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Jenkins, KM, Toske SG, Jensen PR, Fenical W.  1998.  Solanapyrones E-G, antialgal metabolites produced by a marine fungus. Phytochemistry. 49:2299-2304.   10.1016/s0031-9422(98)00211-8   AbstractWebsite

Three new alpha-pyrones, solanapyrones E (1), F (2), and G (3), in addition to the known phytotoxin solanapyrone C (4), were produced by an unidentified filamentous marine fungus isolated from the surface of the green alga Halimeda monile. The new solanapyrones were characterized by one and two-dimensional NMR spectroscopic techniques, and the absolute configuration of 2 was assigned by the Mosher method. The solanapyrones showed toxicity to the marine unicellular alga Dunaliella sp. at concentrations as low as 100 mu g ml(-1). The possible role of these compounds in phytotoxic associations between marine fungi and algae is discussed. (C) 1998 Elsevier Science Ltd. All rights reserved.

Jenkins, KM, Jensen PR, Fenical W.  1998.  Marine microbial chemical ecology, bioassays with marine microorganisms. Methods in chemical ecology. 2( Millar JG, Haynes KF, Eds.).:1-38., New York, NY: Chapman & Hall
Jenkins, KM, Renner MK, Jensen PR, Fenical W.  1998.  Exumolides A and B: Antimicroalgal cyclic depsipeptides produced by a marine fungus of the genus Scytalidium. Tetrahedron Letters. 39:2463-2466.   10.1016/s0040-4039(98)00288-3   AbstractWebsite

Two new cyclic hexadepsipeptides, exumolides A (1) and B (2) were produced by a marine fungus, identified as a Scytalidium sp., collected in the Bahamas. Two dimensional NMR methods, coupled with tandem mass spectrometry (MS-MS), were used to establish the structures of the new The exumolides exhibit antimicroalgal activity against the unicellular chlorophyte Dunaliella sp. at 20 mu g ml(-1) in liquid media cell growth assays. (C) 1998 Elsevier Science Ltd. All rights reserved.

Jenkins, KM, Jensen PR, Fenical W.  1999.  Thraustochytrosides A-C: new glycosphingolipids from a unique marine protist, Thraustochytrium globosum. Tetrahedron Letters. 40:7637-7640.   10.1016/s0040-4039(99)01562-2   AbstractWebsite

Three new glycosphingolipids, thraustochytrosides A-C (1-3) were produced, in culture, by a marine protist, identified as Thraustochytrium globosum, collected in the Bahamas. Two-dimensional NMR methods, coupled with tandem mass spectrometry (MS-MS), were used to establish the structures of the new compounds. (C) 1999 Elsevier Science Ltd. All rights reserved.

Jensen, PR, Kauffman CA, Fenical W.  1996.  High recovery of culturable bacteria from the surfaces of marine algae. Marine Biology. 126:1-7.   10.1007/bf00571371   AbstractWebsite

The culturability of heterotrophic marine bacteria obtained from the surfaces of two species of marine algae (Lobophora variegata and Halimeda copiosa) was assessed by comparing total DAPI-stained cell counts to colony-forming bacterial counts on two agar media. The colony-forming bacterial counts on a low-nutrient medium (LN) consisting of seawater and agar were significantly greater for both algal species than counts obtained on a high-nutrient medium (HN) similar in composition to that typically used for the isolation of heterotrophic marine bacteria. On average, 14 and 58%, respectively, of the total bacteria from L. variegata and H. copiosa were culturable on LN. These recovery rates far exceed those typically reported for marine bacteria. Of 119 LN strains obtained in pure culture, 55% failed to grow on HN. The yeast extract component of HN (1.5 gl(-1)) was responsible for the majority of the observed inhibition, suggesting that this nutrient can be highly toxic to marine bacteria. Eighty-nine percent of the strains inhibited by HN were capable of growth when the nutrients in this medium were diluted by a factor of 100 with seawater. Of 66 epiphytic strains, 30 (45%) initially inhibited by HN showed the ability to adapt to this medium after a period of laboratory handling. The initial inability of low-nutrient-adapted bacteria to grow on high-nutrient media may be due to nutrient shock. The results presented here indicate that the culturability of specific populations of marine bacteria can be dramatically improved by the use of low-nutrient media. Further, the importance of developing new medium formulations that eliminate traditional nutrients, some of which are clearly toxic to bacteria, is demonstrated.

