Marine Chemical Ecology - Chapter 18 (end) doc

567 Metabolites of Free-Living, Commensal, and Symbiotic Benthic Marine Microorganisms Valerie S. Bernan CONTENTS I. Introduction 567 II. Marine Sediments 568 A. Shallow Marine Sediments 568 B. Deep-Sea Marine Sediments 574 III. Commensal Marine Microorganisms 577 IV. Symbiotic Marine Microorganisms 583 V. Summary 589 References 589 I. INTRODUCTION This chapter describes the natural product chemistry that has been identified or associated with marine microorganisms from the benthos and focuses on the marine eubacteria. Most of the compounds described in this chapter resulted from a detailed search of the literature for micro- bially derived natural products. This approach is biased in many respects, since it only describes bioactive compounds and small molecules. However, due to the growing demand for new thera- peutic agents, the discovery of new chemical entities is being driven by these efforts. 1 While comparatively little research has been directed toward the study of natural products from marine microorganisms, the results to date have been encouraging. 2 Data from these investigations demonstrate complex chemical interactions between marine bacteria and their hosts, 2 including systems of signaling and territorial marking. It is estimated that less than 1% of potentially useful chemicals have been discovered from the marine environment, with microbial products represent- ing 1% of that total number. 1 Compounds isolated from marine microorganisms have demonstrated antibiotic, anticancer, anti-inflammatory, and other pharmacological activites. 2,3,4 Hopefully a greater understanding of microbial metabolic diversity, coupled with ecological information, will yield a greater understanding of the complexity of marine environments. This chapter reviews metabolites of microorganisms that occur in sediments, as well as those in commensal associations and symbiotic relationships. 18 9064_ch18/fm Page 567 Tuesday, April 24, 2001 5:30 AM © 2001 by CRC Press LLC 568 Marine Chemical Ecology II. MARINE SEDIMENTS Marine sediments are composed of organic debris resulting from ongoing, seasonal, or catastrophic die-offs of macrobiotic and microbial populations. 2 This sedimenting debris provides energy for the benthic organisms on the sea floor. Organic mineral aggregates that are rich in carbohydrates are produced by deposit-feeding animals such as bivalves, which rework the sediments as they feed. This extensive reworking of the sediments makes them unstable so that the organic aggregates are resuspended by the tidal flow to produce turbid estuarine waters which are important in recycling. Consumption of resuspended organic debris and phytoplankton by bivalve molluscs and other benthic invertebrates produces rich deposits of feces and pseudofeces that coat mineral fragments. These mineral fragments yield additional organic mineral aggregates, which in turn are heavily colonized by microorganisms. Other sources of organic matter include those derived from cordgrass and from beds of seagrasses, such as eelgrass and turtle grass as well as mangroves. As these plants decompose, they are reworked into smaller fragments by deposit feeders, which can support increased populations of microbiota. Within interstitial habitats of sandy beaches, particles are trapped in the upper 5-cm surface layer and give rise to a bacterial–protozoan community. 5 Below this level, a bacterial flora attached to sand grains removes some of the dissolved organic carbon while supporting a meiofauna community comprised of nematods and copepods. The biotic community of these intertidal sandflats is supplemented by the production of organic matter via benthic diatoms which migrate vertically with the tides. Since terrestrial actinomycetes have been such prolific producers of bioactive molecules, it was natural to investigate marine species of the same group. Therefore, it was no surprise that actino- mycetes isolated from the marine sediments have proven to be one of the most prolific sources of bioactive secondary compounds. 