Revealing solvent-dependent folding behavior of mycolic acids from Mycobacterium tuberculosis by advanced simulation analysis

Mycobacterium tuberculosis remains a persistent pathogen, partly due to its lipid rich cell wall, of which mycolic acids (MAs) are a major component. The fluidity and conformational flexibilities of different MAs in the bacterial cell wall significantly influence its properties, function, and observed pathogenicity; thus, a proper conformational description of different MAs in different environments (e.g., in vacuum, in solution, in monolayers) can inform about their potential role in the complex setup of the bacterial cell wall. Previously, we have shown that molecular dynamics (MD) simulations of MA folding in vacuo can be used to characterize MA conformers in seven groupings relating to bending at the functional groups (W, U and Z-conformations). Providing a new OPLS-based forcefield parameterization for the critical cyclopropyl group of MAs and extensive simulations in explicit solvents (TIP4P water, hexane), we now present a more complete picture of MA folding properties together with improved simulation analysis techniques. We show that the 'WUZ' distance-based analysis can be used to pinpoint conformers with hairpin bends at the functional groups, with these conformers constituting only a fraction of accessible conformations. Applying principle component analysis (PCA) and refinement using free energy landscapes (FELs), we are able to discriminate a complete and unique set of conformational preferences for representative alpha-, methoxy- and keto-MAs, with overall preference for folded conformations. A control backbone-MA without any mero-chain functional groups showed significantly less folding in the mero-chain, confirming the role of functionalization in directing folding. Keto-MA showed the highest percentage of WUZ-type conformations and, in particular, a tendency to fold at its alpha-methyl trans-cyclopropane group, in agreement with results from Villeneuve et al. MAs demonstrate similar folding in vacuum and water, with a majority of folded conformations around the W-conformation, although the molecules are more flexible in vacuum than in water. Exchange between conformations, with a disperse distribution that includes unfolded conformers, is common in hexane for all MAs, although with more organization for Keto-MA. Globular, folded conformations are newly defined and may be specifically relevant in biofilms. Graphical abstract Through advanced simulation analysis, including principle component analysis and free energy landscapes, we reveal detailed physical insights into the solvent-dependant folding behavior of mycolic acids from M. tb.

Cationized liposomal keto-mycolic acids isolated from Mycobacterium bovis bacillus Calmette-Guérin induce antitumor immunity in a syngeneic murine bladder cancer model

Intravesical therapy using Mycobacterium bovis bacillus Calmette-Guérin (BCG) is the most established cancer immunotherapy for bladder cancer. However, its underlying mechanisms are unknown. Mycolic acid (MA), the most abundant lipid of the BCG cell wall, is suspected to be one of the essential active components of this immunogenicity. Here, we developed cationic liposomes incorporating three subclasses (α, keto, and methoxy) of MA purified separately from BCG, using the dendron-bearing lipid D22. The cationic liposomes using D22 were efficiently taken up by the murine bladder cancer cell line MB49 in vitro, but the non-cationic liposomes were not. Lip-kMA, a cationic liposome containing keto-MA, presented strong antitumor activity in two murine syngeneic graft models using the murine bladder cancer cell lines MB49 and MBT-2 in comparison to both Lip-aMA and Lip-mMA, which contained α-MA and methoxy-MA, respectively. Interestingly, Lip-kMA(D12), which was made of D12 instead of D22, did not exhibit antitumor activity in the murine syngeneic graft model using MB49 cells, although it was successfully taken up by MB49 cells in vitro. Histologically, compared to the number of infiltrating CD4 lymphocytes, the number of CD8 lymphocytes was higher in the tumors treated with Lip-kMA. Antitumor effects of Lip-kMA were not observed in nude mice, whereas weak but significant effects were observed in beige mice with natural killer activity deficiency. Thus, a cationized liposome containing keto-MA derived from BCG induced in vivo antitumor immunity. These findings will provide new insights into lipid immunogenicity and the underlying mechanisms of BCG immunotherapy.

Mycobacterium tuberculosis complex lipid virulence factors preserved in the 17,000-year-old skeleton of an extinct bison, Bison antiquus

Tracing the evolution of ancient diseases depends on the availability and accessibility of suitable biomarkers in archaeological specimens. DNA is potentially information-rich but it depends on a favourable environment for preservation. In the case of the major mycobacterial pathogens, Mycobacterium tuberculosis and Mycobacterium leprae, robust lipid biomarkers are established as alternatives or complements to DNA analyses. A DNA report, a decade ago, suggested that a 17,000-year-old skeleton of extinct Bison antiquus, from Natural Trap Cave, Wyoming, was the oldest known case of tuberculosis. In the current study, key mycobacterial lipid virulence factor biomarkers were detected in the same two samples from this bison. Fluorescence high-performance liquid chromatography (HPLC) indicated the presence of mycolic acids of the mycobacterial type, but they were degraded and could not be precisely correlated with tuberculosis. However, pristine profiles of C₂₉, C₃₀ and C₃₂ mycocerosates and C₂₇ mycolipenates, typical of the Mycobacterium tuberculosis complex, were recorded by negative ion chemical ionization gas chromatography mass spectrometry of pentafluorobenzyl ester derivatives. These findings were supported by the detection of C₃₄ and C₃₆ phthiocerols, which are usually esterified to the mycocerosates. The existence of Pleistocene tuberculosis in the Americas is confirmed and there are many even older animal bones with well-characterised tuberculous lesions similar to those on the analysed sample. In the absence of any evidence of tuberculosis in human skeletons older than 9,000 years BP, the hypothesis that this disease evolved as a zoonosis, before transfer to humans, is given detailed consideration and discussion.

[Diagnostic utility of the molecular assay GenoType MTBC (HAIN Lifesciences, Germany) for identification of tuberculous mycobacteria]

INTRODUCTION

The GenoType system (HAIN Lifescience, Germany) offers new perspectives of detecting the tuberculous and non-tuberculous mycobacteria at the molecular level. The system compromises five independent tests that could be performed either on direct specimens or isolated strains, to identify the strains and test the resistance against rifampin and isoniazid. Up to now, non GenoType test was applied in Poland. The aim of the study was an evaluation the accuracy of GenoType MTBC test in speciation of the clinical isolates, previously classified as M. tuberculosis complex by HPLC analyze of mycolic acids.

MATERIAL AND METHODS

161 clinical isolates, derived from the TB patients hospitalized in the Warsaw Medical University Hospital between 1999 and 2007 were assayed.

RESULTS

On the basis of the hybridization patterns, all 161 studied strains were identified as M. tuberculosis/M. canettii.

CONCLUSIONS

1. The GenoType MTBC test (HAIN Lifescience, Germany) precisely recognizes M. tuberculosis complex. The 100% accordance in speciation of M. tuberculosis by the GenoType MTBC test as compared to HPLC method was demonstrated. The GenoType MTBC test can replace HPLC in detection of tuberculous mycobacteria in clinical isolates. 2. As the GenoType MTBC test performs well, the other tests of GenoType system may be considered to be verified in diagnostic procedure of mycobacterial infection.

