Sofia K. Mastronicolis

Alteration of the phospho- or neutral lipid content and fatty acid composition in Listeria monocytogenes due to acid adaptation mechanisms for hydrochloric, acetic and lactic acids at pH 5.5 or benzoic acid at neutral pH

This study provides a first approach to observe the effects on Listeria monocytogenes of cellular exposure to acid stress at low or neutral pH, notably how phospho- or neutral lipids are involved in this mechanism, besides the fatty acid profile alteration. A thorough investigation of the composition of polar and neutral lipids from L. monocytogenes grown at pH 5.5 in presence of hydrochloric, acetic and lactic acids, or at neutral pH 7.3 in presence of benzoic acid, is described relative to cells grown in acid-free medium. The results showed that only low pH values enhance the antimicrobial activity of an acid. We suggest that, irrespective of pH, the acid adaptation response will lead to a similar alteration in fatty acid composition [decreasing the ratio of branched chain/saturated straight fatty acids of total lipids], mainly originating from the neutral lipid class of adapted cultures. Acid adaptation in L. monocytogenes was correlated with a decrease in total lipid phosphorus and, with the exception of cells adapted to benzoic acid, this change in the amount of phosphorus reflected a higher content of the neutral lipid class. Upon acetic or benzoic acid stress the lipid phosphorus proportion was analysed in the main phospholipids present: cardiolipin, phosphatidylglycerol, phosphoaminolipid and phosphatidylinositol. Interestingly only benzoic acid had a dramatic effect on the relative quantities of these four phospholipids.

Sphingophosphonolipids, phospholipids, and fatty acids from Aegean jellyfish Aurelia aurita.

The goal of this study is to elucidate and identify several sphingophosphonolipids from Aurelia aurita, an abundant but harmless Aegean jellyfish, in which they have not previously been described. Total lipids of A. aurita were 0.031–0.036% of fresh tissue, and the lipid phosphorus content was 1.3–1.7% of total lipids. Phosphonolipids were 21.7% of phospholipids and consisted of a major ceramide aminoethyl-phosphonate (CAEP-1; 18.3%), as well as three minor CAEP (II, III, IV) methyl analogs at 1.3, 1.1, and 1.0%, respectively. The remaining phospholipid composition was: phosphatidylcholine, 44.5%, including 36.2% glycerylethers; phosphatidylethanolamine, 18.6%, including 4.5% glycerylethers; cardiolipin, 5.6%; phosphatidylinositol, 2.6%; and lysophosphatidylcholine, 5.0%. In CAEP-1; saturated fatty acids of 14–18 carbon chain length were 70.8% and were combined with 57.3% dihydroxy bases and 23.4% trihydroxy bases. The suite of the three minor CAFP methyl analogs were of the same lipid class based on the head group, but they separated into three different components because of their polarity as follows: CAEP-II and CAEP-III differentiation from the major CAEP-I was mainly due to the increased fatty acid unsaturation and not to a different long-chain base, but the CAEP-IV differentiation from CAEP-I, apart from fatty acid unsaturation, was due to the increased content of hydroxyl groups originated from both hydroxy fatty acids and trihydroxy long-chain bases. Saturated fatty acids were predominant in total (76.7%), polar (83.0%), and neutral lipids (67.6%) of A. aurita. The major phospholipid components of A. aurita were comparable to those previously found in a related organism (Pelagia noctiluca), which can injure humans.

Adaptational changes in cellular phospholipids and fatty acid composition of the food pathogen Listeria monocytogenes as a stress response to disinfectant sanitizer benzalkonium chloride

Aims:  This study provides a first approach to observing the alterations of the cell membrane lipids in the adaptation response of Listeria monocytogenes to the sanitizer benzalkonium chloride.

Sphingophosphonolipid molecular species from edible mollusks and a jellyfish.

