Lipids of the Streptomycettes. Structural investigation and biological interrelation a review

Daptomycin: Mechanism of action, mechanisms of resistance, synthesis and structure-activity relationships

Daptomycin is a cyclic lipodepsipeptide antibiotic that is a mainstay for the treatment of serious infections caused by Gram-positive bacteria, including methicillin-resistant Streptococcus aureus and vancomycin resistant enterococci. It is one of the so-called last-resort antibiotics that are used to tackle life-threatening infections that do not respond to first-line treatments. However, resistance to daptomycin is eroding its clinical efficacy motivating the design and/or discovery of analogues that overcome resistance. The strategy of antibiotic analogue synthesis has been used to overcome bacterial resistance to many classes of antibiotics such as the β-lactams. Pursuing this strategy with daptomycin requires a detailed understanding of daptomycin's action mechanism and synthesis. Here, we discuss the action mechanism of daptomycin in a holistic manner and expand this discussion to rationalize conferred modes of resistance. Synthetic efforts, both chemical and biological, are discussed in detail and the structure-activity relationship emanating from these works is distilled into a usable model that can guide the design of new daptomycin analogues.

Characterization of Glucuronosyl-diacyl/monoacylglycerols and Discovery of Their Acylated Derivatives in Tomato Lipid Extracts by Reversed-Phase Liquid Chromatography with Electrospray Ionization and Tandem Mass Spectrometry

Glucuronic acid containing diacylglycerols (3-(O-α-d-glucuronopyranosyl)-1,2-diacyl-sn-glycerols, GlcA-DAG) are glycolipids of plant membranes especially formed under phosphate-depletion conditions. An analytical approach for the structural characterization of GlcA-DAG in red ripe tomato (Solanum lycopersicum L.) extracts, based on reversed-phase liquid chromatography (RPLC) coupled with electrospray ionization (ESI) and tandem mass spectrometry (MS/MS) using a linear ion trap, is described in this paper. At least 14 GlcA-DAG (R₁/R₂) species, including four regioisomers, containing three predominant fatty acyl chains C16:0, C18:2, and C18:3, were identified for the first time. Moreover, 29 GlcA-DAG acylated on the glucuronosyl ring (acyl-R₃ GlcA-DAG) were discovered, alongside 15 acylated lyso-forms, i.e., acylated 3-(O-α-d-glucuronosyl)monoacylglycerols, abbreviated as acyl-R₃ GlcA-MAG (R₁/0) or (0/R₂). Although many of these acylated lyso-forms were isomeric with GlcA-DAG (i.e., acyl chains with equivalent sum composition), they were successfully separated by reversed-phase liquid chromatography (RPLC) using a solid-core C18 column packed with 2.6 μm particle size. Tandem MS (and eventually MS³) data obtained from sodium adducts ([M + Na]⁺) and deprotonated molecules ([M - H]^-) were fundamental to detect diagnostic product ions related to the glucuronosyl ring and then determine the identity of all investigated glycolipids, especially to recognize the acyl chain linked to the ring. A classification of GlcA-MAG, GlcA-DAG, and acylated GlcA-DAG and GlcA-MAG was generated by an in house-built database. The discovery of acylated derivatives emphasized the already surprising heterogeneity of glucuronic acid-containing mono- and diacylglycerols in tomato plants, stimulating interesting questions on the role played by these glycolipids.

More Than a Pore: A Current Perspective on the In Vivo Mode of Action of the Lipopeptide Antibiotic Daptomycin

Daptomycin is a cyclic lipopeptide antibiotic, which was discovered in 1987 and entered the market in 2003. To date, it serves as last resort antibiotic to treat complicated skin infections, bacteremia, and right-sided endocarditis caused by Gram-positive pathogens, most prominently methicillin-resistant Staphylococcus aureus. Daptomycin was the last representative of a novel antibiotic class that was introduced to the clinic. It is also one of the few membrane-active compounds that can be applied systemically. While membrane-active antibiotics have long been limited to topical applications and were generally excluded from systemic drug development, they promise slower resistance development than many classical drugs that target single proteins. The success of daptomycin together with the emergence of more and more multi-resistant superbugs attracted renewed interest in this compound class. Studying daptomycin as a pioneering systemic membrane-active compound might help to pave the way for future membrane-targeting antibiotics. However, more than 30 years after its discovery, the exact mechanism of action of daptomycin is still debated. In particular, there is a prominent discrepancy between in vivo and in vitro studies. In this review, we discuss the current knowledge on the mechanism of daptomycin against Gram-positive bacteria and try to offer explanations for these conflicting observations.