Isolation and analysis of Mycobacterium tuberculosis mycolic acids

Mycolic acids are an important constituent of the mycobacterial cell wall. Changes in the structure or composition of mycolic acids have been associated with modification of cell wall permeability and attenuation of pathogenic Mycobacterium tuberculosis strains. This unit describes the isolation of M. tuberculosis mycolic acids and their analysis by either thin-layer chromatography or high-performance liquid chromatography. Both techniques have been extensively used to study (1) mycolic acid biosynthesis, (2) the role of mycolic acids in mycobacterial virulence, (3) the effect of antituberculosis drugs targeting the cell wall, and (4) taxonomic purposes.

Mycobacterium fluoranthenivorans sp. nov., a fluoranthene and aflatoxin B1 degrading bacterium from contaminated soil of a former coal gas plant

Mycobacterium strain FA4T was isolated with fluoranthene as the single carbon source from soil of a former coal gas plant, polluted with polycyclic aromatic hydrocarbons. The physiological properties, fatty acid pattern, and the 16S ribosomal RNA gene sequence indicated membership to the genus Mycobacterium, but were different from all type strains of Mycobacterium species. Based on comparative 16S rRNA gene sequence analyses strain FA4T could be assigned to the Mycobacterium neoaurum taxon showing 98% sequence similarity to M. diernhoferi as its closest neighbour. The occurrence of epoxymycolate in the cell wall differentiates FA4 from all members of this taxon which synthesize wax-ester mycolates in addition to alpha-mycolates. Strain FA4T is able to degrade aflatoxin B1. This biological attribute might be useful in biological detoxification processes of foods and feeds. From the investigated characteristics it is concluded that strain FA4T represents a new species, for which we propose the name Mycobacterium fluoranthenivorans sp. nov. The type strain of Mycobacterium fluoranthenivorans is FA4T (DSM 44556T = CIP 108203T).

Mycobacterium pseudoshottsii sp. nov., a slowly growing chromogenic species isolated from Chesapeake Bay striped bass (Morone saxatilis)

A group of slowly growing photochromogenic mycobacteria was isolated from Chesapeake Bay striped bass (Morone saxatilis) during an epizootic of mycobacteriosis. Growth characteristics, acid-fastness and 16S rRNA gene sequencing results were consistent with those of the genus Mycobacterium. Biochemical reactions, growth characteristics and mycolic acid profiles (HPLC) resembled those of Mycobacterium shottsii, a non-pigmented mycobacterium also isolated during the same epizootic. Sequencing of the 16S rRNA genes, the gene encoding the exported repeated protein (erp) and the gene encoding the 65 kDa heat-shock protein (hsp65) and restriction enzyme analysis of the hsp65 gene demonstrated that this group of isolates is unique. Insertion sequences associated with Mycobacterium ulcerans, IS2404 and IS2606, were detected by PCR. These isolates could be differentiated from other slowly growing pigmented mycobacteria by their inability to grow at 37 °C, production of niacin and urease, absence of nitrate reductase, negative Tween 80 hydrolysis and resistance to isoniazid (1 μg ml−1), p-nitrobenzoic acid, thiacetazone and thiophene-2-carboxylic hydrazide. On the basis of this polyphasic study, it is proposed that these isolates represent a novel species, Mycobacterium pseudoshottsii sp. nov. The type strain, L15T, has been deposited in the American Type Culture Collection as ATCC BAA-883T and the National Collection of Type Cultures (UK) as NCTC 13318T.

Characterization of Rhodococcus wratislaviensis strain J3 that degrades 4-nitrocatechol and other nitroaromatic compounds

The bacterial strain J3 was isolated from soil by selective enrichment on mineral medium containing 4-nitrocatechol as the sole carbon and energy source. This strain was identified as Rhodococcus wratislaviensis on the basis of morphology, biochemical, physiological and chemotaxonomic characterization and complete sequencing of the 16S rDNA gene. The isolated bacterium could utilize 4-nitrocatechol, 3-nitrophenol and 5-nitroguaiacol as sole carbon and energy sources. Stoichiometric release of nitrites was measured during degradation of 4-nitrocatechol both in growing cultures and for stationary phase cells. The J3 strain was unable to degrade 4-nitroguaiacol, 2-nitrophenol, 4-nitrophenol, 2,4-dinitrobenzoic acid, 4,5-dimethoxy-2-nitrobenzoic acid and 2,3-difluoro-6-nitrophenol. The J3 strain is deposited in the Czech Collection of Microorganisms as CCM 4930.

Mycobacterium pyrenivorans sp. nov., a novel polycyclic-aromatic-hydrocarbon-degrading species

The taxonomic position of a polycyclic-aromatic-hydrocarbon-degrading bacterium, strain 17A3T, isolated from contaminated soil was determined using a combination of phenotypic and genotypic properties. The isolate showed phenotypic properties that were diagnostic for species of the genus Mycobacterium. Comparative 16S rRNA gene sequence analysis assigned 17A3T to the 16S rRNA gene subgroup that contains Mycobacterium aurum, Mycobacterium austroafricanum, Mycobacterium vaccae and Mycobacterium vanbaalenii, but it could clearly be distinguished from these species using a combination of physiological, chemotaxonomic markers and internal rRNA gene spacer analyses. The data showed that strain 17A3T (=DSM 44605T=NRRL B-24244T) merits recognition as the type strain of a novel species of the genus Mycobacterium. The name Mycobacterium pyrenivorans sp. nov. is proposed for the species because of its ability to use pyrene as a sole source of carbon and energy.

Mycobacterium nebraskense sp. nov., a novel slowly growing scotochromogenic species

The characterization of a novel slowly growing, scotochromogenic Mycobacterium species is reported. This previously undescribed mycobacterial species was isolated from five different patients with symptomatic pulmonary infections. All isolates were acid-fast-positive and the mycolic acid profiles were unique and supported placement into the genus Mycobacterium. Phenotypic characteristics of each strain included optimal growth after 3 weeks at a temperature range of 30–35 °C, yellow pigmentation after incubation in the dark and production of a heat-stable catalase. The 16S rRNA gene and internal transcribed spacer 1 sequences were identical for all five strains, but distinct from all known mycobacterial species. Phylogenetic analysis based on the 16S rRNA gene sequence placed the novel species within the slowly growing mycobacteria group in close proximity to Mycobacterium malmoense, Mycobacterium avium, Mycobacterium kansasii and Mycobacterium scrofulaceum. These data support the conclusion that the related five described organisms represent a novel Mycobacterium species, for which the name Mycobacterium nebraskense sp. nov. is proposed, with the type strain UNMC-MY1349T (=ATCC BAA-837T=DSM 44803T).

