Cell Membrane Fatty Acid Composition Research Articles

Alterations in plasma and erythrocyte membrane fatty acid composition following exposure to toxic copper level affect membrane deformability and fluidity in female wistar rats

BackgroundDeformability and fluidity function of the red blood cell membrane are properties defined by the lipid composition. Toxic copper level induces membrane lipid peroxidation which could cause membrane instability. This study therefore investigated the effect of exposure to toxic copper level for 30 days on red blood cell membrane deformability and fluidity in female Wistar rats. MethodsTwelve (12) female Wistar rats (160 ± 10 g) were randomly grouped (n = 6) into control (given 0.1 ml distilled water p.o.) and copper-toxic (100 mg/kg Copper Sulphate, p.o.), and treated for 30 days. Plasma obtained and RBC membrane prepared from blood collected over EDTA post-treatment were assayed for total cholesterol (TC), phospholipids and fatty acid profile using spectrophotometry and Gas chromatography while heparinized blood was subjected to fragility test. Data were analyzed using student T-test for statistical significance at p < 0.05. Results and conclusionPlasma TC increased by 4.33% while RBC membrane TC decreased by 20.32% in copper-toxic group compared to control. Compared to control, excess copper significantly increased membrane phospholipids level (0.72 ± 0.01 vs 0.59 ± 0.04 mg/dL) but reduced membrane cholesterol/phospholipid ratio (46.61 ± 4.72 vs 72.66 ± 6.47) and stability (by 23.53%). Number of cis- and saturated fatty acids increased in copper-treated plasma and RBC membrane compared to control. Exposure to toxic copper level alters erythrocyte membrane fluidity and deformability by disrupting membrane lipid composition, saturation, bond configuration in phospholipids and permeability.

Phosphatase A1 accessory protein PlaS from Serratia marcescens controls cell membrane permeability, fluidity, hydrophobicity, and fatty acid composition in Escherichia coli BL21

Phospholipase A1 (PlaA) plays a pivotal role in diverse applications within the food and biochemical medical industries. Herein, we investigate the impact of the accessory protein encoded by plaS from Serratia marcescens on PlaA activity in Escherichia coli. Notably, PlaS demonstrates the ability to enhance PlaA activity while concurrently exhibiting inhibitory effects on the growth of E. coli BL21 (DE3). Our study revolves around probing the inhibitory action of PlaS on E. coli BL21 (DE3). PlaS exhibits a propensity to heighten both the permeability of outer and inner cell membranes, leading to concomitant reductions in membrane fluidity and surface hydrophobicity. This phenomenon is validated through scanning electron microscopy (SEM) analysis, which highlights PlaS's capacity to compromise membrane integrity. Moreover, through a comprehensive comparative transcriptomic sequencing approach, we identify four down-regulated genes (galM, ybhC, ldtC, and kdpB) alongside two up-regulated genes (rbsB and degP). These genes are intricately associated with processes such as cell membrane synthesis and modification, energy metabolism, and transmembrane transport. Our investigation unveils the intricate gene-level mechanisms underpinning PlaS-mediated growth inhibition and membrane disruption. Consequently, our findings serve as a significant reference for the elucidation of membrane protein mechanisms, shedding light on potential avenues for future exploration.

Red Blood Cell Membrane Fatty Acid Composition, Dietary Fatty Acid Intake and Diet Quality as Predictors of Inflammation in a Group of Australian Adults.

Evidence suggests that diet can play a role in modulating systemic inflammation. This study aims to examine the relationship between fatty acids (FAs) (self-reported dietary intake and red blood cell (RBC) membrane fatty acid concentrations), three diet quality scores, and the plasma concentrations of inflammatory markers (interleukin-6, IL-6; tumour necrosis factor alpha, TNF-α; and C-reactive protein, CRP) in a group of Australian adults (n = 92). Data were collected on their demographic characteristics, health status, supplement intake, dietary intake, RBC-FAs and plasma inflammatory markers over a nine-month period. Mixed-effects models were used to determine the relationship between RBC-FAs, dietary intake of FAs, diet quality scores and inflammatory markers to determine which variable most strongly predicted systemic inflammation. A significant association was identified between dietary saturated fat intake and TNF-α (β = 0.01, p < 0.05). An association was also identified between RBC membrane saturated fatty acids (SFA) and CRP (β = 0.55, p < 0.05). Inverse associations were identified between RBC membrane monounsaturated fatty acids (MUFAs) (β = -0.88, p < 0.01), dietary polyunsaturated fatty acids (PUFAs) (β = -0.21, p < 0.05) and CRP, and the Australian Eating Survey Modified Mediterranean Diet (AES-MED) score and IL-6 (β = -0.21, p < 0.05). In summary, using both objective and subjective measures of fat intake and diet quality, our study has confirmed a positive association between saturated fat and inflammation, while inverse associations were observed between MUFAs, PUFAs, the Mediterranean diet, and inflammation. Our results provide further evidence that manipulating diet quality, in particular fatty acid intake, may be useful for reducing chronic systemic inflammation.

Co-encapsulation of probiotics with acylglycerols in gelatin-gum arabic complex coacervates: Stability evaluation under adverse conditions

Co-encapsulation of acylglycerols and probiotics may improve the resistance of probiotics to adverse conditions. In this study, three probiotic microcapsule models were constructed using gelatin (GE)-gum arabic (GA) complex coacervate as wall material: microcapsules containing only probiotics (GE-GA), microcapsules containing triacylglycerol (TAG) oil and probiotics (GE-T-GA) and microcapsules containing diacylglycerol (DAG) oil and probiotics (GE-D-GA). The protective effects of three microcapsules on probiotic cells under environmental stresses (freeze-drying, heat treatment, simulated digestive fluid and storage) were evaluated. The results of cell membrane fatty acid composition and Fourier transform infrared (FTIR) spectroscopy revealed that GE-D-GA could improve the fluidity of cell membrane, maintain the stability of protein and nucleic acid structure, and decrease the damage of cell membrane. These characteristics supported the high freeze-dried survival rate (96.24 %) of GE-D-GA. Furthermore, regardless of thermotolerance or storage, GE-D-GA showed the best cell viability retention. More importantly, GE-D-GA provided the best protection for probiotics under simulated gastrointestinal conditions, as the presence of DAG reduced cell damage during freeze-drying and the degree of contact between probiotics and digestive fluids. Therefore, co-microencapsulation of DAG oil and probiotics is a promising strategy to resist adverse conditions.

Effect of dietary krill oil supplementation on horse red blood cell membrane fatty acid composition and blood parameters.

Supplementation with marine-derived n-3 long-chain polyunsaturated fatty acids (LC PUFAs), eicosapentaenoic acid (EPA, 20:5 n-3) and docosahexaenoic acid (DHA, 22:6 n-3) is linked to beneficial health effects in both humans and horses. Krill oil (KO), which is extracted from the Antarctic krill (Euphausia superba), is well documented as a safe and biologically available dietary supplement in humans and several animal species, but there is a lack of documentation regarding its effect as a dietary ingredient for horses. The objective of this study was to test whether KO as a dietary supplement had the ability to raise horse red blood cell (RBC) membrane EPA and DHA, expressed as the n-3 index. Five nonworking Norwegian cold-blooded trotter horse geldings (body weight [BW]: 567 ± 38 kg) were supplemented with KO (10 mL/100 kg BW) for 35 days in a longitudinal study. Blood samples were analysed for RBC membrane fatty acid (FA) profile, haematology and serum biochemistry every 7th day. KO was well accepted by all horses, and no adverse health effects were observed during the 35-day trial period. KO supplementation affected the RBC membrane FA profile by increasing the n-3 index from Day 0 to 35 (Day 0: 0.53% vs. Day 35: 4.05% of total RBC FAs). The observed increase in the sum of EPA and DHA (p < 0.001), total n-3 FAs (p < 0.001) and the reduction of n-6 FAs (p < 0.044) resulted in a lower n-6:n-3 ratio (p < 0.001) by Day 35 of KO supplementation. In conclusion, the RBC n-3 index was increased and the general n-6:n-3 ratio was decreased in horses receiving 35-day dietary KO supplementation.

An open-label, multicenter, phase 2 study of a food enriched with docosahexaenoic acid in adults with sickle cell disease

Sickle cell disease (SCD) induces red blood cell sickling, which causes debilitating symptoms including vaso-occlusion and inflammation. We investigated a food enriched with omega-3 fatty acids to determine its effect on certain factors: blood cell membrane fatty acid composition (including anti-inflammatory elements—docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA)—and the pro-inflammatory, arachidonic acid (AA)); the inflammation biomarker, C-reactive protein (CRP); and vaso-occlusive crisis (VOC) pain. Ten adults with SCD ingested the food, daily, for 28 days. Evaluated measures included blood cell membrane fatty acid ratios (AA vs omega-3 (DHA+EPA)), CRP (mg/L) levels, and Visual Analogue Scale (VAS) scores (a VOC assessment). The food was well tolerated and led to a statistically significant CRP reduction (39%). However, changes in omega-3 fatty acid ratios and VAS scores were not significant. Overall, while the omega-3-enriched food reduced inflammation, larger, blinded studies are needed to assess its effectiveness on other measures.

Genomic and Physiological Characterization of Metabacillus flavus sp. nov., a Novel Carotenoid-Producing Bacilli Isolated from Korean Marine Mud.

The newly isolated strain KIGAM252T was found to be facultatively anaerobic, Gram-stain-positive, spore-forming, and rod-shaped. They grew at 10–45 °C, pH 6.0–10.0, and were able to tolerate up to 6% NaCl in the growth medium. Phylogenetic analysis indicated that the KIGAM252T strain was related to the genus Metabacillus. The cell membrane fatty acid composition of strain KIGAM252T included C15:0 anteiso and C15:0 iso (25.6%) as the major fatty acids, and menaquinone 7 was the predominant isoprenoid quinone. The major polar lipids were diphosphatidylglycerol and phosphatidylglycerol. The size of the whole genome was 4.30 Mbp, and the G + C content of the DNA was 43.8%. Average nucleotide and amino acid identity and in silico DNA-DNA hybridization values were below the species delineation threshold. Pan-genomic analysis revealed that 15.8% of all genes present in strain KIGAM252T was unique to the strain. The analysis of the secondary biosynthetic pathway predicted the carotenoid synthetic gene cluster in the strain KIGAM252T. Based on these current polyphasic taxonomic data, strain KIGAM252T represents a novel species of the genus Metabacillus that produces carotenoids, for which we propose the name Metabacillus flavus sp. nov. The type of strain was KIGAM252T (=KCTC 43261T = JCM 34406T).

Cross-Sectional Associations between HDL Structure or Function, Cell Membrane Fatty Acid Composition, and Inflammation in Elderly Adults

BackgroundCell membrane fatty acid composition has been related to inflammation and cardiovascular disease (CVD) risk. Dysregulation of HDL function is also considered a CVD risk factor. ObjectivesWe aimed to investigate whether the content of cell membrane fatty acids and HDL functionality are linked to each other as well as to inflammation. MethodsThis cross-sectional analysis involved 259 participants (mean age: 67.9 y) with overweight/obesity (mean BMI: 29.5 kg/m2) from a coronary artery disease case-control study nested within the PREDIMED (PREvención con DIeta MEDiterránea) trial for which HDL functional parameters [apoA-I, apoA-IV, and apoC-III; cholesterol efflux capacity (CEC); HDL oxidative inflammatory index (HOII); sphingosine-1-phosphate (S1P); serum amyloid A (SAA); and complement-3 (C3) protein] were quantified. We also assessed 22 fatty acids in blood cell membranes using GC and inflammatory markers (IFN-γ and IL-1b, IL-6, IL-8, and IL-10) in serum. Associations of HDL-related variables with cell membrane fatty acids and with inflammatory markers were assessed using multivariable linear regression analyses with elastic net penalty. ResultsApoA-I, apoC-III, CEC, HOII, S1P, and SAA, but not apoA-IV and C3 protein, were associated with membrane fatty acids. S1P and SAA were directly associated with IL-6, whereas apoA-I and C3 protein showed inverse associations with IL-6. Specific fatty acids including myristic acid (14:0) and long-chain n–6 fatty acids being negatively and positively associated with IL-8, respectively, were also found to be positively associated with SAA. ConclusionsThis study suggests interrelations between indicators of inflammation and both blood cell membrane fatty acid composition and HDL structure/functional parameters in a Mediterranean population at high CVD risk.This trial was registered at http://www.isrctn.com www.isrctn.com as ISRCTN35739639.

Insights into molecular pathways and fatty acid membrane composition during the temperature stress response in the murine C2C12 cell model

Daily and seasonal temperature fluctuations are inevitable due to climate change, which highlights the importance of studying the detrimental effects of temperature fluctuations on the health, productivity, and product quality of farm animals. Muscle membrane composition and the molecular signals are vital for muscle cell differentiation and muscle growth, but their response to temperature stress is not well characterized. Temperature changes can lead to modification of membrane components of the cell, which may affect its surroundings and intracellular signaling pathways. Using C2C12 myoblast cells as a model of skeletal muscle development, this study was designed to investigate the effects of high temperature (39 °C and 41 °C) and low temperature (35 °C) on molecular pathways in the cells as well as the cell membrane fatty acid composition. Our results show that several genes were differentially expressed in C2C12 cells cultured under heat or cold stress, and these genes were enriched important KEGG pathways including PI3K-Akt signaling pathway, lysosome and HIF- signaling pathway, Wnt signaling pathway and AMPK signaling pathway. Our analysis further reveals that several membrane transporters and genes involved in lipid metabolism and fatty acid elongation were also differentially expressed in C2C12 cells cultured under high or low temperature. Additionally, temperature stress shifts the fatty acid composition in the cell membranes, including the proportion of saturated, monounsaturated and polyunsaturated fatty acids. This study revealed an interference between fatty acid composition in the membranes and changing molecular pathways including lipid metabolism and fatty acids elongation mediated under thermal stress. These findings will reinforce a better understanding of the adaptive mechanisms in skeletal muscle under temperature stress.

Effects of different initial pH values on freeze-drying resistance of Lactiplantibacillus plantarum LIP-1 based on transcriptomics and proteomics

The growth and the resistance to adverse environments of lactic acid bacteria would be affected by adjusting the initial pH of the medium. In order to explore the effect of changing the initial pH of culture medium on the freeze-drying survival rate of the Lactiplantibacillus plantarum LIP-1, the effect of initial pH on cell membrane fatty acid composition and key enzyme activity were mainly determined, and the internal mechanism was studied by transcriptomics and proteomics methods. We found that compared with initial pH 7.4 group, initial pH 6.8 group could improve the freeze-drying survival rate of the L. plantarum LIP-1. It was possibly due to the lactate dehydrogenase (LDH) was upregulated in the initial pH6.8 group, which led to a rapid decrease in culture pH. To reduce the inhibitory effect of long-term acid environment on growth, the strain upregulated the expression of fatty acid synthesis-related genes and proteins, promoted the relative content of cyclopropane and unsaturated fatty acids, improved integrity of the cell membranes. The adjustment of fatty acid composition maintained the integrity of the cell membrane in a freeze-drying environment to improve the freeze-drying survival rate of the initial pH6.8 group. In addition, the long-term acid environment stimulated a cross-stress tolerance mechanism that significantly upregulated the expression of a cold stress protein. The results indicated that the optimal initial pH of the medium could improve the ability of L. plantarum LIP-1 to resist freeze-drying.

Assessment of Plasma Membrane Fatty Acid Composition and Fluidity Using Imaging Flow Cytometry.

Phospholipid fatty acid (FA) composition influences the biophysical properties of the plasma membrane and plays an important role in cellular signaling. Our previous work has demonstrated that plasma membrane fatty acid composition is an important determinant of oncogenic Ras signaling and that dietary (exogenous) modulation of membrane composition may underlie the chemoprotective benefits of long chain n-3 polyunsaturated fatty acids (PUFA). In this chapter, we describe in vitro methods to modulate membrane phospholipid fatty acid composition of cultured cells using fatty acids complexed to bovine serum albumin (BSA). Furthermore, we describe a method to quantify the biophysical properties of plasma membranes in live cells using Di-4-ANEPPDHQ (Di4) and image-based flow cytometry.

Quercetin affects membrane lipids and apoptosis in three-dimensional fibroblast cultures

The polyphenol quercetin is associated with numerous beneficial health effects in various pathologies such as oxidative stress, neurodegenerative disorders, inflammation, neoplastic processes, age-related diseases, and so on. However, the molecular mechanisms underlying the effects of quercetin and its implication in the pharmaceutical practice require additional clarification. In this study we analyzed the biochemical mechanisms of quercetin effect on membrane lipids of fibroblasts cultured as three-dimensional (3D) cultures, which resemble living tissues more adequately compared to cellular monolayers. Quercetin treatment of 3D fibroblasts induced alterations of the plasma membrane phospholipid and fatty acid composition as well as in the phospholipid metabolizing enzymes sphingomyelinase and phospholipase A2. The level of sphingomyelin (SM), which acts as endogenous membrane antioxidant, was elevated due to quercetin action. Incubation of 3D fibroblasts with quercetin induced augmentation in the saturated fatty acids and reduction of all polyunsaturated fatty acids in the membrane phospholipid molecules of the plasma membranes, indicating an additional increase of the resistance to oxidative damage. Quercetin treatment reduced cholesterol susceptibility to oxidation, a phenomenon which is probably related to the observed increase in the level of SM. In addition, Western blot analysis showed augmented phosphorylation of Akt and expression of Bcl-2 in quercetin-treated cell, indicating that apoptosis was suppressed by quercetin. In conclusion, the reported results contribute to a better understanding of the beneficial effects of quercetin on the structure and functions of plasma membranes of 3D cell cultures, which are a more adequate model of living tissues.

Effects of initial pH on heat resistance of Lactobacillus plantarum LIP-1

In order to study the effect of different initial pH values on heat resistance of the strain, the changes in heat stress survival rates of Lactobacillus plantarum LIP-1 and its potential influencing mechanisms were investigated under different initial pH values. The results showed that the growth L. plantarum LIP-1 did not significantly differ according to initial pH value (P > 0.05), but there were significant differences in heat stress survival rates among initial pH values (P < 0.05). Further analysis revealed that a suitable initial pH value could improve the relative proportion of unsaturated fatty acids in the cell membrane and increase the ratio of unsaturated to saturated fatty acids (U/S), reduce the thermal damage to cell membrane, and improve heat stress survival of the strain. The adjustment of cell membrane fatty acid composition is related to the acidic stress environment caused by the rapid growth of L. plantarum LIP-1 under suitable initial pH conditions. The results confirmed that a suitable initial pH value could improve the heat resistance of the strain. Accordingly, this study provides a theoretical reference for improving the spray drying of probiotics by changing the culture conditions.

Changes in Cell Membrane Fatty Acid Composition of Streptococcus thermophilus in Response to Gradually Increasing Heat Temperature.

In this study, a method of heat adaptation was implemented in an attempt to increase the upper thermal threshold of two Streptococcus thermophilus found in South Korea and identified the alterations in membrane fatty acid composition to adaptive response to heat. In order to develop heat tolerant lactic acid bacteria, heat treatment was continuously applied to bacteria by increasing temperature from 60°C until the point that no surviving cell was detected. Our results indicated significant increase in heat tolerance of heat-adapted strains compared to the wild type (WT) strains. In particular, the survival ratio of basically low heat-tolerant strain increased even more. In addition, the strains with improved heat tolerance acquired cross protection, which improved their survival ratio in acid, bile salts and osmotic conditions. A relation between heat tolerance and membrane fatty acid composition was identified. As a result of heat adaptation, the ratio of unsaturated to saturated fatty acids (UFA/SFA) and C18:1 relative concentration were decreased. C6:0 in only heatadapted strains and C22:0 in only the naturally high heat tolerant strain were detected. These results support the hypothesis, that the consequent increase of SFA ratio is a cellular response to environmental stresses such as high temperatures, and it is able to protect the cells from acid, bile salts and osmotic conditions via cross protection. This study demonstrated that the increase in heat tolerance can be utilized as a mean to improve bacterial tolerance against various environmental stresses.

Metabolic adaptability shifts of cell membrane fatty acids of Komagataeibacter hansenii HDM1-3 improve acid stress resistance and survival in acidic environments.

Komagataeibacter hansenii HDM1-3 (K. hansenii HDM1-3) has been widely applied for producing bacterial cellulose (BC). The yield of BC has been frequently limited by the acidification during sugar metabolism, due to the generation of organic acids such as acetic acid. In this study, the acid resistance mechanism of K. hansenii HDM1-3 has been investigated from the aspect of metabolic adaptability of cell membrane fatty acids. Firstly, we observed that the survival rate of K. hansenii HDM1-3 was decreased with lowered pH values (adjusted with acetic acids), accompanied by increased leakage rate. Secondly, the cell membrane adaptability in response to acid stress was evaluated, including the variations of cell membrane fluidity and fatty acid composition. The proportion of unsaturated fatty acids was increased (especially, C18-1w9c and C19-Cyc), unsaturation degree and chain length of fatty acids were also increased. Thirdly, the potential molecular regulation mechanism was further elucidated. Under acid stress, the fatty acid synthesis pathway was involved in the structure and composition variations of fatty acids, which was proved by the activation of both fatty acid dehydrogenase (des) and cyclopropane fatty acid synthase (cfa) genes, as well as the addition of exogenous fatty acids. The fatty acid synthesis of K. hansenii HDM1-3 may be mediated by the activation of two-component sensor signaling pathways in response to the acid stress. The acid resistance mechanism of K. hansenii HDM1-3 adds to our knowledge of the acid stress adaptation, which may facilitate the development of new strategies for improving the industrial performance of this species under acid stress.

Cell membrane fatty acid and pigment composition of the psychrotolerant cyanobacterium Nodularia spumigena CHS1 isolated from Hopar glacier, Pakistan.

In the present study, cyanobacterium isolate CHS1 isolated from Hopar glacier, Pakistan, was analyzed for the first time for cell membrane fatty acids and production of pigments. Sequencing of the 16-23S intergenetic region confirmed identification of the isolate CHS1 as Nodularia spumigena. All chlorophyll and carotenoid pigments were quantified using high-performance liquid chromatography and experiments to test tolerance against a range of physico-chemical conditions were conducted. Likewise, the fatty acid profile of the cell membrane CHS1 was analyzed using gas chromatography and mass spectroscopy. The cyanobacteriumisolate CHS1 demonstrated tolerance to 8 g/L% NaCl, 35°C and pH 5-9. The characteristic polyunsaturated fatty acid (PUFA) of isolate CHS1, C18:4, was observed in fatty acid methyl esters (FAMEs) extracted from the cell membrane. CHS1 was capable of producing saturated fatty acids (SFA) (e.g., C16:0), monounsaturated fatty acids (MUFA) (e.g., C18:1) and polyunsaturated fatty acids (e.g., C20:5) in the cell membrane. In this study, we hypothesize that one mechanism of cold adaptation displayed by isolate CHS1 is the accumulation of high amounts of PUFA in the cell membrane.

Zygosaccharomyces rouxii Combats Salt Stress by Maintaining Cell Membrane Structure and Functionality.

Zygosaccharomyces rouxii is an important yeast that is required in the food fermentation process due to its high salt tolerance. In this study, the responses and resistance strategies of Z. rouxii against salt stress were investigated by performing physiological analysis at membrane level. The results showed that under salt stress, cell integrity was destroyed, and the cell wall was ruptured, which was accompanied by intracellular substance spillover. With an increase of salt concentrations, intracellular Na+ content increased slightly, whereas intracellular K+ content decreased significantly, which caused the increase of the intracellular Na+/K+ ratio. In addition, in response to salt stress, the activity of Na+/K+-ATPase increased from 0.54 to 2.14 μmol/mg protein, and the ergosterol content increased to 2.42-fold to maintain membrane stability. Analysis of cell membrane fluidity and fatty acid composition showed that cell membrane fluidity decreased and unsaturated fatty acid proportions increased, leading to a 101.21% rise in the unsaturated/saturated fatty acid ratio. The results presented in this study offer guidance in understanding the salt tolerance mechanism of Z. rouxii, and in developing new strategies to increase the industrial utilization of this species under salt stress.

Effect of nicotinic acid on the plasma membrane function and polyunsaturated fatty acids composition during cryopreservation in boar sperm.

This study was conducted to evaluate the effect of nicotinic acid on plasma membrane integrity and fatty acid composition in frozen-thawed boar sperm. Boar semen was cryopreserved using freezing extender containing nicotinic acid (NA), then plasma membrane integrity, osmotic equilibration, lipid peroxidation and fatty acid were analysed. The plasma membrane integrity of frozen-thawed sperm was significantly higher in the 10mM NA than in the 0 and 20mM NA treatment groups (p<0.05). Additionally, the osmotic equilibration ability was not different in treatment groups, but lipid peroxidation was significantly decreased in the 10mM NA treatment group (p<0.05). The saturated fatty acids were significantly decreased in the 10mM NA treatment group, and C18:1n-9, C18:2n-6, C20:4n-6, C22:5n-6 and C22:6n-3, and total polyunsaturated fatty acids (PUFAs) were significantly increased in the 10mM NA treatment groups (p<0.05). In summary, 10mM NA improved plasma membrane integrity, inhibited lipid peroxidation and increased PUFAs in frozen-thawed boar sperm. These results suggest that NA may be useful to protect the plasma membrane and inhibit the loss of PUFAs for sperm cryopreservation in pigs.

Membrane fatty acids composition and fluidity modification in Salmonella Typhimurium by culture temperature and resistance under pulsed electric fields

SummaryEffects of various growth temperatures on cell membrane fatty acid composition of Salmonella Typhimurium (S. Typhimurium) and the resistance to Pulsed Electric Fields (PEF) treatments, as well as PEF combining with mild‐thermal (35, 45, 55 °C) treatments were investigated. Results indicated that the PEF resistance of S. Typhimurium at stationary phase was varied markedly at different growth temperatures. S. Typhimurium grown at 45 °C exhibited greater PEF resistance than cells grown at a lower temperature. Alteration of membrane fatty acid composition decreased in the unsaturated to saturated fatty acids ratio (UFA/SFA) and increased in cyclopropane fatty acids (CFA) proportion as growth temperature increased. It was found that the PEF resistance of S. Typhimurium at stationary phase was in a membrane fluidity dependent manner. Thermal combined PEF treatment improved the PEF lethality which indicated that the PEF resistance of S. Typhimurium was greatly affected by the fluidity of cytomembrane.

Influence of changes in microbial cell membrane composition on isotopic fractionation of nitrate during denitrification

Pure cultures of Thauera aromatica were stressed by the addition of the toxic solvents 1-octanol and 4-chlorophenol causing adaptive modifications in their cell-membrane fatty acid composition. At the same time, we investigated the isotopic fractionation in δ15N-NO3- during denitrification. We observed a change in the degree of saturation (DoS) of the bacteria as a reaction to solvent stress and a higher degree of saturation was directly correlated to the concentration of solvents in the cell membrane. The enrichment factor ε15N-NO3- during denitrification showed a linear dependency to the DoS as well as to the membrane solvent concentration. Denitrifying bacteria thus may express less negative ε15N-NO3- when they are exposed to environmental stress that changes their cell membrane composition.