Jensen, PR, Fenical W.  2005.  New natural product diversity from marine actinomycetes. Natural Products Drug Discovery and Therapeutic Medicine. ( Zhang L, Demain AL, Eds.).:315-328., Totowa, NJ: Humana Press
Jensen, PR, Dwight R, Fenical W.  1991.  Distribution of Actinomycetes in near-Shore Tropical Marine-Sediments. Applied and Environmental Microbiology. 57:1102-1108. AbstractWebsite

Actinomycetes were isolated from near-shore marine sediments collected at 15 island locations throughout the Bahamas. A total of 289 actinomycete colonies were observed, and all but 6 could be assigned to the suprageneric groups actinoplanetes and streptomycetes. A bimodal distribution in the actinomycete population in relation to depth was recorded, with the maximum numbers occurring in the shallow and deep sampling sites. This distribution can be accounted for by a rapid decrease in streptomycetes and an increase in actinoplanetes with increasing depth and does not conform to the theory that actinomycetes isolated from marine sources are of terrestrial origin. Sixty-three of the isolated actinomycetes were tested for the effects of seawater on growth. Streptomycete growth in nonsaline media was reduced by 39% compared with that in seawater. The actinoplanetes had a near obligate requirement of seawater for growth, and this is presented as evidence that actinomycetes can be physiologically active in the marine environment. Problems encountered with the enumeration of actinomycetes in marine sediments are also discussed.

Jensen, PR, Chavarria KL, Fenical W, Moore BS, Ziemert N.  2014.  Challenges and triumphs to genomics-based natural product discovery. Journal of Industrial Microbiology & Biotechnology. 41:203-209.   10.1007/s10295-013-1353-8   AbstractWebsite

Genome sequencing is rapidly changing the field of natural products research by providing opportunities to assess the biosynthetic potential of strains prior to chemical analysis or biological testing. Ready access to sequence data is driving the development of new bioinformatic tools and methods to identify the products of silent or cryptic pathways. While genome mining has fast become a useful approach to natural product discovery, it has also become clear that identifying pathways of interest is much easier than finding the associated products. This has led to bottlenecks in the discovery process that must be overcome for the potential of genomics-based natural product discovery to be fully realized. In this perspective, we address some of these challenges in the context of our work with the marine actinomycete genus Salinispora, which is proving to be a useful model with which to apply genome mining as an approach to natural product discovery.

Jensen, PR, Fenical W.  1996.  Marine bacterial diversity as a resource for novel microbial products. Journal of Industrial Microbiology & Biotechnology. 17:346-351.   10.1007/bf01574765   AbstractWebsite

Marine bacteria are an important and relatively unexplored resource for novel microbial products. In this review, we discuss a number of issues relevant to the industrial potential of marine microorganisms including how marine and terrestrial bacteria differ, both physiologically and taxonomically, and what constitute reasonable expectations of the biosynthetic capabilities of marine bacteria relative to terrestrial bacteria and to marine macroorganisms. Also discussed is the concept that bacterial associations with marine plants and animals, which range from casual encounters to obligate symbioses, provide unique opportunities for bacterial adaptation. It is proposed that some of these adaptations would not be selected for in the absence of environmental parameters associated with the host, and that these adaptations can include the biosynthesis of unique metabolic products.

Jensen, PR, Lauro FM.  2008.  An assessment of actinobacterial diversity in the marine environment. Antonie Van Leeuwenhoek International Journal of General and Molecular Microbiology. 94:51-62.   10.1007/s10482-008-9239-x   AbstractWebsite

The 16S rRNA gene sequence diversity within the Phylum Actinobacteria was assessed from four sources: PCR-generated V6 sequence tags derived from seawater samples, metagenomic data from the Global Ocean Sampling (GOS) expedition, marine-derived sequences maintained in the Ribosomal Database Project (RDP), and select cultured strains for which sequence data is not yet available in the RDP. This meta-analysis revealed remarkable levels of phylogenetic diversity and confirms the existence of major, deeply rooted, and as of yet uncharacterized lineages within the phylum. A dramatic incongruence among cultured strains and those detected using culture-independent techniques was also revealed. Redundancy among the actinobacteria detected using culture-independent techniques suggests that greater sequence coverage or improved DNA extraction efficiencies may be required to detect the rare phylotypes that can be readily cultured from marine samples. Conversely, new strategies need to be developed for the cultivation of frequently observed but yet to be cultured marine actinobacteria.

