Selection of non-conventional yeasts and their use in immobilized form for the bioremediation of olive oil mill wastewaters

The yeast population dynamics in olive wastewaters (OMW), sampled in five mills from Salento (Apulia, Southern Italy), were investigated. Three hundred yeasts were isolated in five industrial mills and identified by molecular analysis. Strains belonging to Geotrichum, Saccharomyces, Pichia, Rhodotorula and Candida were detected. Five G. candidum strains were able to grow in OMW as the sole carbon source and to reduce phenolics, chemical oxygen demand (COD) and antimicrobial compounds. One G. candidum isolate was selected for whole-cell immobilization in calcium alginate gel. The COD and phenolic reduction obtained with immobilized cells showed a 2.2- and 2-fold increase compared to the removal obtained with free cells, respectively. The immobilization system enhanced yeast oxidative activity by avoiding the presence of microbial protease in treated OMW. To our knowledge, this is the first report on G. candidum whole-cell immobilization for OMW bioremediation.

Effect of biosurfactant and fertilizer on biodegradation of crude oil by marine isolates of Bacillus megaterium, Corynebacterium kutscheri and Pseudomonas aeruginosa

This study was conducted to investigate the effects of fertilizers and biosurfactants on biodegradation of crude oil by three marine bacterial isolates; Bacillus megaterium, Corynebacterium kutscheri and Pseudomonas aeruginosa. Five sets of experiments were carried out in shake flask and microcosm conditions with crude oil as follows: Set 1-only bacterial cells added (no fertilizer and biosurfactant), Set 2-with additional fertilizer only, Set 3-with additional biosurfactant only, Set 4-with added biosurfactant+fertilizer, Set 5-with no bacterial cells added (control), all the above experimental sets were incubated for 168 h. The biosurfactant+fertilizer added Set 4, resulted in maximum crude oil degradation within shake flask and microcosm conditions. Among the three bacterial isolates, P. aeruginosa and biosurfactant produced by this strain resulted in maximum crude oil degradation compared to the other two bacterial strains investigated. Interestingly, when biosurfactant and bacterial cells were used (Set 3), significant oil biodegradation activity occurred and the difference between this treatment and that in Set 4 with added fertilizer+biosurfactant were only 4-5% higher degradation level in shake flask and 3.2-7% in microcosm experiments for all three bacterial strains used. It is concluded that, biosurfactants alone capable of promoting biodegradation to a large extent without added fertilizers, which will reduce the cost of bioremediation process and minimizes the dilution or wash away problems encountered when water soluble fertilizers used during bioremediation of aquatic environments.

Antioxidative and antibacterial effects of seeds and fruit rind of nutraceutical plants belonging to the Fabaceae family

In the present study, the seeds and fruit rind of six plants of the Fabaceae family were selected to evaluate their potential as antioxidant and antibacterial agents. The dried powders were individually extracted with various organic solvents by the cold percolation method, were evaluated for antibacterial activity and methanol extracts used for antioxidant activities. Total phenol, protein and sugar contents were also measured. Antioxidant activities were measured by DPPH free radical scavenging activity, superoxide anion radical scavenging activity and reducing capacity assessment. Antibacterial activity was measured by the agar well diffusion method against four Gram positive and four Gram negative bacteria. The methanol extract of the fruit rind of C. indica showed the maximum DPPH free radical scavenging activity, superoxide anion radical scavenging activity, a high reducing capacity assessment and also had the highest total phenol content. There was a direct correlation between the phenol content and the antioxidant activity. The antibacterial activity of all the extracts was more pronounced on Gram positive bacteria than on Gram negative bacteria. Thus, the fruit rind of C. indica showed the best antioxidant and antibacterial activities.