Mycobacterium cosmeticum sp. nov., a novel rapidly growing species isolated from a cosmetic infection and from a nail salon

Four isolates of a rapidly growingMycobacteriumspecies had a mycolic acid pattern similar to that ofMycobacterium smegmatis, as determined by HPLC analyses. Three of the isolates were from footbath drains and a sink at a nail salon located in Atlanta, GA, USA; the fourth was obtained from a granulomatous subdermal lesion of a female patient in Venezuela who was undergoing mesotherapy. By random amplified polymorphic DNA electrophoresis and PFGE of large restriction fragments, the three isolates from the nail salon were shown to be the same strain but different from the strain from the patient in Venezuela. Polymorphisms in regions of therpoB,hsp65and 16S rRNA genes that were shown to be useful for species identification matched for the two strains but were different from those of otherMycobacteriumspecies. The 16S rRNA gene sequence placed the strains in a taxonomic group along withMycobacterium frederiksbergense,Mycobacterium hodleri,Mycobacterium diernhoferiandMycobacterium neoaurum. The strains produced a pale-yellow pigment when grown in the dark at the optimal temperature of 35 °C. Biochemical testing showed that the strains were positive for iron uptake, nitrate reduction and utilization ofd-mannitol,d-xylose, iso-myo-inositol,l-arabinose, citrate andd-trehalose. The strains were negative ford-sorbitol utilization and production of niacin and 3-day arylsulfatase, although arylsulfatase activity was observed after 14 days. The isolates grew on MacConkey agar without crystal violet but not on media containing 5 % (w/v) NaCl or at 45 °C. They were susceptible to ciprofloxacin, amikacin, tobramycin, cefoxitin, clarithromycin, doxycycline, sulfamethoxazole and imipenem. The nameMycobacterium cosmeticumsp. nov. is proposed for this novel species; two strains, LTA-388T(=ATCC BAA-878T=CIP 108170T) (the type strain) and 2003-11-06 (=ATCC BAA-879=CIP 108169) have been designated, respectively, for the strains of the patient in Venezuela and from the nail salon in Atlanta, GA, USA.

Structural analysis of biological aliphatic compounds using surface-enhanced Fourier transform Raman spectroscopy

The surface-enhanced Raman scattering (SERS) technique for Fourier transform Raman spectrometry is employed to reveal the chemical structure of biological aliphatic compounds consisting of folded, long aliphatic chains. The structural analysis is performed via the measurements of the accordion-vibration modes generated in the ordered, long aliphatic chain. The SERS spectra after subtraction of a background spectrum give segment lengths that are almost perfectly consistent with the chemical structures studied by mass spectrometry. The agreement of the SERS results with those of mass spectrometry suggests the positions of kinks in the long hydrocarbon chain. The combination technique of SERS and mass spectrometry is useful to discuss the structure of folded, long biological lipids.

Influence of the growth substrate on the mycolic acid profiles of mycobacteria

The influence of growth substrates on mycolic acid profiles of PAH-degrading Mycobacterium spp. LB501T, LB307T and VM552 was examined by high-performance liquid chromatography (HPLC) using glucose, alkanes, polycyclic aromatic hydrocarbons (PAH) or Luria-Bertani medium (LB) as the sole carbon source. The substrates gave rise to varying mycolic acid profiles, as bacteria growing on poorly water-soluble substrates exhibited more hydrophobic mycolic acids than cells grown on glucose. Our results indicate that mycobacteria respond to the growth substrate by changing the mycolic acid composition of their cell wall, pointing at the importance of the growth substrate for mycolic acid profiling as an identification method of actinomycetes.

Location of functional groups in mycobacterial meromycolate chains; the recognition of new structural principles in mycolic acids

Mycobacterial alpha-, methoxy- and keto-mycolic acid methyl esters were separated by argentation chromatography into mycolates with no double bond, with one trans double bond or with one cis double bond. Meromycolic acids were prepared from each methyl mycolate fraction by pyrolysis, followed by silver oxide oxidation, and analysed by high-energy collision-induced dissociation/fast atom bombardment MS to reveal the exact locations of the functional groups within the meromycolate chain. The locations of cis and trans double bonds, cis and trans cyclopropane rings, methoxy and keto groups, and methyl branches within the meromycolate chain were determined from their characteristic fragment ion profiles, and the structures of the meromycolic acids, including those with three functional groups extracted from Mycobacterium tuberculosis H37Ra, Mycobacterium bovis BCG and Mycobacterium microti, were established. Meromycolic acids with one cis double bond were structurally closely related to those with one cis cyclopropane ring, whereas the meromycolic acids with one trans cyclopropane ring were closely related to the corresponding meromycolic acids with one cis cyclopropane ring. A close relationship between methoxy- and keto-meromycolic acids was also implied. The relationship between the meromycolic acids with a trans double bond and the other meromycolic acids was not clearly revealed, and they did not appear to be immediate substrates for trans cyclopropanation.

Mycolic acid analysis by high-performance liquid chromatography for identification of Mycobacterium species

Mycobacterium tuberculosis is the etiologic agent of tuberculosis and can be accurately detected by laboratories using commercial genetic tests. Nontuberculosis mycobacteria (NTM) causing other mycobacterioses can be difficult to identify. The identification processes are confounded by an increasing diversity of newly characterized NTM species. The ubiquitous nature of NTM, combined with their potential to be opportunistic pathogens in immunocompromised as well as nonimmunodeficient patients, further complicates the problem of their identification. Since clinical case management varies depending on the etiologic agent, laboratories must identify the species in a timely manner. However, only a few identification methods can detect the species diversity within the Mycobacterium genus. Over the last decade, high-performance liquid chromatography analysis of the mycolic acids has become an accepted method for identification of mycobacteria. In this review, we assess its development and usefulness as an identification technique for Mycobacterium species.

Separation and characterization of individual mycolic acids in representative mycobacteria

Total mycolic acid methyl ester fractions were isolated from 24 representatives of Mycobacterium tuberculosis, Mycobacterium bovis (including BCG), Mycobacterium microti, Mycobacterium kansasii and Mycobacterium avium. The total mycolate functional group composition was estimated from (1)H-NMR spectra. Mycolates were separated into alpha-mycolates, methoxymycolates and ketomycolates and each class was further separated by argentation chromatography into mycolates with no double bonds, with one trans-double bond and with one cis-double bond. Mass spectrometry revealed the mycolate chain lengths and (1)H-NMR the cis- and trans-double bond and cyclopropane ring content. The same species had similar mycolate profiles; the major type of each class had cis- or trans-cyclopropane rings and lacked double bonds. Minor proportions of possible unsaturated precursors of the cyclopropane mycolates were commonly encountered. Among unusual alpha-mycolates, many strains had tricyclopropyl components with chains extended by 6 to 8 carbons. Significantly, M. tuberculosis (Canetti) and M. avium had alpha-mycolates with a trans-double bond and cyclopropane ring, whose chain lengths suggested a relationship to possible precursors of oxygenated mycolates. The methoxy- and ketomycolates from a majority of M. tuberculosis strains had minor amounts of components with additional cyclopropane rings, some of whose chains were also extended by 6 to 8 carbons. These latter mycolates were major components in the attenuated M. tuberculosis H37Ra strain, whose mycolate profile was distinct from those of other strains of M. tuberculosis.