Cell Walls and Membranes of Actinobacteria

Actinobacteria is a group of diverse bacteria. Most species in this class of bacteria are filamentous aerobes found in soil, including the genus Streptomyces perhaps best known for their fascinating capabilities of producing antibiotics. These bacteria typically have a Gram-positive cell envelope, comprised of a plasma membrane and a thick peptidoglycan layer. However, there is a notable exception of the Corynebacteriales order, which has evolved a unique type of outer membrane likely as a consequence of convergent evolution. In this chapter, we will focus on the unique cell envelope of this order. This cell envelope features the peptidoglycan layer that is covalently modified by an additional layer of arabinogalactan . Furthermore, the arabinogalactan layer provides the platform for the covalent attachment of mycolic acids , some of the longest natural fatty acids that can contain ~100 carbon atoms per molecule. Mycolic acids are thought to be the main component of the outer membrane, which is composed of many additional lipids including trehalose dimycolate, also known as the cord factor. Importantly, a subset of bacteria in the Corynebacteriales order are pathogens of human and domestic animals, including Mycobacterium tuberculosis. The surface coat of these pathogens are the first point of contact with the host immune system, and we now know a number of host receptors specific to molecular patterns exposed on the pathogen's surface, highlighting the importance of understanding how the cell envelope of Actinobacteria is structured and constructed. This chapter describes the main structural and biosynthetic features of major components found in the actinobacterial cell envelopes and highlights the key differences between them.

A bifunctional glycosyltransferase from Agrobacterium tumefaciens synthesizes monoglucosyl and glucuronosyl diacylglycerol under phosphate deprivation

Glycolipids are mainly found in phototrophic organisms (like plants and cyanobacteria), in Gram-positive bacteria, and a few other bacterial phyla. Besides the function as bulk membrane lipids, they often play a role under phosphate deprivation as surrogates for phospholipids. The Gram-negative Agrobacterium tumefaciens accumulates four different glycolipids under phosphate deficiency, including digalactosyl diacylglycerol and glucosylgalactosyl diacylglycerol synthesized by a processive glycosyltransferase. The other two glycolipids have now been identified by mass spectrometry and nuclear magnetic resonance spectroscopy as monoglucosyl diacylglycerol and glucuronosyl diacylglycerol. These two lipids are synthesized by a single promiscuous glycosyltransferase encoded by the ORF atu2297, with UDP-glucose or UDP-glucuronic acid as sugar donors. The transfer of sugars differing in their chemistry is a novel feature not observed before for lipid glycosyltransferases. Furthermore, this enzyme is the first glucuronosyl diacylglycerol synthase isolated. Deletion mutants of Agrobacterium lacking monoglucosyl diacylglycerol and glucuronosyl diacylglycerol or all glycolipids are not impaired in growth or virulence during infection of tobacco leaf discs. Our data suggest that the four glycolipids and the nonphospholipid diacylglyceryl trimethylhomoserine can mutually replace each other during phosphate deprivation. This redundancy of different nonphospholipids may represent an adaptation mechanism to enhance the competitiveness in nature.

Involvement of thermoplasmaquinone-7 in transplasma membrane electron transport of Entamoeba histolytica trophozoites: a key molecule for future rational chemotherapeutic drug designing

The quinone composition of the transplasma membrane electron transport chain of parasitic protozoa Entamoeba histolytica was investigated. Purification of quinone from the plasma membrane of E. histolytica and its subsequent structural elucidation revealed the structure of the quinone as a methylmenaquinone-7 (thermoplasmaquinone-7), a napthoquinone. Membrane bound thermoplasmaquinone-7 can be destroyed by UV irradiation with a concomitant loss of plasma membrane electron transport activity. The abilities of different quinones to restore transplasma membrane electron transport activity in UV irradiated trophozoites were compared. The lost activity was recovered completely by the addition of thermoplasmaquinone-7, but ubiquinones are unable to restore the same. These findings clearly indicate that thermoplasmaquinone-7 acts as a lipid shuttle in the plasma membrane of the parasite to mediate electron transfer between cytosolic reductant and non permeable electron acceptors. This thermoplasmaquinone-7 differs from that of the mammalian host and can provide a novel target for future rational chemotherapeutic drug designing.

