Basidiochrome – A Novel Siderophore of the Orchidaceous Mycorrhizal Fungi Ceratobasidium and Rhizoctonia spp

A novel trishydroxamate siderophore, named basidiochrome, was isolated as the principal siderophore from low-iron culture filtrates of Ceratobasidium and Rhizoctonia species which are known as mycorrhizal fungi associated with orchid roots. Ion-exchange chromatography and preparative HPLC yielded a pure compound which contained two components according to GC-MS analysis: L: -N(5)-hydroxy-ornithine and 3-methyl-2-cis-pentenedioic acid (3-methyl-cis-glutaconic acid). FTICR-ESI-MS of both the iron-free and ferric form indicated an elemental composition of C(33)H(47)N(6)O(16)Fe (MW = 839) for the ferric form of basidiochrome. The connectivity was further elucidated by 2D-NMR techniques (HSQC, HMBC, COSY, NOESY) indicating that basidiochrome is a novel linear tripeptide consisting of three L: -N(5)-hydroxy-ornithines each linked to 3-methyl-2-cis-pentenedioic acid residues.

Tyramine functions as a toxin in honey bee larvae during Varroa-transmitted infection by Melissococcus pluton

From wounds of honey bee pupae, caused by the mite Varroa destructor, coccoid bacteria were isolated and identified as Melissococcus pluton. The bacterial isolate was grown anaerobically in sorbitol medium to produce a toxic compound that was purified on XAD columns, gelfiltration and preparative HPLC. The toxic agent was identified by GC-MS and FTICR-MS as tyramine. The toxicity of the isolated tyramine was tested by a novel mobility test using the protozoon Stylonychia lemnae. A concentration of 0.2 mg/ml led to immediate inhibition of mobility. In addition the toxicity was studied on honey bee larvae by feeding tyramine/water mixtures added to the larval jelly. The lethal dosis of tyramine on 4-5 days old bee larvae was determined as 0.3 mg/larvae when added as a volume of 20 microl to the larval food in brood cells. Several other biogenic amines, such as phenylethylamine, histamine, spermine, cadaverine, putrescine and trimethylamine, were tested as their hydrochloric salts for comparison and were found to be inhibitory in the Stylonychia mobility test at similar concentrations. A quantitative hemolysis test with human red blood cells revealed that tyramine and histamine showed the highest membranolytic activity, followed by the phenylethylamine, trimethylamine and spermine, while the linear diamines, cadaverine and putrescine, showed a significantly lower hemolysis when calculated on a molar amine basis. The results indicate that tyramine which is a characteristic amine produced by M. pluton in culture, is the causative agent of the observed toxic symptoms in bee larvae. Thus this disease, known as European foulbrood, is possibly an infection transmitted by the Varroa destructor mite.

Liver transplantation in pigs with small-for-size grafts: effect of portocaval shunt

Small-for-size livers are associated with graft dysfunction, probably due to portal hyperperfusion. Modulation of the recipient portal inflow is a new option in these cases. This article sought to analyze the effect of portocaval shunt in small-for-size liver grafts in pigs. Twelve liver transplants were performed in white pigs. The donors' mean weight was 10 kg and the recipient's mean weight was 34 kg. In all cases a standard technique was utilized. A portocaval shunt was added on the back-table in six cases. One hour after the procedure, the livers were sent for histologic examination. In all six cases without a portocaval shunt, the livers showed hemorrhagic necrosis, which was not observed in any of the six livers with a portocaval shunt. In small-for-size liver grafts in pigs, a portocaval shunt prevents hemorrhagic necrosis.

Salmochelins, siderophores of Salmonella enterica and uropathogenic Escherichia coli strains, are recognized by the outer membrane receptor IroN

Members of a family of catecholate siderophores, called salmochelins, were isolated by reversed-phase HPLC from Salmonella enterica serotype Typhimurium and structurally characterized by Fourier transform ion cyclotron resonance-MSMS and GC-MS. The tentative structure of salmochelin 1 contained two 2,3- dihydroxybenzoylserine moieties bridged by a glucose residue, bound to the serine hydroxyl group of one moiety and the carboxylate of the second moiety. Salmochelin 2 contained in addition a second glucose residue linked to a third 2,3-dihydroxybenzoylserine moiety. Salmochelins were not produced by an iroBC mutant, which indicated that the IroB protein might be responsible for the glucosyl transfer predicted by sequence similarities to known glycosyltransferases. Uptake experiments with radiolabeled (55)Fe-salmochelin and growth promotion tests with salmochelins showed that the IroN outer membrane receptor, encoded in the iroA locus of S. enterica and uropathogenic Escherichia coli strains, was the main receptor for ferric salmochelin transport.

Microbial siderophore-mediated transport

Microbial iron chelates, called siderophores, are synthesized by bacteria and fungi in response to low iron availability in the environment. The present review summarizes structural details of siderophore ligands with respect to their transport properties. This presentation is largely centred on the occurrence and function of siderophores in the various bacterial and fungal genera.

Ferricrocin--an ectomycorrhizal siderophore of Cenococcum geophilum

The ectomycorrhizal fungus Cenococcum geophilum was grown in low-iron medium and the excreted siderophores were extracted, purified and analyzed by HPLC. The principal hydroxamate siderophore produced, was identified as ferricrocin as confirmed by analytical HPLC, FAB-mass spectrometry and 1H- and 13C-NMR spectra. Although the occurrence of ferricrocin has been shown earlier to occur in the ericoid mycorrhizal fungi, this is the first report of ferricrocin in a true ectomycorrhizal fungus which is taxonomically related to the ascomycetes.

