Traces Of Fatty Acids Research Articles

The Two Functional Enoyl-Acyl Carrier Protein Reductases of Enterococcus faecalis Do Not Mediate Triclosan Resistance

ABSTRACTEnoyl-acyl carrier protein (enoyl-ACP) reductase catalyzes the last step of the elongation cycle in the synthesis of bacterial fatty acids. The Enterococcus faecalis genome contains two genes annotated as enoyl-ACP reductases, a FabI-type enoyl-ACP reductase and a FabK-type enoyl-ACP reductase. We report that expression of either of the two proteins restores growth of an Escherichia coli fabI temperature-sensitive mutant strain under nonpermissive conditions. In vitro assays demonstrated that both proteins support fatty acid synthesis and are active with substrates of all fatty acid chain lengths. Although expression of E. faecalis fabK confers to E. coli high levels of resistance to the antimicrobial triclosan, deletion of fabK from the E. faecalis genome showed that FabK does not play a detectable role in the inherent triclosan resistance of E. faecalis. Indeed, FabK seems to play only a minor role in modulating fatty acid composition. Strains carrying a deletion of fabK grow normally without fatty acid supplementation, whereas fabI deletion mutants make only traces of fatty acids and are unsaturated fatty acid auxotrophs.

Interaction of tetraphenylphosphonium and dodecyltriphenylphosphonium with lipid membranes and mitochondria

The permeability of a planar lipid membrane (composed of diphytanoylphosphatidylcholine) for tetraphenylphosphonium (TPP) was investigated. The observed level of the diffusion potential generated as a function of the TPP concentration gradient differed from the theoretically expected value, possibly due to proton leakage of the membrane mediated by the traces of fatty acids in the phospholipid forming the membrane. Using the molecular dynamics approach to study movement of TPP and dodecyltriphenylphosphonium (C(12)TPP) with different affinity to the lipid bilayer through a bilayer lipid membrane, it was found that C(12)TPP has a greater affinity to the membrane surface than TPP. However, the two cations have the same activation energy for transmembrane transfer. Interaction of TPP and C(12)TPP with tightly-coupled mitochondria from the yeast Yarrowia lipolytica was also investigated. At low, micromolar concentrations, both cations are "relatively weak, mild uncouplers", do not shunt electron transfer along the respiratory chain, do not disturb (damage) the inner mitochondrial membrane, and profoundly promote the uncoupling effect of fatty acids. At higher concentrations they inhibit respiration in state 3, and at much higher concentrations they induce swelling of mitochondria, possibly due to their detergent action.

Why Are Hydrophobic/Water Interfaces Negatively Charged?

Impure at heart: A pH-dependent negative charge of the interface between a hydrophobic phase and water results from the reaction of hydroxide ions with traces of fatty acids, contained in the hydrophobic phase (see scheme). This reaction explains the uptake of hydroxide ions by the interface with a large free energy change.

Primary and secondary marine organic aerosols over the North Atlantic Ocean during the MAP experiment

[1] The organic chemical composition of atmospheric submicron particles in the marine boundary layer was characterized over the northeast Atlantic Ocean in summer 2006, during the season of phytoplankton blooms, in the frame of the Marine Aerosol Production (MAP) experiment. First measurements of water‐insoluble organic carbon (WIOC) in marine aerosol particles by nuclear magnetic resonance (NMR) spectroscopy showed that it is structurally similar to lipids, resembling the organic fraction of sea spray formed during bubble‐bursting experiments. The composition of the water‐soluble organic carbon (WSOC) fraction was investigated by liquid chromatography – mass spectrometry and by 1D‐ and 2D‐NMR spectroscopy, and showed a less hydrophilic fraction containing traces of fatty acids and rich of alkanoic acids formed by lipid degradation, and a more hydrophilic fraction, containing more functionalized species encompassing short‐chain aliphatic acids and sulfate esters of hydroxyl‐carboxylic acids. The more oxidized fraction of WSOC accounts for the oxidized organic aerosol components, which can form by either gas‐to‐particle conversion or extensive chemical aging of lipid‐containing primary particles, as also suggested by the parallel measurements using online mass spectrometric techniques (presented in a companion paper), showing oxidized organic substances internally mixed with sea salt particles. These measurements are also compared with online measurements using an Aerosol Time‐Of‐Flight Mass Spectrometer (ATOFMS) and Aerodyne Aerosol Mass Spectrometer (AMS). Given the large variability in the chemical composition of marine organic aerosol particles, a multitechnique approach is recommended to reduce method‐dependent categorizations and oversimplifications and to improve the comparability with the results obtained in different oceanic areas.