Structure and function of glycoglycerolipids in plants and bacteria

Phosphoglycerolipids are abundant membrane constituents in prokaryotic and eukaryotic cells. However, glycoglycerolipids are the predominant lipids in chloroplasts of plants and eukaryotic algae and in cyanobacteria. Membrane composition in chloroplasts and cyanobacteria is highly conserved, with monogalactosyldiacylglycerol (MGD) and digalactosyldiacylglycerol (DGD) representing the most abundant lipids. The genes encoding enzymes of galactolipid biosynthesis have been isolated from Arabidopsis. Galactolipids are crucial for growth under normal and phosphate limiting conditions. Furthermore, they are indispensable for maximal efficiency of photosynthesis. A wide variety of glycoglycerolipids is found in different bacteria. These lipids contain glucose or galactose, in some cases also mannose or other sugars with different glycosidic linkages in their head group. Some bacterial species produce unusual glycoglycerolipids, such as glycophospholipids or glycoglycerolipids carrying sugar head groups esterified with acyl residues. A number of genes coding for bacterial glycoglycerolipid synthases have been cloned and the enzymes characterized. In contrast to the breadth of information available on their structural diversity, much less is known about functional aspects of bacterial glycoglycerolipids. In some bacteria, glycoglycerolipids are required for membrane bilayer stability, they serve as precursors for the formation of complex membrane components, or they are crucial to support anoxygenic photosynthesis or growth during phosphate deficiency.

Biosynthesis of phosphatidylcholine in bacteria

Phosphatidylcholine (PC) is the major membrane-forming phospholipid in eukaryotes and can be synthesized by either of two pathways, the methylation pathway or the CDP-choline pathway. Many prokaryotes lack PC, but it can be found in significant amounts in membranes of rather diverse bacteria and based on genomic data, we estimate that more than 10% of all bacteria possess PC. Enzymatic methylation of phosphatidylethanolamine via the methylation pathway was thought to be the only biosynthetic pathway to yield PC in bacteria. However, a choline-dependent pathway for PC biosynthesis has been discovered in Sinorhizobium meliloti. In this pathway, PC synthase, condenses choline directly with CDP-diacylglyceride to form PC in one step. A number of symbiotic (Rhizobium leguminosarum, Mesorhizobium loti) and pathogenic (Agrobacterium tumefaciens, Brucella melitensis, Pseudomonas aeruginosa, Borrelia burgdorferi and Legionella pneumophila) bacteria seem to possess the PC synthase pathway and we suggest that the respective eukaryotic host functions as the provider of choline for this pathway. Pathogens entering their hosts through epithelia (Streptococcus pneumoniae, Haemophilus influenzae) require phosphocholine substitutions on their cell surface components that are biosynthetically also derived from choline supplied by the host. However, the incorporation of choline in these latter cases proceeds via choline phosphate and CDP-choline as intermediates. The occurrence of two intermediates in prokaryotes usually found as intermediates in the eukaryotic CDP-choline pathway for PC biosynthesis raises the question whether some bacteria might form PC via a CDP-choline pathway.

Production of proinflammatory mediators by indoor air bacteria and fungal spores in mouse and human cell lines

We compared the inflammatory and cytotoxic responses caused by household mold and bacteria in human and mouse cell lines. We studied the fungi Aspergillus versicolor, Penicillium spinulosum, and Stachybotrys chartarum and the bacteria Bacillus cereus, Pseudomonas fluorescens, and Streptomyces californicus for their cytotoxicity and ability to stimulate the production of inflammatory mediators in mouse RAW264.7 and human 28SC macrophage cell lines and in the human A549 lung epithelial cell line in 24-hr exposure to 10(5), 10(6), and 10(7) microbes/mL. We studied time dependency by terminating the exposure to 10(6) microbes/mL after 3, 6, 12, 24, and 48 hr. We analyzed production of the cytokines tumor necrosis factor-alpha and interleukins 6 and 1ss (TNF-alpha, IL-6, IL-1ss, respectively) and measured nitric oxide production using the Griess method, expression of inducible NO-synthase with Western Blot analysis, and cytotoxicity with the MTT-test. All bacteria strongly induced the production of TNF-alpha, IL-6 and, to a lesser extent, the formation of IL-1ss in mouse macrophages. Only the spores of Str. californicus induced the production of NO and IL-6 in both human and mouse cells. In contrast, exposure to fungal strains did not markedly increase the production of NO or any cytokine in the studied cell lines except for Sta. chartarum, which increased IL-6 production somewhat in human lung epithelial cells. These microbes were less cytotoxic to human cells than to mouse cells. On the basis of equivalent numbers of bacteria and spores of fungi added to cell cultures, the overall potency to stimulate the production of proinflammatory mediators decreased in the order Ps. fluorescens > Str. californicus > B. cereus > Sta. chartarum > A. versicolor > P. spinulosum. These data suggest that bacteria in water-damaged buildings should also be considered as causative agents of adverse inflammatory effects.