In vitro activities and postantifungal effects of the potent dolastatin 10 derivative auristatin PHE

The pentapeptide dolavaline-valine-dolaisoleuine-dolaproine-phenylalanine-methyl ester (auristatin PHE) is a derivative of the anticancer drug dolastatin 10 (dolavaline-valine-dolaisoleuine-dolaproine-dolaphenine). Broth microdilution assays with a wide variety of yeast and filamentous fungal species demonstrated the specificity of auristatin PHE for Cryptococcus neoformans and several species of Trichosporon. The duration of the postantifungal effect (PAFE) for C. neoformans was determined for exposure times ranging from 30 min to 2 h. For the derivative, a PAFE was detectable after 45 min of exposure. The effect plateaued after 1 h of exposure, with a PAFE of approximately 6.5 h at four or eight times the auristatin PHE MIC. In contrast, there was no measurable PAFE after 1 h of exposure to dolastatin 10. Human serum greatly prolonged the PAFE of auristatin PHE at eight times the MIC. Auristatin PHE arrested C. neoformans in the budding stage, possibly due to a tubulin-inhibitory action. Auristatin PHE has potential as a narrow-spectrum fungicidal agent and as a probe that can be used to study cryptococcal cell division.

Heterobactins: A new class of siderophores from Rhodococcus erythropolis IGTS8 containing both hydroxamate and catecholate donor groups

We report here on a new class of siderophores isolated from Rhodococcus erythropolis IGTS8, the first structurally characterized from any species of Rhodococcus and for which we suggest the name heterobactins. These siderophores consist of a tripeptide of sequence (N-OH)-L-Orn-Gly-D-Orn-(delta-N-dihydroyxbenzoate). The alpha amino group of the D-Orn is derivatized either as a 2-hydroxybenzoxazolate in heterobactin A or remains free in heterobactin B. The structures were determined by a combination of amino acid analysis, mass spectrometry and NMR methods. The two new compounds are true siderophores in that they relieve iron limited growth in the producing strain. The heterobactins are also transported by other non-producing bacteria. Growth promotion tests using various transport mutants revealed that in E. coli heterobactin A is only recognized by the catecholate receptor Cir while heterobactin B is taken up in both E.coli and A. flavescens JG9 via a hydroxamate transport system.

Penicillin V production by Penicillium chrysogenum in the presence of Fe3+ and in low-iron culture medium

Late-exponential-phase Penicillium chrysogenum mycelia grown in a complex medium possessed an intracellular iron concentration of 650 mumol/L (2.2 +/- 0.6 mumol per g mycelial dry mass). This iron reserve was sufficient to ensure growth and antibiotic production after transferring mycelia into a defined low-iron minimal medium. Although the addition of Fe3+ to the Fe-limited cultures increased significantly the intracellular iron levels the surplus iron did not influence the production of penicillin V. Supplements of purified major P. chrysogenum siderophores (coprogen and ferrichrome) into the fermentation media did not affect the beta-lactam production and intracellular iron level. Neither 150 nor 300 mumol/L extracellular Fe3+ concentrations disturbed the glutathione metabolism of the fungus, and increased the oxidative stress caused by 700 mmol/L H2O2. Nevertheless, when iron was applied in the FeII oxidation state the oxidative cell injuries caused by the peroxide were significantly enhanced.

Immunostimulation by bacterial components: II. Efficacy studies and meta-analysis of the bacterial extract OM-89

The bacterial extract OM-89 (Uro-Vaxom) consisting of immunostimulating components derived from 18 Escherichia coli strains is used for the treatment of recurrent urinary tract infections. We investigated in the mouse the immunogenicity of the bacterial extract after oral administration. After repeated administration of OM-89, a specific serum IgG and IgA response against a number of bacterial strains was obtained. Supernatants of cell cultures prepared from the urogenital tract of immunized mice also contained increased levels of strain specific IgG and IgA. We could show a bias towards a Th1 type immune response as indicated by increased IgG2a levels in sera, and increased IFNgamma levels in supernatants of spleen cells. These findings may contribute to an understanding of the therapeutic effect of Uro-Vaxom: the metaanalysis of several clinical studies confirmed that Uro-Vaxom constitutes an effective prophylaxis for urinary tract infections.

Identification and substrate specificity of a ferrichrome-type siderophore transporter (Arn1p) in Saccharomyces cerevisiae

Genes encoding transporters for heterologous siderophores have been identified in Saccharomyces cerevisiae, of which SIT1, TAF1, and ENB1 encode the transporters for ferrioxamines, ferric triacetylfusarinine C and ferric enterobactin, respectively. In the present communication we have shown that a further gene encoding a member of the major facilitator superfamily, ARN1 (YHL040c), is involved in the transport of a specific class of ferrichromes, possessing anhydromevalonyl residues linked to N(delta)-ornithine (ARN). Ferrirubin and ferrirhodin, which both are produced by filamentous fungi, are the most common representatives of this class of ferrichromes. A strain possessing a disruption in the ARN1 gene was unable to transport ferrirubin, ferrirhodin and also ferrichrome A, indicating that the encoded transporter recognizes anhydromevalonyl and the structurally-related methylglutaconyl side-chains surrounding the iron center. Ferrichromes possessing short-chain ornithine-N(delta)-acetyl residues such as ferrichrome, ferricrocin and ferrichrysin, were excluded by the Arn1 transporter. Substitution of the iron-surrounding N-acyl chains of ferrichromes by propionyl residues had no effect, whereas substitution by butyryl residues led to recognition by the Arn1 transporter. This would indicate that a chain length of four C-atoms is sufficient to allow binding. Using different asperchromes (B1, D1) we also found that a minimal number of two anhydromevalonyl residues is sufficient for recognition by Arn1p. Contrary to the iron-surrounding N-acyl residues, the peptide backbone of ferrichromes was not an important determinant for the Arn1 transporter.