Cameroonemide A: a new ceramide from Helichrysum cameroonense

From the extracts of all parts of the plant Helichrysum cameroonense, five compounds were isolated and identified. One of them, a ceramide, named cameroonemide A (1), is reported for the first time as a new natural product. Its structure was determined by comprehensive analyses of their 1D and 2D NMR and HR-EI-MS spectral data. The remaining four known compounds were identified by comparing their spectroscopic data with those reported in the literature as kaurenoic acid (2), 3-acetyloxykaurenoic acid (3), beta-sitosterol (4), and beta-sitosterol glucopyranoside (5). Preliminary studies showed that 3-acetyloxykaurenoic acid (3) inhibited the alga Chlorella fusca, while kaurenoic acid (2) showed strong antibacterial activity against Bacillus megaterium.

Antimicrobial activity investigation on Wuyiencin fractions of different polarity

The aim of this study was to evaluate the antimicrobial activity of Wuyiencin fractions with different polarities against six indicator microorganisms: Rhodotorula rubra, Bacillus subtilis, Bacillus megaterium, Escherichia coli, Cladosporium fulvum and Staphylococcus aureus. The fermentation broth of Wuyiencin was submitted to AB-8 macroporous adsorptive resin and fractionated with solvents of different polarity. The fraction eluted with water had remarkably antimicrobial activity against all the microorganisms investigated except for C. fulvum and S. aureus (MIC Collapse

Key Words

• wuyiencin
• antimicrobial activity
• rhodotorula rubra
• bacillus subtilis
• bacillus megaterium
• escherichia coli
• cladosporium fulvum
• staphylococcus aureus

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MESH Headings

• Anti-Infective Agents/isolation & purification
• Anti-Infective Agents/pharmacology
• Bacillus megaterium/drug effects
• Bacillus subtilis/drug effects
• Chemical Fractionation
• Cladosporium/drug effects
• Escherichia coli/drug effects
• Fermentation
• Hydrophobic and Hydrophilic Interactions
• Microbial Sensitivity Tests
• Plant Extracts/isolation & purification
• Plant Extracts/pharmacology
• Rhodotorula/drug effects
• Staphylococcus aureus/drug effects

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Grants Collapse

Hydroxylated sclerosporin derivatives from the marine-derived fungus Cadophora malorum

The marine-derived fungus Cadophora malorum was isolated from the green alga Enteromorpha sp. Growth on a biomalt medium supplemented with sea salt yielded an extract, from which we have isolated sclerosporin and four new hydroxylated sclerosporin derivatives, namely, 15-hydroxysclerosporin (2), 12-hydroxysclerosporin (3), 11-hydroxysclerosporin (4), and 8-hydroxysclerosporin (5). The compounds were evaluated in various biological activity assays. Compound 5 showed a weak fat-accumulation inhibitory activity against 3T3-L1 murine adipocytes.

Structure-activity relationship of human liver-expressed antimicrobial peptide 2

Liver-expressed antimicrobial peptide 2 (LEAP-2) is a 40-residue cationic peptide originally purified from human blood ultrafiltrate. The native peptide contains two disulfide bonds and is unique regarding its primary structure. Its biological role is not known but a previous study showed that chemically synthesized LEAP-2 exhibited in vitro antimicrobial activities against several Gram-positive bacteria. In order to determine its antimicrobial mode of action, we expressed human recombinant LEAP-2 in Escherichia coli. Circular dichroism spectroscopy and nuclear magnetic resonance analyses showed that the structure of the recombinant peptide was identical to that of the chemically synthesized and oxidized LEAP-2, with two disulfide bonds between Cys residues in relative 1-3 and 2-4 positions. Minimal inhibitory concentration (MIC) of the recombinant human LEAP-2 was determined by a conventional broth dilution assay. It was found to be bactericidal against Bacillus megaterium at a 200microM concentration. Interestingly, the linear LEAP-2 had a greater antimicrobial activity with a MIC value of 12.5microM, which was comparable to that of magainin2. SYTOX Green uptake was used to assess bacterial membrane integrity. Linear LEAP-2 and magainin2 permeabilized B. megaterium membranes with the same efficiency, whereas oxidized LEAP-2 did not induce stain uptake. Binding of the peptides to plasmid DNA was evaluated by gel retardation assays. The DNA-binding efficacy of linear LEAP-2 was three times higher than that of the peptide-containing disulfide bridges. Altogether, these results show that the secondary structure of human LEAP-2 has a profound impact on its antibacterial activity.

