Purification of a mycobacterial adhesin for fibronectin

Previous studies have demonstrated that mycobacteria attach to fibronectin (FN). The attachment of mycobacteria to FN is considered to be biologically important in Mycobacterium bovis BCG therapy for superficial bladder cancer, initiation of delayed hypersensitivity to mycobacterial antigens, and the phagocytosis of mycobacteria by epithelial cells. Therefore, we purified the mycobacterial receptor for FN. Culture supernatants from 3-week cultures of Mycobacterium vaccae, which contained proteins that bound FN and inhibited the attachment of both M. vaccae and BCG to FN, were used as a source of receptor. Lyophilized M. vaccae supernatants were reconstituted in 0.02 M bis-Tris (pH 6.0) and applied sequentially to an ACA 54 gel filtration column and a DEAE-Sephacel anion-exchange column. A purified inhibitory protein of 55 kDa (p55) was obtained. The purified p55 protein was observed to bind to FN and to inhibit 125I-FN binding to viable BCG in a dose-dependent manner. Polyclonal and monoclonal antibodies to the protein were generated. The resulting polyclonal antiserum blotted a single protein band at 55 kDa in crude M. vaccae supernatants, cross-reacted with a 55-kDa BCG protein by Western blot (immunoblot), and recognized a 55-kDa band that was associated with the BCG cell wall, which is consistent with its function as a FN receptor. A monoclonal immunoglobulin M(lambda) was isolated from mice immunized with purified M. vaccae p55 protein that was not functional in Western blots but inhibited the attachment of viable BCG to FN. These studies demonstrate that a protein or antigenically related proteins with M(r)s of 55,000 function as FN receptors for at least two distinct mycobacteria.

Mycobacterium kumamotonense Sp. Nov. recovered from clinical specimen and the first isolation report of Mycobacterium arupense in Japan: Novel slowly growing, nonchromogenic clinical isolates related to Mycobacterium terrae complex

Three mycobacterium strains isolated from clinical specimens in Japan were provisionally assigned to the genus Mycobacterium based on their phenotypical characteristics. These isolates were further investigated to determine their specific taxonomic statuses. Mycolic acid analysis and 16S rRNA gene, rpoB, and hsp65 sequence data for the isolates showed that they are most similar to M. terrae complex. DNA-DNA hybridization studies indicated that the three strains were of two species and were distinguishable from M. terrae, M. nonchromogenicum, and M. hiberniae. Therefore, these strains represent two novel species within the genus Mycobacterium. However, one potential new species should have been considered as M. arupense with the 16S rRNA gene and hsp65 sequences similarities of 99.8% and 100% respectively; it was isolated from human specimens in the United States and was proposed in June 2006 as a new species. This report describes the first isolation of M. arupense in Japan, suggesting that the organism is clinically relevant. In addition, we propose the novel species designation Mycobacterium kumamotonense sp. nov. The type strain is CST 7247(T) (=GTC 2729(T), =JCM 13453(T), =CCUG 51961(T)).

Purification of a novel coenzyme F420-dependent glucose-6-phosphate dehydrogenase from Mycobacterium smegmatis

A variety of Mycobacterium species contained the 5-deazaflavin coenzyme known as F420. Mycobacterium smegmatis was found to have a glucose-6-phosphate dehydrogenase that was dependent on F420 as an electron acceptor and which did not utilize NAD or NADP. The enzyme was purified by ammonium sulfate fractionation, phenyl-Sepharose column chromatography, F420-ether-linked aminohexyl-Sepharose 4B affinity chromatography, and quaternary aminoethyl-Sephadex column chromatography, and the sequence of the first 26 N-terminal amino acids has been determined. The response of enzyme activity to a range of pHs revealed a two-peak pattern, with maxima at pH 5.5 and 8.0. The apparent Km values for F420 and glucose-6-phosphate were, respectively, 0.004 and 1.6 mM. The apparent native and subunit molecular masses were 78,000 and approximately 40,000 Da, respectively.

Determination of the structure of exochelin MN, the extracellular siderophore from Mycobacterium neoaurum

BACKGROUND

Siderophores are compounds produced by bacteria to acquire iron. Exochelin MN, the extracellular siderophore from Mycobacterium neoaurum, is of particular interest because it has been shown to transport iron into M. leprae, which is responsible for the disease leprosy. Exochelins from other species cannot mediate iron transport in M. leprae, suggesting a specific uptake mechanism involving exochelin MN. We set out to determine the structure of exochelin MN and identify the features of the molecule that may account for this specificity.