Unusual lipid composition of the gram-negative, freshwater, stalked bacterium Caulobacter bacteroides NP-105

The extractable lipids of the gram-negative, stalked, freshwater bacterium Caulobacter bacteroides NP-105 account for about 9.5% by weight of dry cells, polar lipids comprising up to 95% of the total. The polar lipids consist of five glycolipids, namely, 1,2-diacyl-3-alpha-D-glucopyranosyl-sn-glycerol (I) (34% of the total), 1,2-diacyl-3-alpha-D-[6'-(1",2"-diacyl-sn-glycero-3-phospho)]glucopyranosyl-sn-glycerol (II) (7%), 1,2-diacyl-3-a-D-glucuronopyranosyl-sn-glycerol (III) (17%), 1,2-diacyl-3-alpha-D-(6'-sulfo)quinovopyranosyl-sn-glycerol (V) (9%), and 1,2-diacyl-3-alpha-D-[4'-(alpha-D-glucopyranosyl)] glucuronopyranosyl-sn-glycerol (VI) (28%), and one glycerophospholipid, 1,2-diacyl-sn-glycero-3-phosphoglycerol (IV) (5%). The main fatty acyls of the lipids are n-16:0, cis-18:1 omega7, and cis-11,12-methyleneoctadecanoic (lactobacillic) acid residue. Of the 6 lipids listed, only 3 (I, IV, and V) can be treated as widely encountered. However, sulfonic glycolipid V is a characteristic lipid component of photosynthetic organisms rather than non-photosynthetic ones. Phosphatidyl derivatives of glycosyldiacylglycerols of type II normally occur in gram-positive bacteria, among gram-negative bacteria they have been revealed only in two species of the Pseudomonas genus. Glucuronosyl and alpha-glucosyl-a-glucuronosyl diacylglycerols such as III and VI, respectively, are very rare lipids, the latter being found so far only in a Streptomyces strain.

N-acyl amino acid biosynthesis in marine bacterium, Deleya marina

We reported previously that the marine bacterium, Deleya marina (ATCC 25374), produced N-acyl leucine and isoleucine, in which nonhydroxy fatty acid was linked to alpha-amino group of amino acid. Further analysis of bacterium lipids revealed the additional production of N-acyl ornithine. The N-acyl ornithine had a 3-hydroxy fatty acid linked by an amide bond to a-amino group of ornithine and a nonhydroxy fatty acid esterified to the hydroxy group of the 3-hydroxy fatty acid. N-acyl ornithine was located in the cell membrane and N-acyl leucine and isoleucine in cytoplasm. N-acyl ornithine is thought to be a functional analogue of phosphatidylethanolamine (PE) because of their similar structure. PE replacement into N-acyl ornithine in the cell membrane under phosphate-limited conditions was observed with other bacteria, so we anticipated the nonbiosynthesis of N-acyl ornithine under phosphate-sufficient conditions. We did not anticipate that N-acyl leucine and isoleucine in cytoplasm, whose structure is dissimilar to that of PE, would be replaced into PE in the cell membrane. Neither N-acyl leucine, N-acyl isoleucine, nor N-acyl ornithine was biosynthesized under phosphate-sufficient condition. Thus, we report here for the first time that N-acyl amino acids in cytoplasm were not biosynthesized under phosphate-sufficient conditions.

Lipid and fatty acid composition of cytoplasmic membranes from Streptomyces hygroscopicus and its stable protoplast-type L form

The cells of an L-form strain of Streptomyces hygroscopicus have been grown for 20 years without a cell wall. Their cytoplasmic membranes have high stability and an unusual structural polymorphism. To clarify the importance of the lipid components for these membrane properties, a comparative analysis has been carried out with purified membranes of L-form cells, of parent vegetative hyphal cells (N-form cells), and of protoplasts derived from the latter. The phospholipid classes and fatty acids were determined by thin-layer chromatography (TLC), two-dimensional TLC, high-performance liquid chromatography, gas chromatography, and mass spectrometry. The qualitative compositions of cardiolipin (CL), lyso-cardiolipin (LCL), phosphatidylethanolamine (PE1 and PE2), lyso-phosphatidylethanolamine (LPE), phosphatidylinositolmannoside (PIM), phosphatidic acid (PA), dilyso-cardiolipin-phosphatidylinositol (DLCL-PI), and the 13 main fatty acids were the same in the three membrane types. However, significant quantitative differences were observed in the L-form membrane. They consist of a three- to fourfold-higher content of total, extractable lipids, 20% more phospholipids, an increased content of CL and PIM, and a reduced amount of the component DLCL-PI. Furthermore, the L-form membrane is characterized by a higher content of branched anteiso 15:0 and anteiso 17:0 fatty acids compared to that of the membranes of the walled vegetative cells. These fatty acids have lower melting points than their straight and iso-branched counterparts and make the membrane more fluid. The phospholipid composition of the protoplast membrane differs quantitatively from that of the N form and the L form. Whereas the phospholipid classes are mostly similar to that of the N form, the fatty acid pattern tends to be closer to that of the L-form membrane. The membranes of both the L-form cells and the protoplasts need to be more fluid because of their spherical cell shape and higher degree of curvature compared with N-form membranes.