Activities of antioxidant enzymes in three bacteria exposed to bensulfuron-methyl

Oxidative stress enzymes, superoxide dismutase (SOD), catalase (CAT), and ATPase, from two Gram-positive bacteria and one Gram-negative bacterium, respectively, were tested for response to the oxidative stress caused by bensulfuron-methyl (BSM). Native PAGE was used to detect the SOD isoenzyme profiles of these bacteria. All three bacteria possessed a basal level of SOD, CAT, and ATPase activity prior to being exposed to BSM. Enzyme activities changed in a BSM-concentration-dependent manner after exposure to BSM for 24 h. Activity of all the enzymes was increased and reached the first activity peak after being exposed to BSM at 1 or 1.5 h, respectively, then a decline occurred, and after that another simulation appeared at 9h or 14 h. Only one and three detectable SOD isoenzyme bands were observed in Gram-positive strains and the Gram-negative strain, respectively. BSM could bring short-term ecotoxicity to three bacteria, but the effect of BSM was not lethal.

The human antimicrobial protein psoriasin acts by permeabilization of bacterial membranes

Psoriasin, a member of the S100 family of calcium-binding proteins (S100A7) is highly upregulated in the skin of psoriasis patients. As it has recently been found to exhibit antimicrobial activity, an important role of psoriasin in surface defence has been suggested. The similarity of the three-dimensional structures of psoriasin and amoebapore A, an ancient antimicrobial, pore-forming peptide from Entamoeba histolytica, intrigued us to investigate whether the human psoriasin is also able to permeabilize bacterial membranes. Here, we demonstrate that psoriasin exerts pore-forming activity at pH values below 6 demonstrating that disruption of microbial membranes is the basis of its antimicrobial activity at low pH. Furthermore, the killing activity of psoriasin shows pH-dependent target specificity. At neutral pH, the Gram-negative bacterium E. coli is killed apparently without compromising its membrane, whereas at low pH exclusively the Gram-positive bacterium B. megaterium is killed by permeabilization of its cytoplasmic membrane.

Myxotyrosides A and B, Unusual rhamnosides from Myxococcus sp

Myxobacteria are gliding bacteria of the delta-subdivision of the Proteobacteria and known for their unique biosynthetic capabilities. Two examples of a new class of metabolites, myxotyrosides A (1) and B (2), were isolated from a Myxococcus sp. The myxotyrosides have a tyrosine-derived core structure glycosylated with rhamnose and acylated with unusual fatty acids such as (Z)-15-methyl-2-hexadecenoic and (Z)-2-hexadecenoic acid. The fatty acid profile of the investigated Myxococcus sp. (strain 131) is that of a typical myxobacterium with a high similarity to those described for M. fulvus and M. xanthus, with significant concentrations of neither 15-methyl-2-hexadecenoic acid nor 2-hexadecenoic acid being detected.

Dephenolization and detoxification of olive-mill wastewater (OMW) by purified biotic and abiotic oxidative catalysts