Jensen, PR, Williams PG, Oh DC, Zeigler L, Fenical W.  2007.  Species-specific secondary metabolite production in marine actinomycetes of the genus Salinispora. Applied and Environmental Microbiology. 73:1146-1152.   10.1128/aem.01891-06   AbstractWebsite

Here we report associations between secondary metabolite production and phylogenetically distinct but closely related marine actinomycete species belonging to the genus Salinispora. The pattern emerged in a study that included global collection sites, and it indicates that secondary metabolite production can be a species-specific, phenotypic trait associated with broadly distributed bacterial populations. Associations between actinomycete phylotype and chemotype revealed an effective, diversity-based approach to natural product discovery that contradicts the conventional wisdom that secondary metabolite production is strain specific. The structural diversity of the metabolites observed, coupled with gene probing and phylogenetic analyses, implicates lateral gene transfer as a source of the biosynthetic genes responsible for compound production. These results conform to a model of selection-driven pathway fixation occurring subsequent to gene acquisition and provide a rare example in which demonstrable physiological traits have been correlated to the fine-scale phylogenetic architecture of an environmental bacterial community.

Jensen, PR.  2010.  Linking species concepts to natural product discovery in the post-genomic era. Journal of Industrial Microbiology & Biotechnology. 37:219-224.   10.1007/s10295-009-0683-z   AbstractWebsite

A widely accepted species concept for bacteria has yet to be established. As a result, species designations are inconsistently applied and tied to what can be considered arbitrary metrics. Increasing access to DNA sequence data and clear evidence that bacterial genomes are dynamic entities that include large numbers of horizontally acquired genes have added a new level of insight to the ongoing species concept debate. Despite uncertainties over how to apply species concepts to bacteria, there is clear evidence that sequence-based approaches can be used to resolve cohesive groups that maintain the properties of species. This cohesion is clearly evidenced in the genus Salinispora, where three species have been discerned despite very close relationships based on 16S rRNA sequence analysis. The major phenotypic differences among the three species are associated with secondary metabolite production, which occurs in species-specific patterns. These patterns are maintained on a global basis and provide evidence that secondary metabolites have important ecological functions. These patterns also suggest that an effective strategy for natural product discovery is to target the cultivation of new Salinispora taxa. Alternatively, bioinformatic analyses of biosynthetic genes provide opportunities to predict secondary metabolite novelty and reduce the redundant isolation of well-known metabolites. Although much remains to be learned about the evolutionary relationships among bacteria and how fundamental units of diversity can be resolved, genus and species descriptions remain the most effective method of scientific communication.

Jensen, PR, Fenical W.  1995.  The Relative Abundance and Seawater Requirements of Gram-Positive Bacteria in near-Shore Tropical Marine Samples. Microbial Ecology. 29:249-257.   10.1007/bf00164888   AbstractWebsite

The relative abundance of gram-positive bacteria in a variety of near-shore marine samples was determined using the KOH method. Gram-positive bacteria accounted for 14%, 25%, 31%, and 12%, respectively, of the colony-forming bacteria obtained from seawater, sediments, and the surfaces of algae and invertebrates. A total of 481 gram-positive strains were isolated representing a wide range of morphological groups including regular and irregular rods, cocci, and actinomycetes. Seventy-seven percent of the strains characterized did not form spores and were aerobic, catalase-positive rods with regular to irregular cell morphologies. Eighty-two percent of the strains tested showed an obligate requirement of seawater for growth. None of the cocci tested required seawater or sodium for growth. This is the first report documenting that gram-positive bacteria can compose a large percentage of the culturable, heterotrophic bacteria associated with the surfaces of tropical marine algae.

Jensen, PR, Jenkins KM, Porter D, Fenical W.  1998.  Evidence that a new antibiotic flavone glycoside chemically defends the sea grass Thalassia testudinum against zoosporic fungi. Applied and Environmental Microbiology. 64:1490-1496. AbstractWebsite

Significantly fewer thraustochytrid protists (zoosporic fungi) were observed in association with healthy leaf tissue of the marine angiosperm Thalassia testudinum than in association with sterilized samples that were returned to the collection site fur 48 h. In support of the hypothesis that sea grass secondary metabolites were responsible for these differences, extracts of healthy T. testudinum leaf tissues inhibited the growth of the co-occurring thraustochytrid Schizochytrium aggregatum and deterred the attachment of S. aggregatum motile zoospores to an extract-impregnated substrate. By using S. aggregatum for bioassay-guided chemical fractionation, a new flavone glycoside was isolated and structurally characterized as luteolin 7-O-beta-D-glucopyranosyl-2 "-sulfate. Whole-leaf tissue concentrations of this metabolite (4 mg/ml of wet leaf tissue) inhibited S. aggregatum attachment, and a significantly lower concentration (270 mu g/ml) reduced thraustochytrid growth by 50%, suggesting that natural concentration are at least 15 times greater than that needed for significant microbiological effects. These results offer the first complete chemical characterization of a sea grass sulfated flavone glycoside and provide evidence that a secondary metabolite chemically defends T. testudinum against fouling microorganisms.