The goal of this study is to supplement the composition and nature of sphingophosphonolipids diversity from edible mollusks (Mytilus galloprovincialis, Eobania vermiculata) and from jellyfish Pelagia noctiluca, organisms rich in phosphonolipids. M. galloprovincialis contained a major ceramide 2-aminoethylphosphonate (CAEP-IM) and a minor ceramide that was detected chromatographically as the methyl analog (CAEP-IIM). In CAEP-IM, saturated fatty acids (FA) of 14, 16 and 18 carbons amounted to 68.8%; also 52.5% dihydroxy bases were detected. On thin layer chromatography, the Rf for CAEP-IIM was smaller than the Rf for CAEP-IM because of an increase of 22.0% in 2OH-16:0 FA, plus 29.2% trihydroxy bases (phytosphingosine). Similarly, a ceramide 2-methylaminoethylphosphonate (CAEP-IIE, 1.5% of phospholipids) was quantitated in Eobania (apart from the previously reported major CAEP, 7.6%). In CAEP-IIE, saturated and hydroxy FA of 14, 16 and 18 carbons amounted to 37.0 and 37.8%; 29.1% dihydroxy and 23.0% trihydroxy bases were detected in the same molecule. Eobanias unsaturated FA percentages (total lipids: 66.3, polar: 47.5, neutral: 59.0) were similar to those previously found for other land snails. A suite of two minor CAEP (CAEP-IIP, CAEP-IIIP) was quantitated in Pelagia at 2.0 and 1.3% of phospholipids (apart from the previously reported major CAEP, 21.0%) identified chromatographically as methyl analogs. In CAEP-IIP, saturated FA of 14, 16, 18 and 19 carbons amounted to 56.0%; 12.6% dihydroxy and 34.1% trihydroxy bases were also detected in CAEP-IIP. The Rf CAEP-IIIP<Rf CAEP-IIP owing to an increase of +8.5% of hydroxy FA and +12.3% of trihydroxy bases. The compositions of CAEP-IIM and CAEP-IIE appear to be specific of each organism, while the composition of molluscan or jellyfish major sphingophosphonolipids appears not specific.

Growth and membrane fluidity of food-borne pathogen Listeria monocytogenes in the presence of weak acid preservatives and hydrochloric acid.

This study addresses a major issue in microbial food safety, the elucidation of correlations between acid stress and changes in membrane fluidity of the pathogen Listeria monocytogenes. In order to assess the possible role that membrane fluidity changes play in L. monocytogenes tolerance to antimicrobial acids (acetic, lactic, hydrochloric acid at low pH or benzoic acid at neutral pH), the growth of the bacterium and the gel-to-liquid crystalline transition temperature point (Tm) of cellular lipids of each adapted culture was measured and compared with unexposed cells. The Tm of extracted lipids was measured by differential scanning calorimetry. A trend of increasing Tm values but not of equal extent was observed upon acid tolerance for all samples and this increase is not directly proportional to each acid antibacterial action. The smallest increase in Tm value was observed in the presence of lactic acid, which presented the highest antibacterial action. In the presence of acids with high antibacterial action such as acetic, hydrochloric acid or low antibacterial action such as benzoic acid, increased Tm values were measured. The Tm changes of lipids were also correlated with our previous data about fatty acid changes to acid adaptation. The results imply that the fatty acid changes are not the sole adaptation mechanism for decreased membrane fluidity (increased Tm). Therefore, this study indicates the importance of conducting an in-depth structural study on how acids commonly used in food systems affect the composition of individual cellular membrane lipid molecules.

Phospho- and phosphonolipids of the Aegean pelagic scyphomedusa Pelagia noctiluca

Abstract The total lipid content found in Pelagia noctiluca (0.19% of the whole-body weight) is comparable to that reported for other stinging jellyfish species. Its polar lipid components were found to represent 26.2% of the total lipids and to contain 75.7% glycerophospholipids and 24.3% sphingophosphonolipids. The individual lipid classes obtained by column Chromatographic fractionation were purified by preparative TLC, and their structure was confirmed by a combination of Chromatographic and analytical determinations before and after mild alkaline hydrolysis or dry acid methanolysis, and by IR analysis. The overall composition of the polar lipids was: cardiolipin, 9.1%; phosphatidylethanolamine, 24.8% (of which 55% was glyceryl ether analog); phosphatidylcholine, 36.3% (of which 62% was glyceryl ether analog); lysophosphatidylethanolamine and lysophosphatidylcholine, 5.0%; ceramide aminoethylphosphonate, 21.0% plus 3.3% (another two minor species). Unsaturated fatty acyl groups represented about 52 and 33%, respectively, in phosphatidylethanolamine and phosphatidylcholine, while their glyceryl ether analogs were found to contain about 41 and 91% unsaturated fatty alkyl chains, respectively (total unsaturation 49 and 51%, respectively). In contrast, saturated fatty acyl groups with 14–16 carbon atoms were almost exclusive components (about 96%) of the major ceramide aminoethylphosphonate species.

