Gas chromatographic and mass spectrometric analysis of molecular species of corynomycolic acids from Corynebacterium ulcerans

Corynebacterium atrinae sp. nov., isolated from the gastrointestinal tract of a pen shell, Atrina pectinata

A novel Gram-stain-positive, non-motile, facultatively anaerobic and rod-shaped bacterium, strain PSPT56T, was isolated from the gastrointestinal tract of a pen shell (Atrina pectinata). Optimal growth of strain PSPT56T was ascertained to occur at 30 °C, pH 8.0 and in the presence of 1–2 % (w/v) NaCl. The strain was catalase-positive and oxidase-negative. The major cellular fatty acids were C18 : 1ω9c, C16 : 0, C17 : 1ω8c and C17 : 0. Tuberculostearic acid was not present. The major cell-wall sugars were ribose, galactose, glucose and arabinose. Peptidoglycan amino acids were meso-diaminopimelic acid, alanine and glutamic acid. The predominant isoprenoid quinone was MK-8(H2). Strain PSPT56T contained phosphatidylglycerol, diphosphatidylglycerol, an unidentified phospholipid, two unidentified lipids and two unidentified amino-lipids. Mycolic acids were detected as constitutive components of the cell wall. A phylogenetic analysis based on 16S rRNA gene sequence similarity showed that strain PSPT56T was most closely related to Corynebacterium testudinoris M935/96/4T and Corynebacterium felinum M714/95/5T with 98.69 % and 97.01 % similarity, respectively. DNA–DNA hybridization experiments indicated less than 29.9 % relatedness to the phylogenetically closest species. The G+C content of genomic DNA was 67.6 mol%. The phenotypic, phylogenetic and genotypic analyses indicated that strain PSPT56T represents a novel species within the genus Corynebacterium , for which the name Corynebacterium atrinae is proposed. The type strain is PSPT56T ( = KACC 17525T = JCM 19266T).

Current knowledge on mycolic acids in Corynebacterium glutamicum and their relevance for biotechnological processes

Corynebacterium glutamicum is the world's largest producer of glutamate and lysine. Industrial glutamate overproduction is induced by empirical processes, such as biotin limitation, supplementation with specific surfactants or addition of sublethal concentration of certain antibiotics to the culture media. Although Gram-positive bacteria, C. glutamicum and related bacterial species and genera contain, in addition to the plasma membrane, an outer permeability membrane similar to that of Gram-negative microorganisms. As the amino acids have to cross both membranes, their integrity, composition and fluidity influence the export process. While the precise mechanism of the export of the amino acids by C. glutamicum is not fully understood, the excretion of amino acids through the inner membrane involved at least a major export system mechanosensitive channel MscS family (MscCG) encoded by NCgl1221. As the various industrial treatments have been shown to affect the lipid content of the bacterial cell, it is strongly believed that defects in the hallmark of the outer membrane, 2-alkyl, 3-hydroxylated long-chain fatty acids (mycolic acids), could be key factors in the glutamate overproduction. This review aims at giving an overview of the current knowledge on mycolic acids structure, biosynthesis and transfer in C. glutamicum and their relevance for amino acid biotechnological production.

Corynebacterium jeikeium jk0268 constitutes for the 40 amino acid long PorACj, which forms a homooligomeric and anion-selective cell wall channel

Corynebacterium jeikeium, a resident of human skin, is often associated with multidrug resistant nosocomial infections in immunodepressed patients. C. jeikeium K411 belongs to mycolic acid-containing actinomycetes, the mycolata and contains a channel-forming protein as judged from reconstitution experiments with artificial lipid bilayer experiments. The channel-forming protein was present in detergent treated cell walls and in extracts of whole cells using organic solvents. A gene coding for a 40 amino acid long polypeptide possibly responsible for the pore-forming activity was identified in the known genome of C. jeikeium by its similar chromosomal localization to known porH and porA genes of other Corynebacterium strains. The gene jk0268 was expressed in a porin deficient Corynebacterium glutamicum strain. For purification temporarily histidine-tailed or with a GST-tag at the N-terminus, the homogeneous protein caused channel-forming activity with an average conductance of 1.25 nS in 1M KCl identical to the channels formed by the detergent extracts. Zero-current membrane potential measurements of the voltage dependent channel implied selectivity for anions. This preference is according to single-channel analysis caused by some excess of cationic charges located in the channel lumen formed by oligomeric alpha-helical wheels. The channel has a suggested diameter of 1.4 nm as judged from the permeability of different sized hydrated anions using the Renkin correction factor. Surprisingly, the genome of C. jeikeium contained only one gene coding for a cell wall channel of the PorA/PorH type found in other Corynebacterium species. The possible evolutionary relationship between the heterooligomeric channels formed by certain Corynebacterium strains and the homooligomeric pore of C. jeikeium is discussed.