Production and partial characterization of anti-cord factor (trehalose-6,6'-dimycolate) IgG antibody in rabbits recognizing mycolic acid subclasses of Mycobacterium tuberculosis or Mycobacterium avium

An ELISA with cord factor (trehalose-6,6'-dimycolate) is useful for the serodiagnosis of tuberculosis. To clarify the exact antigenic epitope in cord factor, recognized by a rabbit anti-cord factor IgG antibody, and to ascertain the most sensitive and specific diagnostic test antigen, rabbits were immunized with two kinds of cord factors isolated from Mycobacterium tuberculosis or Mycobacterium avium and the reactivities of the sera were tested against cord factors or the component mycolic acid methyl esters by ELISA. The serum from rabbits immunized with M. tuberculosis cord factor was highly reactive against M. tuberculosis cord factor, but less reactive against M. avium cord factor. In contrast, the serum from rabbits immunized with M. avium cord factor was highly reactive against M. avium cord factor but less reactive against M. tuberculosis cord factor. Moreover, the serum from rabbits immunized with M. tuberculosis cord factor reacted against mycolic acid methyl esters, especially methoxy mycolic acid methyl ester. On the other hand, the serum from rabbits immunized with M. tuberculosis cord factor was less reactive against trehalose-6-monomycolate and not reactive against sulfolipid (2,3,6,6'-tetraacyl trehalose 2'-sulfate). From these results, it was concluded that the anti-cord factor IgG antibody, produced experimentally in rabbits, recognized the differences in the cord factor structures, i.e. the hydrophobic moiety rather than the carbohydrate moiety. It was also noted that the serum from rabbits immunized with M. tuberculosis cord factor was highly reactive against methoxy mycolic acid as an epitope. This paper is the first to describe how the anti-cord factor IgG antibody can recognize the mycolic acid subclasses, which differ according to the species of mycobacteria.

A mutant of Mycobacterium smegmatis defective in the biosynthesis of mycolic acids accumulates meromycolates

Mycolic acids are a major constituent of the mycobacterial cell wall, and they form an effective permeability barrier to protect mycobacteria from antimicrobial agents. Although the chemical structures of mycolic acids are well established, little is known on their biosynthesis. We have isolated a mycolate-deficient mutant strain of Mycobacterium smegmatis mc2-155 by chemical mutagenesis followed by screening for increased sensitivity to novobiocin. This mutant also was hypersensitive to other hydrophobic compounds such as crystal violet, rifampicin, and erythromycin. Entry of hydrophobic probes into mutant cells occurred much more rapidly than that into the wild-type cells. HPLC and TLC analysis of fatty acid composition after saponification showed that the mutant failed to synthesize full-length mycolic acids. Instead, it accumulated a series of long-chain fatty acids, which were not detected in the wild-type strain. Analysis by 1H NMR, electrospray and electron impact mass spectroscopy, and permanganate cleavage of double bonds showed that these compounds corresponded to the incomplete meromycolate chain of mycolic acids, except for the presence of a beta-hydroxyl group. This direct identification of meromycolates as precursors of mycolic acids provides a strong support for the previously proposed pathway for mycolic acid biosynthesis involving the separate synthesis of meromycolate chain and the alpha-branch of mycolic acids, followed by the joining of these two branches.

Cell envelope composition and organisation in the genus Rhodococcus

A knowledge of the organisation of the rhodococcal cell envelope is of fundamental importance if the environmental and biotechnological significance of these bacteria are to be understood and successfully exploited. The genus Rhodococcus belongs to a distinctive suprageneric taxon, the mycolata, which includes among others the genera Corynebacterium, Mycobacterium and Nocardia. Members of this taxon exhibit an unusual complexity in their cell envelope composition and organisation compared to other Gram-positive bacteria. Models that describe the architecture of the mycobacterial cell envelope are extrapolated here to provide a model of the rhodococcal cell envelope. The rhodococcal cell envelope is dominated by the presence of an arabinogalactan cell wall polysaccharide and large 2-alkyl 3-hydroxy branched-chain fatty acids, the mycolic acids, which are covalently assembled into a peptidoglycan-arabinogalactan-mycolic acid matrix. This review further emphasises that the mycolic acids in this complex form the basis of an outer lipid permeability barrier. The localisation and roles of other cell envelope components, notably complex free lipids, lipoglycans, proteins and lipoproteins are also considered.

Novel rhodococci and other mycolate actinomycetes from the deep sea

A large number of mycolate actinomycetes have been recovered from deep-sea sediments in the NW Pacific Ocean using selective isolation methods. The isolates were putatively assigned to the genus Rhodococcus on the basis of colony characteristics and mycolic acid profiles. The diversity among these isolates and their relationship to type strains of Rhodococcus and other mycolate taxa were assessed by Curie point pyrolysis mass spectrometry (PyMS). Three major (A, C, D) and two minor (B, E) groups were defined by PyMS. Cluster A was a large group of isolates recovered from sediment in the Izu Bonin Trench (2679 m); Cluster C comprised isolates from both the Izu Bonin Trench (6390 and 6499 m) and from the Japan Trench (4418, 6048 and 6455 m). These Cluster C isolates showed close similarity to Dietzia maris and this was subsequently confirmed using molecular methods. Cluster D contained isolates recovered from a sediment taken from a depth of 1168 m in Sagami Bay and were identified as members of the terrestrial species Rhodococcus luteus. Clusters B and E had close affinities with members of the genera Gordonia and Mycobacterium. The presence of Thermoactinomyces in certain of the deep-sea sediments studied was indicative of the movement of terrestrial material into the ocean depths. 16S ribosomal RNA gene sequence analyses produced excellent definition of most genera of the mycolata, and indicated that the among the deep sea isolates (1) were novel species of Corynebacterium, Gordonia and Mycobacterium, and (2) a Sea of Japan isolate the phylogenetic depth of which suggests the possibility of a new genus. Polyphasic taxonomic analysis revealed considerable diversity among the deep sea rhodococci and evidence for recently diverged species or DNA groups.

[Characterization of fatty acids and mycolic acid degradation products in mycobacterial species of major incidence in Argentina]

The human immunodeficiency virus (HIV) epidemic has altered the epidemiological profile of tuberculosis in both industrialized and developing countries. Serious diseases caused by mycobacteria other that M. tuberculosis, mostly belonging to the M. avium-intracellulare complex (MAC), have become very common in association with severe immunosuppression. The increase in mycobacterial disease complexity has stimulated the development of more rapid and efficient methods of diagnosis. In the present study we characterized the cellular fatty acids and the mycolic acid cleavage product from most frequent mycobacteria species in Argentina using gas chromatography in order to develop a rapid technique for their identification. Fatty acids and mycolic acids extracted from saponified mycobacterial cells were examined as methyl esters by capillary has chromatography. The major constituent fatty acids in all species, with the exception of M. smegmatis, were octadecenoic (18:1) and hexadecanoic (16:1) acids. The fatty acids and mycolic acid cleavage product profiles from the studied species were quantitatively but not qualitatively different. Tuberculostearic acid was found in all species. Significantly different amounts of some fatty acids (p < 0.01) were observed among clinical isolates of M. tuberculosis, M. bovis and MAC. Traces of 2-eicosanol were detected in the M. tuberculosis H37Rv strain. Although a limited number of strains and species were tested, preliminary results indicate that this method could be used to characterize mycobacterial cultures.