The capability of two oxidative catalysts, a laccase from Rhus vernicifera and birnessite, a manganese oxide, in the dephenolization and detoxification of two olive-mill wastewater (OMW) samples, C1 and C2, differing for complexity and composition, was evaluated. OMW phenolic extracts (EC1 and EC2) and mono-substrate solutions of phenols mostly present in OMW samples were also tested. Birnessite was more effective than laccase in removing the phenolic content from mono-substrate solutions (more than 70% of each initial phenolic concentration) and of either OMW samples or EC1 and EC2 extracts. For instance, 60% of the total phenolic content of EC1 was removed after 48-h treatment with 5 mg mL(-1) birnessite and the efficiency was lower as greater was the complexity of the OMW sample (only 17% removal from EC2 over the same time span). Phytotoxicity tests with Lepidium sativum and Lycopersicon esculentum seeds and antibacterial toxicity tests with Bacillus megaterium were performed on crude OMW samples and their extract and exhausted fractions before and after the catalytic treatment. Results demonstrated that (a) monomeric phenols were certainly but not exclusively responsible of OMW phytotoxicity, whereas their removal led to a quite complete elimination of the toxicity toward bacterial growth; (b) other components not removable by the oxidative catalysts very likely contribute to OMW phytotoxicity; and (c) the choice of the vegetal species to use in toxicity tests might be crucial for correct and easily interpretable results. Overall the results provided useful information on the possible use of oxidative catalysts for the efficient treatment of complex aqueous wastes such as those deriving from olive industry.

Antiprotozoal activities of heterocyclic-substituted xanthones from the marine-derived fungus Chaetomium sp

Investigations of the marine-derived fungus Chaetomium sp. led to the isolation of the new natural products chaetoxanthones A, B, and C (1-3). Compounds 1 and 2 are substituted with a dioxane/tetrahydropyran moiety rarely found in natural products. Compound 3 was identified as a chlorinated xanthone substituted with a tetrahydropyran ring. The configurational analysis of these compounds employed CD spectroscopy, modified Mosher's method, and selective NOE gradient measurements. Compound 2 showed selective activity against Plasmodium falciparum with an IC50 value of 0.5 microg/mL without being cytotoxic toward cultured eukaryotic cells. Compound 3 displayed a moderate activity against Trypanosoma cruzi with an IC50 value of 1.5 microg/mL.

Controversial role of fungal laccases in decreasing the antibacterial effect of olive mill waste-waters

Antibacterial diffusion tests (against Bacillus megaterium) detected both bacterial growth-promoting and growth-inhibiting components in olive mill waste-water (OMW). Mixtures of OMW aromatic components showed antibacterial effects that did not show antibacterial activity when tested as individual compounds. Strains of white rot fungi (WRF) producing different patterns of lignin modifying enzymes (LMEs) have been evaluated for OMW remediation under nutritional conditions affecting the LMEs produced. The decrease of both the content in OMW phenols and in the OMW antibacterial activity was compared with fungal growth and LMEs production. OMW addition to the cultures increased fungal growth and laccase activity irrespectively of the nutritional conditions of the cultures. Laccase was the sole LME activity that increased after OMW addition to the cultures. Neither the increased growth of WRF in OMW-containing cultures, their content in laccase nor the amount of OMW phenols were direct indications of a greater decrease in OMW antibacterial effect. The higher decrease in OMW antibacterial activity was obtained in cultures of Phanerochaete flavido-alba in an N-rich media.

Assessment of toxicity of the untreated and treated olive mill wastewaters and soil irrigated by using microbiotests

Hazard assessments based on two measures of toxicity were conducted for the untreated olive mill wastewaters (U), untreated olive mill wastewaters organic extract (UOE), treated olive mill wastewaters (T), treated olive mill wastewaters organic extract (TOE) and extracts of soils ferti-irrigated with untreated (SU) and with treated olive mill wastewaters (ST). The measures of toxicity were achieved by the determination of the bioluminescence inhibition percent (I(B)%) of Vibrio fischeri and by the growth inhibition (GI) of Bacillus megaterium, Pseudomonas fluorescens and Escherichia coli. A bioluminescence inhibition of V. fischeri of 100%, 100%, 65%, 47%, 46% and 30% were obtained with U, UOE, T, TOE, SU and ST respectively. Indeed, even diluted 24 times, a significant bioluminescence inhibition of 96% was obtained by U. However, only 30% bioluminescence inhibition was obtained by 24 times diluted T. Whereas, 24 times diluted, SU and ST did not show a bioluminescence inhibition (3% and 1%, respectively). The GI of B. megaterium, P. fluorescens and E. coli were, respectively, 93%, 72% and 100% by U; 100%, 80% and 100% by UOE; 70%, 60% and 89% by T; 63%, 54% and 68% by TOE; 39%, 27% and 43% by SU and 23%, 0% and 34% by ST. The incubation of U or T in the soil during four months reduced their toxicity by 54% and 35%, respectively. As it was expected, the most resistant bacterium to OMW toxicity is P. fluorescens then B. megaterium and E. coli. V. fischeri remained the most sensitive strain to the toxicity of this sewage what proves again its utilisation as standard of measure of the toxicity.