Structural studies of the major glycolipid from Saccharopolyspora genus

A major glycolipid was isolated from the well characterized Saccharopolyspora species, S. hirsuta, S. rectivirgula, S. erythraea and one not completely identified strain (Saccharopolyspora sp.). On the basis of sugar and methylation analysis, specific enzymatic and chemical degradations of the carbohydrate moiety, its FAB mass spectrometry and NMR spectroscopy characterizations, the carbohydrate part was shown to be the glycerol linked dimannoside alpha-D-Manp-(1-->3)-alpha-D-Manp-(1-->1/3)Gro. The internal mannose residue is esterified at C-6 by one fatty acid residue, whereas another fatty acyl chain substitutes the primary methylene position of glycerol. The main fatty acyl residues are anteiso-branched heptadecanoic acid and the iso-branched fatty acids iso-17:0, iso-16:0, and iso-18:0, with the former species being predominant. The major glycolipid has potential value for taxonomic and diagnostic purposes, especially in the specific diagnosis of farmer's lung disease.

Lipid composition of the phosphatidylcholine-producing bacterium Hyphomicrobium vulgare NP-160

The extractable lipids of the PC-producing, methylotrophic, budding bacterium Hyphomicrobium vulgare NP-160 grown in a mineral-salts medium containing methanol as the carbon source, were studied by chromatographic and spectrometric methods. They were found to be comprised of PC (35% of the total lipids), PDME (33%), PMME (1%), PE (9%), PG (10%), DPG (6%), and a non-phosphorus, ornithine-containing lipoamino acid, OL (6%). No low-polarity lipids, such as fatty acid esters of glycerol or of other alcohols, were detected. The sole fatty-acyl constituents of PDME and PMME were cis-octadec-11-enoic (cis-vaccenic) acid residues, whereas the other phospholipids contained, in addition, 1 to 5 mol % of MOA (lactobacillic acid) residues located predominantly at the sn-1 position of their glycerol residues. OL consisted of two molecular species, 2-N-[3'-(cis-octadec-11"-enoyloxy)octadecanoyl]-L- ornithine and 2-N-[3'-(cis-11", 12"-methyleneoctadecanoyloxy)octadecanoyl]-L-ornithine in the molar ratio 94:6. When the culture medium was devoid of phosphate, a threefold increase in OL together with a three-fold decrease in PE were observed, no significant changes in proportions of the remaining lipids occurring. The most striking feature of the lipid composition in this case was the presence of considerable amounts of fatty acid methyl esters, mainly methyl cis-vaccenate, along with minute amounts of wax esters.

Microbial fatty acids and thermal adaptation

The existing literature on the role of fatty acids in microbial temperature adaptation is reviewed. Several modes of change of cellular fatty acids at varying environmental temperatures are shown to exist in yeasts and fungi, Gram-negative bacteria, and bacteria containing iso- and anteiso-branched fatty acids, as well as in a few Gram-positive bacteria. Consequently, the degree of fatty acid unsaturation and cyclization, fatty acid chain length, branching, and cellular fatty acid content increase, decrease, or remain unaltered on lowering the temperature. Moreover, microorganisms seem to be able to change from one mode or alter the cellular fatty acid profile temperature dependently to another on lowering the temperature, as well as even within the same growth temperature range, depending on growth conditions. Therefore, the effect of the temperature on cellular fatty acids appears to be more complicated than known earlier. However, similarities found in the modes of change of cellular fatty acids at varying environmental temperatures in several microorganisms within the above mentioned groups support the existence of a limited amount of common regulatory mechanisms. The models presented enable the prediction of temperature-induced changes occurring in the fatty acids of microorganisms, and enzymatic steps of the fatty acid biosynthesis that possibly are under temperature control.