Thermospray mass spectral analyses of corynomycolic acids and their derivatives

Thermospray mass spectral (TSP-MS) analyses were carried out on methyl corynomycolates, their 3-O-acetyl and 3-O-benzoyl derivatives, and on corynomycolic acids and their 3-O-acetyl derivatives, using an ion generating solvent system consisting of water/isopropanol (99:1, v/v) containing 0.1 M ammonium acetate. Methyl corynomycolates generated three groups of peaks corresponding to adducts M-18 + H, M + H and M + NH4, while two groups of peaks representing adducts M-60 + H and M + H + NH4 were seen in the spectra of 3-O-acetyl methyl corynomycolates. The 3-O-benzoyl methyl corynomycolates gave a series of peaks representing the adducts M-122 + H, M + 2H and M + H + NH4. In the spectra of 3-O-acetyl corynomycolic acids, a series of peaks which represented M-60 + H and M + NH4 was observed, and in turn, mass spectra of corynomycolic acids revealed peaks that represented the adducts M-18 + H and M + NH4. Therefore, methyl corynomycolates, 3-O-acyl derivatives of methyl corynomycolates,. 3-O-acetylated derivatives of corynomycolic acids and the underivatized corynomycolic acids all exhibited the formation of an adduct of the anhydro compounds. These anhydro forms were generated by a generalized process.

Relationship between induction of macrophage chemotactic factors and formation of granulomas caused by mycoloyl glycolipids from Rhodococcus ruber (Nocardia rubra)

Mycoloyl glycolipids cause granulomas in the lungs, liver, and spleen of mice, but the mechanism is not fully understood. To understand the role of macrophage chemotactic factors (MCFs) in granuloma formation, we prepared various mycoloyl glycolipids with different carbohydrate moieties: trehalose dimycolate (TDM), glucose mycolate (GM), mannose mycolate (MM), and fructose mycolate (FM) from Rhodococcus ruber, and examined the relationship between their MCF induction in peritoneal macrophages and the extent of granuloma formation. The molecular mass of each glycolipid was confirmed by fast-atom-bombardment mass-spectrometry. TDM or GM caused granulomas in the lungs, spleen, and liver of ICR mice, but MM and FM did not. The culture supernatant of peritoneal macrophages stimulated with TDM or GM increased macrophage migration, whereas MM and FM had no chemotactic activity. The activity of interleukin-1 (IL-1) in the supernatant was increased equally by each glycolipid and was therefore not related to chemotaxis. Tumor necrosis factor-alpha (TNF-alpha) and granulocyte-macrophage colony-stimulating factor (GM-CSF) were not detected in the four supernatants. The TDM-induced MCF was heat-stable, trypsin-labile, and undialyzable. Furthermore, we separated two MCF active fractions from the supernatant of TDM-stimulated macrophages by gel filtration. These factors acted on macrophages but not on neutrophils. Our results suggested that macrophages recognize the sugar moieties of mycoloyl glycolipids and may, in response, generate a MCF that may play an important role in the macrophage or monocyte recruitment which is essential prior to granuloma formation.

New Nocardia taxon among isolates of Nocardia brasiliensis associated with invasive disease

Nocardia brasiliensis, the second most frequently isolated aerobic actinomycete in the clinical laboratory, is usually associated with localized cutaneous infections. However, 22% of 238 N. brasiliensis isolates from the United States and 12% of 66 isolates from Queensland, Australia, which had been collected over a 17-year period, were associated with extracutaneous and/or disseminated diseases. Of the 62 invasive isolates, 37 (60%) were susceptible to ciprofloxacin and/or were susceptible to clarithromycin and resistant to minocycline, compared with only 6 (3%) of 242 localized cutaneous isolates. The 43 isolates with this susceptibility pattern appeared to define a new taxon. They were similar to Nocardia asteroides complex isolates clinically in proportions from persons with pulmonary (70%), central nervous system (23%), and/or disseminated diseases (37%) in the setting of corticosteroids (74%) or AIDS (14%). This putative new taxon differed from N. brasiliensis in the hydrolysis of adenine (92 versus 4%), beta-lactamase patterns on isoelectric focusing, and the presence of two early mycolic acid-ester peaks by high-performance liquid chromatography. Restriction analysis of a 439-bp fragment of the 65-kDa heat shock protein gene revealed that N. brasiliensis and the new taxon had different restriction patterns with 8 of the 11 enzymes tested. Screening of invasive isolates of N. brasiliensis for susceptibility to ciprofloxacin will identify most isolates of the new taxon, which likely represents a new Nocardia species.

Curvilinear-gradient high-performance liquid chromatography for identification of mycobacteria

Over a 1-year period, 502 mycobacterial cultures submitted to the Microbial Diseases Laboratory were identified by high-performance liquid chromatography (HPLC) in parallel with standard biochemical methods. Identification by HPLC using a curvilinear gradient was achieved by comparing the chromatograms of the unknown cultures to chromatograms for known reference strains, together with calculation of peak height or peak area ratios, as necessary. The overall agreement between HPLC and biochemical identification was 97.2%. In addition, 7 of 12 cultures of Mycobacterium bovis were identified by HPLC as the BCG strain. Of 111 cultures biochemically identified as members of the M. avium complex (MAC), 108 were confirmed as MAC by DNA probe and 106 were confirmed by HPLC. Of the latter 106, 58 probe-positive strains were identified as M. avium, 38 were identified as M. intracellulare, and 10 were identified as Mycobacterium sp. strain "X" by HPLC. Of the remaining five nonchromogenic cultures, four had MAC-like chromatograms that did not match any in our library sufficiently to permit definitive identification. Of the latter four, two were confirmed as MAC strains by DNA probe and two were not. The last of the cultures biochemically identified as MAC (1 of 111) was a mixture of MAC and non-MAC strains. Overall, only 2 of 502 cultures yielded results by HPLC that differed from those obtained by standard biochemical methods. The HPLC result was confirmed in both cases by an independent national reference laboratory. In the 12 instances in which HPLC did not provide identification, the chromatograms were either uninterpretable or did not match available reference chromatograms. These findings show that the identification obtained by HPLC concurs well with that obtained by both the standard biochemical methods and the DNA probes. Thus, identification by HPLC provides mycobacteriology laboratories with a reproducible and specific method for accurate and timely identification of most medically important mycobacteria.

