[On the presence of ornithine in bacterial lipids]

Cell-Envelope Remodeling as a Determinant of Phenotypic Antibacterial Tolerance in Mycobacterium tuberculosis

The mechanisms that lead to phenotypic antibacterial tolerance in bacteria remain poorly understood. We investigate whether changes in NaCl concentration toward physiologically higher values affect antibacterial efficacy against Mycobacterium tuberculosis (Mtb), the causal agent of human tuberculosis. Indeed, multiclass phenotypic antibacterial tolerance is observed during Mtb growth in physiologic saline. This includes changes in sensitivity to ethionamide, ethambutol, d-cycloserine, several aminoglycosides, and quinolones. By employing organism-wide metabolomic and lipidomic approaches combined with phenotypic tests, we identified a time-dependent biphasic adaptive response after exposure of Mtb to physiological levels of NaCl. A first rapid, extensive, and reversible phase was associated with changes in core and amino acid metabolism. In a second phase, Mtb responded with a substantial remodelling of plasma membrane and outer lipid membrane composition. We demonstrate that phenotypic tolerance at physiological concentrations of NaCl is the result of changes in plasma and outer membrane lipid remodeling and not changes in core metabolism. Altogether, these results indicate that physiologic saline-induced antibacterial tolerance is kinetically coupled to cell envelope changes and demonstrate that metabolic changes and growth arrest are not the cause of phenotypic tolerance observed in Mtb exposed to physiologic concentrations of NaCl. Importantly, this work uncovers a role for bacterial cell envelope remodeling in antibacterial tolerance, alongside well-documented allterations in respiration, metabolism, and growth rate.

The monoene and other Wax alcohols of human skin surface lipid and their relation to the fatty acids of this lipid

1) Wax alcohols (as acetates) were isolated from human skin surface lipid and separated into a saturated and a monoene fraction. 2) Four main chain types were found for both saturated and monoene alcohols: normal even, normal odd, iso and anteiso. ("Even" and "odd" refer to the number of C-atoms in the straight chain.) 3) The monoene alcohol acetates were separated into homologues of each chain type by preparative gas-liquid chromatography (GLC) and the positions of the double bonds for each homologue were determined by analytical GLC of the original fraction, its hydrogenated derivative, and the products it formed by reductive ozonolysis. 4) The fragments formed by reductive ozonolysis of the monoene alcohol acetates were compared to those formed from the total monoenoic fatty acids (as methyl esters), both obtained from the same sample of surface lipid. (Comparisons were best made by ozonolysis of a portion of the entire sample of each ester group. a) The terminal ends of both groups of monoene fatty chains yielded a very similar pattern of aldehydes in terms of types and amounts. This could be explained by the hypothesis that both fatty acid and fatty alcohol chains of lengths ranging mainly from C(14) to C(18) were first biosynthesized, then desaturated at Delta6. b) The functional group ends gave a distinct pattern of aldehyde esters for the acids and another for the alcohols. Both patterns consisted nearly entirely of members having aneven number of C-atoms from the double bond to the functional group. This suggested that the members of each pattern were formed by chain extensions of an integral number of C(2) units beyond the lengths arrived at in 4a). Thus 71% of the fatty acid monoenes were not extended, 25% were extended by 1 C(2) unit and the remainder extended from 2 to 5 C(2) units, whereas nearly all the fatty alcohols were extended mainly by 2, 3 or 4 C(2) units, with decreasing amounts up to 8 C(2) units. 5) A small amount ( approximately 5%) of odd chain aldehyde esters for both fatty acids and fatty alcohols were found and some unidentified alcohols were detected.

Cell walls of pseudomonas species sensitive to ethylenediaminetetraacetic Acid

Cell walls of 12 pseudomonads considered to be sensitive to ethylenediaminetetraacetic acid (EDTA) were prepared and analyzed. The wall of each species contained protein, peptidoglycan, loosely bound lipid, and lipopolysaccharide. The walls of Pseudomonas stutzeri and P. syncyanea were unusually susceptible to mechanical disintegration. The wall of P. syncyanea had an unusually high content of lipid and low contents of protein and peptidoglycan. Except for P. syncyanea, all the walls contained less phosphorus than the walls of the highly EDTA-sensitive P. aeruginosa and P. alcaligenes, but more than the walls of EDTA-resistant pseudomonads. The amino acid compositions of wall proteins were similar for all species. Amino sugars detected were glucosamine, galactosamine, muramic acid, and at least five unidentified components (possibly including fucosamine and quinovosamine). Glucose and rhamnose were the major neutral sugars in most walls. Galactose, mannose, fucose, and ribose were also detected, the last two each in a single species. Except for P. stutzeri and P. syncyanea, the walls had rather low contents of phospholipids (mainly cardiolipin, phosphatidylethanolamine, and phosphatidylglycerol in all species). An ornithine-containing nonphospholipid was present in all walls, and a hexuronosyldiglyceride was probably present in most walls. The fatty acid compositions of loosely bound lipids were qualitatively similar for all species: saturated C(16) and monoenoic C(16) and C(18) acids were the major components. Except for P. aureofaciens, the extraction of phosphorus on treatment of walls with EDTA at pH 9.2 was much less than for P. aeruginosa and P. alcaligenes.