Aromatic polyketides from marine algicolous fungi

The investigation of the marine-derived fungi Acremonium sp. and Nodulisporium sp. led to the isolation of the new natural products acremonisol A ( 1) and (3 R)-7-hydroxy-5-methylmellein ( 2). Both fungi are endophytes of marine algae. Compounds 1 and 2 are biosynthetically related by both being aromatic pentaketides belonging to the dihydroisocoumarins. All structures were elucidated by extensive spectroscopic measurements.

A reverse search for antimicrobial peptides in Ciona intestinalis: identification of a gene family expressed in hemocytes and evaluation of activity

In search of antimicrobial peptides in the tunicate Ciona intestinalis, we used the recently completed genome project and the substantial number of expressed sequence tag (EST) data available as a screening matrix. By this means, we identified a putative gene family that exhibits several structural features typical of antimicrobial peptides. We designed and synthesized a peptide corresponding to the core region of a member of this peptide family, which is predicted to adopt an amphipathic alpha-helical structure. The synthetic peptide exerted potent antimicrobial activity against a variety of bacteria and against the yeast Candida albicans but was not cytolytic for mammalian erythrocytes. Moreover, by employing a non-cell-permeable fluorescent dye it became evident that the peptide kills bacteria by permeabilizing their cytoplasmic membranes. Using the synthetic peptide as an antigen, we generated specific antibodies and localized the natural parent molecule to a compartment of a distinct hemocyte type, the univacuolar refractile granulocytes. As C. intestinalis apparently does not possess gene products that resemble well-known antimicrobial peptides of tunicates and of other animals, the aforementioned peptide family may represent a potent armamentarium of the hemocytes to combat microbial infection in sea squirts.

Exploring the use of natural antimicrobial agents and pulsed electric fields to control spoilage bacteria during a beer production process

Different natural antimicrobials affected viability of bacterial contaminants isolated at critical steps during a beer production process. In the presence of 1 mg/ml chitosan and 0.3 mg/ml hops, the viability of Escherichia coli in an all malt barley extract wort could be reduced to 0.7 and 0.1% respectively after 2 hour- incubation at 4 degrees C. The addition of 0.0002 mg/ml nisin, 0.1 mg/ml chitosan or 0.3 mg/ml hops, selectively inhibited growth of Pediococcus sp. in more than 10,000 times with respect to brewing yeast in a mixed culture. In the presence of 0.1 mg ml chitosan in beer, no viable cells of the thermoresistant strain Bacillus megaterium were detected. Nisin, chitosan and hops increased microbiological stability during storage of a local commercial beer inoculated with Lactobacillus plantarum or Pediococcus sp. isolated from wort. Pulsed Electric Field (PEF) (8 kV/cm, 3 pulses) application enhanced antibacterial activity of nisin and hops but not that of chitosan. The results herein obtained suggest that the use of these antimicrobial compounds in isolation or in combination with PEF would be effective to control bacterial contamination during beer production and storage.