Chromatographic and mass spectrometric characterization of 3-O-benzoyl methyl ester derivatives of mycolic acid fractions from Corynebacterium pseudotuberculosis, C. diphtheriae and Rhodococcus rhodochrous

A benzoyl group was attached to the 3-hydroxyl group of the methyl ester derivative of corynomycolic acid fraction isolated from Corynebacterium pseudotuberculosis. The infrared spectrum of the 3-O-benzoylated compound displayed a series of characteristic absorptions found at 1110, 1267 and 1603 cm-1 that confirmed the presence of a monosubstituted phenyl grouping. The 1H-NMR spectrum showed peaks representing protons of the aromatic ring at 7.4 ppm and 8.0 ppm. The UV spectrum revealed two absorption maxima: at 190 and 228 nm. The mass spectrum of the 3-O-benzoylated material exhibited the following peaks: (1) a prominent peak at m/z 105 of the benzoyl group that constituted the base peak; (2) peaks of methyl esters representing the alpha-hydrocarbon side chain plus carbon atoms C1 and C2 of the mycolic acid molecule; and (3) peaks of molecular ion minus benzoic acid and/or molecular ion minus benzoxyl group. When subjected to liquid chromatography (LC) on an octadecylsilane-silica gel column the 3-O-benzoylated methyl ester derivatives of the corynomycolic acid fraction were separated into their constituent homologous fractions corresponding to underivatized corynomycolic acids with the chain length C30, C32 and C34. Reversed phase HPLC of saturated and monounsaturated species of 3-O-benzoylated derivatives of the mycolic acid fraction from C. diphtheriae and Rhodococcus rhodochrous led to the separation of the corresponding homologous fractions. Mass spectrometry by electron impact mode identified both series of the homologous materials differing in mass by 28 units.

Distribution of a novel mycolic acid in species of the genus Mycobacterium

We found that Mycobacterium porcinum ATCC 33776T (T = type strain) contains a new kind of mycolic acid with a methoxy group at the omega-1 position. This mycolic acid was identified by comparing it with the previously described methoxymycolic acids. The patterns of mycolic acid methyl esters from 418 strains belonging to 44 species of mycobacteria were studied by using thin-layer chromatography. In addition to M. procinum ATCC 33776T, representative strains of M. porcinum, Mycobacterium fortuitum, "Mycobacterium peregrinum," Mycobacterium senegalense, and a recently isolated Mycobacterium sp. contained appreciable amounts of the newly described mycolic acid.

High-performance liquid chromatography patterns of mycolic acids as criteria for identification of Mycobacterium chelonae, Mycobacterium fortuitum, and Mycobacterium smegmatis

Rapidly growing mycobacteria of clinical significance were identified by mycolic acids detected with high-performance liquid chromatography. Mycolic acids from whole cells were extracted, derivatized, and detected by a modified high-performance liquid chromatography procedure in less than 3 h. Use of an internal standard allowed differentiation of Mycobacterium chelonae and Mycobacterium fortuitum by comparison of relative retention times. Peak height ratios were used for subidentification of M. chelonae strains; however, M. fortuitum and Mycobacterium smegmatis could not be separated by this system.

Cell-free synthesis of mycolic acids in Mycobacterium aurum: radioactivity distribution in newly synthesized acids and presence of cell wall in the system

Distribution of radiolabelling in different parts of the newly synthesized mycolic acids, by a cell-free system from Mycobacterium aurum previously described, is examined, [1-14C]acetate being the precursor. By oxidation cleavage of mycolic acids and examination of the fragments, it was shown that acetate was not uniformly incorporated into the molecule: the methyl terminal part was not labelled, while the central fragments--between unsaturations or between oxygenated functions (oxo or ester) and unsaturations--presented the major part of radioactivity, suggesting the elongation of a preformed compound that the cell-free extract was unable to synthesize. Moreover, the side-chain R2-CH2-COOH was only weakly labelled compared to the central fragments. Since non-hydroxylated fatty acids were not synthesized by the system, it is suggested that de novo C18 fatty acids may be elongated with C2 units by the cell-free extract into C22 fatty derivative, only a low level of labelling being recorded (two C2 units for all the molecule). A scheme is proposed to summarize the main results. Identification of meso-DAP which is a characteristic amino-acid of the peptidoglycan in Actinomycetes and analysis of the profiles of total fatty esters, demonstrated that the cell-free extract is partly constituted by fragments of the cell wall as has already been noticed by examination of micrographs of the extract.

Mycolic acid synthesis by Mycobacterium aurum cell-free extracts

The first cell-free system capable of synthesizing whole mycolic acids: (R1CH(OH)CH(R2)COOH, with 60 to 90 carbon atoms) from [1-14C]acetate is described and preliminary investigations into some of its requirements and properties are reported. Biosynthetic activity for mycolic acids occurred in an insoluble fraction (40 000 X g pellet) from disrupted cells of Mycobacterium aurum (ATCC 23366-type strain); it produced mycolic acids, but a very small amount of non-hydroxylated fatty acids. The predominant product was unsaturated mycolic acid (type I), while oxo- (type IV) and dicarboxy- (type VI) mycolic acids were synthesized to a lesser extent. When [1-14C]palmitic acid was used as a marker, no labelled mycolic acid was detected. The reaction required a divalent cation (Mg2+ or Mn2+), KHCO3 and O2. Neither CoA, NADH, NADPH nor ATP were necessary, but CoA rather increased the synthesis of non-hydroxylated fatty acids. Glucose or trehalose were not required. Avidin inhibited the biosynthesis of the three types of mycolic acid indicating the presence of a biotin-requiring enzyme in the reaction sequence and therefore a carboxylation step, but citrate had no allosteric effect. Iodoacetamide inhibited the system. These first data are in favor of a complex multienzyme system.

Mycolyl glycolipids stimulate macrophages to release a chemotactic factor

We have previously reported that mycolyl glycolipids from Nocardia rubra such as glucose or trehalose mycolates induced granuloma formation in mice. The structure of the carbohydrate moiety of the mycolyl glycolipids influenced the granuloma forming activity profoundly. Here, we have examined the macrophage-chemotactic activity in the culture supernatants stimulated with various glycolipids differing in carbohydrate moiety (trehalose 6,6'-dimycolate, or TDM; glucose monomycolate, or GM; mannose monomycolate, or MM; and fructose monomycolate, or FM). A distinctive chemotactic activity was detected with TDM or GM, but, little or none with MM or FM.

Granuloma-forming activity and antitumor activity of newly isolated mycoloyl glycolipid from Rhodococcus terrae 70012 (Rt. GM-2)

A newly isolated mycoloyl glycolipid (Rt. GM-2) from Rhodococcus terrae 70012 was identified and the granulomagenic and antitumor activities were studied as compared with trehalose-6,6'-dimycolate (cord factor) also from R. terrae (Rt. TDM). The alkaline hydrolysis products of Rt. GM-2 contained trehalose, methyl-alpha-mycolate and a less-polar ester than the usual methyl-alpha-mycolate, possibly beta-keto mycolate (1:1:1, by mol. ratios). On the other hand, analysis of alditol acetate obtained after the mild permethylation, NaBH4 reduction, and acetylation showed the occurrence of 2,3,4-tri-O-methyl-6-O-acetylglucitol. Therefore, the original glycolipid (Rt. GM-2) was identified tentatively as 6-O-alpha-mycoloyl 6'-O-beta-ketomycoloyl trehalose. Intravenous injection of Rt. GM-2 in the form of water-in-oil-in-water emulsion caused prominent granulomas in lungs and spleen of ICR and BALB/c mice. The granulomagenic effects were as strong as those caused by Rt. TDM. The lung and spleen weights reached peaks one week after an injection of Rt. GM-2 in mice and then gradually decreased. Multiple intravenous injections of Rt. GM-2 and Rt. TDM showed antitumor activity against subcutaneously implanted Sarcoma-180, and caused prominent granulomatous changes and growth suppression of mice.