6,7 Their distribution in sediments varies depending on the depth from which the sample was collected. In several studies, Streptomyces predominated in near-shore marine sediments, but decreased dramatically past the sublittoral zone. In contrast, actinoplanetes are found in greater numbers as the distance from the shoreline increases. A. S HALLOW M ARINE S EDIMENTS The study of the metabolites produced by marine actinomycetes was pioneered by researchers at the Institute of Microbial Chemistry in Tokyo in the early 1970s. One of the first compounds described by Okami was a benzanthraquinone antibiotic isolated from the actinomycete Chainia purpurgensa SS-228 collected in mud samples from Sagami Bay, Japan. 8 This antibiotic selectively inhibited Gram-positive bacteria and was active against Ehrlich ascites tumor cells in mice. It also produced a hypotensive effect in mice, probably due to its inhibition of dopamine hydroxylase in the pathway of epinephrine biosynthesis. Most interestingly, this bacterium only produced the antibiotic when it was fermented in diluted yeast extract containing “Kobu Cha” (the brown seaweed Laminaria ) and with the addition of 3% NaCl. This observation demonstrated that marine micro- organisms have nutritional requirements corresponding to nutrients in their natural habitats. This study was also one of the first to report that bacteria from the order Actinomycetales could be isolated from the marine environment. Actinomycetes were originally thought to have entered the marine environment via rivers or runoff or to have existed as spores of terrestrial species. However, work by Moran et al., 9 using a 16S rRNA genus-specific probe, demonstrated that Streptomyces occurred as indigenous populations, and that populations increased in relative abundance in response to the availability of certain nutrients. Greater abundances of culturable streptomycetes found in coastal environments vs. deepwater marine systems may be attributed to higher amounts of organic detritus, much of which is derived from vascular plants concentrated in shallow marine systems. Unlike the terrestrial actinomycetes, marine actinomycetes have been shown to produce mac- rolides only rarely. One example of this class of compounds is the aplasmomycins A–C 9064_ch18/fm Page 568 Tuesday, April 24, 2001 5:30 AM © 2001 by CRC Press LLC Metabolites of Free-Living, Commensal, and Symbiotic Benthic Marine Microorganisms 569 (Structure 18.1a–c). These compounds were isolated from the fermentation of Streptomyces griseus SS-20 collected from shallow mud in Sagami Bay, Japan. The antibiotic was only produced under low-nutrient media containing “Kobu Cha” and 3% NaCl. The aplasmomycins are inhibitory against Gram-positive bacteria and the bacteria Corynebacterium smegmatis . More importantly, aplasmo- mycin is an effective antimalarial agent in Plasmodium berghei -infected mice. X-ray crystallogra- phy revealed that the active compound contained a symmetric ring in which boron was coordinated in the center with a crown ether-like structure. 10 Fenical’s group 11 from Scripps Institute of Ocean- ography also isolated a new member of a rare class of macrolides, maduralide (Structure 18.2). Maduralide was isolated from the fermentation of a Maduramycete isolated from shallow sediments from Bodega Bay, California. This compound is a member of a rare 24-membered ring lactone group represented by rectilavendomycin. Among the alkaloids, the most unusual example is an acaricidal (lethal to arachnids) monot- erpene derivative, altemicidin (Structure 18.3). This novel alkaloid was purified from a marine strain of Streptomyces sioyaensis SA-1758 isolated from marine sediments collected from the northern part of Japan. It yielded potent antitumor activity in vitro against L1210 murine leukemia and IMC carcinoma cell lines, but was toxic in vivo in mice. Altemicidin is a novel sulfur- and nitrogen- containing microbial metabolite with a monoterpene carbon skeleton. 