Discovery of novel metabolites from marine actinomycetes Kin S Lam

Transcription

1 Discovery of novel metabolites from marine actinomycetes Kin S Lam Recent findings from culture-dependent and cultureindependent methods have demonstrated that indigenous marine actinomycetes exist in the oceans and are widely distributed in different marine ecosystems. There is tremendous diversity and novelty among the marine actinomycetes present in marine environments. Progress has been made to isolate novel actinomycetes from samples collected at different marine environments and habitats. These marine actinomycetes produce different types of new secondary metabolites. Many of these metabolites possess biological activities and have the potential to be developed as therapeutic agents. Marine actinomycetes are a prolific but underexploited source for the discovery of novel secondary metabolites. Addresses Department of Microbiology and Anti-infective Discovery, Nereus Pharmaceuticals, Inc., Wateridge Circle, San Diego, CA 92121, USA Corresponding author: Lam, Kin S (rlam@nereuspharm.com) This review comes from a themed issue on Ecology and industrial microbiology Edited by Arnold Demain and Lubbert Djikhuizen Available online 3rd May /$ see front matter # 2006 Elsevier Ltd. All rights reserved. DOI /j.mib Introduction Actinomycetes are the most economically and biotechnologically valuable prokaryotes. They are responsible for the production of about half of the discovered bioactive secondary metabolites [1], notably antibiotics [1,2], antitumor agents [3], immunosuppressive agents [4] and enzymes [5,6]. Because of the excellent track record of actinomycetes in this regard, a significant amount of effort has been focused on the successful isolation of novel actinomycetes from terrestrial sources for drug screening programs in the past fifty years. Recently, the rate of discovery of new compounds from terrestrial actinomycetes has decreased, whereas the rate of re-isolation of known compounds has increased [7]. Thus, it is crucial that new groups of actinomycetes from unexplored or underexploited habitats be pursued as sources of novel bioactive secondary metabolites. Although the diversity of life in the terrestrial environment is extraordinary, the greatest biodiversity is in the oceans [8]. More than 70% of our planet s surface is covered by oceans and life on Earth originated from the sea. In some marine ecosystems, such as the deep sea floor and coral reefs, experts estimate that the biological diversity is higher than in the tropical rainforests [9]. As marine environmental conditions are extremely different from terrestrial ones, it is surmised that marine actinomycetes have different characteristics from those of terrestrial counterparts and, therefore, might produce different types of bioactive compounds. The living conditions to which marine actinomycetes had to adapt during evolution range from extremely high pressure (with a maximum of 1100 atmospheres) and anaerobic conditions at temperatures just below 0 8C on the deep sea floor, to high acidic conditions (ph as low as 2.8) at temperatures of over 100 8C near hydrothermal vents at the mid-ocean ridges. It is likely that this is reflected in the genetic and metabolic diversity of marine actinomycetes, which remains largely unknown. Indeed, the marine environment is a virtually untapped source of novel actinomycete diversity [10,11] and, therefore, of new metabolites [12 14 ]. However, the distribution of actinomycetes in the sea is largely unexplored and the presence of indigenous marine actinomycetes in the oceans remains elusive. This is partly caused by the lack of effort spent in exploring marine actinomycetes, whereas terrestrial actinomycetes have been, until recently, a successful source of novel bioactive metabolites. Furthermore, skepticism regarding the existence of indigenous populations of marine actinomycetes arises from the fact that the terrestrial bacteria produce resistant spores that are known to be transported from land into sea, where they can remain available but dormant for many years [15 17]. Thus, it has been frequently assumed that actinomycetes isolated from marine samples are merely of terrestrial origin. Indigenous marine actinomycetes Early evidence supporting the existence of marine actinomycetes came from the description of Rhodococcus marinonascene, the first marine actinomycete species to be characterized [18]. Further support has come from the discovery that some strains display specific marine adaptations [19], whereas others appear to be metabolically active in marine sediments [20]. However, these early findings did not generate enough excitement to stimulate the search for novel actinomycetes in the marine environment. Recent data from culture-dependent studies have shown that indigenous marine actinomycetes indeed exist in the oceans. These include members of the genera Dietzia, Rhodococcus, Streptomyces, Salinispora, Marinophilus, Solwaraspora, Salinibacterium, Aeromicrobium marinum,

