New and biologically active imidazole alkaloids from two sponges of the genus Leucetta

Chemical investigation of two sponges, Leucetta chagosensis and Leucetta cf chagosensis, collected from the Great Barrier Reef and the Fiji Islands, respectively, has led to the isolation of three new imidazole alkaloids (1-3), along with the known compounds isonaamine B (4) and naamine A (5). The structures of the new compounds (1-3) were elucidated by employing spectroscopic techniques (NMR, MS, UV, and IR). The structures of the known compounds 4 and 5 were determined by comparison of their (1)H and (13)C NMR spectroscopic data with published values. Compounds 1 and 2 were found to be cytotoxic toward several tumor cell lines (GI(50) values ranged from 1.3 to 7.0 microg/mL).

A new cytotoxic calyculinamide derivative, geometricin A, from the Australian sponge Luffariella geometrica

Geometricin A (1), together with the known compounds (7E,12E,18S,20Z)-variabilin (2), clathryimine A (3), tryptophol (4), and L-tryptophan, has been isolated from the methanol extract of the Australian sponge Luffariella geometrica. The structure of the new compound geometricin A (1) was elucidated by employing spectroscopic techniques (NMR, MS, UV, and IR) and by comparison of its NMR data with those of the calyculins and calyculinamides. Geometricin A (1) was found to be moderately cytotoxic toward the tumor cell lines HM02 and HEPG2 with GI50's of 1.7 and 2.8 microg/mL, respectively, and to have antialgal activity (growth inhibition zone 5 mm at the 50 microg level).

Two novel antifungal peptides distinct with a five-disulfide motif from the bark of Eucommia ulmoides Oliv

Two antifungal peptides, named EAFP1 and EAFP2, have been purified from the bark of Eucommia ulmoides Oliv. Each of the sequences consists of 41 residues with a N-terminal blockage by pyroglutamic acid determined by automated Edman degradation in combination with the tandem mass spectroscopy and the C-terminal ladder sequencing analysis. The primary structurs all contain 10 cysteines, which are cross-linked to form five disulfide bridges with a pairing pattern (C1-C5, C2-C9, C3-C6, C4-C7, C8-C10). This is the first finding of a plant antifungal peptide with a five-disulfide motif. EAFP1 and EAFP2 show characteristics of hevein domain and exhibit chitin-binding properties similar to the previously identified hevein-like peptides. They exhibit relatively broad spectra of antifungal activities against eight pathogenic fungi from cotton, wheat, potato, tomato and tobacco. The inhibition activity of EAFP1 and EAFP2 can be effective on both chitin-containing and chitin-free fungi. The values of IC(50) range from 35 to 155 microg/ml for EAFP1 and 18 to 109 microg/ml for EAFP2. Their antifungal effects are strongly antagonized by calcium ions.

Essential oil constituents and in vitro antimicrobial activity of Decalepis hamiltonii roots against foodborne pathogens

Hydrodistillation of Decalepis hamiltonii roots yielded an essential oil (0.33% v/w) that contained 2-hydroxy-4-methoxybenzaldehyde (37.45%), 2-hydroxybenzaldehyde (31.01%), 4-O-methylresorcylaldehyde (9.12%), benzyl alcohol (3.16%), and alpha-atlantone (2.06%) as major constituents, with aromatic aldehydes constituting the main fraction of this root's essential oil. The oil was tested for its antimicrobial activity against foodborne pathogens responsible for food spoilage and human pathologies using standard antimicrobial assays. It exhibited strong antimicrobial activity against Bacillus cereus, Bacillus megaterium, Candida albicans, Escherichia coli, Micrococcus luteus, Micrococcus roseus, and Staphylococcus aureus at a concentration range of 1:0 with inhibitory activities of 27, 23, 16, 19, 22, 19, and 23 mm, respectively, which are comparable to those of the standards. The roots of D. hamiltonii, therefore, may be considered as an inexpensive source of an essential oil rich in antimicrobial compounds against foodborne pathogens.