12 A sediment-derived Streptomyces sp. was isolated from Laguna de Terminos from the Gulf of Mexico. 13 When the culture was fermented in 50% seawater, a new anti-algal anthranilamide derivative was isolated that was active against several algae including Chlorella spp. and Scenedesmus subspicatus . This new compound was shown to be an N -methyl anthranilamide derivative of phenylpropionic acid (Structure 18.4). A series of analogs was synthesized and their anti-algae properties examined. These methyl ester analogs were found to be more active against algae than the free acids in both agar diffusion and liquid test systems. The compounds did not exhibit any antimicrobial activity against Staphylococcus aureus , Escherichia coli , or Mucor miehei at concentrations up to 200 µ g/mL. Another Streptomyces sp. obtained from black anaerobic intertidal sediment collected near Christchurch, New Zealand was fermented in a saline medium and found to produce modest antibacterial activity against Bacillus subtilis . 14 The isolation of the active compound revealed it to be an actinoflavoside, a molecule of an unprecedented structure class (Structure 18.5). Actinofla- voside resembles the common plant-derived flavonoid glycosides, but this compound contains an O O O O O O O O O O O O B OR R'O - M + 18.1a: Aplasmomycin A R = R' = H 18.1b: Aplasmomycin B R = H, R' = Ac 18.1c: Aplasmomycin C R = R' = Ac 9064_ch18/fm Page 569 Tuesday, April 24, 2001 5:30 AM © 2001 by CRC Press LLC 570 Marine Chemical Ecology additional alkylation at C-5. Due to the general conclusion that prokaryotes do not produce this class of compounds, its origin via the flavinoid biosythetic pathway seems questionable. A marine actinomycete, Streptomyces virdostaticus spp. " litoralis " was isolated from an inter- tidal sample collected in Key West, Florida. Fermentation samples exhibited both antibacterial and DNA-damaging activites. Although activity was observed in a tap-water based medium, the addition of 2% NaCl increased the biomass by 33% and increased activity four-fold. Purification of the active materials revealed four related bioxalomycins (Structure 18.6a and b). The β species were found to be the quinone forms of the corresponding α components. The β components are distin- guished from the antibiotic naphthyridinomycin by the presence of a second oxazolidine ring in a region of the molecule analogous to quinocarcin. Bioxalomycin α 2 was the most potent antibiotic of the group, showing MIC values between 0.002–0.25 µ g/mL, and also exhibited excellent in vitro activity against neoplastic cell lines. This compound was active in vivo in a mouse P388 leukemia model demonstrating an 80% increase in life survival (ILS). Mechanistic studies have shown that following metabolic reduction of the quinone, bioxalomycin α 2 cross-links DNA through alkylation of guanine residues in the minor groove of DNA. 15 A new series of phenazines has been isolated from a strain of marine-derived Streptomyces by Fenical’s group. 