2 246 Ecology and industrial microbiology Williamsia maris and Verrucosispora [10,12,14,21, 22]. Among these, the most exciting finding is the discovery of the first obligate new marine actinomycete genus, Salinispora (formerly known as Salinospora), and the demonstration of the widespread populations of this genus in ocean sediments by Fenical s research group [23,24 ]. Subsequently, Salinispora strains were also isolated from the Great Barrier Reef marine sponge Pseudoceratina clavata [25]. The formal description of Salinispora, with two type species (S. tropica and S. arenicola), has recently been published [26]. Furthermore, Mincer et al. [24 ] have demonstrated that Salinispora strains are actively growing in some sediment samples indicating that these bacteria are metabolically active in the natural marine environment. In this context, Grossart et al. [27] have illustrated that actinomycetes account for approximately 10% of the bacteria colonizing marine organic aggregates (marine snow [28]) and that their antagonistic activity might be highly significant in maintaining their presence, which affects the degradation and mineralization of organic matter. Therefore, actinomycetes are active components of marine microbial communities. They form a stable, persistent population in various marine ecosystems. The discovery of numerous new marine actinomycete taxa, their demonstrated metabolic activity in their natural environments and their ability to form stable populations in different habitats clearly illustrate that indigenous marine actinomycetes indeed exist in the oceans. Another important observation is that novel compounds with biological activities have been isolated from these marine actinomycetes [12 14 ], indicating that marine actinomycetes are an important source for the discovery of novel secondary metabolites. The presence of marine actinomycetes is substantiated by culture-independent studies. The majority of microorganisms from the natural environment resists cultivation in the laboratory. Ribosomal RNA analysis suggests that uncultivated organisms are found in nearly every prokaryotic group, and several divisions have unknown cultivated representatives [29,30]. There is no exception for the cultivation of actinomycetes from the marine environment. Recent culture-independent studies [31,32 ] have shown that the majority of actinomycetes from marine environments, such as sediments and sponges, are not recovered by cultivation-based methods. Culture-independent methods have demonstrated that marine environments contain a wide range of unique actinomycetes not present in the terrestrial environment [31,32 ]. Cultivation of these novel actinomycetes will facilitate the investigation of their ecological roles and provide an important source for discovery of novel metabolites. Distributions of marine actinomycetes Recent findings confirm the presence of indigenous marine actinomycetes in the oceans and indicate that marine actinomycetes are widely distributed in different marine environments and habitats. Both culture-dependent and culture-independent methods demonstrate that novel actinomycetes can be found everywhere in the oceans from deep sea floor to coral reef, from sediments to invertebrates and plants. Actinomycetes are present over the complete depth range found in the ocean realms, from the surface of the oceans, such as in the near-shore and inter-tidal environments in French Guiana [33] and Korean tidal flats [34], right down to the deepest abyss, such as below sub-floor sediments [35]. Marine actinomycetes Dietzia maris, Rhodococcus erythropolis and Kocuria erythromyxa were isolated from a sub-seafloor sediment core collected at a depth of 1225 meters off Hokkaido [36]. Actinomycetes were also isolated from samples collected at the deepest abyss, the Challenger Deep off the Marianas, at a depth of meters [10 ]. Jensen et al. [21 ] isolated five new actinomycete phylotypes from marine sediments collected around the island of Guam. Regardless of the extensive variation among the different marine environments, the presence of actinomycetes that are distantly related to known taxa has been detected in abundance. Actinomycetes have been detected in unique marine environments, such as in marine organic aggregates and deep-sea gas hydrate reservoirs, where they were found to be the major components of the microbial communities. Thus, actinomycete phylotypes comprise up to 30 40% of clone libraries obtained from hydrate-bearing sediments from the Gulf of Mexico [37] and the Nankai Trough near Japan [38,39]. Actinomycetes isolated from the marine organic aggregates in the Wadden Sea have demonstrated high antagonistic activity within this microbial community [27]. Novel actinomycete groups have been found in the Great Barrier Reef sponges Rhopaloeides odorabile, Pseudoceratina clavata and Candidaspongia flabellate, and the Mediterranean sponges Aplysina aerophoba and Theonella swinhoei [25,40 42]. Unusual actinomycetes, belonging to Micrococceae, Dermatophilaceae and Gordoniaceae, have been isolated from sponges [32 ]. Jensen et al. [21 ] reported the isolation of actinomycetes from algal and sponge samples and observed different rates of recovery of actinomycetes, which might have been caused by different methodologies used to process the samples. Novel bioactive metabolites have been obtained from actinomycetes isolated from sponges [32 ]. Actinomycetes isolated from the samples collected at the marine environments mentioned above, such as the deep sea floor, marine invertebrates and marine snow, all represent unique ecosystems that cannot be found anywhere else in the world. The isolation of marine actinomycetes that evolved from, and adapted to, these unique ecosystems is a prolific source for the discovery of novel

3 Discovery of novel metabolites from marine actinomycetes Lam 247 secondary metabolites. For example, marine invertebrates such as corals and sponges are hosts to a multitude of microorganisms. These animals can be considered as miniature ecosystems in which different species of microorganisms compete with each other for resources. Therefore, secondary metabolites originating from symbiotic or commensal microorganisms of marine invertebrates might not necessarily have a function in the chemical ecology of the host animal itself, but they could instead be chemical weapons or signaling agents employed in the fight for growth and survival that is going on among these microorganisms. Novel metabolites produced by marine actinomycetes Although the exploitation of marine actinomycetes as a source for discovery of novel secondary metabolites is at an early stage, numerous novel metabolites have been isolated in the past few years. Table 1 shows some examples of novel secondary metabolites isolated from marine actinomycetes from 2003 to This is by no means an extensive search of all novel secondary metabolites produced by marine actinomycetes during this three-year period, nevertheless this list is impressive, covering many different diverse structures with biological activities. Four compounds from Table 1 are of particular interest. Abyssomicin C (Figure 1a) is a novel polycyclic polyketide antibiotic produced by a marine Verrucosispora strain [43]. It is a potent inhibitor of para-aminobenzoic acid biosynthesis and, therefore, inhibits the folic acid biosynthesis at an earlier stage than the well-known synthetic sulfa drugs [44]. Abyssomicin C possesses potent activity against Gram-positive bacteria, including clinical isolates of multiple-resistant and vancomycin-resistant Staphylococcus aureus. Abyssomicin C or its analog [45] has the potential to be developed as antibacterial agent against drug-resistant pathogens. Diazepinomicin (ECO-4601, Figure 1b) is a unique farnesylated dibenzodiazepinone produced by a Micromonospora strain [46]. It possesses antibacterial, antiinflammatory and antitumor activity. It has a broad spectrum of in vitro cytotoxicity and has demonstrated in vivo activity against glioma, breast and prostate cancer in mouse models. The preclinical development of ECO as an anticancer agent has been completed by Ecopia BioSciences Inc. Ecopia filed Clinical Trial Application (equivalent to Investigational New Drug application in the USA) for ECO-4601 in Canada on 3 January Salinosporamide A (NPI-0052, Figure 1c) is a novel b- lactone-g-lactam isolated from a fermentation broth of a new obligate marine actinomycete, Salinispora tropica [26,47]. NPI-0052 is an orally active proteasome inhibitor that induces apoptosis in multiple myeloma cells with mechanisms distinct from the commercial proteasome inhibitor anticancer drug Bortezomib [48]. NPI-0052 is being developed by Nereus Pharmaceuticals, Inc. and is scheduled to enter clinical studies for treatment of cancer Table 1 Novel metabolites produced by marine actinomycetes during the period Compound Source Activity Refs Abyssomicins Verrucosispora sp. Antibacterial [43] Aureoverticillactam Streptomyces aureoverticillatus Anticancer [55] Bonactin Streptomyces sp. Antibacterial; antifungal [56] Caprolactones Streptomyces sp. Anticancer [57] Chandrananimycins Actinomadura sp. Antialagl; antibacterial; anticancer; antifungal [58] Chinikomycins Streptomyces sp. Anticancer [59] Chloro-dihydroquinones Novel actinomycete Antibacterial; anticancer [60] Diazepinomicin (ECO-4601) Micromonosproa