RESULTS

The structure of exochelin MN was elucidated by a combination of techniques including nuclear magnetic resonance, mass spectrometry, derivatization and gas chromatography. Exochelin MN is a peptide, containing the unusual amino acid beta-hydroxyhistidine and an unusual N-methyl group. The peptide coordinates iron(III) octahedrally using its two cis-hydroxamate groups plus the hydroxyl and imidazole nitrogen of the beta-hydroxyhistidine. The three-dimensional structure of the hexadentate exochelin/gallium complex was deduced from NMR data.

CONCLUSIONS

Exochelin MN has some structural features in common with other siderophores, but has a unique three-dimensional structure, which is presumably important for its specific activity in M. leprae. Exochelin MN may be a target for drug design in the fight against infection with this pathogen.

Characterization of a haemolysin from Mycobacterium tuberculosis with homology to a virulence factor of Serpulina hyodysenteriae

Scrutiny of sequence data from the Mycobacterium leprae genome sequencing project identified the presence of a gene encoding a 268-amino-acid polypeptide which is highly similar to a pore-forming haemolysin/cytotoxin virulence determinant, TlyA, from the swine pathogen Serpulina hyodysenteriae. Using degenerate oligonucleotide primers based on the TlyA sequences, the Mycobacterium tuberculosis homologue was amplified and this product was used to obtain the clone and sequence a 2.5 kb fragment containing the whole M. tuberculosis tlyA gene. tlyA encodes a 267-amino-acid protein with a predicted molecular mass of 28 kDa. TlyA homologues were identified by PCR in M. leprae, Mycobacterium avium and Mycobacterium bovis BCG, but appeared absent in Mycobacterium smegmatis, Mycobacterium vaccae, Mycobacterium kansasii, Mycobacterium chelonae and Mycobacterium phlei. The M. tuberculosis gene appeared to be the first gene in an operon containing at least two other genes. Introduction of the M. tuberculosis tlyA gene into M. smegmatis using a mycobacterial shuttle expression plasmid converted non-haemolytic cells into those exhibiting significant haemolytic activity. Similarly, inducible haemolytic activity was observed in sonicated bacteria when tlyA was expressed as a His6-tagged fusion protein in Escherichia coli. tlyA mRNA was detected in both M. tuberculosis and M. bovis BCG using RT-PCR, confirming that this gene is expressed in organisms cultured in vitro.

Routine application of high-performance liquid chromatography for identification of mycobacteria

Mycolic acid analysis by high-performance liquid chromatography (HPLC) was introduced in our laboratory as the routine technique for identifying all clinical isolates of mycobacteria referred to us. HPLC identified 96.1% of the 1,103 strains analyzed, whereas the biochemical procedures and/or the commercial DNA probes identified 98.3% of strains, for an overall agreement of 94.4%. Compared with the probes, there was 100% specificity and 98.9% sensitivity for Mycobacterium tuberculosis identification. HPLC allowed early detection and identification of the rare mycobacterial species M. haemophilum, M. malmoense, M. shimoidei, and M. fallax as well as uncharacteristic strains of M. simiae. After 18 months of routine use, HPLC proved to be reliable, easy to perform, rapid, and less costly than other identification methods.

Methyl-beta-cyclodextrin alters growth, activity and cell envelope features of sterol-transforming mycobacteria

