Regulation of fatty acid composition in Escherichia coli: a proposed common mechanism for changes induced by ethanol, chaotropic agents, and a reduction of growth temperature.

Growth of Escherichia coli in the presence of ethanol and chaotropic salts resulted in the synthesis of lipids containing elevated levels of unsaturated fatty acids analogous to the effect of a reduction in growth temperature. Both ethanol and chaotropic agents acted at the level of fatty acid biosynthesis and altered lipid composition by decreasing the proportion of saturated acyl chains available for the synthesis of phospholipids. A reduction in temperature causes similar effects on fatty acid biosynthesis in vivo and in vitro. Ethanol, chaotropic salts, and a decrease in temperature all weaken hydrophobic interactions. Antichaotropic salts antagonized and effects of these treatments on fatty acid synthesis in vitro. These results are consistent with a common mechanism for the effects of chaotropic agents, temperature, and ethanol on fatty acid synthesis. The biosynthesis of saturated and unsaturated acyl chains may be regulated by the strength of hydrophobic interactions. Changes in the strength of hydrophobic interactions could alter enzyme structure, substrate structure, or the equilibrium between the soluble enzymes of fatty acid synthesis and their respective acyl carrier protein substrates.     

Fatty acid composition of the lipids in fungi of the genus Aspergillus developing on mineral media with different carbon sources

This work was aimed at studying the effect of different carbon sources in the composition of mineral media on the growth of fungi belonging to the Aspergillus genus and on the fatty acid composition of their lipids. A chemically-defined medium with glucose was shown to be optimal for the growth of 18 Aspergillus strains and for the synthesis of lipids by them. The fatty acid composition of lipids was studied when the fungi grew in media with different carbon sources. The lipids were shown to contain saturated and unsaturated fatty acids with the prevalence of oleic, linoleic and linolenic acids.     

Ethanol-induced changes in lipid composition of Escherichia coli: Inhibition of saturated fatty acid synthesis in vitro

Growth of Escherichia coli in the presence of ethanol results in the synthesis of lipids containing elevated proportions of unsaturated fatty acids. Previous in vivo experiments indicated that the ethanol-induced changes in fatty acid composition result from a preferential inhibition of saturated fatty acid synthesis. In this study, the inhibition of saturated fatty acid synthesis by ethanol was confirmed in vitro. This inhibition was not membrane mediated and resulted from a direct action of ethanol on the soluble enzymes of fatty acid synthesis. The addition of ethanol resulted in a decrease in chain length of both saturated and unsaturated acyl products in vitro. Experiments with enzymes prepared from several fatty acid synthesis mutants of E. coli indicate that β-hydroxydecanoyl-acyl carrier protein dehydrase is not the site of the ethanol inhibition of saturated fatty acid synthesis. The two condensing enzymes are the probable sites for inhibition by ethanol.     

Growth-mediated variations in fatty acids of Xenorhabdus sp

The bacterium Xenorhabdus sp. is symbiotically associated with the entomopathogenic nematode Steinernema riobravis. This nematode is produced in monoxenic culture with Xenorhabdus sp. and is sold as a biological insecticide. Acceptable yields in fermentors can only be achieved in the presence of vigorous growth of the bacterium. We investigated the fatty acid composition of Xenorhabdus species when grown at 15, 20, 25 or 30 degrees C on media containing one of two primary carbon sources: glucose or lipids from the insect host, Galleria mellonella. Both temperature and primary carbon source significantly affected lipid quantity and quality in Xenorhabdus sp. Bacteria grown with insect lipids as a primary carbon source accumulated more lipids with greater proportion of longer chain fatty acids than bacteria grown with glucose as a primary carbon source. Cells grown with insect lipids at 15 degrees C had a lower lipid content than cells grown on the same media at 20, 25 or 30 degrees C. Increasing growth temperature increased saturated fatty acids and decreased unsaturated fatty acids, irrespective of carbon source. We recommend addition of complex fatty acid sources that resemble natural host lipids to growth medium for mass producing entomopathogenic nematodes. This could provide nematode quality similar to in vivo-produced nematodes.     

Lipid acyl chain-dependent effects of sterols in Acholeplasma laidlawii membranes.