sp. Antibacterial; anticancer; anti-inflammatory [46] 3,6-disubstituted indoles Streptomyces sp. Anticancer [61] Frigocyclinone Streptomyces griseus Antibacterial [62] Glaciapyrroles Streptomyces sp. Antibacterial [63] Gutingimycin Streptomyces sp. Antibacterial [64] Helquinoline Janibacter limosus Antibacterial [65] Himalomycins Streptomyces sp. Antibacterial [66] IB Actinomadura sp. Anticancer [67] Komodoquinone A Streptomyces sp. Neuritogenic activity [68] Lajollamycin Streptomyces nodosus Antibacterial [69] Marinomycins Marinispora Antibacterial; anticancer [70] Mechercharmycins Thermoactinomyces sp. Anticancer [71] MKN-349A Nocardiopsis sp. Unknown biological activity [72] Salinosporamide A (NPI-0052) Salinispora tropica Anticancer [47] Sporolides Salinispora tropica Unknown biological activity [49] Trioxacarcins Streptomyces sp. Antibacterial; anticancer; antimalarial [73]

4 248 Ecology and industrial microbiology Figure 1 The Structure of (a) Abyssomicin C, (b) Diazepinomicin (ECO-4601), (c) Salinosporamide A (NPI-0052), (d) Sporolide A and (e) Sporolide B. in humans in NPI-0052 represents the first clinical candidate for the treatment of cancer produced by saline fermentation of an obligate marine actinomycete. In addition to the production of NPI-0052, Salinispora tropica strains also produce two unprecedented macrolides, sporolides A (Figure 1d) and B (Figure 1e) [49]. Sporolides A and B appear to be synthesized from two different polyketides, containing a large number (23 out of 24 carbon skeleton) of oxidized carbons. This, in part, contributes to the highly unusual structures of the sporolides. Even though sporolides have not demonstrated any biological activity in the few antimicrobial and anticancer screens tested, these structures demonstrate the tremendous potential of marine actinomycetes for the production of novel secondary metabolites. Conclusions Because of the immense biological diversity in the sea as a whole, it is increasingly recognized that a large number of novel chemical entities exists in the oceans. As marine microorganisms, particularly actinomycetes, have evolved the greatest genomic and metabolic diversity, efforts should be directed towards exploring marine actinomycetes as a source for the discovery of novel secondary metabolites. Bona fide actinomycetes not only exist in the oceans, but they are also widely distributed in different marine ecosystems. The exploitation of marine actinomycetes as a source for novel secondary metabolites production is in its infancy. Even with the limited screening efforts that have been dedicated to date to marine actinomycetes, the discovery rate of novel secondary metabolites from marine actinomycetes has recently surpassed that of their terrestrial counterparts, as evident by the isolation of many new chemical entities from marine actinomycetes [12,13,50 52]. There is a tremendous potential for the isolation of novel secondary metabolites from marine actinomycetes. In this respect, future success relies on our ability to isolate novel actinomycetes from the marine environments. Although isolation strategies directed towards new marine-derived actinomycetes have been lacking, some progress has recently been made in this area. Recent investigations using enrichment techniques, new selection methods and media [14,21,24 ] have led to the

5 Discovery of novel metabolites from marine actinomycetes Lam 249 isolation of novel actinomycetes from sediment samples. Improved recovery yields of marine actinomycetes from sponges using nutrient supplements and enzymes have been reported [42,53]. These recent successes are the first step in the right direction. Further development work in improving isolation strategies in the recovery of marine actinomycetes is of utmost importance for ensuring success in this area. Recent culture-independent studies have shown that marine environments contain a high diversity of actinomycetes that are rarely, if at all, recovered by culturedependent methods. Most of these unculturable actinomycetes are very different in terms of their 16S rrna sequences from their terrestrial counterparts and the ability to cultivate these novel actinomycetes will provide a new source for the discovery of secondary metabolites. Culture-independent studies are not just a survey of the presence and distribution of marine actinomycetes in the samples; the information obtained from these studies has also been used to design selective isolation schemes, enabling successful isolation of a wide variety of marine actinomycetes, including novel taxa from the same environmental samples [31 ]. Furthermore, recent studies using diffusion chamber design [30] and the technique that combines massively parallel microbial cultivation of encapsulated cells in microdroplets under