Fusarinines and dimerum acid, mono- and dihydroxamate siderophores from Penicillium chrysogenum, improve iron utilization by strategy I and strategy II plants

Cucumber, as a strategy I plant, and Maize as a strategy II plant, were cultivated in hydroponic culture in the presence of a ferrated siderophore mixture (1 microM) from a culture of Penicillium chrysogenum isolated from soil. The siderophore mixture significantly improved the iron status of these plants as measured by chlorophyll concentration to the same degree as a 100-fold higher FeEDTA supply. Analysis of the siderophore mixture from P. chrysogenum by HPLC and electrospray mass spectrometry revealed that besides the trihydroxamates, coprogen and ferricrocin, large amounts of dimerum acid and fusarinines were present which represent precursor siderophores or breakdown products of coprogen. In order to prove the iron donor properties of dimerum acid and fusarinines for plants, purified coprogen was hydrolyzed with ammonia and the hydrolysis products consisting of dimerum acid and fusarinine were used for iron uptake by cucumber and maize. In short term experiments radioactive iron uptake and translocation rates were determined using ferrioxamine B, coprogen and hydrolysis products of coprogen. While the trihydroxamates revealed negligible or intermediate iron uptake rates by both plant species, the fungal siderophore mixture and the ammoniacal hydrolysis products of coprogen showed high iron uptake, suggesting that dimerum acid and fusarinines are very efficient iron sources for plants. Iron reduction assays using cucumber roots or ascorbic acid also showed that iron bound to hydrolysis products of coprogen was more easily reduced compared to iron bound to trihydroxamates. Ligand exchange studies with epi-hydroxymugineic acid and EDTA showed that iron was easily exchanged between coprogen hydrolysis products and phytosiderophores or EDTA. The results indicate that coprogen hydrolysis products are an excellent source for Fe nutrition of plants.

A gene of the major facilitator superfamily encodes a transporter for enterobactin (Enb1p) in Saccharomyces cerevisiae

While in fungi iron transport via hydroxamate siderophores has been amply proven, iron transport via enterobactin is largely unknown. Enterobactin is a catecholate-type siderophore produced by several enterobacterial genera grown in severe iron deprivation. By using the KanMX disruption module in vector pUG6 in a fet3delta background of Saccharomyces cerevisiae we were able to disrupt the gene YOL158c Sce of the major facilitator super family (MFS) which has been previously described as a gene encoding a membrane transporter of unknown function. Contrary to the parental strain, the disruptant was unable to utilize ferric enterobactin in growth promotion tests and in transport assays using 55Fe-enterobactin. All other siderophore transport properties remained unaffected. The results are evidence that in S. cerevisiae the YOL158c Sce gene of the major facilitator super family, now designated ENB1, encodes a transporter protein (Enb1p), which specifically recognizes and transports enterobactin.

Transport and utilization of rhizoferrin bound iron in Mycobacterium smegmatis

Transport and metabolization of iron bound to the fungal siderophore rhizoferrin was analyzed by transport kinetics, Mössbauer and EPR spectroscopy. Saturation kinetics (vmax = 24.4 pmol/(mg min), K(m) = 64.4 microM) and energy dependence excluded diffusion and provided evidence for a rhizoferrin transport system in M. smegmatis. Based on the spectroscopic techniques indications for intracellular presence of the ferric rhizoferrin complex were found. This feature could be of practical importance in the search of novel drugs for the treatment of mycobacterial infections. EPR and Mössbauer spectroscopy revealed different ferritin mineral cores depending on the siderophore iron source. This finding was interpreted in terms of different protein shells, i.e. two types of ferritins.

Identification of a fungal triacetylfusarinine C siderophore transport gene (TAF1) in Saccharomyces cerevisiae as a member of the major facilitator superfamily

Transport proteins of microorganisms may either belong to the ATP-binding cassette (ABC) superfamily or to the major facilitator (MFS)-superfamily. MFS transporters are single-polypeptide membrane transporters that transport small molecules via uniport, symport or antiport mechanisms in response to a chemiosmotic gradient. Although Saccharomyces cerevisiae is a non-siderophore producer, various bacterial and fungal siderophores can be utilized as an iron source. From yeast genome sequencing data six genes of the unknown major facilitator (UMF) family were known of which YEL065w Sce was recently identified as a transporter for the bacterial siderophore ferrioxamine B (Sit1p). The present investigation shows that another UMF gene, YHL047c Sce, encodes a transporter for the fungal siderophore triacetylfusarinine C. The gene YHL047c Sce (designated TAF1) was disrupted using the kanMX disruption module in a fet3 background (strain DEY 1394 delta fet3), possessing a defect in the high affinity ferrous iron transport. Growth promotion assays and transport experiments with 55Fe-labelled triacetylfusarinine C showed a complete loss of iron utilization and uptake in the disrupted strain, indicating that TAF1 is the gene for the fungal triacetylfusarinine transport in Saccharomyces cerevisiae and possibly in other siderophore producing fungi.