16 A study from the shallow sediments of Bodega Bay, California resulted in the N COOH CH 3 O 18.4: Anthranilamides N CONH 2 HN OH COOH SO 2 NH 2 O CH 3 H H 18.3: Altemicidin OH O O OO H OH O O OH OH OCH 3 H OH 18.2: Maduralide O O O O O OH HO NH HO H O HO H 18.5: Actinoflavoside 9064_ch18/fm Page 570 Tuesday, April 24, 2001 5:30 AM © 2001 by CRC Press LLC Metabolites of Free-Living, Commensal, and Symbiotic Benthic Marine Microorganisms 571 isolation of an unknown Streptomyces sp. that was found to produce compounds with broad antibacterial activity. Subsequent fermentation of this isolate in a saltwater based medium produced four new alkaloid esters of the phenazine class which contained the sugar L-quinovose at the 2 ′ and 3 ′ positions (Structures 18.7a and b). These compounds were found to exhibit antibacterial activity against Gram-negative and Gram-positive bacteria. Another set of phenazine derivatives was isolated from the fermentation of a Streptomyces sp. isolated from a sediment sample collected in Laguna de Terminos in the Gulf of Mexico. 17 Cultivation and production occurred in enriched 50% seawater medium and produced the novel 5,10-dihydrophencomycin methyl ester and the known microbial metabolites (2-hydroxyphenyl)acetamide, meanquinone MK9, and phencomycin. The new 5,10-dihydrophencomycin methyl ester (Structure 18.8) exhibited less antimicrobial activ- ity than phencomycin, and the dimerization of identical m -C 7 N units may explain its origin. Four new α -pyrone-containing metabolites, wailupemycins A–C and 3-epi-5-deoxyenterocin (Structures 18.9 a–e) were isolated together with the known compounds enterocin and 5-deoxy- enterocin from the fermentation broth of a new Streptomyces sp. 18 The strain was isolated from the shallow marine sediments collected at Wailupe beach park on the southeast shore of Oahu, Hawaii. The α -pyrone moeity is commonly observed in many antibiotics and toxins. Interestingly, enterocin and 5-deoxyenterocin, along with the 5-behenate and 5-arachidate esters of enterocin, has been isolated from a marine ascidian of the genus Didemnum . The occurrence of the same compounds in both prokaryotes and chordates raises the question of whether symbiotic or asso- ciated microorganisms are responsible for the production of the metabolites isolated from some marine invertebrates. In a study of estuarine microorganisms isolated from Torrey Pines, La Jolla, California, Fenical et al. 19 isolated marinone (Structure 18.10) and its debromo analogue debromomarinone from the fermentation broth of an unidentified actinomycete. Both compounds possess a common naphtho- quinone with rare sesquiterpenoid structural components. In addition, marinone possesses a bromine substituent in the dihydroxybenzene ring, a position typical for bromination in marine metabolites. These new molecules are among a rare group of bacterial metabolites produced via mixed biosyn- thesis involving both acetate and terpene pathways. Marinone and debromomarinone exhibit sig- nificant in vitro antibacterial activity against Gram-positive bacteria. More recently, the same group isolated a different unidentified actinomycete, from a sediment sample collected at 1m depth in Batiquitos Lagoon, California, that also produced marinone in addition to several cytotoxic metab- olites related to marinone. One compound, neomarinone (Structure 18.11), is a novel metabolite possesssing a new sesquiterpene- and polyketide-derived carbon skeleton. The other two derivatives are isomarinone and methoxydebromomarinone. All three compounds are also derived from a mixed biosynthetic pathway involving polyketide and terpene pathways. Connection of the sesquiterpenoid side-chain to the naphthoquinone core occurs on the nonquinone side in neomarinone. The origin of the sesquiterpenoid side-chain appears complex; it is possibly derived from a cation-induced methyl migration as observed in the trichothecenes. All three compounds exhibited moderate in vitro N N N O O OH OH CH 3 O CH 3 R H H OHH H 18.6a: Bioxalomycin α1, R = H 18.6b: Bioxalomycin α2, R = CH 3 9064_ch18/fm Page 571 Tuesday, April 24, 2001 5:30 AM © 2001 by CRC Press