low nutrient flux conditions [54] have led to the isolation of previously uncultured marine microorganisms. Culturing the unculturable, especially the unculturable marine actinomycetes, would represent a unique and promising source for the discovery of novel secondary metabolites. There has been considerable, preliminary exciting ground work set for the exploitation of marine actinomycetes as the next new source of novel secondary metabolites discovery. Marine actinomycetes represent an underexploited source for the discovery of novel secondary metabolites and their potential should not be overlooked. References and recommended reading Papers of particular interest, published within the annual period of review, have been highlighted as: of special interest of outstanding interest 1. Berdy J: Bioactive microbial metabolites. J Antibiot (Tokyo) 2005, 58: Strohl WR: Antimicrobials. In Microbial Diversity and Bioprospecting. Edited by Bull AT. ASM Press; 2004: Cragg GM, Kingston DGI, Newman DJ (Eds): Anticancer Agents from Natural Products. Taylor & Francis; Mann J: Natural products as immunosuppressive agents. Nat Prod Rep 2001, 18: Oldfield C, Wood NT, Gilbert SC, Murray FD, Faure FR: Desulphurisation of benzothiophene and dibenzothiophene by actinomycete organisms belonging to the genus Rhodococcus, and related taxa. Antonie Van Leeuwenhoek 1998, 74: Pecznska-Czoch W, Mordarski M: Actinomycete enzymes. In Actinomycetes in Biotechnology. Edited by Goodfellow M, Williams ST, Mordarski M. London: Academic Press; 1988: Fenical W, Baden D, Burg M, de Goyet CV, Grimes JD, Katz M, Marcus NH, Pomponi S, Rhines P, Tester P, Vena J: Marinederived pharmaceuticals and related bioactive compounds. In From Monsoons to Microbes: Understanding the Ocean s Role in Human Health. Edited by Fenical W. National Academies Press; 1999: Donia M, Hamann MT: Marine natural products and their potential applications as anti-infective agents. Lancet Infect Dis 2003, 3: Haefner B: Drugs from the deep: marine natural products as drug candidates. Drug Discov Today 2003, 8: Bull AT, Stach JEM, Ward AC, Goodfellow M: Marine actinobacteria: perspectives, challenges, future directions. Antonie Van Leeuwenhoek 2005, 87: A comprehensive review on the current state of research on the biology and biotechnology of marine actinobacteria. Two schemes are presented for future marine actinobacterial research. 11. Stach JEM, Maldonado LA, Ward AC, Goodfellow M, Bull AT: New primers for the class Actinobacteria: application to marine and terrestrial environments. Environ Microbiol 2003, 5: Jensen PR, Mincer TJ, Williams PG, Fenical W: Marine actinomycete diversity and natural product discovery. Antonie Van Leeuwenhoek 2005, 87: The authors demonstrate the importance of isolating taxonomically unique populations of marine actinomycetes for the production of novel secondary metabolites. 13. Fiedler H-P, Bruntner C, Bull AT, Ward AC, Goodfellow M, Potterat O, Puder C, Mihm G: Marine actinomycetes as a source of novel secondary metabolites. Antonie Van Leeuwenhoek 2005, 87: In this article the production of a novel class of antibiotics from a new marine actinomycete strain is reported. 14. Magarvey NA, Keller JM, Bernan V, Dworkin M, Sherman DH: Isolation and characterization of novel marine-derived actinomycete taxa rich in bioactive metabolites. Appl Environ Microbiol 2004, 70: The authors report the use of a unique selective enrichment technique for the isolation of new taxa of marine actinomycetes that are able to produce bioactive metabolites. 15. Bull AT, Ward AC, Goodfellow M: Search and discovery strategies for biotechnology: the paradigm shift. Microbiol Mol Biol Rev 2000, 64: Cross T: Aquatic actinomycetes: a critical survey of the occurrence, growth and role of actinomycetes in aquatic habitats. J Appl Bacteriol 1981, 50: Goodfellow M, Haynes JA: Actinomycetes in marine sediments. In Biological, Biochemical, and Biomedical Aspects of Actinomycetes. Edited by Ortiz-Ortiz L, Bojalil LF, Yakoleff V. New York: Academic Press; 1984: Helmke E, Weyland H: Rhodococcus marinonascens sp. Nov., an actinomycete from the sea. Int J Syst Bacteriol 1984, 34: Jensen PR, Dwight R, Fenical W: Distribution of actinomycetes in near-shore tropical marine sediments. Appl Environ Microbiol 1991, 57: Moran MA, Rutherford LT, Hodson RE: Evidence for indigenous Streptomyces populations in a marine environment determined with a 16S rrna probe. Appl Environ Microbiol 1995, 61: Jensen PR, Gontang E, Mafnas C, Mincer TJ, Fenical W: Culturable marine actinomycete diversity from tropical Pacific Ocean sediments. Environ Microbiol 2005, 7: The authors describe methods and media in the isolation of five new marine phylotypes. They provide further support for the existence of indigenous actinomycetes in marine sediments.