Degradation of desferrioxamines by Azospirillum irakense: assignment of metabolites by HPLC/electrospray mass spectrometry

Based on a recent finding that an Azospirillum isolate ASP-1 possessing high 16S rDNA similarity to Azospirillum irakense was able to degrade desferrioxamine type siderophores (Winkelmann et al. BioMetals 9, 78-83, 1996), various members of the genus Azospirillum were analyzed for their ability to degrade desferrioxamines. While the desferrioxamine-degrading activity was absent or scarcely detectable in strains of A. lipoferum, A. brasilense, A. amazonense, degradation activity seemed to be confined to the species A. irakense (KBC-1, KA3). Also the identity of strain ASP-1 as A. irakense could be confirmed by species-specific oligonucleotide hybridization, Inter-LINE PCR fingerprinting and carbon source utilization pattern (BIOLOG) analysis. Products of desferrioxamine B degradation were analyzed by analytical HPLC and HPLC/electrospray mass spectrometry. Using whole cells and purified enzyme it was shown that the trihydroxamate desferrioxamine B (561 amu) is split at the N-terminal amide bond yielding a monohydroxamate (MH1, 219 amu) and a dihydroxamate (DH1, 361 amu) metabolite. A second monohydroxamate (MH2, 319 amu) resulted from DH1 after splitting the acetylhydroxamate bond. Minor amounts of a further dihydroxamate (DH2, 419 amu) originated from splitting the second amide bond in desferrioxamine B. In addition to desferrioxamine B, several other linear and cyclic desferrioxamines and derivatives were degraded, whereas desferricoprogen and desferri-ferrichrome were not degraded, indicating high substrate specificity of the desferrioxamine hydrolase in A. irakense species. A simple microtiter plate assay was developed which can be used to phenotypically discriminate and identify species of A. irakense from other Azospirillum species by their characteristic feature of desferrioxamine degradation.

Molecular recognition of synthetic siderophore analogues: a study with receptor-deficient and fhu(A-B) deletion mutants of Escherichia coli

The biological activity of six synthetic siderophore analogues (two dihydroxamates, two trihydroxamates, one tetrahydroxamate and one 3-hydroxy-4(1H)pyridinone) has been studied in Escherichia coli, Morganella morganii 13 and Proteus mirabilis 8993 strains by using growth promotion tests. Various transport-deficient mutants of E. coli were used to study the route of entry into gram-negative bacteria. The results indicated that the synthetic hydroxamate compounds are transported via Fhu-mediated transport systems, although receptor specificity was low. This could be proven by using a delta (fhuA-B) E. coli mutant as a control in which growth promotion by natural hydroxamates was completely abolished, suggesting that a periplasmic binding-protein-dependent transport system (FhuB, C, D) is required for the transport of all synthetic ferric hydroxamate complexes. Although utilization of the synthetic hydroxamates was generally lower than that of the natural siderophores, differences in growth promotion could be detected. Highest activity was observed with the dihydroxamate DOCYDHAMA ligand which supported growth at concentrations < 1 mM. In comparison with other polyamino-polyhydroxamate ligands studied, this dihydroxamate ligand has an extra diamide backbone that could be important for the interaction with the receptors or with FhuD. The synthetic trihydroxamate and tetrahydroxamate ligands showed a relatively low siderophore activity. Studies with Proteus and Morganella in the presence of increasing bipyridyl concentrations showed a decreased growth promotion with the synthetic ferric hydroxamates, suggesting the involvement of a reduction step during iron mobilization or an increased toxicity of bipyridyl. This was not observed in the case of the 3-hydroxy-4(1H)pyridinone where bipyridyl had no effect.

Combination of behaviour therapy with fluvoxamine in comparison with behaviour therapy and placebo. Results of a multicentre study

BACKGROUND

We investigated whether the combination of multi-modal behaviour therapy (BT) with fluvoxamine is superior to BT and placebo in the acute treatment of severely ill in-patients with obsessive-compulsive disorder (OCD).

METHOD

In a randomised, double-blind design, 30 patients were treated for nine weeks with BT plus placebo and 30 patients with BT plus fluvoxamine (maximum dosage 300 mg, mean dose 288.1 mg). BT included exposure with response prevention, cognitive restructuring and development of alternative behaviours.

RESULTS

Both groups showed a highly significant symptom reduction after treatment. There were no significant differences between the groups concerning compulsions. Obsessions were significantly more reduced in the fluvoxamine and BT group than in the placebo and BT group. Furthermore, the group BT plus fluvoxamine showed a significantly higher response rate (87.5 v. 60%) according to a previously defined response criterion. Severely depressed patients with OCD receiving BT plus placebo presented a significantly worse treatment outcome (Y-BOCS scores) than all other groups.

CONCLUSIONS

The results suggest that BT should be combined with fluvoxamine when obsessions dominate the clinical picture and when a secondary depression is present.