Effects of freezing on the survival of Escherichia coli and Bacillus and response to UV and chlorine after freezing

Escherichia coli (E. coli) and Bacillus megaterium bacteria were frozen at -15 degrees C using a freezer and a spray freezing method. The frozen Bacillus spores were also exposed to UV and free chlorine. An average of 4.7-log inactivation was obtained from the spray ice with 2-day storage time, while the freezer freezing only caused 0.84-log reduction with the same storage time. Significantly higher inactivation levels were observed for the E. coli cells with 2-day storage compared with those without storage. The spray freezing was found more effective in killing the E. coli cells, while more cells were sublethally injured by the freezer freezing. Freezing did not kill the Bacillus megaterium spores, but affected their response to UV and chlorine. Greater inactivation levels were observed at higher free chlorine doses or longer contact time, and the UV fluence-response curve showed initial rapid kill followed by tailing for the frozen spores.

Antimicrobial prenylated anthracene derivatives from the leaves of Harungana madagascariensis

Three new prenylated anthranoids, harunmadagascarins C (1) and D (2) and kenganthranol D (3), together with three known compounds (4-6) were isolated from the leaves of Harungana madagascariensis. Their structures were assigned by spectroscopic methods and by comparison with literature data. In the three new natural products 1-3, one or two prenyl groups are incorporated in furan, pyran, or cyclohexane rings in four different modes of annulation. Compounds 2, 4, and 6 were strongly active against the Gram-positive Bacillus megaterium.

Antibacterial peptides in hemocytes and hematopoietic tissue from freshwater crayfish Pacifastacus leniusculus: characterization and expression pattern

A 14 amino acid residues proline/arginine-rich antibacterial peptide designated as astacidin 2 was purified and characterized from hemocytes of the freshwater crayfish, Pacifastacus leniusculus. Astacidin 2 has a broad range of antibacterial activity against both Gram-positive and Gram-negative bacteria. The primary sequence of astacidin 2 is RPRPNYRPRPIYRP with an amidated C-terminal and the molecular mass is 1838Da determined by mass spectrometry. Furthermore, the cDNA of three different crustin antibacterial homologs were isolated from a crayfish hemocyte EST library. RT-PCR was used to analyze the expression of the genes coding for astacidin 2 and P. leniusculus crustins (Plcrustin) 1-3 after bacterial challenge. The expression of Plcrustin1 was upregulated in both hemocytes and hematopoietic tissue after challenge with Gram-negative Escherichia coli or Acinetobacter ssp. non pathogenic bacteria as well as by a Gram negative crayfish pathogenic bacterium (Aeromonas hydrophila). The PlCrustin3 transcript was only upregulated after inoculation with the non-pathogenic Acinetobacter ssp. while there was no change in expression of Plcrustin2 or astacidin 2 following a bacterial challenge.

PGRP-SB1: an N-acetylmuramoyl L-alanine amidase with antibacterial activity

The peptidoglycan recognition protein (PGRP) family is conserved from insects to mammals and is involved in immune regulation and bacterial clearance. They form at least three functional classes; receptors required for immune gene expression; amidases that degrade peptidoglycan and scavenge the tissues from immune-stimulating peptidoglycan; and as proteins with antibacterial activity. We here report that PGRP-SB1 is an N-acetylmuramoyl l-alanine amidase, which (in contrast to the previously described PGRP-amidases) shows antibacterial activity. PGRP-SB1 is highly active against peptidoglycans that have a diaminopimelic acid (DAP) residue in the cross-linking peptide, but lack activity to most lysine-containing peptidoglycans. The antibacterial activity is pronounced against Bacillus megaterium with an LD(50) of 1.5microg ml(-1). The bactericidal effect of PGRP-SB1 is dependent on its enzymatic activity, as the zinc co-factor is essential. The bactericidal mode of action is thus different from non-enzymatic vertebrate PGRPs that have been reported to be antibacterial.

An alternative bactericidal mechanism of action for lantibiotic peptides that target lipid II

Lantibiotics are polycyclic peptides containing unusual amino acids, which have binding specificity for bacterial cells, targeting the bacterial cell wall component lipid II to form pores and thereby lyse the cells. Yet several members of these lipid II-targeted lantibiotics are too short to be able to span the lipid bilayer and cannot form pores, but somehow they maintain their antibacterial efficacy. We describe an alternative mechanism by which members of the lantibiotic family kill Gram-positive bacteria by removing lipid II from the cell division site (or septum) and thus block cell wall synthesis.