6 250 Ecology and industrial microbiology 22. Stach JEM, Maldonado LA, Ward AC, Bull AT, Goodfellow M: Williamsia maris sp. nov., a novel actinomycete isolated from the Sea of Japan. Int J Syst Evol Microbiol 2004, 54: Mincer TJ, Jensen PR, Kauffman CA, Fenical W: Widespread and persistent populations of a major new marine actinomycete taxon in ocean sediments. Appl Environ Microbiol 2002, 68: Mincer TJ, Fenical W, Jensen PR: Culture-dependent and culture-independent diversity within the obligate marine actinomycete genus Salinispora. Appl Environ Microbiol 2005, 71: A comprehensive study examining the species diversity of Salinispora, the first obligate marine genus within the order of Actinomycetales. 25. Kim TK, Garson MJ, Fuerst JA: Marine actinomycetes related to the Salinospora group from the Great Barrier Reef sponge Pseudoceratina clavata. Environ Microbiol 2005, 7: Maldonado LA, Fenical W, Jensen PR, Kauffman CA, Mincer TJ, Ward AC, Bull AT, Goodfellow M: Salinispora arenicola gen. nov., sp. nov. and Salinispora tropica sp. nov., obligate marine actinomycetes belonging to the family Micromonosporaceae. Int J Syst Evol Microbiol 2005, 55: Grossart H-P, Schlingloff A, Bernhard M, Simon M, Brinkhoff T: Antagonistic activity of bacteria isolated from organic aggregates of the German Wadden Sea. FEMS Microbiol Ecol 2004, 47: Alldrege AL, Silver MW: Characteristics, dynamics and significance of marine snow. Prog Oceanog 1988, 20: Whitman WB, Coleman DC, Wiebe WJ: Prokaryotes: the unseen majority. Proc Natl Acad Sci USA 1998, 95: Kaeberlein T, Lewis K, Epstein SS: Isolating uncultivable microorganisms in pure culture in a simulated natural environment. Science 2002, 296: Maldonado LA, Stach JEM, Pathom-aree W, Ward AC, Bull AT, Goodfellow M: Diversity of cultivable actinobacteria in geographically widespread marine sediments. Antonie Van Leeuwenhoek 2005, 87: This article describes a strategy that uses the information obtained from culture-independent studies on environmental samples to design selective isolation schemes for enhancing the recovery of marine actinomycetes from these environmental samples. 32. Hill RT: Microbes from marine sponges: a trove of biodiversity of natural products discovery. In Microbial Diversity and Bioprospecting. Edited by Bull AT. ASM Press; 2004: A review that demonstrates the diversity of microorganisms associated with sponges and the potential to exploit these microorganisms for production of novel pharmaceuticals. 33. Madrid VM, Aller JY, Aller RC, Chistoserdov AY: High prokaryote diversity and analysis of community structure in mobile mud off French Guiana: identification of two new bacterial candidate divisions. FEMS Microbiol Ecol 2001, 37: Kim BS, Oh HM, Kang H, Park SS, Chun J: Remarkable bacterial diversity in the tidal flat sediment as revealed by 16S rrna analysis. J Microbiol Biotechnol 2004, 14: Parkes RJ, Wellsbury P: Deep biospheres. In Microbial Diversity and Bioprospecting. Edited by Bull AT. ASM Press; 2004: Inagaki F, Suzuki M, Takai K, Oida H, Sakamoo T, Aoki K, Nealson KH, Horikoshi K: Microbial communities associated with geological horizons in coastal sub-seafloor sediments from the Sea of Okhotsk. Appl Environ Microbiol 2003, 69: Lanoil BD, Sassen R, La Duc MT, Sweet ST, Nealson KH: Bacteria and archaea physically associated with Gulf of Mexico gas hydrates. Appl