Identification and characterization of the channel-forming protein in the cell wall of Corynebacterium amycolatum

The mycolic-acid layer of certain gram-positive bacteria, the mycolata, represents an additional permeability barrier for the permeation of small water-soluble solutes. Consequently, it was shown in recent years that the mycolic acid layer of individual bacteria of the group mycolata contains pores, called porins, for the passage of hydrophilic solutes. Corynebacterium amycolatum, a pathogenic Corynebacterium species, belongs to the Corynebacteriaceae family but it lacks corynomycolic acids in its cell wall. Despite the absence of corynomycolic acids the cell wall of C. amycolatum contains a cation-selective cell wall channel, which may be responsible for the limited permeability of the cell wall of C. amycolatum. Based on partial sequencing of the protein responsible for channel formation derived from C. amycolatum ATCC 49368 we were able to identify the gene coram0001_1986 within the known genome sequence of C. amycolatum SK46 that codes for the cell wall channel. The corresponding gene of C. amycolatum ATCC 49368 was cloned into the plasmid pXHis for its expression in Corynebacterium glutamicum ∆porA∆porH. Biophysical characterization of the purified protein (PorAcoram) suggested that coram0001_1986 is indeed the gene coding for the pore-forming protein PorAcoram in C. amycolatum ATCC 49368. The protein belongs to the DUF (Domains of Unknown Function) 3068 superfamily of proteins, mainly found in bacteria from the family Corynebacteriaceae. The nearest relative to PorAcoram within this family is an ORF which codes for PorAcres, which was also recognized in reconstitution experiments as a channel-forming protein in Corynebacterium resistens.

Knoellia locipacati sp. nov., from soil of the Demilitarized Zone in South Korea

A gram-positive, aerobic, rod- or coccus-shaped, non-motile bacterium, designated DMZ1(T), was isolated from soil of the Demilitarized Zone, South Korea. Strain DMZ1(T) grew optimally at 30 °C, at pH 7-8 and with 1 % (w/v) NaCl. The isolate showed high 16S rRNA gene sequence similarity with Knoellia aerolata 5317S-21(T) (98.2 %). The cell-wall sugars were glucose and ribose. The peptidoglycan amino acids were meso-diaminopimelic acid, glutamic acid and glycine. The major cellular fatty acids were iso-C(16 : 0), iso-C(15 : 0) and iso-C(14 : 0). The polar lipids were phosphatidylethanolamine, phosphatidylinositol, diphosphatidylglycerol, phosphatidylglycerol and five unknown phospholipids. The isolate did not contain mycolic acids. The DNA G+C content was 72.6 mol%. The isolate showed <28 % DNA-DNA relatedness with members of the genus Knoellia. Phylogenetic, phenotypic and genotypic analysis indicated that strain DMZ1(T) represents a novel species of the genus Knoellia, for which the name Knoellia locipacati sp. nov. is proposed. The type strain is DMZ1(T) ( = KACC 15114(T)  = JCM 17313(T)).