LLC 572 Marine Chemical Ecology cytotoxicity in the National Cancer Institute’s 60 cancer cell line panel with a mean IC 50 value of 10 µ M. 20 As part of the continuing interest in isolating secondary metabolites from marine estuaries, a Streptomycete was isolated from a sediment sample collected in Mission Bay, California. When the culture was fermented under saline culture conditions, it was found to produce a family of novel cyclic heptapeptides, cyclomarines A, B, and C. While the major metabolite, cyclomarine A (Structure 18.12), is cytotoxic in vitro toward cancer cells, it is more interesting for its significant in vitro and in v ivo anti-inflammatory properties. The compound displays significant topical anti- inflammatory activity in the phorbol ester-induced mouse edema assay, showing 92% inhibition at the standard test dose. Cyclomarine A contains three common and four unusual amino acids. The four unusual amino acids are N -methylhydroxyleucine, β -methoxyphenylalanine, 2-amino- 3,5-dimethylhex-4-enoic acid, and N -(1,1-dimethyl-2,3-epoxypropyl)- β -hydroxytryptophan. The latter two amino acids have not been previously described, although similar N -prenyltryptophan amino acids have been observed in the ilamycins. The amino acid β -methoxyphenylalanine is a well known synthetic building block, but is a rare constituent of natural products, found in only N H H N CO 2 CH 3 CO 2 CH 3 18.8: 5,10-dihydrophencomycin methyl ester N N H 3 COH O O HO CH 3 OH R R O N N CH 3 OH O O HO O R R OH 18.7a: R=OH, R=H 18.7b: R=H, R=OH ′ ′ ′ ′ 9064_ch18/fm Page 572 Tuesday, April 24, 2001 5:30 AM © 2001 by CRC Press LLC Metabolites of Free-Living, Commensal, and Symbiotic Benthic Marine Microorganisms 573 O O OH OH HO O CH 3 OO O O OO OCH 3 HO O O O O H HO O O OCH 3 H O O O OH O CH 3 O HO OH H H O 18.9a: Wailupemycin A 18.9b: Wailupemycin B 18.9c: Wailupemycin C 18.9d: Wailupemycin D H N N H O N O HN O H N O HN O N O O HO N HO CH 3 O O 18.12: Cyclomarin A O HO OH O O 18.11: Neomarinone H H OH HO Br O O 18.10: Marinone 9064_ch18/fm Page 573 Tuesday, April 24, 2001 5:30 AM © 2001 by CRC Press LLC 574 Marine Chemical Ecology the discokiolides, which are cyclic depsipeptides from the marine sponge Discodermia kiiensis . These amino acids may be products of unusual biosynthetic pathways, and it will be interesting to elucidate their biosynthesis. 21 Another estuarine Streptomyces was isolated from the sandy sediment collected near San Diego, California in the San Luis Estuary. Cultivation of the Strep- tomyces sp. resulted in the isolation of two new aromatic tetraols, luisols A and B (Structure 18.13a and b). Luisol A, formally a reduced hydroquinone, appears to be related to the quinones of the granaticin class. The structure of luisol B contains the rare epoxynaphtho[2,3c]furan which is only found in one other natural product, the fungal metabolite anthrinone. 22 Lastly, a Streptomycete sp. was isolated from an estuary near Doheny Beach, California and fermented in a salt-based medium. The culture broth was found to contain a new pentacyclic polyether, arenic acid (Structure 18.14), which is related to two known polyether antibiotics, K41-A and oxolonomycin. The structure of arenaric acid was established by spectroscopic methods involving comprehensive two-dimensional NMR measurements. 23 Although marine actinomycetes are the most prolific source for bioactive metabolites from shallow sediments, marine Bacilli spp. have also been isolated, and unusual secondary metabolites have been reported. For example, a Bacillus sp. was isolated from marine sediment and cultured in an enriched seawater medium to yield a new isocoumarin, PM-94128 (Structure 18.15). 