Modified beta-cyclodextrins have been shown previously to enhance sterol conversion to 4-androstene-3,17-dione (AD) and 1,4-androstadiene-3,17-dione (ADD) by growing Mycobacterium spp. The enhancement effect was mainly attributed to steroid solubilization by the formation of inclusion complexes with modified cyclodextrins. In this work, the influence of randomly methylated beta-cyclodextrin (MCD) on the growth, AD- and ADD-producing activity, cell wall (CW) composition and ultrastructure of sterol-transforming Mycobacterium sp. VKM Ac-1816D was studied. The specific growth rate of the strain on glycerol increased in the presence of MCD (20-100 mM). Washed cells grown in the presence of MCD (20-40 mM) expressed 1.6-fold higher ADD-producing activity than did the cells grown without MCD, and their adhesiveness differed. Electron microscopy showed MCD-mediated CW exfoliation and accumulation of membrane-like structures outside the cells, while preserving cells intact. The analysis of CW composition revealed both a decrease in the proportion of extractable lipids and a considerable shift in fatty acid profile resulting from MCD action. The MCD-mediated enhancement of mycolic and fatty acids content was observed outside the cells. The total secreted protein level rose 2.4-fold, and the extracellular 3-hydroxysteroid oxidase activity 3.2-fold. The composition of the CW polysaccharide was not altered, while the overall proportion of the carbohydrates in the CW of the MCD-exposed mycobacteria increased. The results showed that the multiple mechanisms of MCD-mediated intensification of sterol to AD(D) conversion by mycobacteria include not only solubilization of steroids, but also the increase of CW permeability for both steroids and soluble nutrients, disorganization of the lipid bilayer and the release of steroid-transforming enzymes weakly associated with the CW.

Mycobacterium branderi sp. nov., a new potential human pathogen

A number of mycobacterial strains with similar growth characteristics, metabolic properties, and lipid compositions, which were previously placed in the Helsinki group (E. Brander, E. Jantzen, R. Huttunen, A. Juntunen, and M.-L. Katila, J. Clin. Microbiol. 30:1972-1975, 1992), were characterized by performing 16S rRNA gene sequencing. Of the 14 strains studied, 9 had a unique, previously undescribed sequence in the variable region of 16S rRNA. These nine strains, all of which were isolated from respiratory tract specimens, were nonpigmented and grew at 25 degrees C to 45 degrees C, reaching full colony size after 2 to 3 weeks. They produced arylsulfatase, nicotinamidase, and pyrazinamidase and were negative for Tween 80 hydrolysis, catalase, urease, and nitrate reductase activities, and niacin. Their glycolipid patterns were identical. A mycolic acid analysis performed by using thin-layer chromatography showed that these organisms contained alpha-mycolates, ketomycolates, and carboxy mycolates. Gas-liquid chromatography revealed that 2-eicosanol was the major alcohol and hexacosanoic acid was the major mycolic acid cleavage product. On the basis of their growth, biochemical, and lipid characteristics and their unique 16S rRNA sequence, we propose that these organisms should be assigned to a new species, Mycobacterium branderi. Comparative 16S rRNA sequencing revealed that this new species is closely related to Mycobacterium celatum, Mycobacterium cookii, and Mycobacterium xenopi. Strains 52157T (T = type strain) and 43548 have been deposited in the American Type Culture Collection as strains ATCC 51789 and ATCC 51788, respectively.

Intact molecular characterization of cord factor (trehalose 6,6'-dimycolate) from nine species of mycobacteria by MALDI-TOF mass spectrometry

Cord factor (trehalose 6,6'-dimycolate, TDM) is an unique glycolipid with a trehalose and two molecules of mycolic acids in the mycobacterial cell envelope. Since TDM consists of two molecules of very long branched-chain 3-hydroxy fatty acids, the molecular mass ranges widely and in a complex manner. To characterize the molecular structure of TDM precisely and simply, an attempt was made to determine the mycolic acid subclasses of TDM and the molecular species composition of intact TDM by matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectrometry for the first time. The results showed that less than 1 microg mycolic acid methyl ester of TDM from nine representative species of mycobacteria and TDM from the same species was sufficient to obtain well-resolved mass spectra composed of pseudomolecular ions [M+Na]+. Although the mass ion distribution was extremely diverse, the molecular species of each TDM was identified clearly by constructing a molecular ion matrix consisting of the combination of two molecules of mycolic acids. The results showed a marked difference in the molecular structure of TDM among mycobacterial species and subspecies. TDM from Mycobacterium tuberculosis (H37Rv and Aoyama B) showed a distinctive mass pattern and consisted of over 60 molecular ions with alpha-, methoxy- and ketomycolate. TDM from Mycobacterium bovis BCG Tokyo 172 similarly showed over 35 molecular ions, but that from M. bovis BCG Connaught showed simpler molecular ion clusters consisting of less than 35 molecular species due to a complete lack of methoxymycolate. Mass ions due to TDM from M. bovis BCG Connaught and Mycobacterium kansasii showed a biphasic distribution, but the two major peaks of TDM from M. kansasii were shifted up two or three carbon units higher compared with M. bovis BCG Connaught. Within the rapid grower group, in TDM consisting of alpha-, keto- and wax ester mycolate from Mycobacterium phlei and Mycobacterium flavescens, the mass ion distribution due to polar mycolates was shifted lower than that from the Mycobacterium avium-intracellulare group. Since the physico-chemical properties and antigenic structure of mycolic acid of TDM affect the host immune responses profoundly, the molecular characterization of TDM by MALDI-TOF mass analysis may give very useful information on the relationship of glycolipid structure to its biological activity.