The high mobility group box chromosomal protein 1 is expressed in the human and rat testis where it may function as an antibacterial factor

BACKGROUND

The high mobility group box chromosomal protein 1 (HMGB1) was originally shown to be a nuclear DNA-binding protein that activates transcription and promotes differentiation. More recently, there have been reports that HMGB1 may also function as a pro-inflammatory and antibacterial factor. The aim of this study was to investigate the testicular expression and antibacterial functions of HMGB1 to elucidate a possible role of HMGB1 in the testicular barrier defence against infections.

METHODS AND RESULTS

RT-PCR and in situ hybridization revealed high-level testicular expression of HMGB1 mRNA and localization of this expression to the Sertoli cells and germ cells of the human and rat testis. In addition, immunohistochemical examination demonstrated the presence of the corresponding protein in Sertoli cells and spermatogonia in human and rat testes. Western blotting detected abundant amounts of the HMGB1 protein in the interstitial and intratubular fluids of the intact adult rat testis. Finally, the HMGB1 protein purified from both human and rat testis by reversed-phase high-performance liquid chromatography (HPLC) exerted antibacterial activity towards Bacillus megaterium in an inhibition zone assay.

CONCLUSION

HMGB1 is expressed by Sertoli cells and germ cells in the mammalian testis. In addition, purified testicular HMGB1 shows antibacterial activity, indicating that this protein may function as a paracrine host defence factor in the testis.

Conformational and functional studies of gomesin analogues by CD, EPR and fluorescence spectroscopies

The aim of this work was to examine the bioactivity and the conformational behavior of some gomesin (Gm) analogues in different environments that mimic the biological membrane/water interface. Thus, manual peptide synthesis was performed by the solid-phase method, antimicrobial activity was evaluated by a liquid growth inhibition assay, and conformational studies were performed making use of several spectroscopic techniques: CD, fluorescence and EPR. [TOAC(1)]-Gm; [TOAC(1), Ser(2,6,11,15)]-Gm; [Trp(7)]-Gm; [Ser(2,6,11,15), Trp(7)]-Gm; [Trp(9)]-Gm; and [Ser(2,6,11,15), Trp(9)]-Gm were synthesized and tested. The results indicated that incorporation of TOAC or Trp caused no significant reduction of antimicrobial activity; the cyclic analogues presented a beta-hairpin conformation similar to that of Gm. All analogues interacted with negatively charged SDS both above and below the detergent's critical micellar concentration (cmc). In contrast, while Gm and [TOAC(1)]-Gm required higher LPC concentrations to bind to micelles of this zwitterionic detergent, the cyclic Trp derivatives and the linear derivatives did not seem to interact with this membrane-mimetic system. These data corroborate previous results that suggest that electrostatic interactions with the lipid bilayer of microorganisms play an important role in the mechanism of action of gomesin. Moreover, the results show that hydrophobic interactions also contribute to membrane binding of this antimicrobial peptide.

Arugosins G and H: prenylated polyketides from the marine-derived fungus Emericellanidulans var. acristata

The fungus Emericella nidulans var. acristata was isolated as an endophyte from a Mediterranean green alga. Cultivation of this fungus yielded two new compounds, arugosins G (1) and H (2), together with the known metabolites 3-9. Arugosins (1-4) are benzophenone derivatives, biosynthetically related to the xanthones 5, 6, and 9. The indole alkaloid 7 displayed antitumor activity in a panel of 36 human tumor cell lines, exhibiting a mean IC(50) value of 5.5 microg/mL in an in vitro survival and proliferation assay. Furthermore, compounds 3 and 4 showed moderate antitumor activity toward individual tumor cell lines. None of compounds 1-8 exhibited any immunostimulatory activity assessed as the capacity to induce cytokines in PBMCs from healthy donors.