. For example, phylogenetic approaches have been used to (i) accurately identify natural product-producing strains; 11 (ii) analyze the microbial diversity in natural product-producing assemblages; 12,13 (iii) re-collect specific natural product-producing strains from the environment; 12 and (iv) distinguish cyanobacterial chemotypes. 14 According to basic evolutionary principles, metabolic and biosynthetic pathways are evolving between geographically isolated or distant populations as an adaptation to new environments. This concept of biogeographical diversification corresponds to a major underlying rationale and approach in the search for new natural products. 13,14 While in freshwater cyanobacteria secondary metabolites such as microcystins and cylindrospermopsins have been reported from phylogenetically unrelated genera, the production of secondary metabolites in marine cyanobacteria as well as the distribution of their biosynthetic pathways has been linked with the phylogenetic positions of the secondary metabolite production. 15,3 However, to date, the two concepts of evolutionary relatedness and geographic diversification have not been effectively combined for predictive exploration of new natural products from marine cyanobacteria.

Journal of Natural Products, 2010

Bioassay-guided fractionation of the extract of a consortium of a marine cyanobacterium and a red... more Bioassay-guided fractionation of the extract of a consortium of a marine cyanobacterium and a red alga (Rhodophyta) led to the discovery of a novel compound, palmyramide A, along with the known compounds curacin D and malyngamide C. The planar structure of palmyramide A was determined by one-and two-dimensional NMR studies and mass spectrometry. Palmyramide A is a cyclic depsipeptide which features an unusual arrangement of three amino acids and three hydroxy acids; one of the hydroxy acids is the rare 2,2-dimethyl-3-hydroxyhexanoic acid unit (Dmhha). The absolute configurations of the six residues were determined by Marfey's analysis, chiral HPLC analysis and GC/MS analysis of the hydrolysate. Morphological and phylogenetic studies revealed the sample to be composed of a Lyngbya majuscula-Centroceras sp. association. MALDI-imaging analysis of the cultured L. majuscula indicated that it was the true producer of this new depsipeptide. Pure palmyramide A showed sodium channel blocking activity in neuro-2a cells and cytotoxic activity in H-460 human lung carcinoma cells.

Proceedings of the National Academy of Sciences of the United States of America, Jan 24, 2011

Filamentous cyanobacteria of the genus Lyngbya are important contributors to coral reef ecosystem... more Filamentous cyanobacteria of the genus Lyngbya are important contributors to coral reef ecosystems, occasionally forming dominant cover and impacting the health of many other co-occurring organisms. Moreover, they are extraordinarily rich sources of bioactive secondary metabolites, with 35% of all reported cyanobacterial natural products deriving from this single pantropical genus. However, the true natural product potential and life strategies of Lyngbya strains are poorly understood because of phylogenetic ambiguity, lack of genomic information, and their close associations with heterotrophic bacteria and other cyanobacteria. To gauge the natural product potential of Lyngbya and gain insights into potential microbial interactions, we sequenced the genome of Lyngbya majuscula 3L, a Caribbean strain that produces the tubulin polymerization inhibitor curacin A and the molluscicide barbamide, using a combination of Sanger and 454 sequencing approaches. Whereas ∼ 293,000 nucleotides of...

Environmental Microbiology, 2011

Marine cyanobacteria are prolific producers of bioactive secondary metabolites responsible for ha... more Marine cyanobacteria are prolific producers of bioactive secondary metabolites responsible for harmful algal blooms as well as rich sources of promising biomedical lead compounds. The current study focused on obtaining a clearer understanding of the remarkable chemical richness of the cyanobacterial genus Lyngbya. Specimens of Lyngbya from various environmental habitats around Curaçao were analyzed for their capacity to produce secondary metabolites by genetic screening of their biosynthetic pathways. The presence of biosynthetic pathways was compared with the production of corresponding metabolites by LC-ESI-MS 2 and MALDI-TOF-MS. The comparison of biosynthetic capacity and actual metabolite production revealed no evidence of genetic silencing in response to environmental conditions. On a cellular level, the metabolic origin of the detected metabolites was pinpointed to the cyanobacteria, rather than the sheath-associated heterotrophic bacteria, by MALDI-TOF-MS and multiple displacement amplification of singlecells. Finally, the traditional morphology-based taxonomic identifications of these Lyngbya populations were combined with their phylogenetic relationships. As a result, polyphyly of morphologically similar cyanobacteria was identified as the major explanation for the perceived chemical richness of the genus Lyngbya, a result which further underscores the need to revise the taxonomy of this group of biomedically important cyanobacteria.

Applied and Environmental Microbiology, 2013

Updated information and services can be found at: These include: SUPPLEMENTAL MATERIAL Supplement... more Updated information and services can be found at: These include: SUPPLEMENTAL MATERIAL Supplemental material REFERENCES http://aem.asm.org/content/79/22/7073#ref-list-1 at: This article cites 71 articles, 22 of which can be accessed free CONTENT ALERTS more» articles cite this article), Receive: RSS Feeds, eTOCs, free email alerts (when new http://journals.asm.org/site/misc/reprints.xhtml Information about commercial reprint orders: http://journals.asm.org/site/subscriptions/ To subscribe to to another ASM Journal go to: on May 2, 2014 by WELCH MEDICAL LIBRARY -John Hopkins U http://aem.asm.org/ Downloaded from on May 2, 2014 by WELCH MEDICAL LIBRARY -John Hopkins U

Applied and Environmental Microbiology, 2011

Bacteria of the genus Frankia are mycelium-forming actinomycetes that are found as nitrogen-fixin... more Bacteria of the genus Frankia are mycelium-forming actinomycetes that are found as nitrogen-fixing facultative symbionts of actinorhizal plants. Although soil-dwelling actinomycetes are well-known producers of bioactive compounds, the genus Frankia has largely gone uninvestigated for this potential. Bioinformatic analysis of the genome sequences of Frankia strains ACN14a, CcI3, and EAN1pec revealed an unexpected number of secondary metabolic biosynthesis gene clusters. Our analysis led to the identification of at least 65 biosynthetic gene clusters, the vast majority of which appear to be unique and for which products have not been observed or characterized. More than 25 secondary metabolite structures or structure fragments were predicted, and these are expected to include cyclic peptides, siderophores, pigments, signaling molecules, and specialized lipids. Outside the hopanoid gene locus, no cluster could be convincingly demonstrated to be responsible for the few secondary metabolites previously isolated from other Frankia strains. Few clusters were shared among the three species, demonstrating species-specific biosynthetic diversity. Proteomic analysis of Frankia sp. strains CcI3 and EAN1pec showed that significant and diverse secondary metabolic activity was expressed in laboratory cultures. In addition, several prominent signals in the mass range of peptide natural products were observed in Frankia sp. CcI3 by intact-cell matrix-assisted laser desorption-ionization mass spectrometry (MALDI-MS). This work supports the value of bioinformatic investigation in natural products biosynthesis using genomic information and presents a clear roadmap for natural products discovery in the Frankia genus.

Proceedings of the …, 2008

In all probability, natural selection began as ancient marine microorganisms were required to com... more In all probability, natural selection began as ancient marine microorganisms were required to compete for limited resources. These pressures resulted in the evolution of diverse genetically encoded small molecules with a variety of ecological and metabolic roles. Remarkably, ...