Acholeplasma laidlawii was grown with different fatty acids for membrane lipid synthesis (saturated straight- and branched-chain acids and mono- and di-unsaturated acids). The ability of 12 different sterols to affect cell growth, lipid head group composition, the order parameter of the acyl chains, and the phase equilibria of in vivo lipid mixtures was studied. The following two effects were observed with respect to cell growth: with a given acyl chain composition of the membrane lipids, growth was stimulated, unaffected, reduced, or completely inhibited (lysis), depending on the sterol structure; and the effect of a certain sterol depended on the acyl chain composition (most striking for epicoprostanol, cholest-4-en-3-one, and cholest-5-en-3-one, which stimulated growth with saturated acyl chains but caused lysis with unsaturated chains). The three lytic sterols were the only sterols that caused a marked decrease in the ratio between the major lipids monoglucosyldiglyceride and diglucosyldiglyceride and hence a decrease in bilayer stability when the membranes were enriched in saturated (palmitoyl) chains. With these chains correlations were found for several sterols between the glucolipid ratio and the order parameter of the acyl chains, as well as the lamellar-reversed hexagonal phase transition, in model systems. A shaft experiment revealed a marked decrease in the ratio of monoglucosyldiglyceride to diglucosyldiglyceride with the lytic sterols in unsaturated (oleoyl) membranes. The two cholestenes induced nonlamellar phases in in vivo mixtures of oleoyl A. laidlawii lipids. The order parameters of the oleoyl chains were almost unaffected by the sterols. Generally, the observed effects cannot be explained by an influence of the sterols on the gel-to-liquid crystalline phase transition.     

Lipoidal Components of Bacterial Lipopolysaccharides: Nature and Distribution of Fatty Acids in Aerobacter aerogenes

The fatty acid distribution of Aerobacter aerogenes was studied by comparing the fatty acid composition of the lipoidal component of the endotoxin (lipid A) with the fatty acids of the readily extractable native lipids and total cellular fatty acids. The results for total cellular fatty acids and readily extractable native lipids were generally similar, but both quantitative and qualitative differences exist. In addition, profound differences between these two fractions and lipid A were observed. These differences included fewer fatty acids and lower concentrations of unsaturated and cyclopropane fatty acids in the lipid A. Hydroxy fatty acids persisted in the lipid A. The significance of these differences with respect to mammalian toxicity of endotoxins is discussed.     

Triclosan-Induced Modification of Unsaturated Fatty Acid Metabolism and Growth in Pseudomonas aeruginosa PAO1

Triclosan is a broad-spectrum antimicrobial agent having low toxicity which facilitates its incorporation into numerous personal and health care products. Although triclosan acts against a wide range of gram-positive and gram-negative bacteria by affecting fatty acid biosynthesis, it is ineffective against the opportunistic pathogen Pseudomonas aeruginosa. Wild-type strain P. aeruginosa PAO1 was used as a model system to determine the effects of triclosan on fatty acid metabolism in resistant microorganisms. This was accomplished by cultivating P. aeruginosa PAO1 cultures in the presence of different concentrations of triclosan, monitoring growth rates turbidimetrically, and harvesting in stationary phase. Readily extractable lipids (RELs) were obtained from freeze-dried cells after washing and analyzed using gas chromatography coupled with mass spectrometry. Resultant data demonstrated that triclosan caused dose-dependent increases in the amounts of trans-C_16:1 and trans-C_18:1 fatty acids, with concomitant decreases in their respective cyclopropyl analogs. Triclosan did not affect the relative concentrations of saturated, cis unsaturated, or the overall ratios of combined C₁₆ to C₁₈ fatty acid species. The readily extractable lipid fractions contained triclosan proportional to triclosan concentrations in the growth media. The presence or absence of triclosan in either liquid or solid media did not affect the antimicrobial susceptibilities of P. aeruginosa PAO1 to a battery of unrelated antimicrobials. Triclosan decreased growth rate in a dose-dependant manner at soluble concentrations. Incorporation of triclosan into the REL fraction was accompanied by increased levels of trans unsaturated fatty acids, decreased levels of cyclopropyl fatty acids, and decrease in growth rate. These alterations may contribute to triclosan resistance in P. aeruginosa PAO1.     

Sporulation in Bacillus subtilis is independent of membrane fatty acid composition.