Pyrrolnitrin from Burkholderia cepacia: antibiotic activity against fungi and novel activities against streptomycetes

A bacterial strain identified as Burkholderia cepacia NB-1 was isolated from water ponds in the botanical garden in Tübingen, Germany, and was found to produce a broad spectrum phenylpyrrole antimicrobial substance active against filamentous fungi, yeasts and Gram-positive bacteria. In batch culture containing glycerol and L-glutamic acid, the isolate NB-1 produced the antibiotic optimally late in the growth phase and accumulated a main portion in their cells. Isolation and purification of the antibiotic from Burkholderia (Pseudomonas) cepacia NB-1 by acetone extraction, gel filtration on Sephadex LH-20 and preparative HPLC yielded 0.54 mg l-1 of a pure substance. Spectroscopic data (HPLC, MS and NMR) confirmed that the compound was pyrrolnitrin [3-chloro-4-(2'-nitro-3'-chloro-phenyl) pyrrole]. Pyrrolnitrin has an inhibitory effect on the electron transport system, as demonstrated by isolated mitochondria from Neurospora crassa 74 A. This inhibition was relieved by N,N,N',N'-tetramethyl-p-phenylenediamine dihydrochloride (TMPD), indicating that pyrrolnitrin blocked the electron transfer between the dehydrogenases and the cytochrome components of the respiratory chain. Among Gram-positive bacteria, pyrrolnitrin was most active against certain Streptomyces species, especially S. antibioticus, which has not previously been described in the literature. In the presence of pyrrolnitrin, aerial mycelium and spore formation of Strep. antibioticus was suppressed, although growth continued via substrate mycelium. The new findings of inhibition of streptomycetes and their secondary metabolism by pyrrolnitrin may contribute to the fact that Pseudomonas species predominate in soil and compete even with antibiotic-producing Streptomyces.

Cognitive frontal lobe dysfunction in obsessive-compulsive disorder

BACKGROUND

There is evidence that dysfunction within associative frontostriatal circuits represents a feature of obsessive-compulsive disorder (OCD). Previous neuropsychologic studies have yielded diverging results, which may in part be explained by differences in the selection of subjects and methods. The present study focused on the question of cognitive frontal lobe performance in OCD.

METHODS

Twenty-nine unmedicated OCD patients were compared to a double-size control group of normal subjects matched individually for age, sex, and intelligence. A series of 12 neuropsychologic tests was applied, most of which are thought to be sensitive to different aspects of cognitive frontal lobe function.

RESULTS

OCD patients were unimpaired at tests of abstraction, problem solving, set-shifting, response inhibition, active memory search, and choice reaction speed. Deficits of approximately one standard deviation were observed at timed tests of verbal and nonverbal fluency, attentional processing, and weight sorting.

CONCLUSIONS

OCD patients exhibited selective deficits in tasks involving controlled attentional processing and self-guided, spontaneous behavior. We discuss a link between this neuropsychologic profile and dysfunctioning within the anterior cingulate, but not the dorsolateral prefrontal circuit.

Molecular recognition of siderophores: a study with cloned ferrioxamine receptors (FoxA) from Erwinia herbicola and Yersinia enterocolitica

The outer membrane receptor for ferrioxamines (FoxAErw) of Erwinia herbicola (Pantoea agglomerans) was cloned from a cosmid gene bank and partially sequenced. A comparison of the partial amino acid sequence of FoxAErw with the amino acid sequence of FoxAYer from Yersinia enterocolitica revealed a high sequence homology. A functional analysis of FoxAErw and FoxAYer receptors cloned into a Fhu-negative background (HK97) revealed that ferrioxamines are recognized at very low concentrations (< 10 pmoles) in growth promotion bioassays. A collection of ferrioxamine derivatives containing varying chain lengths and ether bridges within the molecule was also accepted. However, the three ether containing ferrioxamine (Et3) behaved differently in the two FoxA receptors. Coprogen was also recognized to a certain extent, whereas ferrichromes were completely excluded from the FoxA receptors, confirming that coprogens share some structural similarities with the ferrioxamines. FoxA mutants (FM13) of Erwinia herbicola obtained by ferrimycin selection showed no uptake of 55Fe-labelled ferrioxamine E and B any more, while the transport of coprogen and ferrichrome was unaffected or even slightly increased.

Drug specific antibodies: T-cell epitope-lipopeptide conjugates are potent adjuvants for small antigens in vivo and in vitro

To generate conventional or monoclonal antibodies for the serological detection of drugs, antibiotics, toxins and other low molecular mass substances, a suitable and effective adjuvant is needed. Lipopeptides derived from a major component of the bacterial cell wall constitute potent nontoxic and nonpyrogenic immunoadjuvants when mixed with conventional antigens. Here we demonstrate that the synthetic lipopeptide N-palmitoyl-S-[2,3-bis(palmitoyloxy)-(2R,S)-propyl]-(R)-cysteinyl- serine (P3CS) coupled to a Th-cell epitope (P3CS-Th) can efficiently enhance the specific immune response against low molecular weight compounds in different species. In the presence of the synthetic lipopeptide P3CS-Th, the peptides which are per se non-immunogenic stimulated a specific humoral immune response in mice after intraperitoneal application. Mixtures containing adjuvants without the Th sequence showed no significant antibody induction. A marked enhancement of the humoral immune response was obtained with the low molecular mass antigens Iturin AL, Herbicolin A and Microcystin (MLR) coupled to poly-l-lysin (MLR-PLL), in rabbits and in chickens. Lipopeptide-Th cell epitope conjugates also constituted adjuvants for the in vitro immunization of either human mononuclear cells or mouse B-cells with MLR-PLL; after fusion of the immunized cultures with the heteromyeloma cell lines CB-F7 or the mouse myeloma cell line SP 2/0, respectively, we observed a significantly increased yield of antibody secreting hybridomas.