Structure determination of mycolic acids by using charge remote fragmentation

The collision-induced remote site fragmentation process of closed-shell ions, such as carboxylate anions, is a very potent analytical tool for the structural determination of fatty acids. This leads to an easy location of branch points, double bonds, cyclopropane rings and other functional groups. Although corynomycolic acid mixtures from Corynebacterium diphtheriae can be directly analyzed by negative-ion fast atom bombardment combined with collisionally activated decomposition spectra, mycolic acid mixtures from mycobacteria need a preliminary chemical cleavage. They are oxidized to beta-keto esters and then submitted to a retro-Claisen reaction. The resulting fatty acids were then converted into pentafluorobenzyl derivatives and introduced directly into a high pressure ion source working in the negative ion mode. The resulting gas phase carboxylate anions are activated to decompose by collision with helium atoms. When applied to M3-mycolic acids from Mycobacterium fallax, this method allows for the characterization of a new tri-unsaturated mycolic acid, which has the middle and the remote double bonds separated by two methylene groups.

Mycolic acid metabolic filiation and location in Mycobacterium aurum and Mycobacterium phlei

Synchronous cultures of Mycobacterium aurum were used to prove a close relationship between cellular division and active synthesis of mycolic acids (characteristic long-chain 3-hydroxyacids, branched at position 2), confirming previous proposals. Mycolic acid biosynthesis was studied in two species (Mycobacterium phlei and M. aurum) each producing three types of mycolic acids: di-unsatured mycolates, oxomycolates and wax-ester mycolates (ester of dicarboxymycolic acid and 2-icosanol or 2-octadecanol). It was shown that unsaturated mycolates and oxomycolic acids were not directly related, whereas a metabolic filiation was confirmed between oxomycolate and wax ester mycolate: the latter derived from the former by a Baeyer-Villiger oxidation step, as has been proposed on the basis of structural considerations. By observing the labelling of the different mycolate pools in the cell, i.e. the organic-solvent-extractable fraction (essentially containing esters of trehalose and of glycerol) and the cell residue (assumed to be the cell-wall polymers), it was clear that oxomycolates and unsaturated mycolates appeared first in the extractable lipids, then in the wall-linked mycolates while wax-ester mycolates appeared first as wall-linked derivatives. Thus, it is proposed that mycolates could follow separate routes involving differently located enzymes to reach their complex forms either in extractable lipids or in the wall-linked arabino-galactan.

Mycolic acids of Mycobacterium aurum. Structure and biogenetic implications

Mycobacterium aurum (type strain) was analyzed for its mycolate content. Three types of mycolates were identified: di-unsaturated, oxo and dicarboxy mycolates, each type being constituted by two subtypes. The acid released by pyrolysis was identified as docosanoic acid. By use of mass spectrometry and oxidation techniques, the structures of these six subtypes of mycolates were elucidated. They contain Z and E double bonds, the latter having an adjacent methyl branch. No cyclopropane ring was observed. All the methyl branches occurring in these mycolates derived from methionine, the methyl-branched chiral center adjacent to the double bond having an R configuration. The structures of the major di-unsaturated mycolates suggest that they cannot be the precursors of oxo mycolates. The amount of long-chain secondary alcohol (2-octadecanol) obtained from the whole cells was found to be much greater than that expected from hydrolysis of wax ester mycolate (ester of 2-octadecanol and dicarboxy-mycolic acid). Further investigations showed that 2-octadecanol was also present in triacylglycerols, esterifying the omega-carboxyl group of long-chain fatty acids structurally related to dicarboxy-mycolates.

A thin-layer chromatographic method for separating methyl esters of mycobacterial mycolic acids

A two-dimensional thin-layer chromatographic method was developed which allowed separation of the different mycobacterial mycolic acids as methyl esters. Dichloromethane (once) and petroleum ether:acetone (95:5, v/v twice or three times) were used as solvents. Alkaline saponification of freeze-dried cells followed by methylation of the mycolic acids using iodomethane gave satisfactory results, whereas methylation using boron trichloride-methanol complex or trans-esterification through direct acid methanolysis was found to degrade epoxy-mycolates. The chromatographic method developed here is rapid and informative, and should prove valuable in routine mycobacterial differentiation.

Fatty acid composition and mycolic acid pattern of some chromogenic mycobacteria

Twenty-nine strains of chromogenic mycobacteria belonging to the species Mycobacterium aurum (5 strains), M. duvalii (2), M. flavescens (1), M. gordonae (6), M. kansasii (3), M. obuense (1), M. parafortuitum (3), M. phlei (2), M. rhodesiae (1), M. vaccae (2) and Mycobacterium spp. (3) were studied for fatty acid composition and mycolic acid patterns by gas-liquid chromatography and thin-layer chromatography respectively. Fatty acids found ranged from those with 12-24 carbon atoms and were saturated and monounsaturated straight chain fatty acids, along with 10-methyl branched of 16, 17 and 18 (tuberculostearic acid) carbon atoms. Moreover, 2-methyl tetradecanoic acid was found in M. gordonae, M. kansasii and Mycobacterium spp. (2 strains), and 2,4-dimethyl tetradecanoic acid in M. kansasii and Mycobacterium spp. (2 strains). Nonadecenoic acid was found only in M. flavescens and tuberculostearic acid was not detected in M. gordonae. Three patterns of mycolic acids were obtained: the first, found in M. aurum, M. flavescens, M. phlei, M. rhodesiae and Mycobacterium spp. (1 strain), was characterized by the presence of several spots assigned to alpha-mycolates, keto-mycolates and wax-ester mycolates (omega-carboxy-mycolates and 2-eicosanol and related alcohols); the second, found in M. duvalii, M. obuense, M. parafortuitum and M. vaccae was similar to the first, but it contained an additional spot of alpha'-mycolates; the third pattern, found in M. gordonae, M. kansasii and Mycobacterium spp. (2 strains) contained three spots considered to be alpha-mycolates, methoxy-mycolates and keto-mycolates. The results obtained confirm previously reported data on the fatty and mycolic acid composition of the species studied.