Isolation and characterization of a novel glucuronosyl diacylglycerol from Mycobacterium smegmatis

A glucuronic acid-containing diacylglycerol was isolated from exponentially growing Mycobacterium smegmatis. Structural analysis of the purified glycolipid, performed by gas chromatography-mass spectrometry, fast atom bombardment-mass spectrometry, and high resolution proton NMR, indicated the structure 3-(O-alpha-D-glucuronopyranosyl)-1,2-diacyl-sn-glycerol. Two forms of the glycolipid were observed differing in fatty acid composition. Both molecular species contained a hexadecanoic acid residue, whereas the second acyl group was either tuberculostearic acid (10-methylstearic acid) or octadecenoic acid. The inherent antigenicity of the glycolipid was shown by its ability to bind to anti-Mycobacterium avium (serovar 26) and anti-Mycobacterium tuberculosis sera by Western blot-type thin-layer chromatography. This is the second instance of the isolation of a glycosyl diacylglycerol from members of the Mycobacterium genus, further confirming its close relationship to Gram-positive bacteria.

Taxonomic studies of Streptomyces virginiae mutants overproducing virginiamycin M1

By using both the traditional International Streptomycetes Project methods and chemical approaches followed by a hierarchical cluster analysis, Streptomyces virginiae mutants A-1 and B-43 (yielding higher amounts of the M1 component of virginiamycin complex), their wild ancestor ATCC 13161, and another virginiamycin producer, S. pristinaespiralis NRRL 2958, were subjected to taxonomic studies to find kinship or differences among the strains. Of the methods used, only the test of carbon utilization, investigation of spore surface and analysis of sugar constituents of cell walls proved to be reliable enough to demonstrate the species identity of S. virginiae strains and to distinguish them from S. pristinaespiralis. L,L-2,6-Diaminopimelic acid was present in all strains. Analysis of fatty acids and total proteins as well as investigations of morphology and pigmentation of agar cultures led to confusing results.

Relationship between the fatty acid composition and the type of antibiotics produced by Streptomyces lasaliensis

The GC-MS method was used to analyze fatty acids in a parent strain of Streptomyces lasaliensis and its two mutants producing only lasalocid or quinomycin. The biosynthesis of these substances bears relation to differences in the relative proportion of fatty acids. Biosynthetic relationships were revealed between the starter fatty acid units, their precursors, i.e. valine, leucine and isoleucine, and the type of the antibiotic produced.

Isolation and structural characterization of a new non-phosphorylated lipoamino acid from Mycobacterium phlei

A new non-phosphorylated lipoamino acid was extracted from Mycobacterium phlei, strain IST. It is particularly sensitive to alkaline hydrolysis, and contains a lysine residue joined to a 1,2-diglyceride via an ester linkage. The FAB-positive mass spectrum shows the presence of various molecular species of which the most abundant contains a palmitic and a tuberculostearic acid residue. An analogue of this lipid was synthesized, 1,2-dipalmitoyl 3-lysyl glycerol. Both its chromatographic behavior (TLC), and the decomposition pathways of the MH+ ions, studied by FAB MS and MIKE spectroscopy, were identical to the natural product.

[Composition of the complex lipids of Flavobacterium meningosepticum]

The free lipids of Flavobacterium meningosepticum were separated by thin layer chromatography, and the main lipid fractions were analysed by FAB (fast atom bombardment) mass spectrometry. The major products were di-iso-C15- and iso-C15-iso-C17-phosphatidylethanolamine, and two ninhydrin + and phosphorus- fractions. The structures of the latter two fractions were established as ornithine lipids by using MIKE (mass ions kinetic energy) mass spectrometry, GC/MS (gas chromatography coupled with mass spectrometry) and conventional methods. The presence of small amounts of sphingolipids with C17- and C16-sphinganines was demonstrated. F. meningosepticum can be distinguished from F. multivorum and F. spiritivorum by easy characterization of the ornithine lipids by thin layer chromatography.

Menaquinone composition in the classification and identification of aerobic actinomycetes

Menaquinones were the only isoprenoid quinones found in 36 strains representing different species of the genera Nocardia, Mycobacterium, Rhodococcus, Amycolatopsis, Saccharothrix, Streptomyces, Nocardiopsis and Actinomadura. Dihydrogenated menaquinones with nine isoprene units [MK-9(H2)] were the main components isolated from Mycobacterium. Dihydrogenated and tetrahydrogenated menaquinones with eight isoprene units were the predominant compounds identified in typical Rhodococcus and Nocardia strains, respectively. "Nocardia phenotolerans" differed from all of the other Nocardia species included in the study, in that it contained the MK-9(H2) [MK-8(H2)] menaquinone system. Nocardioform bacteria lacking mycolic acids contained tetrahydrogenated menaquinones with nine isoprene units as the main component. The Streptomyces strains studied exhibited complex mixtures of partially saturated menaquinones with nine isoprene units with the hexa- and/or octahydrogenated components predominating. Actinomadurae contained major amounts of hexahydrogenated menaquinones with nine isoprene units. In contrast, the single Nocardiopsis strain examined possessed complex mixtures of menaquinones with ten isoprene units, the dihydrogenated components being main constituents.

