Neutral Lipid Fatty Acid Research Articles

Effects of fungal food quality and starvation on the fatty acid composition of Protaphorura fimata (Collembola)

The lipid pattern of animals is influenced by species, life stage, environmental conditions and diet. We investigated the effects of food quality and starvation on the phospholipid (PLFA) and neutral lipid (NLFA) fatty acid pattern of the collembolan Protaphorura fimata. Collembolans were fed with two common soil fungi, Agrocybe gibberosa and Chaetomium globosum, of which the cellular lipid composition was analysed. A. gibberosa was grown on agar with different nitrogen contents, resulting in altered fatty acid patterns and C:N ratios, i.e. fungi of different food quality. Collembolans did not mirror the lipid composition of the fungal diet as the pattern of major NLFAs in P. fimata was vice versa. Presumably, altered food quality of fungi caused compensatory responses by the collembolans, thereby diminishing the fungal signal. In a further experiment P. fimata (previously maintained with C. globosum) was kept without food for up to 4 weeks. Starvation resulted in a decline in the total amount of NLFAs; however, it did not affect the fatty acid pattern, indicating that NLFAs were degraded indiscriminately. Generally, the PLFA profile of the collembolans changed only slightly due to variations in diet quality or starvation.

Effects of breed, diet and muscle on fat deposition and eating quality in pigs

A study in 192 entire male pigs examined the effects of breed, diet and muscle on growth, fatness, sensory traits and fatty acid composition. There were four breeds: two modern breeds, Duroc and Large White and two traditional breeds, Berkshire and Tamworth. The diets differed in energy:protein ratio, being conventional (C) and low protein (LP) diets, respectively. Muscles investigated were the `white' longissimus dorsi (LD) and the `red' psoas major (PS). Breed influenced growth rate and fatness, the modern breeds being faster-growing with leaner carcasses. However, the concentrations of neutral lipid fatty acids and marbling fat (neutral lipid + phosopholipid fatty acids) were higher in Berkshire and Duroc, in both LD and PS. Relationships between marbling fat and P2 fat thickness showed clear breed effects, with Duroc having high marbling fat at low P2 and Tamworth low marbling fat at high P2. Breed effects on sensory scores given by the trained taste panel to griddled LD and PS steaks were relatively small. Breed affected the fatty acid composition of intramuscular neutral lipid, with high % values for the saturated fatty acids, 14:0 and 16:0 in Berkshire and Tamworth (fat carcasses) and high values for polyunsaturated fatty acids in Duroc and Large White (lean carcasses). Duroc had particularly high concentrations of the long-chain polyunsaturated fatty acids, 20:5 n−3 and 22:6 n−3 in phospholipid of both muscles. Diet influenced growth rate and fatness, the LP diet slowing growth and producing fatter meat, more so in the two modern breeds, and particularly in intramuscular rather than subcutaneous fat. This diet produced more tender and juicy meat, although pork flavour and flavour liking were reduced. The PS muscle had higher tenderness, juiciness, pork flavour, flavour liking and overall liking scores than LD. The concentration of phospholipid fatty acids was higher in PS than LD but neutral lipid fatty acid content and marbling fat were higher in LD.

Physiology and lipid metabolism of Littorina saxatilis infected with trematodes

Physiological and biochemical alterations in Littorina saxatilis infected with larval trematodes were investigated and compared with the metabolism of non-parasitized snails. Oxygen consumption rates of infected snails differed from those of non-infected controls in medium sized individuals (30 to 130 mg) but not in very large infected individuals (> 200 mg). Small snails (0.5 to 8.5 mg) were seldom infected by parasites, and this size-class consisted only of non-infected specimens. The specific oxygen consumption rate of infected snails was not dependent on their mass and remained constant over the size ranges investigated. Alterations in the snail metabolism appeared to be connected to injuries to digestive gland tissues caused by the parasites. The glycogen concentration and fatty acids of neutral lipids and phospholipids in the digestive gland were determined. Infected snails differed from uninfected snails in the complete absence of glycogen in digestive gland and had proportionally higher quantities of eicosenoic (20:1) acid in the total phospholipids. It remains unclear whether infection by trematodes activates enzymes in the snail's digestive gland to synthesize eicosenoic (20:1) acid, or whether the sporocysts themselves possess these enzymes. The role of phospholipid fatty acids in the regulation and maintenance of the parasite's metabolism is briefly considered. Biochemical alterations observed in the fatty acid composition may have an adaptive significance, by helping to stabilize the host-parasite system.