Mycobacterium hassiacum sp. nov., a new rapidly growing thermophilic mycobacterium

A new rapidly growing, scotochromogenic mycobacterium was isolated from urine. This strain is thermophilic (it grows at 65 degrees C), tolerates 5% NaCl, and was unable to utilize any of the sugars tested or citrate or to take up iron. The isolate splits benzamide, urea, nicotinamide, and pyrazinamide and is sensitive to streptomycin, ethambutol, cycloserine, ciprofloxacin, and chlarithromycin but resistant to isoniazid, rifampin, and prothionamide. These characteristics clearly place this organism in a new mycobacterial species, which was confirmed by the unique 16S rRNA nucleotide sequence. The high level of similarity between this rapid grower and Mycobacterium xenopi is surprising. For this new rapidly growing scotochromogenic and thermophilic mycobacterium we propose the name Mycobacterium hassiacum sp. nov.

Burden of unidentifiable mycobacteria in a reference laboratory

Modern identification techniques at the genomic level have greatly improved the taxonomic knowledge of mycobacteria. In adjunct to nucleic acid sequences, mycobacterial identification has been endorsed by investigation of the lipidic patterns of unique mycolic acids in such organisms. In the present investigation, the routine use of high-performance liquid chromatography (HPLC) of mycolic acids, followed by the sequencing of the 16S rRNA, allowed us to select 72 mycobacterial strains, out of 1,035 screened, that do not belong to any of the officially recognized mycobacterial species. Most strains (i.e., 47) were isolated from humans, 13 were from the environment, 3 were from animals, and 9 were from unknown sources. The majority of human isolates were grown from the respiratory tract and were therefore most likely not clinically significant. Some, however, were isolated from sterile sites (blood, pleural biopsy, central venous catheter, or pus). Many isolates, including several clusters of two or more strains, mostly slow growers and scotochromogenic, presented unique genetic and lipidic features. We hope the data reported here, including the results of major conventional identification tests, the HPLC profiles of strains isolated several times, and the whole sequences of the 16S rRNA hypervariable regions of all 72 mycobacteria, may encourage reporting of new cases. The taxonomy of the genus Mycobacterium is, in our opinion, still far from being fully elucidated, and the reporting of unusual strains provides the best background for the recognition of new species. Our report also shows the usefulness of the integration of novel technology to routine diagnosis, especially in cases involving slow-growing microorganisms such as mycobacteria.

The first total synthesis of a highly branched arabinofuranosyl hexasaccharide found at the nonreducing termini of mycobacterial arabinogalactan and lipoarabinomannan

[reaction--see text] The first total synthesis of the arabinofuranosyl hexasaccharide present at the nonreducing termini of mycobacterial arabinogalactan and lipoarabinomannan is reported. The oligosaccharide was prepared as its methyl glycoside via a route that is both highly efficient and convergent. Addition of two beta-D-arabinofuranosyl residues simultaneously in high yield and with excellent stereocontrol was the key step of the synthesis.

Mycobacterium tusciae sp. nov

A new, slow-growing, scotochromogenic mycobacterium was isolated from a lymph node of an immunocompromised child and subsequently from tap water and from a respiratory specimen of a patient with chronic fibrosis. Alcohol-acid-fastness, lipid patterns and the G + C content clearly support the placement of this organism in the genus Mycobacterium. The isolates grew very slowly at temperatures ranging from 25 to 32 degrees C and showed activities of nitrate reductase, catalase, urease, arylsulfatase and Tween 80 hydrolysis. The organism was susceptible to all antimycobacterial drugs tested. The 16S rDNA sequence was unique and phylogenetic analysis placed the organism close to fast-growing species such as Mycobacterium farcinogenes, Mycobacterium komossense and Mycobacterium aichiense. These data support the conclusion that the isolates represent a new mycobacterial species, for which the name Mycobacterium tusciae sp. nov. is proposed. The type strain is strain FI-25796T; a culture of this strain has been deposited in the DSMZ as strain DSM 44338T.