Corynebacterium nuruki sp. nov., isolated from an alcohol fermentation starter

A novel Gram-positive, strictly aerobic and non-motile bacterial strain, S6-4(T), was isolated from a Korean alcohol fermentation starter. Optimal growth occurred at 37 °C, at pH 8 and in 1 % (w/v) NaCl. The isolate was positive for oxidase and catalase. It assimilated various sugars and acids were produced from several carbohydrates. The major cell-wall sugars were galactose and arabinose. The major fatty acids of strain S6-4(T) were C(16 : 0), C(17 : 1)ω9c, C(18 : 1)ω9c and 10-methyl C(18 : 0) (tuberculostearic acid). The predominant isoprenoid quinone was menaquinone MK-9(H(2)) and peptidoglycan amino acids were meso-diaminopimelic acid, alanine, glycine and glutamic acid. The strain contained mycolic acids. According to phylogenetic analysis based on 16S rRNA gene sequences, strain S6-4(T) was most closely related to Corynebacterium variabile DSM 20132(T) (98.1 % similarity). The genomic DNA G+C content of strain S6-4(T) was 73.6 mol% and DNA-DNA hybridization values with related strains were below 33±4 %. On the basis of phenotypic, genotypic and phylogenetic data, strain S6-4(T) represents a novel species in the genus Corynebacterium, for which the name Corynebacterium nuruki sp. nov. is proposed; the type strain is S6-4(T) ( = KACC 15032(T)  = JCM 17162(T)).

A putative alpha-helical porin from Corynebacterium glutamicum

The cell wall of Corynebacterium glutamicum contains a mycolic acid layer, which is a protective nonpolar barrier similar to the outer membrane of Gram-negative bacteria. The exchange of material across this barrier requires porins. Porin B (PorB) is one of them. Recombinant PorB has been produced in Escherichia coli, purified, crystallized and analyzed by X-ray diffraction, yielding 16 independent molecular structures in four different crystal forms at resolutions up to 1.8 A. All 16 molecules have the same globular core, which consists of 70 residues forming four alpha-helices tied together by a disulfide bridge. The 16 structures vary greatly with respect to the 29 residues in the N- and C-terminal extensions. Since corynebacteria belong to the group of mycolata that includes some prominent human pathogens, the observed structure may be of medical relevance. Due to the clearly established solid structure of the core, the native porin has to be oligomeric, and the reported structure is one of the subunits. An alpha-helical porin in a bacterial outer envelope is surprising because all presently known structures of such porins consist of beta-barrels. Since none of the four crystal packing arrangements was compatible with an oligomeric membrane channel, we constructed a model of such an oligomer that was consistent with all available data of native PorB. The proposed model is based on the required polar interior and nonpolar exterior of the porin, on a recurring crystal packing contact around a 2-fold axis, on the assumption of a simple C(n) symmetry (a symmetric arrangement around an n-fold axis), on the experimentally established electric conductivity and anion selectivity and on the generally observed shape of porin channels.

Corynebacterium diphtheriae: identification and characterization of a channel-forming protein in the cell wall

The cell wall fraction of the gram-positive, nontoxic Corynebacterium diphtheriae strain C8r(-) Tox- (=ATCC 11913) contained a channel-forming protein, as judged from reconstitution experiments with artificial lipid bilayer experiments. The channel-forming protein was present in detergent-treated cell walls and in extracts of whole cells obtained using organic solvents. The protein had an apparent molecular mass of about 66 kDa as determined on Tricine-containing sodium dodecyl sulfate-polyacrylamide gel electrophoresis gels and consisted of subunits having a molecular mass of about 5 kDa. Single-channel experiments with the purified protein suggested that the protein formed channels with a single-channel conductance of 2.25 nS in 1 M KCl. Further single-channel analysis suggested that the cell wall channel is wide and water filled because it has only slight selectivity for cations over anions and its conductance followed the mobility sequence of cations and anions in the aqueous phase. Antibodies raised against PorA, the subunit of the cell wall channel of Corynebacterium glutamicum, detected both monomers and oligomers of the isolated protein, suggesting that there are highly conserved epitopes in the cell wall channels of C. diphtheriae and PorA. Localization of the protein on the cell surface was confirmed by an enzyme-linked immunosorbent assay. The prospective homology of PorA with the cell wall channel of C. diphtheriae was used to identify the cell wall channel gene, cdporA, in the known genome of C. diphtheriae. The gene and its flanking regions were cloned and sequenced. CdporA is a protein that is 43 amino acids long and does not have a leader sequence. cdporA was expressed in a C. glutamicum strain that lacked the major outer membrane channels PorA and PorH. Organic solvent extracts of the transformed cells formed in lipid bilayer membranes the same channels as the purified CdporA protein of C. diphtheriae formed, suggesting that the expressed protein is able to complement the PorA and PorH deficiency of the C. glutamicum strain. The study is the first report of a cell wall channel in a pathogenic Corynebacterium strain.