Conjugated linoleic acid content of the lamb muscle and liver fed different supplements

Conjugated linoleic acids (CLA), a mixture of positional and geometric isomers of octadecadienoic acids with conjugated double bonds, natural components of ruminant tissues and milk and have been demonstrated to have anti-cancer and metabolic activities-of potential benefit to human health. The effect of breed, Vitamin E and the feeding growing lambs fat supplements containing polyunsaturated fatty acids (PUFA) was investigated on the levels of CLA in lamb muscle and liver neutral lipids. A total of 96 male lambs were used in a 2×3×2 factorial design: 2 breeds, Suffolk×Lleyn and Scottish Blackface, 3 diet supplements, Megalac, linseed and linseed plus fish oil (a 50:50 mixture on an oil weight basis of fish oil and linseed, linfish) and two levels of Vitamin E (100 or 500 mg/kg feed). The lambs were fed isonitrogenous diets containing 50 g fat/kg DM ad libitum. At approximately half of the mature live weight for each breed, animals were slaughtered. Semi-membranosus muscle samples were removed 24 h post-mortem and lipids extracted with chloroform–methanol. Neutral lipids were isolated from the lipid extract using silicic acid chromatography. Lambs fed the Megalac supplement had significantly less muscle neutral lipid fatty acids than lambs fed linseed and linfish supplemented diets (Megalac 1859, linseed 2535 and linfish 2500 mg/100 g muscle, respectively). Muscle content of neutral lipid CLA (mg/100 g muscle) was 12.3, 20.7 and 25.8 for the three feeds, respectively (S.E. 1.8, P<0.01) and trans 18:1 was 39, 53 and 94 mg/100 g muscle (S.E. 7.0, P<0.01) for Megalac, linseed and linfish diets, respectively. Liver content of neutral lipid CLA were 27.0, 24.4, and 20.9 mg/100 g liver (S.E. 2.9, NS) and trans 18:1 content were 58, 69, 97 mg/100 g liver (S.E. 10.0, P<0.01) for Megalac, linseed and linfish fed lambs, respectively. The present study demonstrates that CLA concentrations in lamb meat can be enhanced by the addition of polyunsaturated fatty acids to the diets and further research is needed to characterise breed and Vitamin E effects on CLA content of lamb tissues.

Combined effect of an arbuscular mycorrhizal fungus and a biocontrol bacterium againstPythium ultimum in soil

The combined effect of the arbuscular mycorrhizal (AM) fungusGlomus intraradices and the bacteriumBurkholderia cepacia onPythium ultimum was studied in a growth system with root-free soil compartments allowing examination of microbial interactions without direct interference from roots. Signature fatty acids were used to quantify individual microbial populations. Biomass and amount of energy reserves were estimated using specific phospholipid fatty acids (PLFA) and neutral lipid fatty acids (NLFA), respectively. Population density ofP. ultimum was estimated by colony forming units on selective media. Both biocontrol agents (BCAs) reduced population density ofP. ultimum. Biomass ofB. cepacia measured using signature fatty acids was inhibited by the presence of mycelium ofG. intraradices, which might explain why no additive effect onP. ultimum was found when combining the two BCAs. In conclusion, combiningG. intraradices andB. cepacia did not enhance the biocontrol efficacy againstP. ultimum.

The use of neutral lipid fatty acids to indicate the physiological conditions of soil fungi.