Production of PHB by a Bacillus megaterium strain using sugarcane molasses and corn steep liquor as sole carbon and nitrogen sources

Poly(hydroxybutyric acid) (PHB) and other biodegradable polyesters are promising candidates for the development of environment-friendly, totally biodegradable plastics. The use of cane molasses and corn steep liquor, two of the cheapest substrates available in Egypt, may help to reduce the cost of producing such biopolyesters. In this work, the effect of different carbon sources was studied. Maximum production of PHB was obtained with cane molasses and glucose as sole carbon sources (40.8, 39.9 per mg cell dry matter, respectively). The best growth was obtained with 3% molasses, while maximum yield of PHB (46.2% per mg cell dry matter) was obtained with 2% molasses. Corn steep liquor was the best nitrogen source for PHB synthesis (32.7 mg per cell dry matter), on the other hand, best growth was observed when ammonium chloride, ammonium sulphate, ammonium oxalate or ammonium phosphate were used as nitrogen sources.

Rare sesquiterpenes from the algicolous fungus Drechslera dematioidea

From the inner tissue of the marine red alga Liagora viscida the fungus Drechslera dematioidea was isolated. After mass cultivation, the fungus was investigated for its secondary metabolite content, and 10 new sesquiterpenoids [isosativenetriol (1), drechslerines A (2) and B (3), 9-hydroxyhelminthosporol (5), drechslerines C-G (6-10), and sativene epoxide (12)] were isolated. Compounds 8 and 10 exhibited antiplasmodial activity against Plasmodium falciparum strains K1 and NF54. The known compounds helminthosporol (4), cis-sativenediol (11), isocochlioquinone A (14), isocochlioquinone C (15), and cochlioquinone B (16) were also isolated. All structures were elucidated using spectroscopic methods, mainly 1D and 2D NMR and MS.

Antibacterial effect of the culture fluid of Lentinus edodes mycelium grown in submerged liquid culture

The antimicrobial activity of the culture fluid of Lentinus edodes mycelium grown in submerged liquid culture was tested against some common bacterial species and Candida albicans. The mycelium-free culture fluid was bacteriostatic against Streptococcus pyogenes, Staphylococcus aureus and Bacillus megaterium. The substance responsible for the activity was heat-stable, could be extracted with chloroform and had a molecular weight under 10000. These characteristics suggested that the component might be lenthionine, an antibacterial and antifungal sulphur-containing compound. The culture fluid was less toxic to human tissue culture cells than to microbes. The antibacterial activity and toxicity could not be attributed to the same component.

Method to sensitize bacterial spores to subsequent killing by dry heat or ultraviolet irradiation

Hydrogen peroxide and ultraviolet irradiation are known to interact synergistically for killing of bacterial spores. Synergy could be demonstrated with spores of Bacillus megaterium ATCC19213 adsorbed to filter paper strips or glass coverslips treated first with the peroxide and then dried for as long as 48 h prior to UV irradiation. This delayed action was considered to be due to absorption of the peroxide by the spores in an active but not readily vaporized form, which could become sporicidal also if the spores were heated to 50 degrees C. B. megaterium spores mixed with 0.1% (32.6 mM) H(2)O(2) solution appeared to absorb as much as 15 micromol/mg dry weight or about 0.5 mg/mg, but only a third to half of the peroxide could be recovered by water washing. A part of the unrecovered peroxide was degraded in reactions resulting in measurable production of oxygen. Degradation was not reduced by heating the spores to 65 degrees C or by azide and so appeared to be non-enzymatic. Spores of the anaerobe Clostridium sporogenes were also sensitized to ultraviolet killing by H(2)O(2) treatment followed by drying. They appear to absorb less peroxide, only about 2 micromol/mg, but had lower capacities to degrade H(2)O(2) so that nearly all of the peroxide could be recovered by washing with water. The findings presented should be helpful in the design of new methods for synergistic killing of spores by H(2)O(2) and UV irradiation or dry heat, especially involving, for example, packaging materials.

LEAP-1, a novel highly disulfide-bonded human peptide, exhibits antimicrobial activity

We report the isolation and characterization of a novel human peptide with antimicrobial activity, termed LEAP-1 (liver-expressed antimicrobial peptide). Using a mass spectrometric assay detecting cysteine-rich peptides, a 25-residue peptide containing four disulfide bonds was identified in human blood ultrafiltrate. LEAP-1 expression was predominantly detected in the liver, and, to a much lower extent, in the heart. In radial diffusion assays, Gram-positive Bacillus megaterium, Bacillus subtilis, Micrococcus luteus, Staphylococcus carnosus, and Gram-negative Neisseria cinerea as well as the yeast Saccharomyces cerevisiae dose-dependently exhibited sensitivity upon treatment with synthetic LEAP-1. The discovery of LEAP-1 extends the known families of mammalian peptides with antimicrobial activity by its novel disulfide motif and distinct expression pattern.