Identification and characterization of PorH, a new cell wall channel of Corynebacterium glutamicum

The cell wall of Corynebacterium glutamicum contains the cation-selective channel (porin) PorA(C.glut) and the anion-selective channel PorB(C.glut) for the passage of hydrophilic solutes. Lipid bilayer experiments with organic solvent extracts of whole C. glutamicum cells cultivated in minimal medium suggested that also another cation-selective channel-forming protein, named PorH(C.glut), is present in C. glutamicum. The protein was purified to homogeneity by fast-protein liquid chromatography across a HiTrap-Q column. The pure protein had an apparent molecular mass of about 12 kDa on SDS-PAGE. Western blot analysis suggested that the cell wall channel is presumably formed by protein oligomers. The purified protein forms cation-selective channels with an average single-channel conductance of about 2.5 nS in 1 M KCl in the lipid bilayer assay. The PorH(C.glut) protein was partially sequenced, and based on the resulting amino acid sequence, the corresponding gene, designated as porH(C.glut), was identified in the published genome sequence of C. glutamicum ATCC13032. PorH(C.glut) contains only the inducer methionine but no N-terminal extension, which suggests that the export and assembly of the protein follow a yet unknown pathway. PorH(C.glut) is coded in the bacterial chromosome by a gene that is localized in the vicinity of porA(C.glut), within a putative operon of 13 genes. RT-PCR revealed that both porins are cotranscribed. They coexist according to immunological detection experiments in the cell wall of C. glutamicum together with PorB(C.glut) and PorC(C.glut).

PorH, a new channel-forming protein present in the cell wall of Corynebacterium efficiens and Corynebacterium callunae

Corynebacterium callunaeandCorynebacterium efficiensare close relatives of the glutamate-producing mycolata speciesCorynebacterium glutamicum. The properties of the pore-forming proteins, extracted by organic solvents, were studied. The cell extracts contained channel-forming proteins that formed ion-permeable channels with a single-channel conductance of about 2 to 3 nS in 1 M KCl in a lipid bilayer assay. The corresponding proteins from both corynebacteria were purified to homogeneity and were named PorHC.calland PorHC.eff. Electrophysiological studies of the channels suggested that they are wide and water-filled. Channels formed by PorHC.callare cation-selective, whereas PorHC.effforms slightly anion-selective channels. Both proteins were partially sequenced. A multiple sequence alignment search within the known chromosome ofC. efficiensdemonstrated that it contains a gene that fits the partial amino acid sequence of PorHC.eff. PorHC.callshows high homology to PorHC.eff. PorHC.effis encoded in the bacterial chromosome by a gene that is localized within the vicinity of theporAgene ofC. efficiens. PorHC.effhas no signal sequence at the N terminus, which means that it is not exported by the Sec-secretion pathway. The structure of PorH in the cell wall of the corynebacteria is discussed.

Identification of a cation-specific channel (TipA) in the cell wall of the gram-positive mycolata Tsukamurella inchonensis: the gene of the channel-forming protein is identical to mspA of Mycobacterium smegmatis and mppA of Mycobacterium phlei

Detergent extracts of whole cells of the Gram-positive bacterium Tsukamurella inchonensis ATCC 700082, which belongs to the mycolata, were studied for the presence of ion-permeable channels using lipid bilayer experiments. One channel with a conductance of about 4.5 nS in 1 M KCl was identified in the extracts. The channel-forming protein was purified to homogeneity by preparative SDS-PAGE. The protein responsible for channel-forming activity had an apparent molecular mass of about 33 kDa as judged by SDS-PAGE. Interestingly, the protein showed cross-reactivity with polyclonal antibodies raised against a polypeptide derived from MspA of Mycobacterium smegmatis similarly as the cell wall channel of Mycobacterium phlei. Primers derived from mspA were used to clone and sequence the gene of the cell wall channels of T. inchonensis (named tipA for T. inchonensis porin A) and M. phlei (named mppA for M. phlei porin A). Surprisingly, both genes, tipA and mppA, were found to be identical to mspA of M. smegmatis, indicating that the genomes of T. inchonensis, M. phlei and M. smegmatis contain the same genes for the major cell wall channel. RT-PCR revealed that tipA is transcribed in T. inchonensis and mppA in M. phlei. The results suggest that despite a certain distance between the three organisms, their genomes contain the same gene coding for the major cell wall channel, with a molecular mass of 22 kDa for the monomer.