24 Comparison of IR and UV data with known substances and one-dimensional 1 H and 13 C NMR data and a 1 H– 1 H COSY suggested a dihydroisocoumarine derivative with a prenyl group substi- tuted with a ketide extended leucine. PM-94128 was quite potent with cytoxicity against several tumor cell lines (IC 50 0.05 µ M to P388, A-549, HT-29, and MEL-28) and may act by inhibiting protein synthesis. B. D EEP -S EA M ARINE S EDIMENTS Many interesting metabolites have also been isolated from deep-sea sediments. 2 The energy input to the sea floor below a depth of 2 km is thought to be less than 10% of the primary productivity in the euphotic zone. At these depths, food consists of a slow rain of fecal pellets and zooplankton along with the carcasses of larger organisms from the nekton. Most of these carcasses are consumed quickly by fish who scatter the remains in the form of feces over large areas to be utilized by benthic microorganisms. A bacterial isolate from deep-sea mud collected at a depth of 3300 m off the Aomori coast of the Japan Sea required a seawater medium to grow and produce bioactive substances. Even though the strain was isolated at 700 atm pressure, it appeared to grow well at surface pressure and temperature. The strain was identified as Alteromonas haloplanktis and was found to produce a new bioactive siderophore metabolite called bisucaberin (Structure 18.16). 25 This compound had little cytotoxicity but, when added to a mixed macrophage-tumor cell culture, induced macrophage-mediated cytolysis of tumor cells. Its dimeric structure contains two hydrox- amates and two amide functionalitites and is similar to other siderophores such as nocardimin and desferioxamine. While screening for antitumor effects, Fenical et al. 26 isolated a deep-sea bacterium from a sediment sample obtained from a 1000-m depth along the California coast. Fermentation of the slow-growing bacterium in a salt-based medium yielded a series of novel cytotoxic and antiviral macrolides, the macrolactins A–F. This bacterium was an unidentified Gram-positive organism that produced six macrolides and two open-chain hydroxy acids when fermented in the presence of salt at atmospheric pressure. Macrolactin A (Structure 18.17) was the predominate compound produced, showing moderate antibacterial activity, yet it was quite potent against B16-F10 murine melanoma in vitro with an IC 50 of 3.5 µg/ml. Of potentially greater significance, macrolactin A inhibited several viruses, including Herpes simplex (IC 50 = 5.0 µg/ml) and HIV, the human immunodeficiency virus (IC 50 = 10.0 µg/mL). Two new caprolactams were isolated by Davidson and Schumacher 27 from an unidentified Gram- positive bacterium cultured from deep-sea sediments. The caprolactams A and B (Structure 18.18a 9064_ch18/fm Page 574 Tuesday, April 24, 2001 5:30 AM © 2001 by CRC Press LLC Metabolites of Free-Living, Commensal, and Symbiotic Benthic Marine Microorganisms 575 and b) were obtained as an inseparable mixture and were composed of cyclic-L-lysine linked to 7-methyloctanoic acid and 6-methyloctanoic acid, respectively. Natural products containing a cyclized lysine are uncommon and have only been reported in several sponges and fungi. In fact, these structures are quite similar to the bengamides, which are sponge-derived caprolactams with oxidized acyl side-chains. Thus, one may speculate that the bengamides isolated from sponges may truly be produced by a symbiotic microorganism. The compounds are mildly cytotoxic toward human epidermoid carcinoma and colorectal adenocarcinoma cells with MIC values of 10 and 5 µg/mL, respectively, and exhibit antiviral activity toward Herpes simplex type II virus at a concentration of 100 µg/mL. The same group also isolated a new pluramycin metabolite, γ- indomycinone (Structure 18.19), from a Streptomyces species isolated from a deep-sea sediment core sample. 