Phosphatidylethanolamine Lipids Research Articles

Generation of a Nonbilayer Lipid Nanoenvironment after Epitope Binding Potentiates Neutralizing HIV-1 MPER Antibody.

Establishment of interactions with the envelope lipids is a cardinal feature of broadly neutralizing antibodies (bnAbs) that recognize the Env membrane-proximal external region (MPER) of HIV. The lipid envelope constitutes a relevant component of the full "quinary" MPER epitope, and thus antibodies may be optimized through engineering their capacity to interact with lipids. However, the role of the chemically complex lipid nanoenvironment in the mechanism of MPER molecular recognition and viral neutralization remains poorly understood. To approach this issue, we computationally and experimentally investigated lipid interactions of broadly neutralizing antibody 10E8 and optimized versions engineered to enhance their epitope and membrane affinity by grafting bulky aromatic compounds. Our data revealed a correlation between neutralization potency and the establishment of favorable interactions with small headgroup lipids cholesterol and phosphatidylethanolamine, evolving after specific engagement with MPER. Molecular dynamics simulations of chemically modified Fabs in complex with an MPER-Transmembrane Domain helix supported the generation of a nanoenvironment causing localized deformation of the thick, rigid viral membrane and identified sphingomyelin preferentially occupying a phospholipid-binding site of 10E8. Together, these interactions appear to facilitate insertion of the Fabs through their engagement with the MPER epitope. These findings implicate individual lipid molecules in the neutralization function of MPER bnAbs, validate targeted chemical modification as a method to optimize MPER antibodies, and suggest pathways for MPER peptide-liposome vaccine development.

Unraveling autophagic imbalances and therapeutic insights in Mecp2-deficient models.

Loss-of-function mutations in MECP2 are associated to Rett syndrome (RTT), a severe neurodevelopmental disease. Mainly working as a transcriptional regulator, MeCP2 absence leads to gene expression perturbations resulting in deficits of synaptic function and neuronal activity. In addition, RTT patients and mouse models suffer from a complex metabolic syndrome, suggesting that related cellular pathways might contribute to neuropathogenesis. Along this line, autophagy is critical in sustaining developing neuron homeostasis by breaking down dysfunctional proteins, lipids, and organelles.Here, we investigated the autophagic pathway in RTT and found reduced content of autophagic vacuoles in Mecp2 knock-out neurons. This correlates with defective lipidation of LC3B, probably caused by a deficiency of the autophagic membrane lipid phosphatidylethanolamine. The administration of the autophagy inducer trehalose recovers LC3B lipidation, autophagosomes content in knock-out neurons, and ameliorates their morphology, neuronal activity and synaptic ultrastructure. Moreover, we provide evidence for attenuation of motor and exploratory impairment in Mecp2 knock-out mice upon trehalose administration. Overall, our findings open new perspectives for neurodevelopmental disorders therapies based on the concept of autophagy modulation.

Structural and Functional Characterization of a Novel Class A Flavin Monooxygenase from Bacillus niacini.

A gene cluster responsible for the degradation of nicotinic acid (NA) in Bacillus niacini has recently been identified, and the structures and functions of the resulting enzymes are currently being evaluated to establish pathway intermediates. One of the genes within this cluster encodes a flavin monooxygenase (BnFMO) that is hypothesized to catalyze a hydroxylation reaction. Kinetic analyses of the recombinantly purified BnFMO suggest that this enzyme catalyzes the hydroxylation of 2,6-dihydroxynicotinic acid (2,6-DHNA) or 2,6-dihydroxypyridine (2,6-DHP), which is formed spontaneously by the decarboxylation of 2,6-DHNA. To understand the details of this hydroxylation reaction, we determined the structure of BnFMO using a multimodel approach combining protein X-ray crystallography and cryo-electron microscopy (cryo-EM). A liganded BnFMO cryo-EM structure was obtained in the presence of 2,6-DHP, allowing us to make predictions about potential catalytic residues. The structural data demonstrate that BnFMO is trimeric, which is unusual for Class A flavin monooxygenases. In both the electron density and coulomb potential maps, a region at the trimeric interface was observed that was consistent with and modeled as lipid molecules. High-resolution mass spectral analysis suggests that there is a mixture of phosphatidylethanolamine and phosphatidylglycerol lipids present. Together, these data provide insights into the molecular details of the central hydroxylation reaction unique to the aerobic degradation of NA in Bacillus niacini.