Jensen, PR.  2016.  Natural products and the gene cluster revolution. Trends in Microbiology. 24:968-977.   10.1016/j.tim.2016.07.006   AbstractWebsite

Genome sequencing has created unprecedented opportunities for natural product discovery and new insight into the diversity and distributions of natural-product biosynthetic gene clusters (BGCs). These gene collectives are highly evolved for horizontal exchange, thus providing immediate opportunities to test the effects of small molecules on fitness. The marine actinomycete genus Salinispora maintains extraordinary levels of BGC diversity and has become a useful model for studies of secondary metabolism. Most Salinispora BGCs are observed infrequently, resulting in high population-level diversity while conforming to constraints associated with maximum genome size. Comparative genomics is providing a mechanism to assess secondary metabolism in the context of evolution and evidence that some products represent ecotype-defining traits while others appear selectively neutral.

Jensen, PR, Mafnas C.  2006.  Biogeography of the marine actinomycete Salinispora. Environmental Microbiology. 8:1881-1888.   10.1111/j.1462-2920.2006.01093.x   AbstractWebsite

Marine actinomycetes belonging to the genus Salinispora were cultured from marine sediments collected at six geographically distinct locations. Detailed phylogenetic analyses of both 16S rRNA and gyrB gene sequences reveal that this genus is comprised of three distinct but closely related clades corresponding to the species Salinispora tropica, Salinispora arenicola and a third species for which the name 'Salinispora pacifica' is proposed. Salinispora arenicola was cultured from all locations sampled and provides clear evidence for the cosmopolitan distribution of an individual bacterial species. The co-occurrence of S. arenicola with S. tropica and S. pacifica suggests that ecological differentiation as opposed to geographical isolation is driving speciation within the genus. All Salinispora strains cultured to date share greater than 99% 16S rRNA gene sequence identity and thus comprise what has been described as a microdiverse ribotype cluster. The description of this cluster as a new genus, containing multiple species, provides clear evidence that fine-scale 16S rDNA sequence analysis can be used to delineate among closely related species and that more conservative operational taxonomic unit values may significantly underestimate global species diversity.

Jensen, PR, Fenical W.  1994.  Strategies for the Discovery of Secondary Metabolites from Marine-Bacteria - Ecological Perspectives. Annual Review of Microbiology. 48:559-584.   10.1146/annurev.mi.48.100194.003015   AbstractWebsite

Marine-microorganisms have become an important point of study in the search for novel microbial products. Today, both academic and industrial interest in marine microorganisms is on the rise, in part-because of the growing number of unique, biologically active secondary metabolites reported from marine bacteria. Our ability to assess the biosynthetic potential of marine bacteria, however, is inevitably coupled to our basic understanding of their biology. This review summarizes the chemical discoveries and biological activities reported from marine bacteria and focuses upon several microbiological topics as they relate to natural product discovery, including the distributions, diversity, and culturability of marine bacteria, as well as the role of symbiotic bacteria in the production of substances previously ascribed to other sources.

Jensen, PR, Fenical W.  2002.  Secondary metabolites from marine fungi. Fungi in marine environments. ( Hyde KD, University of Hong Kong. Centre for Research in Fungal D, Eds.).:293-315., Hong Kong: Fungal Diversity Press
Jensen, PR, Fenical W.  2000.  Marine microorganisms and drug discovery: current status and future potential. Drugs from the sea. ( Fusetani N, Ed.).:6-29., Basel ; New York: Karger
Jensen, PR, Gontang E, Mafnas C, Mincer TJ, Fenical W.  2005.  Culturable marine actinomycete diversity from tropical Pacific Ocean sediments. Environmental Microbiology. 7:1039-1048.   10.1111/j.1462-2920.2005.00785.x   AbstractWebsite