28 γ-Indomycinone is composed of an anthraquinone-γ-pyrone nucleus with a 1- hydroxy-1-methylpropyl side-chain. The compound exhibits only mild cytotoxicity against a human colon cancer cell line HCT-116 but shows a differential cytotoxicity against the Chinese hamster ovary cell lines UV20 (deficient in DNA excision repair) and BR1 (proficient in DNA repair). These results suggests that γ-indomycinone may act by forming a bulky DNA adduct. Another Streptomycete species was isolated from deep-sea sediments collected at 1500 m in the sea surrounding Tokyo, Japan. When this culture was fermented in the presence of seawater, O O OH N H O OH OH NH 2 18.15: PM-94128 O O O O O CH 3 O CH 3 CH 3 OH H HH H CH 3 OCH 3 CH 3 CH 3 OCH 3 H H OCH 3 CH 3 OCH 3 CH 3 OH COOH HO H 18.14: Arenic acid O OH HO HO OH H O O H H H OH HO HO H H OO HO 18.13b: Luisol B 18.13a: Luisol A 9064_ch18/fm Page 575 Tuesday, April 24, 2001 5:30 AM © 2001 by CRC Press LLC 576 Marine Chemical Ecology growth was enhanced as was the production of two β-glucosidase inhibitors which have the potential to be developed as antimetastasis or anti-HIV drugs. The two inhibitors were character- ized as D-glucono-1,5-lactam and D-mannono-1,5-lactam (Structure 18.20). The two lactams had never been isolated from nature but were found in marine organisms, suggesting that they are of microbial origin. 29 Simidu et al. 30 isolated 49 bacterial strains from deep-sea core sediments collected at a depth of 4000 m and examined them for the production of tetrodotoxin. This study indicates that tetro- dotoxin-producing bacteria are not restricted to certain taxonomic groups. A variety of groups of bacteria, including Bacillus, Micrococcus, Acinetobacter, Aeromonas, Alteromonas, Moraxella, Vibrio, and one unidentified bacterium, all produce tetrotoxin. Although the strains are limited in number, the tetrodotoxin-producing bacteria are quite widespread among various bacterial groups in marine sediments. It has been postulated that the tetrodotoxins are synthesized solely by bacteria in sediments and subsequently accumulated by benthic organisms, such as fish and crabs, that acquire them through the food web. Another cyclic peptide, halobacillin, was isolated from a marine-derived Bacillus sp. isolated from a deep-sea sediment core. 31 Halobacillin (Structure 18.21) was only produced in sea-water- based media and is similar in structure to the surfactins and iturins. Interestingly, the compound exhibits cytotoxicity against the human colon tumor cell line HCT-116 but lacks the antibacterial activity associated with surfactin. H N HO OH OH OH O 18.20: D-Glucono-1,5-lactam N N H H N N OH HO O O O O 18.16: Bisucaberin HO HO O OH O 18.17: Macrolactin A HN O H N O R 18.18a: Caprolactin A, R = (CH 2 ) 5 CH(CH 3 ) 2 18.18b: Caprolactin B, R = (CH 2 ) 4 CH(CH 3 )CH 2 CH 3 O OH O O CH3 OH O 18.19: γ-indomycinone 9064_ch18/fm Page 576 Tuesday, April 24, 2001 5:30 AM © 2001 by CRC Press LLC [...]... H H O O H O H N H SCH3 N OH OH H NH H HO H NH 18. 26: Alteramide A O O 18. 27: Cyclo-(L-proline-L-methionine) HH S O O OH O OH NH2 O NH OH OH OH S N N H OH O 18. 28: o-aminophenol © 2001 by CRC Press LLC 18. 29: Sesbanimide A 18. 30: Agrochelin O 9064_ch18/fm Page 581 Tuesday, April 24, 2001 5:30 AM Metabolites of Free-Living, Commensal, and Symbiotic Benthic Marine Microorganisms 581 an enriched microbial... feeding with various leucine analogs (L-butyrine, L-norvaline, L-cyclopropylalanine, etc.) but the supply was not sufficient for testing The same group also isolated © 2001 by CRC Press LLC 9064_ch18/fm Page 578 Tuesday, April 24, 2001 5:30 AM 578 Marine Chemical Ecology O NH2 O H N N H O O n-C12H25 O O H NH O O HN NH O N H O COOH 18. 21: Halobacillin O OH O O N H 18. 22: Koromicin O O CH3 O OH N O HN N... 2001 by CRC Press LLC 9064_ch18/fm Page 582 Tuesday, April 24, 2001 5:30 AM 582 Marine Chemical Ecology OH O 10 HN HO3S 8 OH 18. 