Lipid metabolites and sarcopenia-related traits: a Mendelian randomization study

ObjectiveTo explore the influence of lipid metabolism on the risk of sarcopenia.MethodsTwo-sample Mendelian randomization (MR) analysis was used to determine causality. A total of 179 lipid metabolism data points were used for exposure, and the data were obtained from a plasma lipid metabolite study of 7174 participants. The total muscle mass and total muscle strength, as well as the muscle strength and muscle mass of different sex groups, were selected as the relevant traits of sarcopenia. Data for outcomes were obtained from the UK Biobank, and sample sizes ranged from 135 468 to 450 243. Inverse-variance weighted (IVW), as the main method for evaluating the causal relationship between lipid metabolites and sarcopenia, uses the false discovery rate (FDR) for multiple comparisons and conducts heterogeneity, pleiotropy, and reverse causality tests.ResultsTwenty-seven lipid metabolites, mainly phosphatidylcholine, phosphatidylethanolamine, ceramide, triacylglycerol, sphingomyelin, and sterol ester, were found to be associated with the risk of sarcopenia. Ceramide (d40:1), ceramide (d40:2), and sterol ester are risk factors for decreased muscle mass and strength. There is a positive causal relationship between various phosphatidylcholine lipids and muscle mass and strength. Sphingomyelin (d42:2) is a protective factor for total muscle strength and female muscle strength. There are inconsistent effects between different lipid metabolites, triacylglycerol, and muscle strength and muscle mass.ConclusionsThere was a causal relationship between 27 lipid metabolites and sarcopenia traits, and targeting specific lipid metabolites may benefit sarcopenia diagnosis, disease assessment, and treatment.

Lipidomic analyses reveal distinctive variations in homeoviscous adaptation among clinical strains of Acinetobacter baumannii, providing insights from an environmental adaptation perspective.

Acinetobacter baumannii is known for its antibiotic resistance and is increasingly found outside of healthcare settings. To survive colder temperatures, bacteria, including A. baumannii, adapt by modifying glycerophospholipids (GPL) to maintain membrane flexibility. This study examines the lipid composition of six clinical A. baumannii strains, including the virulent AB5075, at two temperatures. At 18°C, five strains consistently show an increase in palmitoleic acid (C16:1), while ABVal2 uniquely shows an increase in oleic acid (C18:1). LC-HRMS2 analysis identifies shifts in GPL and glycerolipid composition between 18°C and 37°C, highlighting variations in phosphatidylethanolamine (PE) and phosphatidylglycerol (PG) lipids. ABVal2 shows increased PE with C18:1 and C16:1 at 18°C, but no change in PG, in contrast to other strains that show increased PE and PG with C16:1. Notably, although A. baumannii typically lacks FabA, a key enzyme for unsaturated fatty acid synthesis, this enzyme was found in both ABVal2 and ABVal3. In addition, ABVal2 contains five candidate desaturases that may contribute to its lipid profile. The study also reveals variations in strain motility and biofilm formation over temperature. These findings enhance our understanding of A. baumannii's physiological adaptations, survival strategies and ecological fitness in different environments.IMPORTANCEAcinetobacter baumannii, a bacterium known for its resistance to antibiotics, is a concern in healthcare settings. This study focused on understanding how this bacterium adapts to different temperatures and how its lipid composition changes. Lipids are the building blocks of cell membranes. By studying these changes, scientists can gain insights into how the bacterium survives and behaves in various environments. This understanding improves our understanding of its global dissemination capabilities. The results of the study contribute to our broader understanding of how Acinetobacter baumannii works, which is important for developing strategies to combat its impact on patient health.