Growth and sporulation of a Bacillus subtilis mutant deficient in branched fatty acid synthesis (gene symbol bfmB) were examined. The mutant, which produces an acyl-coenzyme A:acyl carrier protein transacylase with reduced affinity for branched fatty acid primers, could grow in media containing any one of a wide range of low-molecular-weight fatty acids having branched, cyclic, saturated, or unsaturated carbon chains. The fatty acid composition of cellular lipids depended on the compound used to support growth. Cultures of the bfmB mutant grown in the presence of 3-methylcrotonate contained an unusually high fraction (73%) of straight-chain fatty acids in the cellular lipids. The mutant sporulated with any one of the precursors of branched fatty acids in the medium; isolated spores contained mainly this branched fatty acid and only 10% or less straight-chain fatty acids regardless of the straight-chain fatty acid content of vegetative cells. Exceptional were spores grown in the presence of cyclobutane-carboxylic acid, which contained 28% straight-chain fatty acids. The branched fatty acid composition of spores could be modified greatly by changing the supply of precursors in the medium.     

Long-chain fatty acid assimilation By rhodopseudomonas sphaeroides

Exogenously supplied long-chain fatty acids have been shown to markedly alleviate the inhibition of phototrophic growth of cultures of Rhodopseudomonas sphaeroides caused by the antibiotic cerulenin. Monounsaturated and polyunsaturated C18 fatty acids were most effective in relieving growth inhibition mediated by cerulenin. Medium supplementation with saturated fatty acids (C14 to C18) failed to influence the inhibitory effect of cerulenin. The addition of mixtures of unsaturated and saturated fatty acids to the growth medium did not enhance the growth of cerulenin-inhibited cultures above that obtained with individual unsaturated fatty acids as supplements. Resolution and fatty acid analysis of the extractable lipids of R. sphaeroides revealed that exogenously supplied fatty acids were directly incorporated into cellular phospholipids. Cells treated with cerulenin displayed an enrichment in their percentage of total saturated fatty acids irrespective of the presence of exogenous fatty acids. Cerulenin produced comparable inhibitions of the rates of both fatty acid and phospholipid synthesis and was further found to preferentially inhibit unsaturated fatty acid synthesis.     

Fatty acids ofStreptomyces cinnamonensis,producer of monensin

Using the gas chromatography-mass spectrometry (GC-MS) method we found inStreptomyces cinnamonensis saturated fatty acids of iso-and anteiso-types, cyclopropyl acids, and unsaturated fatty acids where the double bond position was determined by MS of their pyrrolidine derivatives.     

Batch growth of Saccharomycopsis lipolytica on animal fats

Summary Solid animal fats aggregated when first added to aqueous media and strong agitation was necessary to accomplish and maintain their dispersion. The growth rate of Saccharomycopsis lipolytica accelerated as fat dispersion proceeded until similar rates of exponential growth were attained with either lard, mutton tallow or beef tallow as sole carbon source. The major fatty acids in all substances were oleic, palmitic, and stearic. A major proportion of both saturated acids were consumed during the yeast's growth on animal fats, but the growth rates were greatly reduced after exhaustion of the preferentially consumed unsaturated acid. At this time, substantial amounts of saturated acids, present both as free fatty acid and in glycerides, remained. The amounts of these residual acids were markedly affected by the distribution of acyl groups within the original triglycerides. With individual fatty acids as the sole carbon source, the yeast grew at comparable rates on palmitic and oleic acids but did not grow on stearic acid.     

Development and Quality Evaluation of Hypoallergenic Bakery Products Suitable for Patients with Wheat-associated Allergy

The influence of growth temperature (21–41°C) and light intensity on compositions of four carotenoids, and of fatty acids from carotenoid glucoside ester (carotenoid K-G-FA) and from the cellular lipids in Rhodococcus rhodochrous RNMS1 were quantitatively investigated. Lowering the temperature increased the total carotenoid content and the proportion of carotenoid K-G-FA. It increased the proportion of unsaturated fatty acids in both carotenoid K-G-FA and the cellular lipids, decreased that of saturated ones, and slightly decreased that of branched-chain ones. This bacterium adapted itself to low temperature by desaturating its fatty acids. The light intensity affected neither the content and the composition of carotenoids nor the composition of the fatty acids in carotenoid K-G-FA and the cellular lipids. This bacterium was a scotochromogenic strain.     

Iso- and anteiso-fatty acids in bacteria: biosynthesis, function, and taxonomic significance.