Composition analysis of organic matter released by cosmopolitan coral reef-associated green algae

Coral reef-associated benthic algae can control important metabolic processes in reef ecosystems via organic matter release. However, information about the chemical composition of macroalgae exudates is very limited. We therefore quantified total and dissolved organic carbon (TOC, DOC) and total and dissolved organic nitrogen (TON, DON) of exudates released by 2 cosmopolitan coral reef-associated green algae species, Halimeda opuntia and Caulerpa serrulata. Glycosyl com- position and content analyses, along with protein, lipid and chlorophyll a (chl a) quantifications of algae exudates were conducted. Findings revealed that organic matter released from both algae pre- dominately consisted of carbohydrates (59 ± 5%) and proteins (32 ± 7%), which mainly (89 to 93%) dissolved in surrounding waters. Traces of fatty acids (C16:0; C18:0) and chl a were also found in algae incubation waters, but in a quantitatively negligible amount. Carbohydrate analysis further showed that glucose was the dominant glycosyl released by algae, accounting for 77 ± 8% of the carbohydrate fraction and 42 ± 8% of TOC. Galactose (9 ± 4% of carbohydrate fraction), mannose (6 ± 3%), xylose (4 ± 1%), rhamnose (3 ± 1%) and fucose (2 ± 1%) were also detected in all incubation water samples. High glucose and protein contents of algae exudates found in the present study con- firm assumptions on the fast microbial degradability of these exudates, with ensuing potential nega- tive effects on O2 availability and on interactions between corals and algae in coral reef ecosystems.

Traces of Fatty Acids from a Byzantine Sounding Lead Recovered off the Israeli Coast

Fatty acids, typical to large herbivores, were isolated from a 7th century Byzantine sounding lead recovered from a shipwreck off Dor, an ancient anchorage in Northern Israel. The fatty acids survived by being sheltered in an anaerobic environment provided through a site formation process induced by the disintegrating wreck. Previously established identification criteria for fatty acids, absorbed in ceramics, were used to show that tallow was used in this navigational instrument in the Eastern Mediterranean during late antiquity.

The front basitarsal brush in Pachycondyla apicalis and its role in hydrocarbon circulation

Worker postpharyngeal gland (PPG) chemistry of Pachycondyla apicalis constitutes a blend of hydrocarbons including alkanes, alkenes, and alkadienes, with 5,9-pentacosadiene, 5,9-heptacosadiene and 5,9-nonacosadiene as the major products as well as fatty acids. There is a large congruency between the PPG and cuticular hydrocarbons, however the latter had higher proportion of tricosane and pentacosane, but only traces of fatty acids. These ants have a well-developed cuticular hair brush on the front legs that they frequently pass through the mouth while grooming. Since these brushes have higher amounts of hydrocarbons than either the middle or hind legs, we hypothesized that they are involved in hydrocarbon circulation. We assessed the role of the front basitarsal brush in hydrocarbon circulation by isolating them from the buccal cavity, either by restraining the front legs or by blocking the mouth with glue. In both experiments, preventing contacts between the basitarsal brushes and the mouth for 24 hrs resulted in a considerable increase in hydrocarbon amounts in the brushes with a parallel decrease in the PPG. When the ants were kept alive for an additional 24 hrs after their legs were freed, hydrocarbon amounts in both the PPG and the front legs returned to normal. Analyses of crop content revealed the same hydrocarbons profile as in the PPG, but their amounts were very variable and there were no differences in amounts between the treatment and the control. We assume that part of the PPG hydrocarbons are cleared via the alimentary canal. Grooming behavior of ants restrained for 24 hrs and then freed was followed for four hours thereafter. There was a significant increase in total grooming during the first third and fourth hour, but not during the second. Grooming involving the front legs-mouth, and front legs-antennae, and the front and hind legs was especially intensive during the first hour. Grooming involving the hind legs – body was more intensive in the treated ants during the third hour following their release. We conclude that the front basitarsal brush is a site of hydrocarbon accumulation and that the PPG receives frequent charging during self-grooming.