Maltophilin: a new antifungal compound produced by Stenotrophomonas maltophilia R3089

Strains of Stenotrophomonas maltophilia R3089, isolated from the rhizosphere of rape plants (Brassica napus L.), produced a novel antifungal compound, named maltophilin, which inhibited the growth of various saprophytic, human-pathogenic and phytopathogenic fungi but was inactive against Gram-positive and Gram-negative bacteria. Maltophilin is a novel macrocyclic lactam antibiotic with a molecular mass of 510 mu. The compound was isolated from the culture filtrate by ethyl acetate extraction and gel filtration on Sephadex LH20 and purified by preparative HPLC on reversed phase. The structure of maltophilin was elucidated by electrospray mass spectrometry and 1H and 13C NMR spectroscopy.

Characterization of a novel Spirillum-like bacterium that degrades ferrioxamine-type siderophores

A novel Gram-negative Spirillum-like bacterium (ASP-1) was isolated from lake water by enrichment culture on desferrioxamine B as sole source of carbon and energy. ASP-1 was able to degrade the siderophores desferrioxamine B and E. The property of siderophore degradation was inducible in the presence of desferrioxamine B. The ferric complexes, however, were not measurably degraded but served as an iron source. Degradation of desferrioxamines in culture was followed by measuring the residual ferrioxamines colorimetrically at 430 nm after addition of iron. Degradation in cell-free assays was followed quantitatively by HPLC on a reversed-phase column measuring the time-dependent disappearance of the desferrioxamines B and E. Cell-free assays also revealed that degradation of the cyclic desferrioxamine E was rapid and complete, whereas degradation of the linear desferrioxamine B yielded two intermediate iron-binding metabolites of shorter chain length. Preparative isolation by HPLC and mass spectrometric analysis of the metabolites revealed masses at 361 and 419 a.m.u., respectively, suggesting a splitting at the two amide bonds. ASP-1 is a nitrogen fixing Spirillum bacterium which could also use ammonium and glucose or several organic acids as a carbon source but grew poorly with amino acids. Physiological comparisons with Aquaspirillum and Azospirillum failed to assign ASP-1 to any of the presently known Spirillum species. Based on 16S rDNA sequence analysis the strain could be placed within the radiation of the Azospirillum/Rhodocista group. The closest relative was Azospirillum irakense, showing 98.8% similarity.

Ornibactin production and transport properties in strains of Burkholderia vietnamiensis and Burkholderia cepacia (formerly Pseudomonas cepacia)

Several strains of Burkholderia vietnamiensis, isolated from the rhizosphere of rice plants, and four strains formerly known as Pseudomonas cepacia including two collection strains and two clinical isolates were compared for siderophore production and iron uptake. The B. vietnamiensis (TVV strains) as well as the B. cepacia strains (ATCC 25416 and ATCC 17759) and the clinical isolates K132 and LMG 6999 were all found to produce ornibactins under iron starvation. The two ATCC strains of B. cepacia additionally produced the previously described siderophores, pyochelin and cepabactin. Analysis of the ratio of isolated ornibactins (C4, C6 and C8) by HPLC revealed nearly identical profiles. Supplementation of the production medium with ornithine (20 mM) resulted in a 2.5-fold increase in ornibactin synthesis. Ornibactin-mediated iron uptake was independent of the length of the acyl side chain and was observed with all strains of B. vietnamiensis and B. cepacia, but was absent with strains of Pseudomonas aeruginosa, Pseudomonas fluorescens and Pseudomonas stutzeri, known to produce pyoverdines or desferriferrioxamines as siderophores. These results suggest that ornibactin production is a common feature of all Burkholderia strains and that these strains develop an ornibactin-specific iron transport system which is distinct from the pyoverdine-specific transport in Pseudomonas strains.

[Obsessive-compulsive disorders--inpatient behavior therapy]

Exposure therapy with response prevention is regarded as the most effective treatment in obsessive compulsive disorder. This procedure has been applied in outpatients as well as inpatients.

A seizure, and electroencephalographic signs of a lowered seizure threshold, associated with fluvoxamine treatment of obsessive-compulsive disorder

A 38-year-old patient with severe obsessive-compulsive disorder received fluvoxamine in a clinical study. Psychometric ratings showed marked clinical improvement in the third week of fluvoxamine administration, but after 8 weeks, at a dose of 300 mg per day, he suffered a grand mal seizure after drinking a glass of beer (0.2 liter). He had no history of previous epileptic seizures. Careful neurological evaluation including computer tomography and magnetic resonance imaging of the brain revealed no signs of acute disease. EEG before the fit did not show epileptiform activity; after the fit, spikes and spike-wave complexes appeared, which disappeared upon discontinuation of fluvoxamine. Since his obsessive-compulsive symptoms had responded well to fluvoxamine and worsened after its discontinuation, the drug was cautiously reintroduced. Improvement of the obsessive-compulsive symptoms was observed again, but spikes and spike-wave complexes reappeared at a dose of 50 mg per day. Under anticonvulsant treatment with carbamazepine, fluvoxamine was increased to 100 mg per day. No seizures occurred during a follow-up to two years.