Identification of an anion-specific channel in the cell wall of the Gram-positive bacterium Corynebacterium glutamicum

A cation-selective channel (porin), designated PorA, facilitates the passage of hydrophilic solutes across the cell wall of the mycolic acid-containing actinomycete Corynebacterium glutamicum. Biochemical and electrophysiological investigations of the cell wall of the mutant strain revealed the presence of an alternative channel-forming protein. This porin was purified to homogeneity and studied in lipid bilayer membranes. It forms small anion-selective channels with a diameter of about 1.4 nm and an average single-channel conductance of about 700 pS in 1 M KCl. The PorBCglut channel could be blocked by citrate in a dose-dependent manner. This result was in agreement with growth experiments in citrate as sole carbon source where growth in citrate was impaired as compared with growth in other carbon sources. The PorBCglut protein was partially sequenced and based on the resulting amino acid sequence of the corresponding gene, which was designated as porB, was identified as an unannotated 381 bp long open reading frame (ORF) in the published genome sequence of C. glutamicum ATCC13032. PorBCglut contains 126 amino acids with an N-terminal extension of 27 amino acids. One hundred and thirty-eight base pairs downstream of porB, we found an ORF that codes for a protein with about 30% identity to PorBCglut, which was named PorCCglut. The arrangement of porB and porC on the chromosome suggested that both genes belong to the same cluster. RT-PCR from overlapping regions between genes from wild-type C. glutamicum ATCC 13032 and its ATCC 13032DeltaporA mutant demonstrated that this is the case and that porB and porC are cotranscribed. The gene products PorBCglut and PorCCglut represent obviously other permeability pathways for the transport of hydrophilic compounds through the cell wall of C. glutamicum.

PorA represents the major cell wall channel of the Gram-positive bacterium Corynebacterium glutamicum

The cell wall of the gram-positive bacterium Corynebacterium glutamicum contains a channel (porin) for the passage of hydrophilic solutes. The channel-forming polypeptide PorA is a 45-amino-acid acidic polypeptide with an excess of four negatively charged amino acids, which is encoded by the 138-bp gene porA. porA was deleted from the chromosome of C.glutamicum wild-type strain ATCC 13032 to obtain mutant ATCC 13032deltaporA. Southern blot analysis demonstrated that porA was deleted. Lipid bilayer experiments revealed that PorA was not present in the cell wall of the mutant strain. Searches within the known chromosome of C. glutamicum by using National Center for Biotechnology Information BLAST and reverse transcription-PCR showed that no other PorA-like protein is encoded on the chromosome or is expressed in the deletion strain. The porA deletion strain exhibited slower growth and longer growth times than the C. glutamicum wild-type strain. Experiments with different antibiotics revealed that the susceptibility of the mutant strain was much lower than that of the wild-type C. glutamicum strain. The results presented here suggest that PorA represents a major hydrophilic pathway through the cell wall and that C. glutamicum contains cell wall channels which are not related to PorA.

Immunological properties of trehalose dimycolate (cord factor) and other mycolic acid-containing glycolipids--a review

Mycolic acids are characteristic fatty acids of Mycobacteria and are responsible for the wax-like consistence of these microorganisms. Decades of research revealed that mycolic acid-containing glycolipids, in particular trehalose-6,6'-dimycolate (TDM, cord factor) as their best-studied representative, exert a number of immunomodifying effects. They are able to stimulate innate, early adaptive and both humoral and cellular adaptive immunity. Most functions can be associated with their ability to induce a wide range of chemokines (MCP-1, MIP-1alpha, IL-8) and cytokines (e.g., IL-12, IFN-gamma, TNF-alpha, IL-4, IL-6, IL-10). This review tries to link well-known properties of mycolic acid-containing glycolipids, e.g., stimulation of cellular and humoral immunity, granuloma formation and anti-tumor activity, with recent findings in molecular immunology and to give an outlook on potential practical applications.