Fatty acids and production of tylosin-like compounds in Streptomyces fradiae

The composition of fatty acids and the spectrum of macrolide antibiotics produced in 7 mutant strains of Streptomyces fradiae, a tylosin producer, were investigated. The strains under investigation differed in the production level and representation of individual tylosin-like compounds. The composition of fatty acids in the mycelium did not depend on the total production. However, the strains producing relomycin in addition to tylosin produced a significantly higher fraction of fatty acids with a higher melting point, and, on the contrary, the strains producing only tylosin or tylosin and desmycosin synthesized a significantly lower proportion of these acids. The results obtained indicate that in addition to the activity and substrate specificity of secondary metabolism enzymes, the composition of the tylosin-like compounds produced can be influenced by the cell membrane and its function.

Kinetics of phosphate uptake, growth, and accumulation of cyclic diphosphoglycerate in a phosphate-limited continuous culture of Methanobacterium thermoautotrophicum

The archaebacterium Methanobacterium thermoautotrophicum was grown in continuous culture at 65 degrees C in a phosphate-limited medium at specific growth rates from 0.06 to 0.28 h-1 (maximum growth rate [mu max] = 0.36 h-1). Cyclic-2,3-diphosphoglycerate (cyclic DPG) levels ranged from 2 to 20 mM in Pi-limited cells, compared with about 30 mM in batch-grown cells. The Monod constant for Pi-limited growth was 5 nM. Pi uptake rates were determined by following the disappearance of 32Pi from the medium. Interrupting the H2 supply stopped the uptake of Pi and the release of organic phosphates. Little or no efflux of Pi occurred in the presence or absence of H2. Pi uptake of cells adapted to nanomolar Pi concentrations could be accounted for by the operation of one uptake system with an apparent Km of about 25 nM and a Vmax of 58 nmol of Pi per min per g (dry weight). Uptake curves at 30 microM Pi or above were biphasic due to a sevenfold decrease in Vmax after an initial phase of rapid movement of Pi into the cell. Under these conditions the growth rate slowed to zero and the cyclic DPG pool expanded before growth resumed. Thus, three properties of M. thermoautotrophicum make it well adapted to live in a low-P environment: the presence of a low-Km, high-Vmax uptake system for Pi; the ability to accumulate cyclic DPG rapidly; and a growth strategy in which accumulation of Pi and cyclic DPG takes precedence over a shift-up in growth rate when excess Pi becomes available.

Occurrence of squalene and dehydrosqualene in streptomycetes

Squalene, dehydrosqualene and related hydrocarbons were found to constitute an essential part of the neutral lipid fraction extracted from mycelia and membranes of S. hygroscopicus, S. griseus and S. noursei. In comparison with the fraction of the triglycerides, these terpenoid compounds failed to incorporate (U-14C)-acetic acid throughout pulse labelling experiments. This suggested that the pertinent precursors were formed via alternative routes, for instance by catabolising branched-chain amino acids.

Menaquinone composition of mycolic acid-containing actinomycetes and some sporoactinomycetes

The menaquinones of 141 actinomycetes representing the genera Caseobacter, Mycobacterium, Nocardia, Rhodococcus and some related taxa lacking mycolic acids were examined by mass spectrometry. The mycolic acid-containing strains were assigned to four groups on the basis of the predominant isoprenologue detected: Rhodococcus coprophilus, R. equi, R. erythropolis, R. globerulus, R. rhodnii, R. rhodochrous and R. ruber contained dihydrogenated menaquinones with eight isoprene units; Nocardia asteroides, N. brasiliensis, N. carnea, N. otitidis-caviarum and N. transvalensis contained tetrahydrogenated menaquinones with eight isoprene units; Caseobacter polymorphus, R. bronchialis, R. rubropertinctus and R. terrae and representatives of twenty-one approved species of Mycobacterium contained dihydrogenated menaquinones with nine isoprene units; a single strain of 'Mycobacterium album', contained unsaturated menaquinones with nine isoprene units. Actinomycetes containing meso-diaminopimelic acid, arabinose and galactose in the wall peptidoglycan but lacking mycolic acids were recovered in two groups: tetrahydrogenated menaquinones with eight isoprene units were the main components from 'Nocardia' autotrophica and Pseudonocardia thermophila whereas Saccharopolyspora hirsuta and Pseudonocardia spp. contained tetrahydrogenated menaquinones with nine isoprene units. Promicromonospora citrea and 'skin coryneforms' with LL-diaminopimelic acid and glycine in the wall peptidoglycan also contained tetrahydrogenated menaquinones with nine isoprene units as the major isoprenologue. In contrast, representatives of the genera Kitasatoa, Microellobosporia, Streptomyces and Streptoverticillium were characterized by the presence of complex mixtures of tetra-, hexa- and octa-hydrogenated menaquinones with nine isoprene units. The menaquinone data correlate well with other developments in actinomycete systematics and confirm earlier suggestions that menaquinone analyses are of value in both the classification and identification of actinomycetes. Indeed, the data suggest that minimal descriptions of wall chemotype IV taxa should ideally include information on menaquinone composition.