In vitro synthesis of mycolic acids by the fluffy layer fraction of Bacterionema matruchotii

Biosynthetic activity for mycolic acid occurred in the fluffy layer fraction but not in the 5000g supernatant of Bacterionema matruchotii. With [1-14C]palmitic acid as precursor for the in vitro system, the predominant product was identified as C32:0 mycolic acid by radio-gas-liquid chromatographic (radio-GLC) and gas chromatographic/mass spectroscopic analyses; if [1-14C]stearic acid was used, two major radioactive peaks appeared on GLC: one corresponding to the peak of (C34:0 + C34:1) mycolic acids and the other to (C36:0 + C36:1) mycolic acids. By pyrolysis/radio-GLC analysis, C32:0 mycolic acid synthesized by [1-14C]palmitic acid was pyrolyzed at 300 degrees C to form palmitaldehyde (the mero moiety) and methyl palmitate (the branch moiety). The pH optimum for the incorporation of [1-14C]palmitate into bacterionema mycolic acids was 6.4 and the reaction required a divalent cation. The in vitro system utilized myristic, palmitic, stearic and oleic acids (probably via their activated forms) well as precursors, among which myristic and palmitic acids were more effective than the rest. Avidin showed no effect on the biosynthesis of mycolic acid from 14C-palmitate whereas cerulenin, a specific inhibitor of beta-ketoacyl synthetase in de novo fatty acid synthesis, inhibited the reaction at a relatively higher concentration. Thin-layer chromatographic analysis of lipids extracted from the reacting mixture without alkaline hydrolysis showed that both exogenous [1-14C]fatty acid and synthesized mycolic acids were bound to an unknown compound by an alkali-labile linkage and this association seemed to occur prior to the condensation of two molecules of fatty acid.

Separation and analysis of novel polyunsaturated mycolic acids from a psychrophilic, acid-fast bacterium, Gordona aurantiaca

More than 30 molecular species of highly unsaturated mycolic acids, ranging from C60 to C78 and possessing between two and seven double bonds, have been obtained from a new genus of acid-fast bacteria, Gordona aurantiaca. They were fully separated and identified as their trimethylsilyl ether derivatives by a combination of silica gel thin-layer chromatography (TLC), argentation thin-layer chromatography and gas chromatography/mass spectrometry (GC/MS). On silica gel thin-layer chromatography two adjacent spots, corresponding to mycolic acids possessing different structures of straight-chain and alpha-alkyl branch, were detected. The lower spot was separated by argentation TLC into four subclasses: monoenoic (including a small amount of saturated), dienoic, trienoic and tetraenoic mycolic acids ranging from C62 to C74 and possessing a C16:0, C18:0 or C20:0 alkyl branch at the C-2 position. The upper spot was separated by argentation TLC into five subclasses: dienoic (including a small amount of monoenoic), trienoic, tetraenoic, pentaenoic and hexaenoic (heptaenoic) acids ranging from C64 to C78 and possessing a C18:1 or C20:1 alkyl branch at the C-2 position. These types of mycolic acid structure differ from those reported previously in Mycobacteria and Nocardia, in the numbers of both carbon atoms and double-bonds and the intermediate length of the alpha-alkyl branch. The characteristic polyenoic structure of the straight-chain alkyl unit was also confirmed by GC/MS analysis of the meromycolaldehydes obtained after pyrolysis of the methyl mycolates. The major aldehydes obtained from the lower-spot mycolic acids were C44, C46, C48, C50 and C52, while those from the upper-spot mycolic acids were C48, C50, C52, C54 and C56, centering at C54. These aldehydes were also shown to possess between two and four double bonds in the lower-spot and between two and seven double bonds in the higher-spot mycolic acids, respectively. The physiological role of such highly polyunsaturated mycolic acids in psychrophilic acid-fast bacteria is discussed.

Isolation and identification of mycolic acids in Mycobacterium leprae and Mycobacterium lepraemurium

Mycolic acids with a characteristic structure were isolated by high performance-liquid-chromatography (HPLC) and mass-spectrometry from a foot pad of a nude mouse inoculated with Mycobacterium leprae. Mycolic acids with the same structure were also obtained from mycobacteria collected from the liver of an armadillo with experimental leprosy. Mycolic acids were isolated from Mycobacterium lepraemurium grown both in vivo and in vitro and these mycolic acids had different structures from those of M. leprae. Mycolic acid structures have great taxonomical significance. The methods used for isolating and analyzing mycolic acids appear applicable for the rapid identification of M. leprae in samples containing at least 10(9)-10(10) mycobacterial cells. Using our method, mycolic acids with the same structure were found in mycobacteria from armadillos experimentally infected with M. leprae and from armadillos with naturally acquired leprosy-like disease. It is likely, therefore, that the pathogenic mycobacteria of the naturally acquired disease are the same as, or at least closely related to, M. leprae. The present work suggests that M. leprae has a special position in mycobacterial phylogeny.

Identification of Mycobacterium leprae: use of wall-bound mycolic acids

A simple method for extraction and analysis of wall-bound mycolic acids from small samples of mycobacteria is described. Separation of mycolic acid classes according to their functional groups by thin-layer chromatography showed a difference between Mycobacterium leprae and a number of strains of acid-fast bacilli cultured from leprosy biopsies in vitro. This technique is proposed as a convenient preliminary test in the identification of possible cultures of M. leprae.

Mycolic acids. A reinvestigation

Mycolic acids derived from the cell walls of Mycobacterium bovis BCG, Mycobacterium bovis Bovinus I, Mycobacterium smegmatis, and Mycobacterium tuberculosis H37Rv have been fractionated as their p-bromophenacyl esters by a two-step high performance liquid chromatographic procedure: 1) adsorption chromatography on 10-micrometer particle size silica gel, and 2) reverse phase partition chromatography on a 10-micrometer particle size support containing a C18 bonded phase. This procedure has resulted in the isolation of approximately 24 mycolic acids from each bacterium (very likely homologs of various mycolate types) instead of the two to four that have previously been described. The implication of these results on the previously determined structures of these fatty acids is discussed.

Characterization of the purified components of a new homologous series of alpha-mycolic acids from Mycobacterium tuberculosis H37Ra

Homologous series of alpha-mycolic acids from Mycobacterium tuberculosis H37Ra were separated according to size as their p-bromophenacyl ester by bonded C18 reverse-phase, high performance liquid chromatography. Mass spectrometry of the prominent components separated by high performance liquid chromatography gave relatively simple spectra and showed a series of components differing by 28 atomic mass units. A total of different structures were identified. The structures were established as follow: (formula see text) where a = 17, 18, 19; b = 10; c = 15, 17, 19, 21; and d = 21, 23. The C76 and C78 acids contained some C24 alpha-branch acid (d - 21), whereas the C80 and C82 acids contained some a = 19 acids. Several new homologous series were revealed.

Structure of mycobacterial bis-cyclopropane mycolates by mass spectrometry

Methyl mycolate from a human strain (Brévannes) of Mycobacterium tuberculosis has been converted to the corresponding methyl neromycolate, the monketo-meromycolate, and the meromycolic pyrrolidide. The fragmentation pattern of each of these materials has been determined, and with information from a synthetic meromycolate serving as a basis of comparison, has been analyzed to obtain reliable structural assignments.