Synthesis of the N-((1E)-alkenyl)-(2Z,4Z)-heptadienamide side chain of salicylihalamide A and apicularens A and B

[reaction: see text] The unstable N-((1E)-alkenyl)-(2Z,4Z)-heptadienamide side chain of salicylihalamide A (1) and apicularens A and B (3 and 4) has been prepared in one pot by the addition of (1Z,3Z)-hexadienylcuprate, prepared in situ from EtLi, CuBr.SMe2, and acetylene, to a (1 E)-alkenyl isocyanate.

Mycobacterium novocastrense sp. nov., a rapidly growing photochromogenic mycobacterium

A strain isolated from a biopsy sample taken from a slowly spreading skin granulation on a child's hand was found to have properties consistent with its classification in the genus Mycobacterium. An almost complete gene sequence of the 16S rRNA of the strain was determined following the cloning and sequencing of the amplified gene. The sequence was aligned with those available for mycobacteria, and phylogenetic trees were inferred with four tree-making algorithms. The organism, which formed a distinct phyletic line within the evolutionary radiation occupied by rapidly growing mycobacteria, was readily distinguished from members of validly described species of rapidly growing mycobacteria on the basis of its mycolic acid pattern and a number of other phenotypic features, notably its ability to form yellow pigmented colonies when incubated in the light. The name proposed for this new species is Mycobacterium novocastrense. The type strain is DSM 44203.

Gamma interferon production by bovine gamma delta T cells following stimulation with mycobacterial mycolylarabinogalactan peptidoglycan

A large percentage of lymphocytes in the blood of cattle express the gamma delta T-cell receptor, but specific functions for these cells have not yet been clearly defined. There is evidence, however, that human, murine, and bovine gamma delta T cells have a role in the immune response to mycobacteria. This study investigated the ability of bovine gamma delta T cells to expand and produce gamma interferon (IFN-gamma) in response to stimulation with mycobacterial products. Bovine gamma delta T cells, isolated from the peripheral blood of healthy cattle, expanded following in vitro stimulation with live mycobacteria, mycobacterial crude cell wall extract, and Mycobacterium bovis culture filtrate proteins. In addition, purified gamma delta T cells, cocultured with purified monocytes and interleukin-2, consistently produced significant amounts of IFN-gamma in response to mycobacterial cell wall. The IFN-gamma-inducing component of the cell wall was further identified as a proteolytically resistant, non-sodium dodecyl sulfate-soluble component of the mycolylarabinogalactan peptidoglycan.

Rendering of mycobacteria safe for molecular diagnostic studies and development of a lysis method for strand displacement amplification and PCR

Two criteria must be met before mycobacterial specimens can be tested by DNA amplification methods: (i) the sample must be rendered noninfectious, and (ii) the organisms must be lysed to free the DNA. Previous publications reporting DNA amplification of mycobacteria have concentrated on lysis and amplification procedures and have not addressed the issue of sample safety. We have shown that heating of samples below 100 degrees C may not consistently kill mycobacteria; however, heating at 100 degrees C in a boiling-water bath or a forced-air oven for a minimum of 5 min kills mycobacteria, including Mycobacterium thermoresistibile. Furthermore, heating at 100 degrees C for 30 min consistently lyses mycobacteria to produce short fragments of DNA that are suitable for amplification by PCR and strand displacement amplification. This procedure works with clinical samples digested by the n-acetyl cysteine-NaOH method as well as with suspensions of organisms in phosphate buffer. This paper also demonstrates the feasibility of using strand displacement amplification with clinical specimens.