Lipid composition and protoplast-forming capacity of Streptomyces antibioticus

The lipid and fatty acid composition of a strain of Streptomyces antibioticus has been studied as a function of culture age and glycine concentration in the growth medium. Under all conditions, the main polar lipids were phosphatidylethanolamine, cardiolipin and phosphomannoinositides in order of decreasing abundance; no ornithinolipids were detected. Acylglucoses and menaquinones were found among the nonpolar lipids. The main fatty acids present were anteiso 15:0 and anteiso 17:0. The lipid composition of the cells varied with the age of the culture, but no uniform pattern of variation was found in the cultures grown on different amounts of glycine. Among the cells harvested at the end of the exponential phase of growth, those grown on 2% glycine give the highest yield of protoplast formation. These cells were found to contain low amounts of nonpolar lipids and of phosphatidylethanolamine, and high proportions of anteiso fatty acids. We propose that the membrane bilayer of these cells, because of its peculiar lipid composition, is particularly stable and fluid. As a consequence, the yield and stability of derived protoplasts should be increased.

Modification by genetic changes of the pleiotropic interference of butyrolactone-type autoregulators with differentiation of Streptomyces griseus

Two series of aerial-mycelium-negative (Amy-), anthracycline-nonproducing (Ant-) mutants were obtained from ancestral Amy+Ant+ strains of S. griseus: a) derivatives represented by the met- strain 39 which could not differentiate although they were still producing both the butyrolactone-type autoregulator 1 and NADP-glycohydrolase, and b) mutants whose incapability to form spores and anthracycline pigments was apparently caused by the loss of autoregulator production. These latter mutants responded to the addition of 1 or the naturally occurring dihydro derivative 2 with complete or at least partial reconstitution of differentiation-associated functions. All of the b)-type mutant strains exhibited similar biochemical alterations in the presence of 1 or 2 regardless of the presence of additional genetic changes in the primary metabolism. Two mutants, however, displayed an altered pattern of secondary product formation. In submerged cultures the major biochemical changes observed in presence of 1 (or 2) were an increase of the lipid level in the mycelium, an alteration of the lipid composition, and a stimulation of neutral proteinase production. All of the blocked autoregulator-negative mutants were discernible from the ancestral strains and strain 39 by their lack of NADP-glycohydrolase production. This suggested the existance of a common genetic locus or a common pleiotropic regulator gene controling both gene functions. Present ideas concerning the role of butyrolactone-type autoregulator 1 as a pleiotropic effector molecule interacting with development of S. griseus are summarized in a hypothetical scheme.

Molecular species analysis of lipids by metastable ion mass spectrometry

A convenient universal and fast mass spectrometrical method designed for the molecular species analysis of natural lipids is described. In contrast to the commonly employed procedures the method does not require chemical or enzymatic treatment and does not include chromatographic steps. The method relies on the recognition of ions characteristic of individual molecular species in the mass spectrum of a particular lipid fraction, that is accomplished on the basis of metastable ion spectra. The efficiency of this approach is demonstrated with a variety of natural lipids: triglycerides, glycerophospholipids, sphingomyelin and ornithinolipids. The advantages and limitations of the method as well as possible further developments are discussed.

Effect of l-valine and l-isoleucine on fatty acid composition of Streptomyces hygroscopicus and S. griseus

The effects of L-valine and L-isoleucine on the composition of mycelial fatty acids were investigated during growth of differentiating parent strains of Streptomyces hygroscopicus and Streptomyces griseus as well as their non-differentiating derivatives (Amy-strains) on a synthetic medium. Both in the Amy+ and Amy- strains, in the presence of L-valine, the portion of the isopalmitic acid (iC16:0) increased, but the addition of L-isoleucine led to an elevated level of the 12-methyltetradecanoic acid (aC15:0). The results suggest that the genetically determined alterations in the ratio of both fatty acids in the non-differentiating derivatives may be due to specific changes in the biosynthetic pathways of both amino acid precursors rather than due to changes of their catabolism.