HPLC separation of enterobactin and linear 2,3-dihydroxybenzoylserine derivatives: a study on mutants of Escherichia coli defective in regulation (fur), esterase (fes) and transport (fepA)

Reversed-phase HPLC separation of enterobactin and its 2,3-dihydroxybenzoylserine derivatives was used for a comparative analysis of mutants of Escherichia coli, defective in the regulation of enterobactin biosynthesis (fur), enterobactin transport (fepA) and enterobactin esterase (fes). A complete separation of all 2,3-dihydroxybenzoylserine compounds was achieved: the monomer (DHBS), the linear dimer (DHBS)2 and trimer (DHBS)3, the cyclic trimer, enterobactin, as well as 2,3-dihydroxybenzoic acid. The production of all these compounds was followed after ethylacetate extraction from acidified culture fluids. Enterobactin was found to be the predominant product in all mutant strains. The mutant strains behaved differently with regard to the breakdown products. All degradation products, such as DHBS, (DHBS)2 and (DHBS)3, were detected in the overproducing fur mutant where both transport and esterase are still functioning, while only the monomer, DHBS, was detected in the fepA mutant and no degradation was found in the esterase-deficient fes mutant. From the pattern of breakdown products it may be inferred that the esterase acts in two different ways, depending on whether transport is functioning or not. Thus, esterolytic cleavage of ferric enterobactin after entering the cells results in a mixture of all three hydrolysis products, i.e. DHBS, (DHBS)2 and (DHBS)3, while cleavage of iron-free enterobactin subsequent to its biosynthesis yields only the monomer. Thus, the results of quantitative HPLC analysis of enterobactin and its breakdown products show that different enterobactin esterase products arise, depending on whether iron is bound to enterobactin or not.

Sleep EEG of patients with obsessive-compulsive disorder

Twenty-two patients suffering from an obsessive and compulsive disorder (OCD) according to DSM-III-R were investigated by polysomnographic sleep EEG recordings under drug-free conditions and compared to age- and sex-matched healthy controls. Sleep efficiency was significantly lower and wake % SPT was significantly increased in the patient group compared to healthy subjects. Sleep architecture did not differ among the two samples. Especially REM sleep measures, in particular, REM latency did not differ among the groups. No positive correlation was found between sleep variables and rating inventories for obsession and compulsions (Y-BOCS), depression (Hamilton) and anxiety (CAS). A secondary depression did not influence sleep EEG variables. The results of this study contradict the assumption that OCD patients show REM sleep and slow wave sleep abnormalities similar to those shown by patients with primary depression.

Iron supply of Pasteurella multocida and Pasteurella haemolytica

Pasteurella multocida and Pasteurella haemolytica do not produce hydroxamate- or phenolate type siderophores. However, transport- and utilization systems could be detected for the well known siderophores ferrioxamine B, E, G, rhizoferrin and the intermediate 2,3-dihydroxybenzoic acid by means of cross-feeding tests in both Pasteurella species. Enterobactin and ferrichrome did not feed any of the Pasteurella strains tested. Additionally, alpha-ketoacids and alpha-hydroxyacids such as pyruvic acid, alpha-hydroxyisovaleric acid and others acting as primary metabolites enabled growth of P. multocida and P. haemolytica under iron limitation.

Alpha-keto acids are novel siderophores in the genera Proteus, Providencia, and Morganella and are produced by amino acid deaminases

Growth promotion and iron transport studies revealed that certain alpha-keto acids generated by amino acid deaminases, by enterobacteria of the Proteus-Providencia-Morganella group (of the tribe Proteeae), show significant siderophore activity. Their iron-binding properties were confirmed by the chrome azurol S assay and UV spectra. These compounds form ligand-to-metal charge transfer bands in the range of 400 to 500 nm. Additional absorption bands of the enolized ligands at 500 to 700 nm are responsible for color formation. Siderophore activity was most pronounced with alpha-keto acids possessing an aromatic or heteroaromatic side chain, like phenylpyruvic acid and indolylpyruvic acid, resulting from deamination of phenylalanine and tryptophan, respectively. In addition, alpha-keto acids possessing longer nonpolar side chains, like alpha-ketoisocaproic acid or alpha-ketoisovaleric acid and even alpha-ketoadipic acid, also showed siderophore activity which was absent or negligible with smaller alpha-keto acids or those possessing polar functional groups, like pyruvic acid, alpha-ketobutyric acid, or alpha-ketoglutaric acid. The fact that deaminase-negative enterobacteria, like Escherichia coli and Salmonella spp., could not utilize alpha-keto acids supports the view that specific iron-carboxylate transport systems have evolved in members of the tribe Proteeae and are designed to recognize ferric complexes of both alpha-hydroxy acids and alpha-keto acids, of which the latter can easily be generated by L-amino acid deaminases in an amino acid-rich medium. Exogenous siderophores, like ferric hydroxamates (ferrichromes) and ferric polycarboxylates (rhizoferrin and citrate), were also utilized by members of the tribe Proteeae.

Ornibactins--a new family of siderophores from Pseudomonas

Novel linear hydroxamate/hydroxycarboxylate siderophores from strains of Pseudomonas cepacia were isolated and named ornibactins. The ornibactins represent modified tetrapeptide siderophores, possessing the sequence L-Orn1(N delta-OH, N delta-acyl)-D-threo-Asp(beta-OH)-L-Ser-L-Orn4(N delta-OH, N delta-formyl)-1,4-diaminobutane. The N delta-acyl groups of Orn1(N delta-OH, N delta-acyl) may vary and represent the three acids 3-hydroxybutanoic acid, 3-hydroxyhexanoic acid and 3-hydroxyoctanoic acid, leading to a mixture of three different ornibactins, designated according to their acyl chain length as ornibactin-C4, ornibactin-C6 and ornibactin-C8. Each of the siderophores is accompanied by a small amount of a more hydrophilic component with a 16 a.m.u. higher mass. The structure elucidation was based on results from gas chromatography amino acid analysis, electrospray mass spectrometry, and one- and two-dimensional nuclear magnetic resonance techniques.