The usefulness of measuring neutral lipid fatty acids (NLFAs) and phospholipid fatty acids (PLFAs) separately in order to interpret perturbation effects on soil and compost microorganisms has been studied. Initially the NLFA/PLFA ratios were studied in different soils. Low ratios were found for fatty acids common in bacteria, especially for cyclopropane fatty acids. Higher ratios were found for fatty acids common in eukaryotic organisms such as fungi (18:1omega9 and 18:2omega6,9) or in saturated fatty acids, common to many types of organisms. Adding glucose to a forest soil increased the amounts of the fungal NLFAs 18:1omega9 and 18:2 omega6,9 up to 60 and 10 times, respectively, after 10 days, followed by a gradual decrease. After 3 months incubation, higher levels of these NLFAs were still found compared with the control samples. Adding glucose together with nitrogen (N) and phosphorus (P) resulted in no increase in NLFAs but a 10-fold increase in the PLFAs 18:1omega9 and 18:2omega6,9. Thus, the NLFA/PLFA ratios for these fatty acids were lower than in the no-addition control when glucose was added together with N and P, but higher when glucose was added alone, even 3 months after the addition. Adding N+P without glucose did not affect the NLFA/PLFA ratio for any fatty acid. Increasing NLFA/PLFA ratios for the fungal fatty acids were also found with time after the thermophilic phase in a compost, indicating increased availability of easily available carbon.

Fatty acid composition and sensory quality of Musculus longissimus and carcass parameters in red deer (Cervus elaphus) grazed on natural pasture or fed a commercial feed mixture

AbstractThe effects of feeding regimen on carcass characteristics, fatty acid composition and sensory quality of Musculus longissimus were studied in 16 male red deer. All animals were farm raised; eight were grazed on pasture and eight were fed a pelleted commercial feed mixture for 10 weeks prior to slaughter. The pellet‐fed deer had a significantly higher dressing percentage than the pasture group. No differences were found in ultimate pH values and muscle glycogen content when comparing the treatment groups. Polar and neutral lipid fatty acid composition of the meat were analysed separately. Meat from pasture‐fed deer showed a high content of the fatty acid 18 : 3 n‐3 in the polar lipid fraction. In the same lipid fraction, the fatty acid 18 : 2 n‐6 was dominant in meat from the pellet fed animals. Similar differences in the neutral lipid fraction were found when comparing fatty acid composition between treatment groups; however, the abundance of these fatty acids was much less. A trained expert panel using a descriptive test assessed the sensory profile of the meat. There was a significant difference between the two treatment groups for the sensory attribute of grassy flavour, with the pellet‐fed animals having less grassy flavour than the animals grazing pasture. It was concluded that further research is needed to explore the effects of various feeding regimens applied to deer on parameters associated with meat lipids, including antioxidants and oxidation products. Copyright © 2003 Society of Chemical Industry

Physico-chemical characteristics of M. Longissimus dorsi from three lines of free-range reared Iberian pigs slaughtered at 90 kg live-weight and commercial pigs: a comparative study

Longissimus dorsi muscles from three lines of Iberian pig and those from commercial pigs were analysed in order to evaluate their quality for fresh consumption. Iberian pigs were reared in a natural outdoor production system with access to grass, while m. Longissimus dorsi from commercial pigs were procured from a local slaughterhouse. Iberian pigs’ Longissimus dorsi showed a higher fat ( P<0.05) and lower phospholipid contents (g PL/g fat; P<0.05) than Longissimus dorsi from commercial pigs. Iberian pigs’ Longissimus dorsi muscles had a higher content of haem iron ( P<0.05) than those from commercial pigs and consequently m. Longissimus dorsi exhibited a redder colour (higher a*-value) that diverged less from the true red axis (lower hue value; P<0.05) than those from commercial pigs which resulted paler (higher L*-value; P<0.05). Total fat and neutral lipid fatty acid profiles showed higher percentages of palmitic, oleic, total saturated fatty acids (SFA) and monounsaturated fatty acids (MUFA) m. Longissimus dorsi of Iberian pigs than in the commercial ones ( P<0.05). m. Longissimus dorsi from the commercial pigs contained higher proportions of polyunsaturated fatty acids and a higher n-6/n-3 ratio value ( P<0.05).