Branched-chain fatty acids of the iso and anteiso series occur in many bacteria as the major acyl constituents of membrane lipids. In addition, omega-cyclohexyl and omega-cycloheptyl fatty acids are present in several bacterial species. These two types of fatty acids are synthesized by the repeated condensation of malonyl coenzyme A with one of the branched-chain and cyclic primers by the same enzyme system. The pathway of de novo branched-chain fatty acid synthesis differs only in initial steps of synthesis from that of the common straight-chain fatty acid (palmitic acid) present in most organisms. The cell membranes composed largely of iso-, anteiso-, and omega-alicyclic acids support growth of bacteria, which inhabit normal as well as extreme environments. The occurrence of these types of fatty acids as major cellular fatty acids is an important criterion used to aid identification and classification of bacteria.     

Fatty Acids Associated with the Cell Wall in Film Strains of Saccharomyces

Fatty acid contents were estimated in the cell wall of Saccharomyces. The fatty acids responsible for cell wall hydrophobicity were classified by ease of extraction to ‘readily extractable’ and ‘bound’ acids. The readily extractable fatty acids were easily extracted with pentane and chloroform-methanol. The fatty acids extracted with chloroform-methanol were quite effective for cell wall hydrophobicity, but the fatty acids extracted with pentane were not. The bound fatty acids comprised in the phospholipids phosphatidylethanolamine and phosphatidylserine, which were rigidly associated with the cell wall. These phospholipids were not extractable until they were released from the cell wall by pronase. Chloroform-methanol extraction caused a reduction in cell wall phospholipid content, particularly after treatment with pronase. The fatty acid content of the resultant cell wall was lowered to below 7% of initial content. Phospholipids contained more saturated fatty acid than readily extractable lipids. Phospholipids greatly contributed to cell wall hydrophobicity of various film strains of Saccharomyces.     

Lipid remodeling in Rhodopseudomonas palustris TIE‐1 upon loss of hopanoids and hopanoid methylation

The sedimentary record of molecular fossils (biomarkers) can potentially provide important insights into the composition of ancient organisms; however, it only captures a small portion of their original lipid content. To interpret what remains, it is important to consider the potential for functional overlap between different lipids in living cells, and how the presence of one type might impact the abundance of another. Hopanoids are a diverse class of steroid analogs made by bacteria and found in soils, sediments, and sedimentary rocks. Here, we examine the trade‐off between hopanoid production and that of other membrane lipids. We compare lipidomes of the metabolically versatile α‐proteobacterium Rhodopseudomonas palustris TIE‐1 and two hopanoid mutants, detecting native hopanoids simultaneously with other types of polar lipids by electrospray ionization mass spectrometry. In all strains, the phospholipids contain high levels of unsaturated fatty acids (often >80 %). The degree to which unsaturated fatty acids are modified to cyclopropyl fatty acids varies by phospholipid class. Deletion of the capacity for hopanoid production is accompanied by substantive changes to the lipidome, including a several‐fold rise of cardiolipins. Deletion of the ability to make methylated hopanoids has a more subtle effect; however, under photoautotrophic growth conditions, tetrahymanols are upregulated twofold. Together, these results illustrate that the ‘lipid fingerprint’ produced by a micro‐organism can vary depending on the growth condition or loss of single genes, reminding us that the absence of a biomarker does not necessarily imply the absence of a particular source organism.     

Effect of ammonium ions on spiramycin biosynthesis in Streptomyces ambofaciens

The physiological significance of trans unsaturated fatty acids, which are constituents of membrane lipids of the phenol-degrading bacterium Pseudomonas putita P8, was studied. The addition of phenol or phenol derivatives to the cells induced the formation of trans unsaturated fatty acids, yielding an overall maximal amount of 41.3% of total fatty acids. The inhibition of de-novo lipid synthesis by cerulenin prevented the change in the degree of saturation in the lipids. However, the cells could still respond to phenols with an amplified conversion of cis into trans unsaturated fatty acids, which is apparently a post-synthesis mechanism of isomerization of the double bond. The cis/trans conversion correlated with growth inhibition induced by toxic concentrations of 4-chlorophenol, whereas only growing cells were able to change the degree of saturation. In cells that were protected against phenol by immobilization in calcium alginate, the conversion of cis into trans fatty acids occurred at higher toxin concentrations compared with free cells. Cells entering the stationary growth phase increased the prodortion of saturated to unsaturated fatty acids but maintained a constant trans/cis ratio.P. putida P8 reacted to an increase or decrease in the growth temperature with an appropriate change in the ratio of saturated to unsaturated fatty acids and in cells inhibited by cerulenin with a change in the trans/cis ratio. This study shows that the physiological role of the cis/trans conversion is probably the regulation of membrane fluidity when the most important mechanism for this, the modification of the degree of saturation, cannot by used by the cells due to inhibition of growth and lipid biosynthesis. Correspondence to: H. Keweloh     