Ornithine-containing lipids in Thiobacillus A2 and Achromobacter sp

20 bacterial strains (corresponding to 16 species) were screened for ornithine lipids. Only two species (Thiobacillus A2 and Achromobacter sp.) turned out to contain ornithine lipids (2.71 mmol/100 g and 0.38 mmol/100 g bacterial dry weight, respectively). In both ornithine lipids, a 3-hydroxy fatty acid was amide-linked to the alpha-amino group of ornithine, a normal fatty acid was ester-linked to the 3-hydroxy group of the former. The predominant fatty acids were 18:1(11) and 3-hydroxy-20:1(13) in Thiobacillus A2, 16:0 and 3-hydroxy-18:1(11) in Achromobacter sp. All monounsaturated fatty acids (with one exception) belonged to the (n-7) family. 11, 12-Epoxy octadecanoic acid was identified among the ester-linked fatty acids of Thiobacillus A2. Phosphatidylcholine was the principal phospholipid in both bacterial species.

Isolation and characterization of an ornithine-containing lipid from Desulfovibrio gigas

The isolation and characterization of an ornithine-containing lipid obtained from Desulfovibrio gigas are reported. The general structure for this aminolipid is represented by NH2-CH2-(CH)2-CHNH(CO-CH2CH(O-COR2)-R1)-COOH, where R1 represents 3-hydroxy palmitate linked through an amide bond to the alpha-amino group of ornithine, and R2 represents a complex variety of fatty acids esterified to the hydroxyl group of 3-hydroxy palmitate. Fatty acids characterized were n-C14:0 (21%), iso-C14:0 (14%) anteiso-C15:0 (43%), n-C16:0 (2%), n-C18:0 (8%), and n-C 18:1 (11%). The quantitative relationships between aminolipid and phospholipids showed the aminolipid to represent the major polar lipid. Isolation of the cytoplasmic and outer membranes of D. gigas showed the aminolipid to be evenly distributed between both membrane fractions, suggesting a compensatory role in phospholipid-deficient membranes.

Skin lipids: their biochemical uniqueness

Two key words characterize the uniqueness of skin lipids: complexity and perversity. Each suggests a function. Complexity manifests itself in the large number and variety of both saturated and unsaturated fatty chains synthesized by human skin. Functionally, this allows each individual to have a distinct odor or chemical fingerprint. Perversity manifests itself when one compares the lipids synthesized by skin with those synthesized by internal tissues. For example, skin makes odd instead of only even chains, branched instead of only straight chains, free instead of only esterified acids, places double bonds in unusual positions in the fatty chains, extends chains to extreme lengths, and accumulates intermediates in the synthesis of a biologically valuable compound such as cholesterol. Functionally, these products may pose metabolic problems to potential pathogens and thus contribute to the survival of only compatible microorganisms.

Complex lipids of Rhodomicrobium vannielii

Eight components, seven of which contained phosphorus, were found in the phospholipid fraction of Rhodomicrobium vannielii. The major components were lipoamino acid (o-ornithine ester of phosphatidyl glycerol, 46.5%) and phosphatidyl choline (26.5%). The other six components were phosphatidyl glycerol (9.7%), bisphosphatidic acid (6.7%), phosphatidyl ethanolamine (4.5%), phosphatidic acid (1.8%), lysophosphatidyl glycerol-o-ornithine ester (3.2%), and N,N-ornithine amide of unidentified fatty acid (0.95%). Total phospholipid accounted for 4.2% of cell dry weight. The major fatty acid was vaccenic acid, C(18:1), which accounted for approximately 90% of the total fatty acids of the complex lipid fraction. The other four fatty acids were C(16:0) (6.25%), C(18:0) (3.8%), C(14:0) (0.7%), and C(16:1) (0.35%). The sulfolipid content was 0.01% of the cell dry weight or 0.14 mumoles per g of dried cells, assuming that its fatty acid component is vaccenic acid. No steroids were detected.