Determination of molecular species composition of C80 or longer-chain alpha-mycolic acids in Mycobacterium spp. by gas chromatography-mass spectrometry and mass chromatography

The molecular species composition of alpha-mycolic acids ranging from C68 to C86 in 13 rapidly growing and 12 slowly growing mycobacterial species was determined by gas chromatography, gas chromatography-mass spectrometry, and mass chromatography. In gas chromatographic analysis, the molecular species of alpha-mycolic acids were well separated as trimethylsilyl ether derivatives of the methyl esters, according to their total carbon numbers. The total carbon and double-bond numbers of mycolic acids at each peak on gas chromatograms were determined from the [M]+, [M - 15]+, and [M - 90]+ ions on the mass spectrum, and straight and branched chain structures were identified by the mass fragment ions [A]+, due to C2--C3 cleavage [R-CH-O-Si(CH3)3]+, and [B]+, due to C3--C4 cleavage [(CH3)3-Si-O-CH-CH(R')-COOCH3]+. The concentration of odd- and even-carbon-numbered mycolic acids, which often overlap each other on gas chromatograms, and the composition of three homologous mycolic acids with different alpha units (C22:0, C24:0, and C26:0) were clearly determined by mass chromatography monitoring [M - 15]+ ions and [B - 29]+ ions, respectively. The molecular species composition of alpha-mycolic acids and their average carbon numbers (av. cn.) as a simple expression of the composition were calculated from the mass chromatograms. Each mycobacterial species examined was demonstrated to possess a characteristic profile of alpha-mycolic acid composition, and based on this the species were classified approximately into eight groups: C68 to C76 (av. cn. 72), dienoic, possessing a C20 alkyl branch at the 2 position (C22 alpha-unit) for Mycobacterium diernhoferi and Mycobacterium sp. strain 3707, a chromogenic rapid grower; C72 to C78 (av. cn. 75), dienoic with both C22 and C24 alpha units, containing a small or a large amount of odd-carbon-numbered molecules, for M. vaccae, M. rhodesiae, and M. phlei (chromogenic rapid growers); C72 to C80 (av. cn. 75 to 77), dienoic with C24 alpha-unit, containing a moderate or a large amount of odd-carbon-numbered molecules, for M. smegmatis, M. chitae, M. chelonae (M. chelonei), and M. fortuitum (nonchromogenic rapid growers); C78 to C82 (av. cn. 80), even-carbon-numbered dienoic with C24 alpha unit for M. agri and M. thermoresistible (rapid growers); C75 to C81 (av. cn. 77 to 79), odd-carbon-numbered dienoic with C24 alpha unit for M. nonchromogenicum complex (M. nonchromogenicum, M. terrae, and "M. novum") (slow growers); (vi) C76 to C84 (av. cn. 79 to 81), even-carbon-numbered dienoic with C24 alpha unit for MAIS complex including M. scrofulaceum, M. avium, and M. intracellulare (slow growers); (vii) C72 to C80 (av. cn. 77 to 79), even-carbon-numbered dienoic with C24 alpha unit for M. szulgai, M. gordonae, and M. kansasii (chromogenic slow growers); and (viii) C76 to C86 (av. cn. 79 to 81), even-carbon-numbered dienoic with C26 alpha unit M. bovis Ravenol and BCG and M. tuberculosis H37Rv. This study demonstrated that gas chromatography-mass spectrometric analysis of the molecular species composition of alpha-mycolic acid can give rapid, important, and very precise information for the identification of pathogenic and nonpathogenic mycobacterial species.

Structures of coenzyme F(420) in Mycobacterium species

The structure of coenzyme F(420) in Mycobacterium smegmatis was examined using proton NMR, amino acid analysis, and HPLC. The two major F(420) structures were shown to be composed of a chromophore identical to that of F(420) from Methanobacterium thermoautotrophicum, with a side chain of a ribityl residue, a lactyl residue and five or six glutamate groups (F(420)-5 and F(420)-6). Peptidase treatment studies suggested that L-glutamate groups are linked by gamma-glutamyl bonds in the side chain. HPLC analysis indicated that Mycobacterium tuberculosis, Mycobacterium bovis BCG, and Mycobacterium fortuitum have F(420)-5 and F(420)-6 as the predominant structures, whereas Mycobacterium avium contains F(420)-5, F(420)-6 and F(420)-7 in significant amounts. 7,8-Didemethyl 8-hydroxy 5-deazariboflavin (FO), an intermediate in F(420) biosynthesis, accounted for about 1-7% of the total deazaflavin in cells. Peptidase treatment of F(420) created F(420) derivatives that may be useful for the assay of enzymes involved in F(420) biosynthesis.