Actinomycetes were cultivated using a variety of media and selective isolation techniques from 275 marine samples collected around the island of Guam. In total, 6425 actinomycete colonies were observed and 983 (15%) of these, representing the range of morphological diversity observed from each sample, were obtained in pure culture. The majority of the strains isolated (58%) required seawater for growth indicating a high degree of marine adaptation. The dominant actinomycete recovered (568 strains) belonged to the seawater-requiring marine taxon 'Salinospora', a new genus within the family Micromonosporaceae. A formal description of this taxon has been accepted for publication (Maldonado et al., 2005) and includes a revision of the generic epithet to Salinispora gen. nov. Members of two major new clades related to Streptomyces spp., tentatively called MAR2 and MAR3, were cultivated and appear to represent new genera within the Streptomycetaceae. In total, five new marine phylotypes, including two within the Thermomonosporaceae that appear to represent new taxa, were obtained in culture. These results support the existence of taxonomically diverse populations of phylogenetically distinct actinomycetes residing in the marine environment. These bacteria can be readily cultured using low nutrient media and represent an unexplored resource for pharmaceutical drug discovery.

Jensen, PR, Mincer TJ, Williams PG, Fenical W.  2005.  Marine actinomycete diversity and natural product discovery. Antonie Van Leeuwenhoek International Journal of General and Molecular Microbiology. 87:43-48.   10.1007/s10482-004-6540-1   AbstractWebsite

Microbial natural products remain an important resource for drug discovery yet the microorganisms inhabiting the world's oceans have largely been overlooked in this regard. The recent discovery of novel secondary metabolites from taxonomically unique populations of marine actinomycetes suggests that these bacteria add an important new dimension to microbial natural product research. Continued efforts to characterize marine actinomycete diversity and how adaptations to the marine environment affect secondary metabolite production will create a better understanding of the potential utility of these bacteria as a source of useful products for biotechnology.

Jensen, PR, Harvell CD, Wirtz K, Fenical W.  1996.  Antimicrobial activity of extracts of Caribbean gorgonian corals. Marine Biology. 125:411-419.   10.1007/bf00346321   AbstractWebsite

Extracts of 39 species of Caribbean gorgonians were tested for antimicrobial activity against 15 strains of marine bacteria. The bacteria consisted of three opportunistic pathogens, Vibrio parahaemolyticus, Leucothrix mucor, and Aerococcus viridans, and 12 strains isolated from either healthy or decayed gorgonians. Overall, only 15% (79 out of 544) of the tests resulted in antibacterial activity with 33% (13 out of 39) of the gorgonians inhibiting only one bacterial strain and 23% (9 out of 39) showing no activity. The extracts of four Pseudopterogorgia species showed relatively high levels of activity, inhibiting 43 to 86% of the bacterial strains. The potency of the active Pseudopterogorgia species was variable, however, and three additional Pseudopterogorgia species were inactive against all bacterial strains. With the exception of one sensitive strain, Vibrio species were resistant to gorgonian metabolites. Our results indicate that organic extracts of most Caribbean gorgonians do not possess potent, broad-spectrum antibacterial activity inhibitory to the growth of opportunistic marine pathogens and bacteria associated with healthy and decayed gorgonian surfaces. These findings suggest that the inhibition of bacterial growth is not the primary ecological function of gorgonian secondary metabolites and that bacteria may not be important selective agents in the evolution of gorgonian secondary chemistry.

Jiang, ZD, Jensen PR, Fenical W.  1999.  Lobophorins A and B, new antiinflammatory macrolides produced by a tropical marine bacterium. Bioorganic & Medicinal Chemistry Letters. 9:2003-2006.   10.1016/s0960-894x(99)00337-6   AbstractWebsite

Two new antiinflammatory macrolides, lobophorins A and B (1 and 2), have been isolated from fermentation broths of a marine bacterium isolated from the surface the Caribbean brown alga Lobophora variegata (Dictyotales). The new compounds, distantly related to antibiotics of the kijanimicin class, are potent inhibitors of topical PMA-induced edema in the mouse ear assay when administered either topically or IP. (C) 1999 Published by Elsevier Science Ltd. All rights reserved.

Jiang, ZD, Jensen PR, Fenical W.  1997.  Actinoflavoside, a novel flavonoid-like glycoside produced by a marine bacterium of the genus Streptomyces. Tetrahedron Letters. 38:5065-5068.   10.1016/s0040-4039(97)01127-1   AbstractWebsite

Actinoflavoside (1), a novel glycoside composed of a rare 2, 3, 6-trideoxy-3-amino-ribopyranoside (ristosamine) aminosugar and an aglycone reminiscent of the plant flavonoids, was isolated from the culture broth of a marine Streptomyces sp. The structure of actinoflavoside was established by spectroscopic analysis and by chemical degradation. (C) 1997 Elsevier Science Ltd.