Penaeidins, a family of antimicrobial peptides from penaeid shrimp (Crustacea, Decapoda)

The production of antimicrobial peptides represents a first-line host defense mechanism of innate immunity that is widespread in nature. Only recently such effectors were isolated in crustacean species, whereas numerous antimicrobial peptides have been characterized from other arthropods, both insects and chelicerates. This review presents findings on a family of antimicrobial peptides, named penaeidins, isolated from the shrimp Penaeus vannamei. Their structure and antimicrobial properties as well as their immune function will be discussed through analyses of penaeidin gene expression and peptide distribution upon microbial challenge.

Spice extracts as dose-modifying factors in radiation inactivation of bacteria

Three spices, chili, black pepper, and turmeric, were tested for the effect of their aqueous extracts on the sensitivity of three bacteria, Escherichia coli, Bacillus megaterium, and Bacillus pumilusspores, to gamma-radiation. It was found that the extracts of the three spices offered protection to these organisms against inactivation by gamma-radiation. These spice extracts were also tested for their protection of naked plasmid DNA. Radiation-induced degradation of plasmid pUC18 DNA was reduced in the presence of the spice extracts. The maximum protection was offered by the chili extract followed by that of black pepper and turmeric. The two known antioxidants, curcumin and piperine from turmeric and black pepper, respectively, were shown to protect the plasmid DNA from the degradation by gamma-radiation. Experiments with the plasmid pUC18 DNA indicated that the spice extracts probably protected microorganisms by protecting their DNA. These studies indicated the importance of spices among ingredients in food as dose-modifying factors during radiation processing.

Structure and organization of hemolytic and nonhemolytic diastereomers of antimicrobial peptides in membranes

Recently, we reported on a new group of diastereomers of short-model peptides (12 amino acids long) composed of leucine and lysine with varying ratios, possessing several properties that make them potentially better than native or de novo-designed all L-amino acid antimicrobial peptides. Preliminary studies have revealed that modulating the hydrophobicity and positive charges of these diastereomers is sufficient to confer antibacterial activity and cell selectivity. However, the relationship between their biological function, structure, and mode of action was not investigated. Here we synthesized and investigated three types of linear model diastereomers (12 amino acids long) with varying lysine:leucine (or tryptophan) ratios (i.e., K(3)L(8)W, K(5)L(6)W, and K(7)L(4)W), which confer different levels of lytic activities. For each K:L ratio, tryptophan was introduced in the middle or the N- or C-terminus of the peptides, as an intrinsic fluorescent probe. Only the hemolytic peptide K(3)L(8)W binds to both negatively charged and zwitterionic phospholipid membranes. K(5)L(6)W and K(7)L(4)W bind similarly, but only to negatively charged membranes, despite the fact that K(5)L(6)W is substantially more lytic to bacteria than K(7)L(4)W. Interestingly, although K(3)L(8)W contains 33% D-amino acids, ATR-FTIR spectroscopy revealed a structure of approximately 90% alpha-helix in both types of membranes. In addition, K(5)L(6)W contains approximately 40% 3(10)-helix and K(7)L(4)W is predominantly a random coil in membranes. Polarized ATR-FTIR and tryptophan-quenching experiments, using brominated phospholipids, revealed a similar depth of penetration and an orientation that was parallel to the membrane surface for all the peptides, but with K(3)L(8)W affecting the lipid order more than the others. The results provide insight into the mode of action of this group of diastereomeric peptides, and the effect of hydrophobicity and positive charges on their membrane structure, function, and cell selectivity. Moreover, this research should assist in the development of suitable diastereomeric peptide antibiotics for therapeutic use that would overcome the problem the increasing resistance of bacteria to conventional antibiotics.