The low-molecular-mass subunit of the cell wall channel of the Gram-positive Corynebacterium glutamicum. Immunological localization, cloning and sequencing of its gene porA

The 5-kDa protein PorA of the Gram-positive bacterium Corynebacterium glutamicum is the subunit of the cell wall channel. Antibodies raised against PorA specifically detected the protein on the cell surface. PorA was sequenced using Edman degradation and a gas phase sequencer. The primary sequence was used to create degenerate oligonucleotide primers. The gene of the channel-forming protein and its flanking regions were obtained by PCR followed by inverse PCR. The gene porA comprises 138 bp and encodes a 45-amino-acid-long acidic polypeptide with an excess of four negatively charged amino acids in agreement with the high cation selectivity of the PorA cell wall channel. PorA does not contain an N-terminal extension. A ribosomal-binding site was recognized 6 bp before the start codon ATG of porA. It codes for the smallest subunit of a membrane channel known so far and for the first cell wall channel protein of a corynebacterium. Southern blots demonstrated that only the chromosomes of corynebacteria contain homologous sequences to porA; no hybridization could be detected with DNA from other mycolata.

Analysis of the structural diversity of mycolic acids of Rhodococcus and Gordonia [correction of Gordonla] isolates from activated sludge foams by selective ion monitoring gas chromatography-mass spectrometry (SIM GC-MS)

A method using Selective Ion Monitoring (SIM) gas chromatography-mass spectrometry is described for analysis of mycolic acids which reveals a hitherto unrecognised chemical structural diversity among these in some members of the Mycolata. The structural interpretation of mass spectral data of mycolic acids from Rhodococcus spp and Gordonia [corrected] spp using SIM is discussed.

Biochemical and biophysical characterization of the cell wall porin of Corynebacterium glutamicum: the channel is formed by a low molecular mass polypeptide

The cell wall of the Gram-positive bacterium Corynebacterium glutamicum contains a channel (porin) for the passage of hydrophilic solutes. The channel-forming protein was identified, by lipid bilayer experiments, in the cell envelope fractions isolated by sucrose-density centrifugations and in organic solvent of whole cells. It was purified to homogeneity by fast-protein liquid chromatography across a Mono-Q column. The pure protein had a rather low molecular mass of about 5 kDa as judged by SDS-PAGE, which suggested that the cell wall channel is formed by a protein oligomer. The monomer has according to partial sequencing no significant homology to known protein sequences. The purified protein formed large ion-permeable channels in lipid bilayer membranes from phosphatidylcholine/phosphatidylserine mixtures with a single-channel conductance of 5.5 nS in 1 M KCl. Experiments with different salts suggested that the cell wall channel of C. glutamicum was highly cation-selective caused by negative charges localized at the channel mouth. The analysis of the single-channel conductance data using the Renkin correction factor suggested that the diameter of the cell wall channel is about 2.2 nm. Channel-forming properties of the cell wall channel of C. glutamicum were compared with those of mycobacteria. These channels share common features because they form large and water-filled channels that contain point net charges.

The cell wall porin of Nocardia farcinica: biochemical identification of the channel-forming protein and biophysical characterization of the channel properties

A channel-forming protein was identified in cell wall extracts of the Gram-positive, strictly aerobic bacterium Nocardia farcinica. The cell wall porin was purified to homogeneity and had an apparent molecular mass of about 87 kDa on tricine-containing SDS-PAGE. When the 87 kDa protein was boiled for a longer time in sodium dodecylsulphate (SDS) it dissociated into two subunits with molecular masses of about 19 and 23 kDa. The 87 kDa form of the protein was able to increase the specific conductance of artificial lipid bilayer membranes from phosphatidylcholine (PC) phosphatidylserine (PS) mixtures by the formation of ion-permeable channels. The channels had on average a single-channel conductance of 3.0 nS in 1M KCl, 10mM Tris-HCl, pH8, and were found to be cation selective. Asymmetric addition of the cell wall porin to lipid bilayer membranes resulted in an asymmetric voltage dependence. The single-channel conductance was only moderately dependent on the bulk aqueous KCl concentration, which indicated point charge effects on the channel properties. The analysis of the single-channel conductance data in different salt solutions using the Renkin correction factor, and the effect of negative charges on channel conductance suggested that the diameter of the cell wall porin is about 1.4-1.6nm. Channel-forming properties of the cell wall porin of N. farcinica were compared with those of mycobacteria and corynebacteria. The cell wall porins of these members of the order Actinomycetales share common features because they form large and water-filled channels that contain negative point charges.