Influence of selected sugars and temperature on fatty acids composition in Candida lipolytica

Summary An investigation was made of the effects of temperature and of mono- and disaccharides on lipids, biomass, odd-chain and unsaturated fatty acids production of Candida lipolytica. With different sugars as carbon source at 30°C, the order for biomass production was: fructose > glucose > sucrose > lactose > galactose, while lipids production/g biomass decreased as follows: lactose, sucrose, galactose, fructose and glucose. On the other hand, the odd-chain fatty acids contents decreased in the following order: fructose, lactose, glucose, sucrose and galactose. Lowering the temperature of cultivation to 15°C, biomass, lipids and unsaturated fatty acids decreased. However, a notable decrease in the content of odd-chain fatty acids was detected.     

The effects of temperature and growth rate on the proportion of unsaturated fatty acids in bacterial lipids

The effects of temperature and growth rate on the fatty acid composition of the extractable lipids of four mesophilic and three psychotrophic bacteria were examined. Two of the mesophiles (Escherichia coli and Pseudomonas aeruginosa) increased the proportion of unsaturated fatty acids in their lipids with decreasing temperature over their whole growth temperature range. The other mesophiles (Enterobacter aerogenes and Lactobacillus casei) increased the proportion of unsaturated fatty acids with decreasing temperature only over the lower half of their growth temperature ranges. The psychrotrophs Pseudomonas fluorescens and Enterobacter sp. had a constant proportion of unsaturated acids over the lower half of their growth temperature range, while the psychotrophic Lactobacillus sp. showed no consistent change in its unsaturated fatty acid composition with temperature. All species showed some variation of unsaturated fatty acid composition with growth rate at the highest and lowest growth temperatures, although such variations were small in some species (Ent. aerogenes and Lactobacillus sp.).     

Effect of environmental factors on the limpid composition membrane structure and permeability ofMicrosporum gypseum

Supplementation with unsaturated fatty acids, substitution of glucose by glycerol as carbon source and lowered growth temperature (20°C) increased the total phospholipid content ofMicrosporum gypseum spheroplasts. Levels of sterols increased with glycerol substitution and decreased in other growth conditions. Substantial changes were seen in the ratios of unsaturated to saturated fatty acids and phosphatidylcholine to phosphatidylethanolafne under all the experimental conditions. Changed lipid composition resulted in altered uptake of amino acids (L-lysine, L-aspartic acid and L-glycine) and increased number of binding sites for a fluorescent probe, 1-anilinonaphthalene-8-sulfonate.     

Equivalent carbon number-based targeted odd-chain fatty acyl lipidomics reveals triacylglycerol profiling in clinical colon cancer

Odd-chain FAs (OCFAs) are present in very low level at nearly 1% of total FAs in human plasma, and thus, their functions were usually ignored. Recent epidemiological studies have shown that OCFAs are inversely associated with a variety of disease risks. However, the contribution of OCFAs incorporated into complex lipids remains elusive. Here, we developed a targeted odd-chain fatty acyl-containing lipidomics method based on equivalent carbon number and retention time prediction. The method displayed good reproducibility and robustness as shown by peak width at half height within 0.7 min and coefficient of variation under 20%. A total number of 776 lipid species with odd-chain fatty acyl residues could be detected in the ESI mode of reverse-phase LC-MS, of which 309 lipids were further validated using multiple reaction monitoring transitions. Using this method, we quantified odd-chain fatty acyl-containing lipidome in tissues from 12 colon cancer patients, revealing the remodeling of triacylglycerol. The dynamics of odd-chain fatty acyl lipids were further consolidated by the association with genomic and proteomic features of altered catabolism of branched-chain amino acids and triacylglycerol endogenous synthesis in colon cancer. This lipidomics approach will be applicable for screening of dysregulated odd-chain fatty acyl lipids, which enriches and improves the methods for diagnosis and prognosis evaluation of cancer using lipidomics.