Identification of an anti-mycobacterial domain in NK-lysin and granulysin

NK-lysin and granulysin are homologous cationic anti-bacterial peptides produced by pig and human cytolytic lymphocytes, respectively. The solution structure of NK-lysin comprises five amphipathic alpha-helices. To investigate the properties of a helix-loop-helix region postulated to be a membrane-docking part of NK-lysin, we synthesized 22- and 29-residue peptides reproducing this region for both NK-lysin and granulysin. CD spectroscopy of the synthetic peptides in a liposomal solution showed spectra typical of alpha-helical peptides. The peptides were active against Gram-positive and Gram-negative bacteria, with the two NK-lysin peptides showing higher anti-bacterial activities than the two from granulysin. One NK-lysin peptide was active against Pseudomonas aeruginosa and Staphylococcus aureus, two organisms against which NK-lysin is inactive. Granulysin peptides were inactive against these bacteria, in contrast with granulysin, which is known to be active against them. Both NK-lysin and all synthetic analogues killed Mycobacterium tuberculosis and K562 tumour cells, but did not display haemolytic activity. These results identify a potent anti-mycobacterial domain in NK-lysin and granulysin consisting of a 22-residue (helix 3) sequence plus a disulphide-constrained loop.

In vitro disinfection of dentinal tubules by various endodontics irrigants

Effectiveness of endodontic irrigants within dentinal tubules of human teeth was evaluated. Mid-sections of single-rooted teeth were prepared into dentin wedges. The pulpal sides of the sections were exposed to Micrococcus luteus or Bacillus megaterium that grew into the tubules. Irrigants used in the study included: 0.525% NaOCl, 0.12% chlorhexidine, RC Prep, 0.5% betadine iodine, and sterile H2O (as a control). Pulpal surfaces were exposed to an irrigant and then rinsed in sterile water. The samples were then cracked, exposing a fresh surface. Culture of the exposed dentin surfaces showed that selected irrigants reached to the far ends of the dentinal tubules in a concentration sufficient to kill 100% of the M. luteus. However B. megaterium was neither killed nor apparently inhibited by any irrigant. We conclude that endodontic irrigants permeate throughout dentinal tubules, but their effectiveness is dependent on the type of bacteria found within the tubules.

Identification of three merB genes and characterization of a broad-spectrum mercury resistance module encoded by a class II transposon of Bacillus megaterium strain MB1

The complete structure of a broad-spectrum mercury resistance module was shown by sequencing the Gram-positive bacterial transposon TnMERI1 of Bacillus megaterium MB1. The regions encoding organomercury resistance were identified. Upstream of a previously identified organomercurial lyase merB (merB1) region of TnMERI1, a second merR (merR2) and a second merB gene (merB2) were found. These genes constitute a second operon (mer operon 2) following a promoter/operator (P(merR2)) region. A third organomercurial lyase gene (merB3) was found immediately upstream of the mer operon (mer operon 1) followed by a promoter/operator (P(merB3)) region homologous to that of the mer operon 1 (P(merR1)-merR1-merE-like-merT-merP-merA). The complete genetic structure of the mercury resistance module is organized as P(merB3)-merB3-P(merR1)-merR1-merE-like-merT+ ++ -merP-merA-P(merR2)-merR2 -merB2-merB1. The subcloning analysis of these three merB genes showed distinct substrate specificity as different organomercury lyase genes.

Structure analysis of a class II transposon encoding the mercury resistance of the Gram-positive Bacterium bacillus megaterium MB1, a strain isolated from minamata bay, Japan

A unique transposon was found in the chromosome of Bacillus megaterium MB1, a Gram-positive bacterium isolated from mercury-polluted sediments of Minamata Bay, Japan. The transposon region of a 14.5kb DNA fragment was amplified by PCR using a single PCR primer designed from the nucleotide sequence of an inverted repeat of class II transposons. The molecular analysis revealed that the PCR-amplified DNA fragment encodes a transposition module similar to that of Tn21. The transposon also encodes a broad-spectrum mercury resistance region having a restriction endonuclease map identical to that of Bacillus cereus RC607, a strain isolated from Boston Harbor, USA. The result of a phylogenetic analysis of the amino acid sequence of putative resolvase of the transposon showed that the transposon is phylogenetically closer to the transposons of Gram-positive bacteria than those of Gram-negative bacteria. Besides the transposition module and mer operon, the transposon encodes a mobile genetic element of bacterial group II introns between the resolvase gene and mer operon. The intron, however, does not intervene in any exon gene. The discovery of this newly found combination of the complex mobile elements may offer a clue to understanding the horizontal dissemination of broad-spectrum mercury resistance among microbes.