31: Flavocristamide A R O H N O O O O NH O O O HN O O O HN O O O O NH O H N O O 18. 32a: Cerulide, R=H 18. 32b: Homocerulide, R=CH3 OH O O O CH3O OH O O O H H O NH O O O O H 18. 33: Lobophorin A © 2001 by CRC Press LLC H HO H NH2 O O HO OH 9064_ch18/fm Page 583 Tuesday, April... 9064_ch18/fm Page 588 Tuesday, April 24, 2001 5:30 AM 588 Marine Chemical Ecology OCH3 OMe O O H O NMe O OH O N MeO O O OH O OH OCH3 OH O O OH 18. 42: Renieramycin HO O OCH3 HO OMe O O OH O O HO H O NMe O N MeO O NH OCH3 O O 18. 44: Swinholide 18. 43: Saframycin B HOOC O CO2Me NH HO O OH HO HN O Br HN OH O O OH HN N H H2NOC O HN O OH N O O OH NH O H H N N H O HO H N NH O HO O O OH O CO2Me 18. 46: Bryostatin 18. 45:... sponges This symbiont is a rod-shaped Gram-negative bacterium localized in the larvae of B neritina Bryostatin is also found in the larvae © 2001 by CRC Press LLC 9064_ch18/fm Page 587 Tuesday, April 24, 2001 5:30 AM Metabolites of Free-Living, Commensal, and Symbiotic Benthic Marine Microorganisms 587 O O O NH N H N H O R O 18. 38a: Andrimid, R = H 18. 38b: Moiramid C, R = β-OH O CH3 O S S S CH3 CH3 S... Gram-positive antibacterial activity.39 Fractionation of the culture broth identified a new diketopiperazine, cyclo-(L-prolineL-methionine) (Structure 18. 27), five known diketopiperzines, and two known phenazine alkaloids Investigations of the sponge revealed that neither metabolite was present This suggests © 2001 by CRC Press LLC 9064_ch18/fm Page 580 Tuesday, April 24, 2001 5:30 AM 580 Marine Chemical. .. from a marine Streptomyces sp., J Antibiot., 51, 333, 1998 14 Jiang, Z., Jensen, P R., and Fenical, W., Actinoflavoside, a novel flavonoid-like glycoside produced by a marine bacterium of the genus Streptomyces, Tetrahedron Lett., 38, 5065,1997 © 2001 by CRC Press LLC 9064_ch18/fm Page 590 Tuesday, April 24, 2001 5:30 AM 590 Marine Chemical Ecology 15 Bernan, V S., Greenstein, M., and Maiese, W., Marine. .. Fenical, W., Rare phenazine L-quinovose esters from a marine actinomycete, J Org Chem., 57, 740, 1992 17 Pusecker, K., Laatsch, H., Helmke, E., and Weyland, H., Dihydrophencomycin methyl ester, a new phenazine derivative from a marine Streptomycete, J Antibiot., 50, 479, 1997 18 Sitachitta, N., Gadepalli, M., and Davidson, B S., New α-pyrone-containing metabolites from a marine- derived actinomycete, Tetrahedron... share structural © 2001 by CRC Press LLC 9064_ch18/fm Page 579 Tuesday, April 24, 2001 5:30 AM Metabolites of Free-Living, Commensal, and Symbiotic Benthic Marine Microorganisms 579 OH NH2 O N H HN H N N H O O R1 O HN O O HOOC O N H X OO O N H N O N H NH R2 NH2 18. 25a: Loloatin A R1= OH R2= X=H R2= 18. 25b: Loloatin B R1= X=H N H 18. 25c: Loloatin C R1= R2= H H 18. 25d: Loloatin D R1= X=H N N R2= X=OH N H... terrestrial bacteria and Gram-positive marine bacteria, but was active against 11 marine Gram-negative bacteria During the course of an anticancer screening program, a new marine bacterium, Pelagiobacter variabilis, was isolated from the blades of the tropical brown alga Pocockiella variegata.35 This Gram-negative, pleomorphic, halophillic bacterium represents a new genus of marine eubacteria Fermentation . anti-HIV drugs. The two inhibitors were character- ized as D-glucono-1,5-lactam and D-mannono-1,5-lactam (Structure 18. 20). The two lactams had never been isolated from nature but were found in marine. leaving N S OH N S OH O OH H H H 18. 30: Agrochelin H N NH H H H H H HO OH O O O OH 18. 26: Alteramide A N NH SCH 3 H H O O 18. 27: Cyclo -( L-proline-L-methionine) OH NH 2 18. 28: o -aminophenol O O NH O OH OH O O 18. 29:. Cyclomarine A contains three common and four unusual amino acids. The four unusual amino acids are N -methylhydroxyleucine, β -methoxyphenylalanine, 2-amino- 3,5-dimethylhex-4-enoic