Phosphonolipids in the Mussel Mytilus galloprovincialis

One of the possible roles of phosphonolipids is that they have a contribution to the protection of cellular integrity and survival of aquatic organisms (mollusca, cnidaria) as these lipids are included at high percentages. The total lipids of the edible mussel Mytilus galloprovincialis (Mollusca, Bivalvia, Mytilidae) were found to constitute 1.27% of fresh tissue. Polar lipid components constitute 61.5% of the total lipids. After separation by Solid Phase Extraction, the polar lipid fraction was separated by two dimensional thin-layer chromatography and the total phosphorus of each component, was determined. The main polar lipids found were: Phosphatidylcholine, 41.6 ± 0.8% (of which 11.3 ± 0.5% was glyceryl ether analog); ceramide aminoethylphosphonate 11.2 ± 0.2% plus 2.8 ± 0.1% another minor species; phosphatidylethanolamine, 26.6 ± 0.5% (of which 12.2 ± 0.3% was glyceryl ether analog). The individual ceramide aminoethylphosphonate species were isolated by preparative thin layer chromatography and the structure of the major one was confirmed by a combination of analytical and chromatographic methods. Saturated fatty acyl groups with 16 carbon atoms were the main components (48.4%) of the major ceramide aminoethylphosphonate species. Diglyceride aminoethyl phosphonates were not found in lipids of M. galloprovincialis.

Lipid Composition and Structural Studies on Lipids from the Land Snail Eobania vermiculata

The total lipids of the commercial land snail Eobania vermiculata (Gastropoda, Pulm onata, Stylom m atophora) are found to constitute a small percentage (0.8% ) of the wet tissue, which is comparable to that reported for other gastropods. Polar lipid components comprise 61.4% of the total lipids. The individual lipid classes obtained by column chromatographic fractionation were purified by preparative TLC or by column chromatography and their structure was confirmed by a combination of chromatographic and analytical determinations before and after mild alkaline hydrolysis and/or (dry) acid methanolysis and by IR analysis. Neutral lipids represent 36.4% of total lipids, containing cholesterol, cholesterol esters and triglycerides as their major components (26.2% , 29.1% and 25.5% respectively). They contain also a significant amount (14%) of free glyceryl ethers, which are found in a mollusc for the first time. The overall composition of the polar lipids (mol/100 mol lipid-P) was found as follows: Cardiolipin, 2.9; phosphatidylethanolamine, 24.9 (of which 19.8% plasmalogen analog); phosphatidylcholine, 49.2 (of which 45.6% glycerylether analog); ceramide aminoethylphosphonate, 7.5 plus 0.01 (another three minor species); diglyceride-am noethylphosphonate, 6.3; Sphingoethanolamine 1.65 (for the first time found and structurally studied in a land gastropod); and phosphatidic acid 1.1. Unsaturated fatty acyl groups represent about 72.6 and 44.1 respectively in phosphatidylethanolamine and phosphatidylcholine. A significant amount (70.5% ) of unsaturated fatty acids is concentrated in neutral lipids. The C16:0 alk-1-enyl chain was found to predominate (55.6% ) in the side chains of ethanolamine plasmalogen. Batyl alcohol was found as the main glycerylether bound to choline phosphate (97.5% ). Saturated fatty acyl groups with 16 carbon atoms were main components (54%) of the major ceramide aminoethylphosphonate species.

A Micromethod for Rapid Quantitative Determination of Phosphonate Phosphorus

A rapid method for initial quantitative estimation of the phosphate present in compound containing a carbon-phosphorus bond is described. Two phosphorus assays are employed. One assay is for total phosphorus, which can be determined by digesting with perchloric acid and the other assay is for total non phosphonate phosphorus which can be determined by digesting with sulfuric acid simultaneously. The difference between total phosphorus and the non phosphonate phosphorus determined represents the amount of phosphorus present in a carbon-phosphorus linkage in a crude phospholipids sample

Identification of the lipid components of honey.

ZusammenfassungDie im griechischen Honig vorkommenden Lipide wurden isoliert und untersucht, und zwar durch Extrahierung und durch chromatographische Trennung an Kieselsäure. Hierfür wurden die Fraktionen gesammelt und vor und nach der Verseifung dünnschichtchromatographisch untersucht und die Methylester gaschromatographisch bestimmt. Danach enthält der Honig Kohlenwasserstoffe, Wachse, Cholesterinester, Fettsäureester, Sterine, Dihydroxy- und Trihydroxyverbindungen sowie einige Polyolester.SummaryThe constituent lipids of Greek Honey have been isolated and studied by an initial simple extraction procedure (comparable to that of counter-current distribution) and consequent chromatographic separation on a silicic acid column. The fractions collected were subjected to: (I) qualitative T.L.C. before or after saponification and (II) gas-chromatographic analysis of methyl esters. In addition to the fatty acids mentioned by other investigators, honey has been found to contain a number of neutral lipids, albeit in small amounts, i.e. hydrocarbons, waxes, cholesterol esters, fatty acid esters, fatty acids, fatty alcohols, sterols, dihydroxy and trihydroxy compounds, as well as some esters of polyols. The probable nature of another three unknown constituents is also discussed.