Mycotic acid composition of Corynebacterium glutamicum and its cell surface mutants: effects of growth with glycine and isonicotinic acid hydrazide

Auxotrophic mutants of Corynebacterium glutamicum strain ATCC 13059 (parent of AS019, a rifampicin-resistant variant), which were morphologically distinct from the parent and formed protoplasts more readily, had been isolated previously. Mutants MLB130-133 and MLB194 were more sensitive to growth inhibition by isonicotinic acid hydrazide (INH) and glycine, which caused branching and budding. Fatty acid and mycolic acid (MA) profiles were determined after growth in LBG (Luria broth plus glucose), LBG-glycine (LBG- and LBG-INH (LBG-I). The fatty acid profiles of all strains were similar, except that mutant MLB133 showed some increase in stearic acid (C18:0), normally a minor component, late in the growth cycle and oleic acid proportionately decreased. All strains had five major types of MAs (C32:0, C34:0, C34:1, C36:1, C36:2) but the relative proportion of each varied with the strain, age of culture and medium composition. Mutants MLB133 and MLB194 showed slightly higher levels of non-covalentiy bound MAs than the parent and normally showed a higher proportion of longer-chained, unsaturated MAs. The proportion of extracellular MAs increased with culture age for these mutants. Typically, by late stationary phase, mycolic acids in culture fluids increased to 6.5% of the total MAs for MLB194 and 7.9% for MLB133 compared with 3.5% for the parent strain grown in LBG. The main effect of glycine (2%, w/v) addition was to increase the proportion of mycolic acids found in extracellular fluids (16.1 % for AS019 and 31% for MLB133). The most significant effects of INH were seen when strains were cultured in LBG with 8 mg INH ml−1. When harvested at late stationary phase, strains MLB133 and MLB194 had 18.8% and 21.2% extracellular mycolic acids respectively, with a significant increase in the relative proportion of unsaturated mycolic acids. This effect was not as marked for AS019, which also showed a similar decrease in C32:0 relative to increases in the proportion of C34:1 and C36:2 plus a corresponding increase in the overall proportion of unsaturated mycolic acids and increased extracellular mycolates (8.5%). These results suggest that the mutations in strains MLB133 and MLB194 are associated with synthesis of specific mycolic acids (e.g. C32:0) and attachment of mycolic acids to the cell surface, both of which are likely target sites for glycine and INH action for cell-surface modifications. In addition to previously reported targeting of the peptidoglycan cross-linking, these results show that glycine affects mycolic acid attachment to the cell surface of C. glutamicum.

Possible existence of a novel amphipathic immunostimulator in the phenol-water extracts of Mycobacteriaceae

The extracts having diverse immunostimulating activities were obtained as a water-phase fraction from four bacterial species representing the 4 genera (Mycobacterium, Nocardia, Gordona, and Rhodococcus) of Mycobacteriaceae by the phenol-water method, which is commonly used for extraction of endotoxic lipopolysaccharides (LPS) from gram-negative bacteria and amphipathic substances from gram-positives. These fractions, especially those of G. aurantiaca and R. terrae, showed strong stimulatory effects on murine splenocytes, macrophages of mice and guinea pigs, the immunoadjuvant activities in guinea pigs and mice, and the distinct activities inducing a tumor necrosis factor and interferons alpha/beta and gamma in primed mice. The fractions from G. aurantiaca and R. terrae exhibited potent pyrogenicity and the ability to activate the clotting enzyme cascade of the horseshoe crab (Tachypleus tridentatus). Some of these biological activities were not very different from the potency of the reference endotoxic LPS derived from Escherichia coli or Fusobacterium nucleatum. But the test fractions neither showed the activity to prepare rabbit skin to the local Shwartzman reaction, nor reacted with anti-lipid A conventional and monoclonal antibodies. Furthermore, unlike LPS, these fractions stimulated the splenocytes of C3H/HeJ mice (LPS-Nonresponder). Although the fractions showing the above biological activities have not yet been adequately purified, they contained polysaccharides, whose main constituent sugar is mannose with a smaller amount of arabinose, fatty acids consisting primarily of palmitic, stearic, and tuberculostearic acids, and small amounts of peptides and amino sugars. Since components characteristic of known immunomodulators of bacterial origin, namely endotoxins (lipid A's), cell wall peptidoglycans, lipoteichoic acids, cord factors (trehalose dimycolates), or deoxyribonucleic acids, were practically not detected in these fractions, the agent responsible for the above bioactivities is considered to be a novel substance different from the known, bacterial immunomodulators.