Rhizoferrin: a complexone type siderophore of the Mucorales and entomophthorales (Zygomycetes)

The present investigation presents evidence that rhizoferrin, a novel polycarboxylate or complexone-type siderophore, originally isolated from Rhizopus microsporus, represents the common siderophore within the Zygomycetes. Thus, rhizoferrin could be detected by HPLC analysis in various families of the Mucorales, e.g., Rhizopus microsporus var. rhizopodiformis, Mucor mucedo and Phycomyces nitens (Mucoraceae), Chaetostylum fresenii and Cokeromyces recurvatus (Thamnidiaceae), Cunninghamella elegans and Mycotypha africana (Choanephoraceae) and Mortierella vinacea (Mortierellaceae) and in Basidiobolus microsporus (Entomophthorales). The function of rhizoferrin as a siderophore in the fungus R. microsporus var. rhizopodiformis was demonstrated by time- and concentration-dependent uptake of [55Fe]-labelled rhizoferrin, yielding saturation kinetics with values of Km = 8 microM and V(max) = 1.2 nmol min-1 (mg dry wt)-1.

Fermentation and isolation of herbicolin A, a peptide antibiotic produced by Erwinia herbicola strain A 111

Erwinia herbicola (Enterobacter agglomerans), belonging to the Enterobacteriaceae, produces the lipopeptide antibiotics herbicolin A and B, which are active against sterol-containing fungi. Fermentation of these antibiotics was performed in 20-l stirred glass fermentors in a batch process. Best yields of antibiotic production were found at low cultivation temperatures in a TRIS-buffered chemically defined medium. Under these conditions the amount of impurities aggravating the purification was minimized. Isolation was performed by adsorption, and gel and ion exchange chromatographic techniques. In a final purification step preparative high performance liquid chromatography (PHPLC) yielded pure herbicolin A.

Identification of enterobactin and linear dihydroxybenzoylserine compounds by HPLC and ion spray mass spectrometry (LC/MS and MS/MS)

The production of catecholate siderophores was studied in some selected species of Enterobacter (Enterobacteriaceae). The extracted catecholates were separated as iron-free compounds by HPLC on a C18 reversed-phase column using methanol/0.1% phosphoric acid or methanol/0.1% formic acid as a solvent system and identified by ion spray mass spectrometry (LC/MS, MS/MS). Five catecholate compounds were identified which include 2,3-dihydroxybenzoylserine, its linear dimer and trimer, the cyclic enterobactin and an unidentified isomer of enterobactin. In addition, a new large-scale method for the isolation of catecholate siderphores is described which is based on adsorption on XAD-2 and subsequent purification on Sephadex LH20.

Transport and utilization of ferrioxamine-E-bound iron in Erwinia herbicola (Pantoea agglomerans)

We have analyzed ferrioxamine-E-mediated iron uptake and metabolization in Erwinia herbicola K4 (Pantoea agglomerans) by means of in vivo Mössbauer spectroscopy and radioactive labeling techniques. A comparison of cell spectra with the spectrum of ferrioxamine clearly demonstrates that ferrioxamine E is not accumulated in the cell, indicating a fast metal transfer. Only two major components of iron metabolism can be detected, a ferric and a ferrous species. At 30 min after uptake, 86% of the internalized metal corresponded to a ferrous ion compound and 14% to a ferric iron species. Metal transfer apparently involves a reductive process. With progressing growth, the oxidized species of the two major proteins becomes dominant. The two iron metabolites closely resemble species previously isolated from Escherichia coli. These components of iron metabolism differ from bacterio-ferritin, cytochromes and most iron-sulfur proteins. All other iron-containing cellular components are at least one order of magnitude lower in concentration. We suggest that the ferrous and ferric iron species correspond to two different oxidation states of a low-molecular mass protein.

Chiral linear hydroxamates as biomimetic analogues of ferrioxamine and coprogen and their use in probing siderophore-receptor specificity in bacteria and fungi

Linear hydroxamate derivatives, possessing chiral alpha-amino acid moieties, were synthesized and their iron transport activities were studied in bacteria and fungi. No growth-promoting activity could be detected in the Gram-positive hydroxamate-auxotroph Aureobacterium flavescens JG9. However, Gram-negative enterobacteria, such as Escherichia coli, Pantoea agglomerans and Hafnia alvei were able to utilize iron from these analogues. Uptake of 55Fe-labeled analogues was inhibited by sodium azide, suggesting an active transport process. The receptors involved during uptake in enterobacteria were identified by using appropriate indicator organisms which are defective in the transport of either ferrioxamines (P. agglomerans FM13), coprogens (H. alvei), or both of these siderophore classes (E. coli fhuE). Our data suggest that the chiral hydroxamates are recognized by the ferrioxamine receptor (FoxA) and the coprogen receptor (FhuE) at a ratio which depends on the optical lambda/delta isomer fraction and the nature of side chains. Transport was also observed in the fungus Neurospora crassa, known to take up coprogen rather than ferrioxamines, suggesting that in this fungus the synthetic analogues behave like coprogen.

The specificity of bacterial siderophore receptors probed by bioassays

The ability to utilize siderophores of bacterial and fungal origin has been studied in wild-type and mutant strains of the enterobacterial genera Salmonella, Escherichia, Shigella, Moellerella, Klebsiella, Enterobacter, Hafnia, Pantoea, Ewingella, Tatumella, Yersinia, and in the non-enterics Aeromonas, Pseudomonas and Aureobacterium. Although only a few representative strains were tested, the results show characteristic genus-specific differences in the utilization of hydroxamate and catecholate siderophores. Moreover, the different response to structural alterations of certain siderophore classes by some wild-type and mutant strains points to variable interacting receptor domains.