Phosphorus uptake of an arbuscular mycorrhizal fungus is not effected by the biocontrol bacterium Burkholderia cepacia

The biocontrol bacterium Burkholderia cepacia is known to suppress a broad range of root pathogenic fungi, while its impact on other beneficial non-target organisms such as arbuscular mycorrhizal (AM) fungi is unknown. Direct interactions between five B. cepacia strains and the AM fungus, Glomus intraradices (BEG87) were studied in root-free soil compartments separated from a rooting compartment by a fine nylon-mesh. B. cepacia had no effect on AM fungal biomass and energy reserves measured using the signature fatty acid 16:1ω5 from phospholipid fatty acids (PLFAs) and neutral lipid fatty acids (NLFAs), respectively. Hyphal P transport was also unaffected by the biocontrol bacterium, which either stimulated, reduced or had no effect on length of the external mycelium of G. intraradices. The cyclic PLFAs cy17:0 and cy19:0 were suggested to be useful markers for estimation of biomass of B. cepacia. The presence of mycelium of G. intraradices reduced the biomass of three out of five B. cepacia strains as indicated by a reduction in PLFAs cy17:0 and cy19:0, while other bacterial PLFAs were unaffected by mycelium of G. intraradices. On the other hand, two out of five B. cepacia strains reduced the amount of branched PLFAs suggesting a reduction in the population of Gram-positive bacteria in these cases. In conclusion, the B. cepacia seems to have no impact on neither mycorrhiza formation nor on the functioning of the AM fungus G. intraradices in terms of P transport, whereas our results suggest that mycorrhiza might have adverse effects on B. cepacia.

Muscle lipids, vitamins E and A, and lipid oxidation as affected by diet and RN genotype in female and castrated male Hampshire crossbreed pigs

The objectives of this study were to investigate the polar and neutral lipid fatty acid composition, content of retinol, α-tocopherol, γ-tocopherol and level of oxidation of the pig muscle ( M. longissimus dorsi). Female and castrated male Hampshire crossbreeds were produced in two systems. One group was raised indoors with a more polyunsaturated diet and the other raised outdoors with a more saturated diet. The level of polyunsaturated fatty acids in muscle was higher in the indoor females compared with the outdoor females, indoor castrated males and outdoor castrated males. The increased level of polyunsaturated fatty acids in the muscle, which was accompanied by a relatively low content of α-tocopherol, increased the susceptibility to lipid oxidation in the form of MDA (malondialdehyde) in the indoor female pigs. Finally, the level of polyunsaturated fatty acids in the polar lipids was affected by the RN genotype, and this difference was dependent on sex. In conclusion, diet has a major effect on the fatty acid composition and oxidation stability in pork muscle, but additional factors such as sex and RN genotype might also contribute.

Fatty acid composition and dynamics of selected fungal-feeding nematodes and fungi

Fatty acid profiles of fungal-feeding nematodes, Aphelenchus avenae and Aphelenchoides composticola, and selected fungi were determined in microcosm cultures of agar, broth, or sand amended with organic matter. Fatty acids of A. avenae and A. composticola included 16:0 18:0, 18:1ω7, 18:1ω9, 18:2, 20:0, 20:1, 20:2, 20:3 and 20:4 phospholipid fatty acids (PLFAs) and neutral lipid fatty acids (NLFAs). The nematodes differed in relative amounts of saturated and C 18 fatty acids. Similar C 16 and C 18 PLFAs and whole-cell fatty acids were found in Rhizoctonia solani, Fusarium oxysporum and Trichoderma sp. with 18:2ω6 as the major component. The C 20 fatty acids were not found in these fungi. Although only present in the nematodes, C 20 PLFAs were only detected when nematode population levels were ≥22 per gram of sand, suggesting that there is a detection threshold that might limit their use as biomarkers in the soil community. After removal of nematodes from a food source, the relative amount of C 20 PLFAs (structural components of nematode cell membranes) decreased more slowly than the C 16 and C 18 PLFAs, which may have reflected ingested fungal cytoplasm in the nematode intestine. In the early stage of organic matter decomposition, total and fungal PLFAs were lower in the presence of A. composticola then in its absence at C:N ratios ≥30:1.

Effect of rearing system on muscle lipids of gilts and castrated male pigs

The objective of this study was to investigate the polar and neutral lipid fatty acid composition of pig muscle as influenced by rearing conditions and sex. A total of 120 Hampshire crossbreeds were divided in two groups, one reared free-range in a strip grazing fashion and one reared indoors in a large pen (120 m2). Free-range rearing produced a more unsaturated fatty acid composition (M. biceps femoris) in the neutral lipids, although the effect was small. In the polar lipids the effect of rearing condition was sex dependent. In the muscle of free-range gilts, there was a higher level of C18:2 n-6, compared with indoor gilts, indoor castrates, and free-range castrates. Moreover, muscle of gilts irrespective of rearing condition, had a higher level of the C⩾20 polyunsaturated fatty acids in the polar lipids (16.75 and 14.60, respectively). Thus, we suggest that the difference between castrates and gilts with respect to fatty acid composition in the polar lipids, might be affected by rearing condition.

Fatty acid composition of M. longissimus lumborum, ultimate muscle pH values and carcass parameters in reindeer (Rangifer tarandus tarandus L) grazed on natural pasture or fed a commercial feed mixture

The effects of feeding regimen on the fatty acid composition of M. longissimus, ultimate pH values in three muscles (Mm. longissimus, triceps brachii and biceps femoris) and carcass quality were studied in15 reindeer bulls. Nine animals came from natural pasture and six had been fed a pelleted commercial feed mixture for two months prior to slaughter. The pellet fed reindeer had significantly better carcass grading scores (EUROP conformation), higher trim fat content, more intramuscular fat and lower ultimate pH values in all three muscles than the group from pasture. The polar and neutral lipid fatty acid composition of the meat was analysed separately. Meat from pasture fed reindeer showed a high content of the fatty acid 18:3 n-3 in the polar lipid fraction. In the same lipid fraction, the fatty acid 18:2 n-6 was dominant in meat from the pellet fed animals. Similar differences in the neutral lipid fraction were found when comparing fatty acid composition between treatment groups, however the abundance of these fatty acids was much less. The present results confirm previous findings that reindeer fed typical pelleted commercial feed mixtures generally have an improved nutritional status.

Interactions between pea root-inhabiting fungi examined using signature fatty acids.

• Interactions are investigated between the arbuscular mycorrhizal fungus, Glomus mosseae, and the root pathogen, Aphanomyces euteiches, on pea (Pisum sativum) roots, as arbuscular mycorrhiza are known to suppress a broad range of root pathogens. • Phospholipid (PLFA) and neutral lipid (NLFA) fatty acids were used as indicators of biomass and energy reserves, respectively, of A. euteiches and G. mosseae in inoculated roots of pot-grown pea seedlings. • Symbiosis between pea and G. mosseae had no effect on the severity of disease caused by A. euteiches, which decreased pea shoot and root dry weight. However, the presence of G. mosseae in pea roots reduced both biomass and energy reserves of A. euteiches, indicated by a reduction in PLFA 14:0 and both NLFAs 14:0 and 14:1ω9. Similarly, a reduction in PLFA and NLFA 16:1ω5 indicated reduced biomass and energy reserves of G. mosseae in A. euteiches-infected roots. • Signature fatty acids can be used to quantify biomass and energy reserves of G. mosseae and A. euteiches simultaneously, in pea root; this appears to be a promising method for studying interactions between arbuscular mycorrhizal fungi and root pathogens in planta.

What do root pathogens see in mycorrhizas?

○ Interactions are investigated between the arbuscular mycorrhizal fungus, Glomus mosseae, and the root pathogen, Aphanomyces euteiches, on pea (Pisum sativum) roots, as arbuscular mycorrhiza are known to suppress a broad range of root pathogens. ○ Phospholipid (PLFA) and neutral lipid (NLFA) fatty acids were used as indicators of biomass and energy reserves, respectively, of A. euteiches and G. mosseae in inoculated roots of pot-grown pea seedlings. ○ Symbiosis between pea and G. mosseae had no effect on the severity of disease caused by A. euteiches, which decreased pea shoot and root dry weight. However, the presence of G. mosseae in pea roots reduced both biomass and energy reserves of A. euteiches, indicated by a reduction in PLFA 14: 0 and both NLFAs 14: 0 and 14: 1ω9. Similarly, a reduction in PLFA and NLFA 16: 1ω5 indicated reduced biomass and energy reserves of G. mosseae in A. euteiches-infected roots. ○ Signature fatty acids can be used to quantify biomass and energy reserves of G. mosseae and A. euteiches simultaneously, in pea root; this appears to be a promising method for studying interactions between arbuscular mycorrhizal fungi and root pathogens in planta.

The Effect of Diclofop-Methyl and Its Antagonist, Vitamin E, on Membrane Lipids in Oat (Avena sativa L.) and Leafy Spurge (Euphorbia esula L.)

Diclofop-methyl (DM) increased the total and unsaturated free fatty acid content (FFA) in leaves of oat (Avena sativa L.), a DM-susceptible monocotyledon, and in mature leaves of leafy spurge (Euphorbia esula L.), a dicotyledonous perennial weed whose mature leaves are killed by DM. In oat the total and unsaturated FFAs increased 9.0- and 17.4-fold over control levels, respectively. In leafy spurge these fractions increased 5.7- and 7.2-fold over control levels, respectively. Linolenic acid, the major component of the free polyunsaturated fatty acid fraction, increased dramatically in both oat and leafy spurge. The DM-induced increase in the FFA fraction was accompanied by decreases in both the total and unsaturated polar lipid fatty acid (PL-FA) fractions to approximately 25 and 60% of control in oat and leafy spurge, respectively. The PL fraction contains phospholipids and glycolipids and is likely the source of the the FFAs. DM treatment increased the total and unsaturated neutral lipid fatty acid fraction 1.9- and 2.2-fold over controls, respectively, in oat. The effect on leafy spurge was negligible. A protective effect of vitamin E, a free radical scavenger, against membrane deterioration (as indicated by changes in lipid profiles) caused by DM was apparent in both oat and leafy spurge. The total and unsaturated FFA levels of oat leaves treated with a vitamin E+DM combination increased 4.5- and 8.4-fold over those of controls, respectively. In leafy spurge these fractions increased 4.2- and 5.1-fold over those of controls. These increases were significantly lower than the levels reported for DM alone. The total and unsaturated PL-FA fraction of oat increased from approximately 25% with DM alone to 47% with the vitamin E+DM combination. The constitutive enzyme phospholipase D (PLD), involved with membrane disassembly, and lipoxygenase (LOX), involved in the generation of reactive oxygen species, were assayed. The activity of PLD was high in both controls and DM-treated oat at pH 6.0, with little activity above pH 7.0. Lipoxygenase activity was unaffected by either DM or vitamin E. However, 2,4-D (shown by others to protect against DM treatment in the field) decreased LOX activity approximately 50% in etiolated oat leaves in vitro. Taken collectively, the lipid analysis and enzymatic data support the hypothesis that the primary lethal mechanism of DM is accelerated senescence via membrane disassembly, membrane lipid catabolism, and oxidative stress that is mediated by metabolically induced active oxygen species.

Lipids and fatty acids of two pelagic cottoid fishes ( Comephorus spp.) endemic to Lake Baikal

Matured females of two Lake Baikal endemic fish species, Comephorus baicalensis and Comephorus dybowski, have been investigated for lipid of the whole body and specific tissues (liver, muscles, ovaries), phospholipid classes and fatty acids of neutral and polar lipids. Total lipid in the body (38.9% fresh weight), liver (23.5%) and muscles (14.5%) of C. baicalensis were greater than those of C. dybowski (4.7, 8.7 and 2.6%, respectively); only their ovaries were similar (5.3 and 5.6% lipid, respectively). In both species, phosphatidylcholine and phosphatidylethanolamine were the major phospholipids, ranging from 60.7 to 75.1% of total phospholipid and 14.5–25.7%, respectively. In most cases, monounsaturated fatty acids (MUFA) were the major fatty acid group in C. baicalensis, whereas polyunsaturated fatty acids (PUFA) were the major group in C. dybowski. The MUFA 18:1(n-9) prevailed over other fatty acids in C. baicalensis and varied from 19% in polar lipids of muscles to 56.1% in neutral lipids of muscles. In polar lipid of C. dybowski, the PUFA 22:6(n-3) prevailed over other fatty acids in muscles and ovaries, while 16:0 dominated polar liver lipids and neutral lipids of all tissues. Other major fatty acids included 16:1(n-7), 18:1(n-7), and 20:5(n-3). Values of the (n-3)/(n-6) fatty acid ratio for neutral lipids of C. baicalensis (0.5–0.9) are well below the range of values characteristic either for marine or freshwater fish, while these values for polar lipids (1.6–1.8) are in the range typical of freshwater fish. Neutral lipid fatty acid ratios in C. dybowski (2.5–3.1) allow it to be assigned to freshwater fish, but polar lipids (2.8–3.7) leave it intermediary between freshwater and marine fish.

Quantification of Aphanomyces euteiches in pea roots using specific fatty acids

The fatty acid composition of pea roots with and without the root pathogen Aphanomyces euteiches was studied using whole cell fatty acids (WCFA), phospholipid fatty acids (PLFA) and neutral lipid fatty acids (NLFA). Initial screening for A. euteiches markers using WCFA analysis showed that the fatty acids 14:1·9, 14:0, 20:4 and 20:5 were specific to roots infected with A. euteiches . The amounts of these fatty acids correlated positively with the percentage of the root system containing A. euteiches oospores, suggesting that they could be useful indicators of A. euteiches root-infection levels. Analysis of the composition of phospholipid fatty acids (PLFA) and neutral lipid fatty acids (NLFA) of pea roots with and without A. euteiches showed similar specificity as found with WCFA analysis. PLFAs and NLFAs specific to roots inoculated with A. euteiches were also present in mycelium from pure culture of A. euteiches . The PLFAs 14:0, 20:4 and 20:5 were used to estimate biomass of A. euteiches and the NLFAs 14:1·9, 14:0, 20:4 and 20:5 were used as indicators of energy reserves of the pathogen. The possible use of specific fatty acids to study growth and development of A. euteiches in pea roots is discussed.

The growth of external AM fungal mycelium in sand dunes and in experimental systems.

We estimated the biomass and growth of arbuscular mycorrhizal (AM) mycelium in sand dunes using signature fatty acids. Mesh bags and tubes, containing initially mycelium-free sand, were buried in the field near the roots of the dune grass Ammophila arenaria L. AM fungal mycelia were detected at a distance of about 8.5 cm from the roots after 68 days of growth by use of neutral lipid fatty acid (NLFA) 16:1ω5. The average rate of mycelium extension during September and October was estimated as 1.2 mm day−1. The lipid and fatty acid compositions of AM fungal mycelia of isolates and from sand dunes were analysed and showed all to be of a similar composition. Phospholipid fatty acids (PLFAs) can be used as indicators of microbial biomass. The mycelium of G. intraradices growing in glass beads contained 8.3 nmol PLFAs per mg dry biomass, and about 15% of the PLFAs in G. intraradices, G. claroideum and AM fungal mycelium extracted from sand dunes, consisted of the signature PLFA 16:1ω5. We thus suggest a conversion factor of 1.2 nmol PLFA 16:1ω5 per mg dry biomass. Calculations using this conversion factor indicated up to 34 μg dry AM fungal biomass per g sand in the sand dunes, which was less than one tenth of that found in an experimental system with Glomus spp. growing with cucumber as plant associate in agricultural soil. The PLFA results from different systems indicated that the biomass of the AM fungi constitutes a considerable part of the total soil microbial biomass. Calculations based on ATP of AM fungi in an experimental growth system indicated that the biomass of the AM fungi constituted approximately 30% of the total microbial biomass.

Unusual fatty acid composition of storage lipids in the bresilioid shrimp Rimicaris exoculata couples the photic zone with MAR hydrothermal vent sites

Lipid and stable carbon isotope analyses of Rimicaris exoculata, the dominant bresilioid shrimp found at the MAR (Mid-Atlantic Ridge) vent sites, have indicated that these animals possess a highly unusual storage lipid composition. The dominant neutral lipid classes, triacylglycerols and wax esters, contained very high levels of polyunsaturated fatty acids (PUFA, up to 89% of neutral lipid fatty acids). Gas chromatography isotope ratio mass spectrometry (GC-IRMS) analysis of the PUFA from neutral lipid gave d13C (v-PDB) values of -17.6 to -27.1[per thou], which is within the range expected for a photosynthetic origin for these compounds. Fatty acid analyses of bacterial/detrital material collected from the vent sites contained only very low amounts of PUFA. It is clear from these findings that R. exoculata has evolved a highly specialized lipid metabolism which allows it to store substantial amounts of PUFA during its early planktotrophic life stages. These PUFA reserves will be subsequently mobilized to enable growth and maturation of the shrimp on return to a suitable vent site and are therefore an important factor allowing R. exoculata to inhabit deep sea vent ecosystems.