Sites of interaction of streptogramin A and B antibiotics in the peptidyl transferase loop of 23 S rRNA and the synergism of their inhibitory mechanisms

Streptogramin antibiotics contain two active A and B components that inhibit peptide elongation synergistically. Mutants resistant to the A component (virginiamycin M1 and pristinamycin IIA) were selected for the archaeon Halobacterium halobium. The mutations mapped to the universally conserved nucleotides A2059 and A2503 within the peptidyl transferase loop of 23 S rRNA (Escherichia coli numbering). When bound to wild-type and mutant haloarchaeal ribosomes, the A and B components (pristinamycins IIA and IA, respectively) produced partially overlapping rRNA footprints, involving six to eight nucleotides in the peptidyl transferase loop of 23 S rRNA, including the two mutated nucleotides. An rRNA footprinting study, performed both in vivo and in vitro, on the A and B components complexed to Bacillus megaterium ribosomes, indicated that similar drug-induced effects occur on free ribosomes and within the bacterial cells. It is inferred that position 2058 and the sites of mutation, A2059 and A2503, are involved in the synergistic inhibition by the two antibiotics. A structural model is presented which links A2059 and A2503 and provides a structural rationale for the rRNA footprints.

Production and structure elucidation of di- and oligosaccharide lipids (biosurfactants) from Tsukamurella sp. nov

The bacterium Tsukamurella sp. nov., isolated from soil, was found to produce novel glycolipids when grown on sunflower oil as the sole carbon source. The glycolipids were isolated by chromatography on silica columns and their structures elucidated using a combination of multidimensional NMR and MS techniques. The three main components are 2,3-di-O-acyl-alpha-D-glucopyranosyl-(1-1)-alpha-D-glucopyranose, 2,3-di-O-acyl-beta-D-glucopyranosyl-(1-2)-4,6-di-O-acyl-alpha-D- glucopyranosyl-(1-1)-alpha-D-glucopyranose and 2,3-di-O-acyl-beta-D-glucopyranosyl-(1-2)-beta-D-galactopyranosyl- (1-6)-4,6-di-O-acyl-alpha-D-glucopyranosyl-(1-1)-alpha-D- glucopyranosyl which are linked to fatty acids varying in chain length from C4 to C18. The glycolipids are mainly extracellular but are also found attached to the cell walls. During the cultivation the composition of the glycolipids changed from disaccharide- to tri- and tetrasaccharide lipids. The glycolipids show good surface-active behaviour and have antimicrobial properties.

The repressor protein, Bm3R1, mediates an adaptive response to toxic fatty acids in Bacillus megaterium

Bm3R1 is a helix-turn-helix transcriptional repressor from Bacillus megaterium whose binding to DNA is inhibited by fatty acids and a wide range of compounds that modulate lipid metabolism. The inactivation of Bm3R1/DNA binding activity results in the activation of transcription of the operon encoding a fatty acid hydroxylase, cytochrome P450 102. The metabolic role of this operon is unknown. It is possible that it is involved in the synthesis of modified fatty acids as part of normal cellular metabolism or may represent a protective mechanism by which B. megaterium detoxifies harmful foreign lipids. In this report we demonstrate that polyunsaturated fatty acids (PUFA) activate the transcription of the CYP102 operon. These PUFA are the most potent activators of the CYP102 operon observed to date, and we show that their effects are due to binding directly to Bm3R1. In addition, cultures that have been treated with the CYP102 inducer, nafenopin, are protected against PUFA toxicity. Resistance to PUFA toxicity is also seen in a Bm3R1-deficient strain that constitutively expresses CYP102. The resistant phenotype of this Bm3R1 mutant strain is reversed by specific chemical inactivation of CYP102. These data demonstrate that Bm3R1 can act as a direct sensor of toxic fatty acids and, in addition, provide the first direct evidence of fatty acids binding to a prokaryotic transcription factor.