2-O-methyl-d-xylose containing sheath in the cyanobacterium Gloeothece sp. PCC 6501

The sheath of the unicellular cyanobacterium Gloeothece sp. PCC 6501 was isolated from cell homogenates by differential and sucrose gradient centrifugation, followed by lysozyme treatment and hot sodium dodecyl sulfate extraction. The sheath contains a major fraction of carbohydrate consisting of galactose, glucose, mannose, rhamnose, 2-O-methyl-d-xylose, xylose, glucuronic and galacturonic acids, but only traces of fatty acids and phosphate. A protein content of about 2% (of fraction dry weight) could not be removed by the detergent treatment.

Component from the cell surface of the hydrocarbon-utilizing yeast Candida tropicalis with possible relation to hydrocarbon transport.

A polysaccharide-fatty acid complex was isolated from the cell surface of Candida tropicalis growing on alkanes. This complex was solubilized by Pronase treatment of whole cells. A decrease in alkane-binding affinity was observed after Pronase treatment, resulting in 10 to 12% of the yeast dry cell weight being released as polysaccharide. The isolated polysaccharide contained 2.5% fatty acids. C. tropicalis and Saccharomyces cerevisiae grown with glucose contained only traces of fatty acids in the corresponding polysaccharide fraction. The fatty acids were not removed from the polysaccharide moiety by gel filtration. Extraction of the polysaccharide with chloroform-methanol showed that fatty acids were covalently bound to the polysaccharide. The amphipathic nature of the isolated polysaccharide and the hydrocarbon-induced formation suggest a possible role in alkane metabolism.

The I antigen of human red cell membrane.

A high-active I antigen was isolated from human red cells after papainization. Investigations on its chemical composition and its serological properties are reported. 1. The I antigen activity was clearly demonstrated by hemagglutination inhibition studies and by the immuno-double-diffusion with all available anti-I sera. 2. The I antigen did not react with other antibodies directed against red cell antigens thus proving its specificity. Any relationships to antigen activities within the Pr-1/Pr-2, MN, and ABO systems could be excluded. 3. The substance was shown to be a glycoprotein and not a glycolipid. This was confirmed by different delipidation procedures promoting always an increase of I activity. The delipidized material contained only traces of fatty acids, and did not move on thin-layer chromatography in solvent systems normally used for glycolipid development. 4. The I determinant resides on alkali-stable oligosaccharide chains. The main sugars are galactose and N-acetylglucosamine which might be involved in the immunodeterminants.

Metamorphic changes in midgut lipids of the southwestern corn borer, Diatraea grandiosella

The midgut lipids of the southwestern corn borer, Diatraea grandiosella Dyar, were examined during its metamorphosis from larva to pupa. Results showed that the highest midgut lipid content (approximately 0.38 mg. per insect) was found in actively feeding, 14-day larvae. Following pupation the midgut lipid content dropped to only 0.04 mg. per insect. Thin-layer chromatography revealed that five neutral lipid classes could generally be detected in midgut extracts. For example, 14-day larval midguts contained the highest concentration of neutral lipids in the following proportions: triglycerides, 42 per cent; sterol esters, 29 per cent; sterols, 16 per cent; 1,2-diglycerides, 6 per cent; and traces of fatty acids and hydrocarbons. The titres of triglycerides, diglycerides, and sterol esters varied more than those of the other constituents at different nutritional and developmental stages. These lipid classes, along with free sterols, are apparently involved in neutral lipid storage or transport in midgut cells. Results obtained from midguts of insects which had been starved or fed lipid-free diets supported this interpretation. Possible mechanisms for lipid absorption, storage, and transport were evaluated.

Fatty acid composition of bacterial membrane and wall lipids

A survey has been made of the fatty acid composition of the lipids extracted from isolated membranes of 5 Gram-positive bacteria and the “wall” or “envelope” fractions of 16 Gram-negative organisms. The lipids of the membranes of the aerobic Gram-positive species contained a high proportion of C 15 branched-chain fatty acid. The thermophilic organism, Bacillus stearothermophilus, contained a substantial amount of both C 15 and C 17 branched-chain fatty acids in its membrane lipid. Lipid extracted from “walls” or “envelopes” of the Gram-negative bacteria was composed mainly of palmitic, palmitoleic and oleic acids. Cyclopropane acids were detected in “wall” lipid of some of the Gram-negatives and several unidentified methyl esters (possibly of the cyclopropane type) were also found. Only traces of fatty acids were detected in the lipid extracted from the envelopes of the halophile, Halobacterium halobium.