Environ Microbiol 2001, 67: Colwell F, Matsumoto R, Reed D: A review of gas hydrates, geology, and biology of Nankai Trough. Chem Geol 2004, 205: Reed DW, Fujita Y, Delwiche ME, Blackwelder DB, Sheridian PP, Uchida T, Colwell FS: Microbial communities from methane hydrate-bearing deep marine sediments in a forearc basin. Appl Environ Microbiol 2002, 68: Burja AM, Hill RT: Microbial symbionts of the Australian Great Barrier Reef sponge Candidaspongia flabellate. Hydrobiologia 2001, 461: Hentschel U, Hopke J, Horn M, Friedrich AB, Wagner M, Hacker J, Moore BS: Molecular evidence for a uniform microbial community in sponges from different oceans. Appl Environ Microbiol 2002, 68: Webster NS, Wilson KJ, Blackall LL, Hill RT: Phylogenetic diversity of bacteria associated with the marine sponge Rhopaloeides odorabile. Appl Environ Microbiol 2001, 67: Riedlinger J, Reicke A, Zahner H, Krismer B, Bull AT, Maldonado LA, Ward AC, Goodfellow M, Bister B, Bischoff D et al.: Abyssomicins, inhibitors of the para-aminobenzoic acid pathway produced by the marine Verrucosispora strain AB J Antibiot (Tokyo) 2004, 57: Bister B, Bischoff D, Strobele M, Riedlinger J, Reicke A, Wolter F, Bull AT, Zahner H, Fiedler H-P, Sussmuth RD: Abyssomicin C a polycyclic antibiotic from a marine Verrucosispora strain as an inhibitor of the p-aminobenzoic acid/tetrahydrofolate biosynthesis pathway. Angew Chem Int Ed Engl 2004, 43: Rath J-P, Kinast S, Maier ME: Synthesis of the full functionalized core structure of the antibiotic abyssomicin C. Org Lett 2005, 7: Charan RD, Schlingmann G, Janso J, Bernan V, Feng X, Carter GT: Diazepinomicin, a new antimicrobial alkaloid from marine Micromonospora sp. J Nat Prod 2004, 67: Feling RH, Buchanan GO, Mincer TJ, Kauffman CA, Jensen PR, Fenical W: Salinosporamide A: a highly cytotoxic proteasome inhibitor from a novel microbial source, a marine bacterium of the new genus Salinospora. Angew Chem Int Ed Engl 2003, 42: Chauhan D, Catley L, Li G, Podar K, Hideshima T, Velankar M, Mitsiades C, Mitsiades N, Yasui H, Letai A et al.: A novel orally active proteasome inhibitor induces apoptosis in multiple myeloma cells with mechanisms distinct from Bortezomib. Cancer Cell 2005, 8: Buchanan GO, Williams PG, Feling RH, Kauffman CA, Jensen PR, Fenical W: Sporolides A and B: structurally unprecedented halogenated macrolides from the marine actinomycete Salinispora tropica. Org Lett 2005, 7: Blunt JW, Copp BR, Munro MHG, Northcote PT, Prinsep MR: Marine natural products. Nat Prod Rep 2004, 21: Blunt JW, Copp BR, Munro MHG, Northcote PT, Prinsep MR: Marine natural products. Nat Prod Rep 2005, 22: Blunt JW, Copp BR, Munro MHG, Northcote PT, Prinsep MR: Marine natural products. Nat Prod Rep 2006, 23: Olson JB, Lord CC, McCarthy PJ: Improved recoverability of microbial colonies from marine sponge samples. Microb Ecol 2000, 40: Zengler K, Toledo G, Rappe M, Elkins J, Mathur EJ, Short JM, Keller M: Cultivating the uncultured. Proc Natl Acad Sci USA 2002, 99: Mitchell SS, Nicholson B, Teisan S, Lam KS, Potts BCM: Aureoverticillactam, a novel 22-atom macrocyclic lactam from the marine actinomycete Streptomyces aureoverticillatus. J Nat Prod 2004, 67: Schumacher RW, Talmage SC, Miller SA, Sarris KE, Davidson BS, Goldberg A: Isolation and structure determination of an antimicrobial ester from a marine-derived bacterium. J Nat Prod 2003, 66: Stritzke K, Schulz, Laatsch H, Helmke E, Beil W: Novel caprolactones from a marine streptomycete. J Nat Prod 2004, 67:

7 Discovery of novel metabolites from marine actinomycetes Lam Maskey RP, Li FC, Qin S, Fiebig HH, Laatsch H: Chandrananimycins A C: production of novel anticancer antibiotics from a marine Actinomadura sp. isolate M048 by variation of medium composition and growth conditions. J Antibiot (Tokyo) 2003, 56: Li F, Maskey RP, Qin S, Sattler I, Fiebig HH, Maier A, Zeeck A, Laatsch H: Chinikomycins A and B: isolation, structure elucidation, and biological activity of novel antibiotics from a marine Streptomyces sp. Isolate M045. J Nat Prod 2005, 68: Soria-Mercado IE, Prieto-Davo A, Jensen PR, Fenical W: Antibiotic terpenoid chloro-dihydroquinones from a new marine actinomycete. J Nat Prod 2005, 68: Sanchez Lopez JM, Martinez Insua M, Perez Baz J, Fernandez Puentes JL, Canedo Hernandez LM: New Cytotoxic indolic metabolites from a marine Streptomyces. J Nat Prod 2003, 66: Bruntner C, Binder T, Pathom-aree W, Goodfellow M, Bull AT, Potterat O, Puder C, Horer S, Schmid A, Bolek W et al.: Frigocyclinone, a novel angucyclinone antibiotic produced by a Streptomyces griseus strain from Antarctica. J Antibiot (Tokyo) 2005, 58: Macherla VR, Liu J, Bellows C, Teisan S, Lam KS, Potts BCM: Glaciapyrroles A, B and C, pyrrolosesquiterpenes from a Streptomyces sp. isolated from an Alaskan marine sediment. J Nat Prod 2005, 68: Maskey RP, Sevvana M, Uson I, Helmke E, Laatsch H: Gutingimycin: a highly complex metabolite from a marine streptomycete. Angew Chem Int Ed Engl 2004, 43: Asolkar RN, Schroder D, Heckmann R, Lang S, Wagner-Dobler I, Laatsch H: Helquinoline, a new tetrahydroquinoline antibiotic from Janibacter limosus Hel 1. J Antibiot (Tokyo) 2004, 57: Maskey RP, Helmke E, Laatsch H: Himalomycin A and B: isolation and structure elucidation of new fridamycin type antibiotics from a marine Streptomyces isolate. J Antibiot (Tokyo) 2003, 56: Rodriguez JC, Fernandez Puentes JL, Perez Baz J, Canedo LM: IB-00208, a new cytotoxic polycyclic xanthone produced by a marine-derived Actinomadura. II. Isolation, physico-chemical properties and structure determination. J Antibiot (Tokyo) 2003, 56: Itoh T, Kinoshita M, Aoki S, Kobayashi M: Komodoquinone A, a novel neutritogenic anthracycline, from marine Streptomyces sp. KS3. J Nat Prod 2003, 66: Manam RR, Teisan S, White DJ, Nicholson B, Grodberg J, Neuteboom STC, Lam KS, Mosca DA, Lloyd GK, Potts BCM: Lajollamycin, a nitro-tetraene spiro-b-lactone-g-lactam antibiotic from the marine actinomycete Streptomyces nodosus. J Nat Prod 2005, 68: Kwon HC, Kauffman CA, Jensen PR, Fenical W: Marinomycins a-d, antitumor antibiotics of a new structure class from a marine actinomycete of the recently discovered genus Marinispora. J Am Chem Soc 2006, 128: Kanoh K, Matsuo Y, Adachi K, Imagawa H, Nishizawa M, Shizuri Y: Mechercharmycins A and B, cytotoxic substances from marine-derived Thermoactinomyces sp. YM J Antibiot (Tokyo) 2005, 58: Shin J, Seo Y, Lee HS, Rho JR, Mo SJ: A new cyclic peptide from a marine derived bacterium of the genus Nocardiopsis. J Nat Prod 2003, 66: Maskey RP, Helmke E, Kayser O, Fiebig HH, Maier A, Busche A, Laatsch H: Anti-cancer and antibacterial trioxacarcins with high anti-malaria activity from a marine streptomycete and their absolute stereochemistry. J Antibiot (Tokyo) 2004, 57: