Membrane Fatty Acid Composition Research Articles

RNase R Affects the Level of Fatty Acid Biosynthesis Transcripts Leading to Changes in membrane Fluidity

Previous studies on RNase R have highlighted significant effects of this ribonuclease in several processes of Streptococcus pneumoniae biology. In this work we show that elimination of RNase R results in overexpression of most of genes encoding the components of type II fatty acid biosynthesis (FASII) cluster. We demonstrate that RNase R is implicated in the turnover of most of transcripts from this pathway, affecting the outcome of the whole FASII cluster, and ultimately leading to changes in the membrane fatty acid composition. Our results show that the membrane of the deleted strain contains higher proportion of unsaturated and long-chained fatty acids than the membrane of the wild type strain. These alterations render the RNase R mutant more prone to membrane lipid peroxidation and are likely the reason for the increased sensitivity of this strain to detergent lysis and to the action of the bacteriocin nisin.Reprogramming of membrane fluidity is an adaptative cell response crucial for bacterial survival in constantly changing environmental conditions. The data presented here is suggestive of a role for RNase R in the composition of S. pneumoniae membrane, with strong impact on pneumococci adaptation to different stress situations.

Acorus calamus L. rhizome extract and its bioactive fraction exhibits antibacterial effect by modulating membrane permeability and fatty acid composition.

Ethnopharmacological relevanceIndia's ancient texts, the Charak Samhita and Sushruta Samhita, make reference to the traditional medicinal usage of Acorus calamus L. In India and China, it has long been used to cure stomach aches, cuts, diarrhea, and skin conditions. This ability of the rhizome is attributed to its antimicrobial properties. Research studies to date have shown its antimicrobial properties. However, scientific evidence on its mode of action is still lacking. Aim of the studyAcorus calamus L. rhizome extract and its bioactive fraction exhibits antibacterial effect by modulating membrane permeability and fatty acid composition. Material and methodThe secondary metabolites in the rhizome of A. calamus L. were extracted in hexane using Soxhlet apparatus. The ability of the extract to inhibit multidrug resistant bacterial isolates, namely Bacillus cereus, Escherichia coli, Acinetobacter baumannii, and Pseudomonas aeruginosa were evaluated using checkerboard assay. Further, the extract was purified using thin layer chromatography, gravity column chromatography, and combiflash chromatography. Structure elucidation of the active compound was done using GC-MS, FT-IR, and UV–Vis spectral scan. The mode of action of the bioactive fraction was determined. Bacterial membrane damage was analyzed using SEM, membrane permeability was determined using SYBR green I and PI dye, leakage of cytoplasmic contents were analyzed using Bradford assay and Fehling’s reagent. The ability to inhibit efflux pump of A. baumannii was determined using EtBr accumulation assay and β-lactamase inhibition was analyzed using nitrocefin as substrate. Also, the biofilm inhibition of B. cereus was determined using crystal violet dye. Moreover, the effect of the bioactive fraction on the fatty acid profile of the bacterial membrane was determined by GC-FAME analysis using 37 component FAME mix as standard. ResultsAcorus calamus L. rhizome hexane extract (AC-R-H) demonstrated broad-spectrum antibacterial activity against all the isolates tested. AC-R-H extract also significantly reduced the MIC of ampicillin against all tested bacteria, indicating its bacterial resistance modulating properties. The assay guided purification determined Asarone as the major compound present in the bioactive fraction (S-III-BAF). S-III-BAF was found to reduce the MIC of ampicillin against Escherichia coli (100–25 mg/mL), Pseudomonas aeruginosa (15–3.25 mg/mL), Acinetobacter baumannii (12.5–1.56 mg/ml), and Bacillus cereus (10–1.25 mg/mL). Further, it recorded synergistic activity with ampicillin against B. cereus (FICI = 0.365), P. aeruginosa (FICI = 0.456), and A. baumannii (FICI = 0.245). The mode of action of S-III-BAF can be attributed to its ability to disturb the membrane integrity, enhance membrane permeability, reduce biofilm formation, and possibly alter the fatty acid composition of the bacterial cell membranes. ConclusionThe bioactive fraction of AC-R-H extract containing Asarone as the active compound showed antibacterial activity and synergistic interactions with ampicillin against the tested bacterial isolates. Such activity can be attributed to the modulation of fatty acids present in bacterial membranes, which enhances membrane permeability and causes membrane damage.

Abstract PO5-23-11: Elevated linoleic acid levels in red blood cells membrane predicts response to neoadjuvant chemotherapy in breast cancer patients

Abstract Introduction: Fatty acids (FA) consumed in the diet have been implicated in increasing the risk of breast cancer (BC). Humans have a wide variety of FAs, including saturated (SFA), monounsaturated (MUFA), and polyunsaturated (PUFA) FAs. PUFAs can be further classified into omega-3 (n-3) and omega-6 (n-6) PUFAs. While n-3 has been associated with reducing inflammation and promoting apoptosis in BC cells, n-6 has been linked to increased inflammation, oxidative stress, and the promotion of BC cell proliferation and treatment resistance. In healthy women, the n-3 content in mammary tissue correlates with n-3 content in red blood cells (RBCs). The FA profile of the RBC membrane provides an unbiased option to assess lipid intake and composition, reflecting long-term FA intake and providing an objective and sensitive measure of lipid intake and body fat deposits. Notably, BC patients have been found to display a high n-6:n-3 ratio in RBCs, which is associated with inflammatory and oxidative stress biomarkers. The neoadjuvant chemotherapy treatment (NACT) model presents a unique opportunity to study resistance mechanisms in non-metastatic BC patients. In this approach, the absence of tumor (pathologic complete response: pCR, or Residual Cancer Burden (RCB) = 0) after NACT indicates treatment sensitivity and better overall survival (OS). Objective: The objective of this study is to determine whether differences in FA profiles determined in the RBC membrane and plasma are associated with the response to NACT in non-metastatic BC patients. Methods: A prospective study was conducted, including non-metastatic BC patients scheduled to receive NACT. Blood samples were collected before the first cycle of NACT to measure plasma and RBC FA derivatives, SFAs, MUFAs, and PUFAs. The pathological complete response (pCR) and residual cancer burden (RCB) were assessed. Results: A total of twenty-eight BC patients were included in the study. When comparing pCR vs. no-pCR using total SFA, MUFA, and PUFA plasma samples, no significant differences were observed. However, in RBC, an increase in PUFA was associated with a higher rate of no-pCR (**p< 0.01). Furthermore, comparing omega-6 and omega-3 (both PUFA) levels, an increase in omega-6 was associated with no-pCR (**p< 0.01), while no significant differences were observed with omega-3. No differences were obtained in plasma samples for either omega-6 and omega-3. To determine which specific omega-6 PUFAs were responsible for the association with no-pCR, elevated levels of linoleic acid (LA) in RBC were found to be associated with no-pCR (**p< 0.01). Other omega-6 PUFAs, including gamma-linolenic acid (GLA), eicosadienoic acid (EDA), dihomo-gamma linolenic acid (DGLA), and arachidonic acid (ARA), showed no significant associations. Multivariate and regression analysis confirmed LA (C18:2 n-6, LA) as the most relevant FA when assessing RCB (0-1 vs. 2-3) in RBC membranes, but not in plasma. The receiver operating characteristic (ROC) curve analyzing LA levels in RBC showed an area under the curve (AUC) of 0.855 for RCB (sensitivity: 76.9%, specificity: 92.3%). Conclusions: To the best of our knowledge, this is the first study demonstrating a clear connection between RBC membrane FA composition, specifically LA concentration, and the pathological response in BC patients after NACT. The measurements taken in plasma did not show significant associations, suggesting that RBC membrane FA profile of could serve as a relevant prognostic biomarker for studying resistance mechanisms to NACT in early BC patients Table. Measured FAs in RBC membrane and plasma by pathologic complete response *Indicates p<0.05; abbreviations: pCR: pathological complete response; SD: standard deviation; yr: years; BMI: body mass index; HR: hormone receptor; HER2: human epidermal growth factor receptor type-2; NLR: neutrophil to lymphocyte ratio; HG: histological grade; RCB: residual cancer burden; NA: not applicable Citation Format: Benjamin Walbaum, César Sánchez, Francisco Acevedo. Elevated linoleic acid levels in red blood cells membrane predicts response to neoadjuvant chemotherapy in breast cancer patients [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO5-23-11.

Fatty acid composition of erythrocyte membranes in carries of rs174544 polymorphism of FADS1 gene and rs174583 polymorphism of FADS2 gene from central region of the Russian Federation before and after supplementation of their diet with ω-3 PUFAs

Numerous publications have demonstrated that polymorphisms in FADS1 and FADS2 gene cluster influence the levels of long chain polyunsaturated fatty acids (LC PUFAs) synthesized in the body from essential precursors. They can be consumed through the diet as well. These LC PUFAs perform important plastic and regulatory functions in the body. The associations between the polymorphisms of FADS genes and the fatty acid (FA) composition of the body with some inflammatory and chronic diseases were shown. To date, very few studies in the Russian Federation researched the distribution of polymorphic variants in FADS1 and FADS2 genes and no studies examined the effects of these polymorphisms on the level of FAs in tissues.So, the purpose of this paper was to study the frequency of genotypes and alleles of the rs174544 polymorphism of the FADS1 gene and the rs174583 polymorphism of the FADS2 gene and their influence on the FA composition of erythrocyte membranes in residents of the Central region of the Russian Federation (RF). Additionally, the effect of ω-3 PUFAs fortified food products on this composition was examined. MethodsThe study included 70 volunteers aged 23–69 years from Moscow region who provided informed consent. They were genotyped for rs174544 polymorphism of FADS1 gene and rs174583 polymorphism of FADS2 gene by real-time PCR. The participants of the study consumed fruit or vegetable smoothies enriched with either vegetable (chia seeds flour) or animal (fish oil flour) sources of ω-3 PUFAs for 1 month. The fatty acid composition of erythrocyte membranes in some of the volunteers was analysed using gas-chromatography before and after fortification of their diet with ω-3 PUFAs. Statistical analysis was performed using SPSS 23. ResultsThe frequency of genotypes and alleles of polymorphisms studied were similar to those published for the European region. For rs174544, the genotype frequencies were CC (61%), CA (29%), and AA (10%), frequency of allele A was 24%. For rs174583, the genotype frequencies were CC (51%), CT (39%), and TT (10%), frequency of allele T was 29%. Carriers of minor alleles of both polymorphisms studied had significantly higher levels of ω-6 and ω-3 LC PUFAs in erythrocyte membranes compared to those carrying other genotypes. This differs from the results of other studies where carriers of minor alleles as were shown to be slow converters of precursors to LC PUFAs. The reason of the discrepancy was most likely associated with the obesity and dietary preferences of our study participants who carry the minor alleles. Over the period of one-month consumption of food sources providing an additional intake of either 2 g/day ω-3 PUFAs from fish oil or 6.5 g/day of ω-3 PUFAs from chia seed flour markedly reduced the incorporation of ω-6 PUFAs into erythrocyte membranes in carriers of minor alleles. Additionally, there was an increase in the content of saturated palmitic acid in the membranes that noticeably changed the fatty acid composition of erythrocyte membranes. ConclusionOur results confirm the observation that blood fatty acid composition related to polymorphisms of FADS gene is highly influenced by BMI. The incorporation of ω-6 PUFAs into erythrocyte membranes decreases when the diet is fortified with ω-3 PUFAs. This decrease can help reduce the formation of pro-inflammatory eicosanoids and the risk of various inflammatory and chronic diseases, especially in carriers of minor alleles of the genetic polymorphisms studied.

Impact of chronic psychological stress on platelet membrane fatty acid composition in a rat model of type 1 diabetes Mellitus

BackgroundChronic stress and diabetes mellitus are highly associated with oxidative stress and inflammation, resulting in cell membrane disruption and platelet activity. This study aims to evaluate the impact of chronic psychological stress on the composition of the platelet phospholipid membrane and platelet activation in type 1 diabetes mellitus (T1DM).MethodsWe enrolled 35 mature healthy female Wistar rats and randomly divided them into 4 groups, namely the control group (n = 9), stress group (n = 10), T1DM group (n = 8), and T1DM + Stress group (n = 8). The Wistar rats were treated in different experimental conditions for 28 days while being provided free access to feed and water. The concentration of corticosterone in blood serum and hair samples was measured using a competitive enzyme-linked immunosorbent assay. Gas chromatography-mass spectrometry was conducted to identify the methyl esters of fatty acids (FAs) in the platelet phospholipid membrane. A quantitative determination of 11-dehydro-thromboxane B2 in the blood serum was also performed using a competitive enzyme-linked immunosorbent assay.ResultsAfter 28 days, the concentration of corticosterone in blood serum (ng/mL) was observed to be higher in the stress group as compared to the T1DM and T1DM + Stress groups (P = 0.031 and P = 0.008, respectively). The percentage of C 16:0 FA in the platelet membrane was greater in the T1DM + Stress group, but its levels of C 20:1 omega (ω) 9 FA, including C 18:3ω3 FA, C 20:5ω3 FA, and the total sum of ω3 FAs, were lower as compared to the control group (P = 0.016; P = 0.016; P = 0.031; P = 0.016, P = 0.031). The concentration of 11-dehydro-thromboxane B2 in blood serum (pg/mL) was observed to be higher in the stress group than in rats with T1DM (P = 0.063).ConclusionChronic psychological stress is related to higher levels of corticosterone, saturated FAs acids in the platelet membrane, and greater platelet activation. This study proves how a low percentage of unsaturated fatty acids in the DM and stress groups indicates the disturbing impact of the oxidative/inflammatory environment to lipid metabolism and neuroendocrine response.

HtrA, fatty acids, and membrane protein interplay in Chlamydia trachomatis to impact stress response and trigger early cellular exit.

Chlamydia trachomatis is an important obligate intracellular pathogen that has a unique biphasic developmental cycle. HtrA is an essential stress or virulence protease in many bacteria, with many different functions. Previously, we demonstrated that HtrA is critical for Chlamydia using a novel inhibitor. In the present study, we characterized genetic variants of Chlamydia trachomatis with reduced susceptibility to the HtrA inhibitor. The variants were changed in membrane fatty acid composition, outer membrane proteins, and transcription of stress genes. Earlier and more synchronous cellular exit was observed. Combined, this links stress response to fatty acids, membrane proteins, and HtrA interplay with the outcome of disrupted timing of chlamydial cellular exit.

Lipid membrane remodeling and metabolic response during isobutanol and ethanol exposure in Zymomonas mobilis

BackgroundRecent engineering efforts have targeted the ethanologenic bacterium Zymomonas mobilis for isobutanol production. However, significant hurdles remain due this organism’s vulnerability to isobutanol toxicity, adversely affecting its growth and productivity. The limited understanding of the physiological impacts of isobutanol on Z. mobilis constrains our ability to overcome these production barriers.ResultsWe utilized a systems-level approach comprising LC–MS/MS-based lipidomics, metabolomics, and shotgun proteomics, to investigate how exposure to ethanol and isobutanol impact the lipid membrane composition and overall physiology of Z. mobilis. Our analysis revealed significant and distinct alterations in membrane phospholipid and fatty acid composition resulting from ethanol and isobutanol exposure. Notably, ethanol exposure increased membrane cyclopropane fatty acid content and expression of cyclopropane fatty acid (CFA) synthase. Surprisingly, isobutanol decreased cyclopropane fatty acid content despite robust upregulation of CFA synthase. Overexpression of the native Z. mobilis’ CFA synthase increased cyclopropane fatty acid content in all phospholipid classes and was associated with a significant improvement in growth rates in the presence of added ethanol and isobutanol. Heterologous expression of CFA synthase from Clostridium acetobutylicum resulted in a near complete replacement of unsaturated fatty acids with cyclopropane fatty acids, affecting all lipid classes. However, this did not translate to improved growth rates under isobutanol exposure.Correlating with its greater susceptibility to isobutanol, Z. mobilis exhibited more pronounced alterations in its proteome, metabolome, and overall cell morphology—including cell swelling and formation of intracellular protein aggregates —when exposed to isobutanol compared to ethanol. Isobutanol triggered a broad stress response marked by the upregulation of heat shock proteins, efflux transporters, DNA repair systems, and the downregulation of cell motility proteins. Isobutanol also elicited widespread dysregulation of Z. mobilis’ primary metabolism evidenced by increased levels of nucleotide degradation intermediates and the depletion of biosynthetic and glycolytic intermediates.ConclusionsThis study provides a comprehensive, systems-level evaluation of the impact of ethanol and isobutanol exposure on the lipid membrane composition and overall physiology of Z. mobilis. These findings will guide engineering of Z. mobilis towards the creation of isobutanol-tolerant strains that can serve as robust platforms for the industrial production of isobutanol from lignocellulosic sugars.

An experimental model of western diet in female Wistar rats leads to cardiac hypoxia related to a stimulated contractility.

Previous studies in Western diet (WD)-fed male rats have highlighted a link between the stimulation of cardiac contractility, mitochondrial adaptations and a pro-inflammatory fatty acid profile of phospholipids in the heart. Our objectives were to determine (1) if WD-fed female Wistar rats and obese humans display a similar pro-inflammatory profile in their cardiac phospholipids and (2) if this lipid profile is associated with deleterious effects on the heart of the female rodents. Female Wistar rats were fed WD for 5weeks or a laboratory chow as a control. Ionic homeostasis, redox status, inflammation markers, and fatty acid composition of phospholipids were analysed in the heart. WD increased the abdominal fat mass without modifying the body weight of female rats. As previously found in males, a WD induced a shift in membrane fatty acid composition toward a pro-inflammatory profile in the female rats, but not in obese humans. It was associated with an increased COX2 expression suggesting an increased pro-inflammatory eicosanoid production. Signs of increased intracellular calcium strongly supported a stimulation of cardiac contractility without any induction of apoptosis. The heart of WD-fed rats exhibited a hypoxic state as a higher HIF1-α expression was reported. The expressions of antioxidant enzymes were increased, but the redox reserves against reactive oxygen species were lowered. In conclusion, as previously observed in males, we suppose that cardiac abnormalities are magnified with severe obesity in female rats, leading to hypoxia and intense oxidative stress which could ultimately induce cell death and heart failure.

Evaluation of the fatty acid-based erythrocyte membrane lipidome in cats with food responsive enteropathy, inflammatory bowel disease and low-grade intestinal T-cell lymphoma.

Feline chronic enteropathies (FCE), include food-responsive-enteropathy (FRE), inflammatory bowel disease (IBD), and low-grade intestinal T-cell lymphoma (LGITL), and are common causes of chronic gastrointestinal signs in cats. Distinguishing between different subgroups of FCE can be challenging due to the frequent overlap of anamnestic, clinical, and laboratory data. While dysregulation in lipid metabolism has been reported in humans and dogs with chronic IBD, similar changes in cats are not yet completely understood. Assessing the fatty acid (FA) profile of red blood cell (RBC) membranes offers a valuable method for evaluating the quantity and quality of structural and functional molecular components in the membranes. Therefore, this study aimed to examine the FA composition of RBC membranes in FCE in comparison to healthy cats (HC). Gas-chromatography was used to quantitatively analyze a cluster of 11 FA, and based on these results, parameters of lipid homeostasis and enzyme activity indexes were calculated. A total of 41 FCE cats (17 FRE, 15 IBD, 9 LGITL) and 43 HC were enrolled. In FCE cats, the values of docosapentaenoic acid (p = 0.0002) and docosahexaenoic acid (p = 0.0246), were significantly higher, resulting in an overall increase in ω-3 polyunsaturated fatty acids (PUFA) (p = 0.006), and that of linoleic acid (p = 0.0026) was significantly lower. Additionally, FCE cats exhibited an increased PUFA balance (p = 0.0019) and Δ6-desaturase index (p = 0.0151), along with a decreased ω-6/ω-3 ratio (p = 0.0019). No differences were observed among cats affected by FRE, IBD and LGITL. Like humans and dogs, the results of this study indicate that FCE cats also display changes in their FA lipid profile at the level of the RBC membrane. The non-invasive analysis of RBC membrane shows promise as a potential tool for gaining a better understanding of lipid imbalances in this disease.

Sex differences in erythrocyte fatty acid composition of first-diagnosed, drug-naïve patients with major depressive disorders.

Background: Since depression, sex hormones, and fatty acid status are interrelated, it is important to understand their relationships. In this study, we aimed to investigate sex differences in erythrocyte membrane fatty acid composition among first-diagnosed, drug-naïve patients with major depressive disorders. Methods: The study included 139 individuals with first-diagnosed, drug-naïve depression (male/female = 48/91) and 55 healthy controls (male/female = 24/31). The levels of erythrocyte membrane fatty acids were analyzed to compare the difference between males and females in both patients with depression and healthy controls, as well as to study their correlation with depressive symptoms. Results: In first-diagnosed, drug-naïve patients with major depressive disorders, sex disparities were observed in the levels of erythrocyte saturated fatty acids (SFAs) and n-6 PUFAs (such as C18:0, C20:4n6 and C22:4n6), where higher levels evident in females compared to in males. We found a noteworthy correlation between fatty acid levels and depressive symptoms, in which there is a significant association between female patients and depression but a weaker association between male patients and depression. Conclusion: Our findings demonstrate higher levels of n-6 PUFAs and SFAs in female patients with depression. The relationship between fatty acid composition and depressive symptoms was more prominent in females than males. These findings highlight the significance of considering sex as a crucial and interconnected factor in future investigations and potential adjunctive treatment for mood disorders by targeting fatty acid metabolism.

Alterations in Gene Expression and the Fatty Acid Profile Impact but Do Not Compromise the In Vitro Maturation of Zebrafish (Danio rerio) Stage III Ovarian Follicles after Cryopreservation.

The vitrification of ovarian follicles is a strategic tool that may contribute to advances in aquaculture and the conservation of many important species. Despite the difficulties inherent to the cryopreservation of oocytes, some successful protocols have been developed for different species, but little is known about the capacity of oocytes to develop after thawing. Therefore, the profiles of the reproductive pathway genes and fatty acid membrane composition during the initial stages of development were analyzed in fresh ovarian follicles and follicles after the vitrification process. There were differences in the expression of the hypothalamic-pituitary-gonad axis genes during the follicular development in the control group as well as in the vitrified group. Similarly, alterations in the composition of fatty acids were observed after vitrification. Despite this, many alterations were observed in the vitrified group; more than half of the stage III ovarian follicles were able to grow and mature in vitro. Therefore, the vitrification of ovarian follicles may impact them at molecular and membrane levels, but it does not compromise their capability for in vitro maturation, which indicates that the technique can be a strategic tool for aquaculture.

Acyl-AcpB, a FabT corepressor in Streptococcus pyogenes.

Membranes are a universal barrier to all cells. Phospholipids, essential bacterial membrane components, are composed of a polar head and apolar fatty acid (FA) chains. Most bacterial FAs are synthesized by the Type II FA synthesis pathway (FASII). In Streptococcaceae, Enterococci, and Lactococcus lactis, a unique feedback mechanism controls the FASII gene expression. FabT, encoded in the FASII main locus, is the repressor, and it is activated by long-chain acyl-acyl carrier protein (acyl-ACP). Many Streptococci, Enterococcus faecalis, but not L. lactis, possess two ACPs. The AcpA-encoding gene is within the FASII locus and is coregulated with the FASII genes. Acyl-AcpA is the end product of FASII. The AcpB-encoding gene is in operon with plsX encoding an acyl-ACP:phosphate acyltransferase. The role of acyl-AcpB as FabT corepressor is controversial. Streptococcus pyogenes, which causes a wide variety of diseases ranging from mild non-invasive to severe invasive infections, possesses AcpB. In this study, by comparing the expression of FabT-controlled genes in an acpB-deleted mutant with those in a wild-type and in a fabT mutant strain, grown in the presence or absence of exogenous FAs, we show that AcpB is the S. pyogenes FabT main corepressor. Its deletion impacts membrane FA composition and bacterial adhesion to eucaryotic cells, highlighting the importance of FASII control. Importance Membrane composition is crucial for bacterial growth or interaction with the environment. Bacteria synthesize fatty acids (FAs), membrane major constituents, via the Type II FAS (FASII) pathway. Streptococci control the expression of the FASII genes via a transcriptional repressor, FabT, with acyl-acyl carrier proteins (ACPs) as corepressor. Streptococcus pyogenes that causes a wide variety of diseases ranging from mild non-invasive to severe invasive infections possesses two ACPs. acpA, but not acpB, is a FASII gene. In this study, we show that acyl-AcpBs are FabT main corepressors. Also, AcpB deletion has consequences on the membrane FA composition and bacterial adhesion to host cells. In addition to highlighting the importance of FASII control in the presence of exogeneous FAs for the adaptation of bacteria to their environment, our data indicate that FASII gene repression is mediated by a corepressor whose gene expression is not repressed in the presence of exogenous FAs.

Implication of Mn-cofactored superoxide dismutase in the tolerance of swarmer Pseudomonas aeruginosa to polymixin, ciprofloxacin and meropenem antibiotics.

The protective role of superoxide dismutase (Sod) against oxidative stress, resulting from the common antibiotic pathway of action, has been studied in the wild type and mutant strains of swarmer Pseudomonas aeruginosa, lacking Cytosolic Mn-Sod (sodM), Fe-Sod (sodB) or both Sods (sodMB).Our results showed that inactivation of sodB genes leads to significant motility defects and tolerance to meropenem. This resistance is correlated with a greater membrane unsaturation as well as an effective intervention of Mn-Sod isoform, in antibiotic tolerance.Moreover, loss of Mn-Sod in sodM mutant, leads to polymixin intolerance and is correlated with membrane unsaturation. Effectivelty, sodM mutant showed an enhanced swarming motility and a conserved rhamnolipid production. Whereas, in the double mutant sodMB, ciprofloxacin tolerance would be linked to an increase in the percentage of saturated fatty acids in the membrane, even in the absence of superoxide dismutase activity.The overall results showed that Mn-Sod has a protective role in the tolerance to antibiotics, in swarmer P.aeruginosa strain. It has been further shown that Sod intervention in antibiotic tolerance is through change in membrane fatty acid composition.

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.

Supply of palmitic, stearic, and oleic acid changes rumen fiber digestibility and microbial composition

The concept that fat supplementation impairs total-tract fiber digestibility in ruminants has been widely accepted over the past decades. Nevertheless, the recent interest in the dietary fatty acid profile to dairy cows enlightened the possible beneficial effect of specific fatty acids (e.g., palmitic, stearic, and oleic acids) on total-tract fiber digestibility. Because palmitic, stearic, and oleic acids are the main fatty acids present in ruminal bacterial cells, we hypothesize that the dietary supply of these fatty acids will favor their incorporation into the bacterial cell membranes, which will support the growth and enrichment of fiber-digesting bacteria in the rumen. Our objective in this experiment was to investigate how dietary supply of palmitic, stearic, and oleic acid affect fiber digestion, bacterial membrane fatty acid profile, microbial growth, and composition of the rumen bacterial community. Diets were randomly assigned to 8 single-flow continuous culture fermenters arranged in a replicated 4 × 4 Latin square with four 11-d experimental periods. Treatments were (1) a control basal diet without supplemental fatty acids (CON); (2) the control diet plus palmitic acid (PA); (3) the control diet plus stearic acid (SA); and (4) the control diet plus oleic acid (OA). All fatty acid treatments were included in the diet at 1.5% of the diet (dry matter [DM] basis). The basal diet contained 50% orchardgrass hay and 50% concentrate (DM basis) and was supplied at a rate of 60 g of DM/d in 2 equal daily offers (0800 and 1600 h). Data were analyzed using a mixed model considering treatments as fixed effect and period and fermenter as random effects. Our results indicate that PA increased in vitro fiber digestibility by 6 percentage units compared with the CON, while SA had no effect and OA decreased fiber digestibility by 8 percentage units. Oleic acid decreased protein expression of the enzymes acetyl-CoA carboxylase compared with CON and PA, while fatty acid synthase was reduced by PA, SA, and OA. We observed that PA, but not SA or OA, altered the bacterial community composition by enhancing bacterial groups responsible for fiber digestion. Although the dietary fatty acids did not affect the total lipid content and the phospholipid fraction in the bacterial cell, PA increased the flow of anteiso C13:0 and anteiso C15:0 in the phospholipidic membrane compared to the other treatments. In addition, OA increased the flow of C18:1 cis-9 and decreased C18:2 cis-9,cis-12 in the bacterial phospholipidic membranes compared to the other treatments. Palmitic acid tended to increase bacterial growth compared to other treatments, whereas SA and OA did not affect bacterial growth compared with CON. To our knowledge, this is the first research providing evidence that palmitic acid supports ruminal fiber digestion through shifts in bacterial fatty acid metabolism that result in changes in growth and abundance of fiber-degrading bacteria in the microbial community.

Effects of Potassium and Nanocapsule of Potassium on Pepper Growth and Physiological Changes in High-Temperature Stress

Abiotic stresses have been observed to cause alterations in the morphology, physiology, and biochemistry of plants. However, in recent years, the utilization of nanocompounds has emerged as a strategy to induce modifications in multiple facets of plant biology. These modifications include plant growth, nutrient absorption, the production of significant secondary metabolites, and the improvement of plants’ resistance against both abiotic and biotic stress factors. A completely randomized factorial experiment with 12 replications was created. Potassium sources including control, potassium (K), and nanocapsule-potassium (N-K) with concentration 1 µM and temperature treatments including control temperature (25 °C) and high-temperature stress (35 °C) were applied as treatments. In the control treatment, proline was increased at the high temperature, whereas proline was reduced at both treated temperatures by K and N-K. High temperature raised electrolyte leakage (EL), which peaked in the control treatment but was lowered by K and N-K. Temperature-dependent increase in glucose and fructose was observed in control and K treatments when the temperature was 35 °C, but no significant difference was observed between different levels of K at 35 °C. When K was not applied at high temperatures, the main stress indicators such as antioxidant activity (DPPH) and malondialdehyde (MDA) rose significantly, as did the water potential and linoleic acid. When high temperatures were applied, nanocapsule-potassium applied in high temperatures had the lowest stress indices. In conclusion, stress indices diminish when nanocapsule-potassium is applied under high temperatures. Additionally, nanocapsule-potassium applied at high temperatures was preferable to K applied at high temperatures in terms of pepper growth and resistance measures. Likewise, the application of nanocapsule-potassium at high temperatures alters the fatty acid composition of membranes and antioxidant enzymes.

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.

Fatty Acids Profile and the Relevance of Membranes as the Target of Nutrition-Based Strategies in Atopic Dermatitis: A Narrative Review.

Recently, the prevalence of atopic dermatitis has increased drastically, especially in urban populations. This multifactorial skin disease is caused by complex interactions between various factors including genetics, environment, lifestyle, and diet. In eczema, apart from using an elimination diet, the adequate content of fatty acids from foods (saturated, monounsaturated, and polyunsaturated fatty acids) plays an important role as an immunomodulatory agent. Different aspects regarding atopic dermatitis include connections between lipid metabolism in atopic dermatitis, with the importance of the MUFA levels, as well as of the omega-6/omega-3 balance that affects the formation of long-chain (C20 eicosanoic and C22 docosaenoic) fatty acids and bioactive lipids from them (such as prostaglandins). Impair/repair of the functioning of epidermal barrier is influenced by these fatty acid levels. The purpose of this review is to drive attention to membrane fatty acid composition and its involvement as the target of fatty acid supplementation. The membrane-targeted strategy indicates the future direction for dermatological research regarding the use of nutritional synergies, in particular using red blood cell fatty acid profiles as a tool for checking the effects of supplementations to reach the target and influence the inflammatory/anti-inflammatory balance of lipid mediators. This knowledge gives the opportunity to develop personalized strategies to create a healthy balance by nutrition with an anti-inflammatory outcome in skin disorders.

Improved Membrane Permeability via Hypervesiculation for In Situ Recovery of Lycopene in Escherichia coli.

Lycopene biosynthesis is frequently hampered by downstream processing hugely due to its inability to be secreted out from the producing chassis. Engineering cell factories can resolve this issue by secreting this hydrophobic compound. A highly permeable E.coli strain was developed for a better release rate of lycopene. Specifically, the heterologous mevalonate pathway and crtEBI genes from Corynebacterium glutamicum were overexpressed in Escherichia coli BL21 (DE3) for lycopene synthesis. To ensure in situ lycopene production, murein lipoprotein, lipoprotein NlpI, inner membrane permease protein, and membrane-anchored protein in TolA-TolQ-TolR were deleted for improved membrane permeability. The final strain, LYC-8, produced 438.44 ± 8.11 and 136.94 ± 1.94 mg/L of extracellular and intracellular lycopene in fed-batch fermentation. Both proteomics and lipidomics analyses of secreted outer membrane vesicles were perfect indicators of hypervesiculation. Changes in the ratio of saturated fatty acids, unsaturated fatty acids, and cyclopropane fatty acids coupled with the branching and acyl chain lengths altered the membrane fatty acid composition. This ensured membrane fluidity and permeability for in situ lycopene release. The combinatorial deletion of these genes altered the cellular morphology. The structural and morphological changes in cell shape, size, and length were associated with changes in the mechanical strength of the cell envelope. The enhanced lycopene production and secretion mediated by improved membrane permeability established a cell lysis-free system for an efficient releasing rate and downstream processing, demonstrating the importance of vesicle-associated membrane permeability in efficient lycopene production.

Shigella flexneri Adapts to Niche-Specific Stresses through Modifications in Cell Envelope Composition and Decoration.

Shigella flexneri is the primary causative agent of worldwide shigellosis. As the pathogen transverses the distinct niches of the gastrointestinal tract it necessitates dynamic adaptation strategies to mitigate host antimicrobials such as dietary fatty acids (FAs) and the bile salt, deoxycholate (DOC). This study investigates the dynamics of the S. flexneri cell envelope, by interrogating adaptations following FA or DOC exposure. We deciphered the effects of FAs and DOC on bacterial membrane fatty acid and lipopolysaccharide (LPS) compositions. We identified novel LPS-based strategies by the pathogen to support resistance to these host compounds. In particular, expression of S. flexneri very-long O antigen (VL-Oag) LPS was found to play a central role in stress mitigation, as VL-Oag protects against antimicrobial FAs, but its presence rendered S. flexneri susceptible to DOC stress. Collectively, this work underpins the importance for S. flexneri to maintain appropriate regulation of cell envelope constituents, in particular VL-Oag LPS, to adequately adapt to diverse stresses during infection.