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.

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.

Analysis of mycolic acids from a group of corynebacteria by capillary gas chromatography and mass spectrometry

The cell wall of leprosy-derived corynebacteria (a group of 'diphtheroids' isolated from human leprosy lesions and patients' blood) was previously shown to contain, in addition to peptidoglycan and arabinogalactan, mycolic acids. These alpha-branched beta-hydroxy fatty acids were attributed to the corynomycolic group, according to their RF in monodimensional thin-layer chromatography. In the present work, mycolic acids from leprosy-derived and reference corynebacteria have been fractionated by monodimensional and bidimensional thin-layer chromatography and by gas chromatography. Pyrolyzed mycolic acids have been analyzed on conventional packed columns, whereas intact methyl esters of mycolic acids with free and silylated beta-hydroxyl group have been analyzed on capillary columns, and their structure has been established by mass spectrometry. In all leprosy-derived corynebacteria, some 20 components containing 24-36 carbon atoms and 0-4 double bonds were obtained. The three major groups had 32, 34 and 36 carbons, and the frequency of unsaturated versus saturated chains increased proportionally to the molecular weight. For comparison, the main components of a reference corynebacterium. Corynebacterium diphtheriae PW8, had 30 and 32 carbons, and their hydrocarbon chains were essentially saturated. This work confirms the relative chemical homogeneity of different leprosy-derived corynebacteria and describes some peculiar traits in the chemical structure of this group of organisms. In addition, it shows the complexity of the mycolic acid fraction of corynebacterial cell wall and suggests that the mycolic acid pattern is a sort of fingerprint of each bacterial strain grown under standard conditions. Finally, the fractionation of intact corynomycolic acid methyl esters with free or silylated beta-hydroxyl group by capillary gas chromatography proved to be the best analytical procedure at present available for resolving this complex mixture of corynomycolate isomers. Structural determination of silylated samples by mass spectrometry is preferred because they have more diagnostic fragments.

Property and activity of mycoloyl esters of methyl glucoside and trehalose. Effect on mitochondrial oxidative phosphorylation related to organization of suspensions and to acyl-chain structures

Methyl alpha-D-glucoside and alpha, alpha'-D-trehalose acylated on their primary hydroxyl group by alpha-alkyl-beta-hydroxy acids (mycolic acids) with 18, 32 and more than 80 carbon atoms were studied. These cord factors and analogues when dispersed in water gave hydrated and organized phases which bore resemblances and differences to phospholipid liposomes. Phase transition temperature was determined by fluorescence for the C32 derivatives and by differential scanning calorimetry for the C80 derivatives. A narrow temperature interval between the gel and the fluid states was observed, indicating that this transition was a strongly cooperative phenomenon. The activity on mitochondria of these diacyl trehaloses was studied with succinate as substrate. The fluid suspensions were more active than the rigid ones. There was no influence of the relative configuration of the mycoloyl residue. Acyl chains with 18, 32 and more than 80 carbon atoms had rather similar activities on phosphorylation, but differences appeared when considering effects on respiration. Electron microscopy suggested that cord factor weakened the peripheral part of the inner membrane, but cristae looked unchanged. These observations, together with the results of our previous monolayer studies of these glycolipids, led us to propose a model for interaction of cord factor with mitochondria.