Evidence for the existence of PAH-quinone reductase and catechol-O-methyltransferase in Mycobacterium vanbaalenii PYR-1

Polycyclic aromatic hydrocarbon (PAH) quinone reductase (PQR) and catechol-O-methyltransferase (COMT), from the PAH-degrading Mycobacterium vanbaalenii PYR-1, were demonstrated to be constitutive enzymes located in the soluble fraction of cell extracts. PQR activities for the reduction of 9,10-phenanthrenequinone and 4,5-pyrene- quinone were 1.40+/-0.13 and 0.12+/-0.01 micromol min(-1) mg-protein(-1), respectively. The exogenous catechols alizarin, anthrarobin, 2,3-dihydroxynaphthalene and esculetin inhibited PQR activity. Anthrarobin (100 microM) and esculetin (100 microM) inhibited 4,5-pyrenequinone reduction by 64-92%. COMT was involved in the O-methylation of 1,2-dihydroxyphenanthrene to form 1-methoxy-2-hydroxyphenanthrene and 1,2-dimethoxyphenanthrene. Both pyrene and 1-hydroxypyrene were metabolized by M. vanbaalenii PYR-1 to form 1-methoxypyrene, 1-methoxy-2-hydroxypyrene, 1-hydroxy-2-methoxypyrene and 1,2-dimethoxypyrene. Among the catechols tested, anthrarobin showed the highest COMT activity (1.06+/-0.04 nmol/30 min(-1) mg-protein(-1)). These results suggest that the PQR and COMT activities of M. vanbaalenii PYR-1 may play an important role in the detoxification of PAH catechols.

Total synthesis of exochelin MN and analogues

The first total synthesis of exochelin MN is described along with rationally designed analogues. The required L-threo-beta-hydroxyamino acid components were constructed using either Sharpless asymmetric aminohydroxylation reactions or an aldol reaction of imidazolidinone 19. A new concise procedure for the preparation of the constituent six-membered cyclic hydroxamate was developed. In addition, a plausible mechanism for exochelin MN-mediated iron(III) transport was proposed. Biological studies of these compounds will be used to evaluate this hypothesis.

Transporters Involved in the Biogenesis and Functionalization of the Mycobacterial Cell Envelope

The biology of mycobacteria is dominated by a complex cell envelope of unique composition and structure and of exceptionally low permeability. This cell envelope is the basis of many of the pathogenic features of mycobacteria and the site of susceptibility and resistance to many antibiotics and host defense mechanisms. This review is focused on the transporters that assemble and functionalize this complex structure. It highlights both the progress and the limits of our understanding of how (lipo)polysaccharides, (glyco)lipids, and other bacterial secretion products are translocated across the different layers of the cell envelope to their final extra-cytoplasmic location. It further describes some of the unique strategies evolved by mycobacteria to import nutrients and other products through this highly impermeable barrier.

Two polycyclic aromatic hydrocarbon o-quinone reductases from a pyrene-degrading Mycobacterium

Polycyclic aromatic hydrocarbon (PAH) o-quinone reductase (PQR) plays a crucial role in the detoxification of PAH o-quinones by reducing them to catechols. Two constitutive PQRs were found in cell extracts of a pyrene-degrading Mycobacterium sp. strain PYR100. The enzymes had an activity towards 9,10-phenanthrenequinone (PQ) and/or 4,5-pyrenequinone (PyQ), and the relative amounts varied with the pH of the culture media. PQR1, containing an FAD cofactor, was a monomer (20.1 kDa), and PQR2, with no flavin cofactor, was a homodimer (26.5 kDa subunits). There was no homology between the N-terminal sequences of PQR1 and PQR2. Dicumarol and quercetin inhibited PQR2 more strongly than PQR1. PQR1 had much lower specificity constants (k(cat)/K(m), 10(5)M(-1)s(-1)) for menadione (0.80) and PQ (5.19) than PQR2 (13.9 for menadione and 176 for PQ). Additionally, PQR2 exhibited a broad substrate specificity with high specificity constants for 1,4-naphthalenequinone, 1,2-naphthalenequinone, and PyQ.