The inhibition of SOS-responses and MDR by phenothiazine-metal complexes

The gene of multidrug resistance (mdr) is inducible by different environmental stresses (SOS gene). We tested the inhibitory action of some new metal complexes of phenothiazines on megacin encoding bacterial gene induced by mitomycin-C as an example of "SOS induction" and on efflux pump of mouse lymphoma cells. The interaction of compounds to DNA was measured by thermal stability of DNA. It was found that metal co-ordination complexes of trifluoperazine (TFP) and chlorpromazine (CPZ) added before mitomycin administration have an inhibitory action on megacine induction. The TFP-V(IV) complex was effective at a lower concentration than TFP alone. The inhibitory effect of some metal coordinating complexes (TFP-Cu(II) and TFP- V(IV)) exceeded the action of TFP alone on efflux pumps. We propose that these compounds can form a complex with the regulatory protein or DNA resulting in the inhibition of SOS response and inhibit the mdr function by inactivating the P-glycoprotein as well.

Inactivation of enzymes within spores of Bacillus megaterium ATCC 19213 by hydroperoxides

The organic hydroperoxides t-butyl hydroperoxide, cumene hydroperoxide, and peracetic acid were found to act similarly to hydrogen peroxide in causing inactivation of enzymes within intact spores of bacillus megaterium ATCC 19213 concomitant with mortality. Spores treated with lethal levels of the agents were germinated and permeabilized for enzyme assays. The hierarchy of sensitivities among enolase, glucose-6-phosphate dehydrogenase (G6Pdh), and pyruvate kinase to inactivation varied somewhat with the specific hydroperoxide used, possibly because of the differences in the types of radicals generated. However, each agent inactivated each of the enzymes, albeit at different rates. Comparative assessments of enzyme inactivation by lethal levels of H2O2 or by moist heat showed that some enzymes, such as G6Pdh, are highly sensitive to inactivation, while others, such as ATPases, are much more resistant. The enzymes G6Pdh and aldolase were highly sensitive to hydroperoxide inactivation and also to moist heat, while pyruvate kinase was much more sensitive to hydroperoxides than to moist heat. Our overall interpretation of the findings is that hydroperoxides and moist heat can produce cumulative damage to sensitive enzymes within spores, which progressively diminishes the capacities of the cells to undergo the outgrowth required for return to vegetative life.

Antibacterial activity of lonchocarpol A

Lonchocarpol A, a flavanone, demonstrates in vitro inhibitory activity against methicillin-resistant Staphylococcus aureus and vancomycin-resistant Enterococcus faecium. This activity is antagonized by mouse plasma, which may account for its lack of in vivo activity. This compound demonstrates no differentiation with respect to the inhibition of RNA, DNA, cell wall, and protein synthesis.

Induction of CYP102 (cytochrome P450BM-3) in Bacillus megaterium by 17 beta-estradiol and 4-sec-butylphenol

CYP102 (Cytochrome P450BM-3) is induced in Bacillus megaterium by barbiturates, peroxisome proliferators, and nonsteroidal anti-inflammatory drugs. We now describe the induction of CYP102 in B. megaterium by 17 beta-estradiol and by 4-sec-butylphenol. These estrogens interact with the repressor protein Bm3R1, causing it to dissociate with the operator of the CYP102 gene and allowing transcription to occur. We have developed a stable transfection of a construct into B. megaterium of a truncated CYP102 gene coupled with the luciferase gene in a promoterless plasmid and have used this construct to test the induction of CYP102 by these estrogens. Estradiol demonstrated a dose-dependent induction of CYP102 which saturated at a 2-fold increase at 150 microM 4 hr post-addition. 4-sec-Butylphenol produced a dose-dependent and time-dependent induction up to 300 microM and 6 hr post-induction.

Contribution of glucose kinase to glucose repression of xylose utilization in Bacillus megaterium

The glk gene from Bacillus megaterium, which encodes glucose kinase, was isolated and analyzed. Disruption by a transcriptional glk-luxAB fusion indicated that glk is the only glucose kinase gene in that strain but did not affect growth of that mutant on glucose. Determination of luciferase activity under various growth conditions revealed constitutive transcription of glk. Expression of a xylA-lacZ fusion was repressed by glucose in the strain with the glk disruption about twofold less efficiently than in the wild type. The potential contribution of glk expression to glucose repression is discussed.