Can calmodulin bind to lipids of the cytosolic leaflet of plasma membranes?

Calmodulin (CaM) is a ubiquitous calcium-sensitive messenger in eukaryotic cells. It was previously shown that CaM possesses an affinity for diverse lipid moieties, including those found on CaM-binding proteins. These facts, together with our observation that CaM accumulates in membrane-rich protrusions of HeLa cells upon increased cytosolic calcium, motivated us to perform a systematic search for unmediated CaM interactions with model lipid membranes mimicking the cytosolic leaflet of plasma membranes. A range of experimental techniques and molecular dynamics simulations prove unambiguously that CaM interacts with lipid bilayers in the presence of calcium ions. The lipids phosphatidylserine (PS) and phosphatidylethanolamine (PE) hold the key to CaM-membrane interactions. Calcium induces an essential conformational rearrangement of CaM, but calcium binding to the headgroup of PS also neutralizes the membrane negative surface charge. More intriguingly, PE plays a dual role-it not only forms hydrogen bonds with CaM, but also destabilizes the lipid bilayer increasing the exposure of hydrophobic acyl chains to the interacting proteins. Our findings suggest that upon increased intracellular calcium concentration, CaM and the cytosolic leaflet of cellular membranes can be functionally connected.

Gilvirhabdus luticola gen. nov., sp. nov., a mesophilic and halophilic bacterium isolated from tidal flat sediment.

Two novel bacteria, MJ-SS3T and MJ-SS4, were isolated from tidal flat sediment sampled in Gochang, Republic of Korea. The isolates were Gram-stain-negative, aerobic, non-motile, rod-shaped, yellow-coloured, oxidase-positive, and catalase-positive. Strains MJ-SS3T and MJ-SS4 grew at 20-37 °C (optimum, 30 °C), at pH 6-8 (optimum, pH 7.0) and in the presence of 0-7 % (w/v) NaCl (optimum, 2.0 % NaCl). Strains MJ-SS3T and MJ-SS4 showed 99.9 % 16S rRNA gene sequence similarity. Phylogenetic analysis based on genome and 16S rRNA gene sequences indicated that strains MJ-SS3T and MJ-SS4 were affiliated with the family Flavobacteriaceae and most closely related to Formosa maritima 1494T (95.3 %), Hanstruepera flava NBU2984T (95.2 %), Yeosuana marina JLT21T (95.2 %), Meridianimaribacter flavus NH57NT (95.1 %), and Geojedonia litorea YCS-16T (95.1 %). The major respiratory quinone was menaquinone-6. The major identified polar lipids were phosphatidylethanolamine, phosphatidylglycerol, phosphatidylcholine, and amino lipids. The major cellular fatty acids of strain MJ-SS3T were iso-C15 : 1 G (24.6 %), iso-C15 : 0 (21.6 %), and iso-C17 : 0 3-OH (15.8 %). The genome length of strain MJ-SS3T is 3.1 Mbp (DNA G+C content, 32.5 mol%) and it has 2822 coding and 59 tRNA genes. The average amino acid identity and average nucleotide identity values, as well as biochemical, phylogenetic, and physiological characteristics, strongly supported the genotypic and phenotypic differentiation of strains MJ-SS3T and MJ-SS4 from other members of the family Flavobacteriaceae. Hence, strains MJ-SS3T and MJ-SS4 are considered to represent a novel species of a new genus in the family Flavobacteriaceae, for which the Gilvirhabdus luticola gen. nov., sp. nov. is proposed. The type strain is MJ-SS3T (=KCTC 102114T=KEMB 20189T=JCM 36595T), with reference strain MJ-SS4 (=KCTC 102115=KEMB 20190).

Thalassospira aquimaris sp. nov. and Winogradskyella marincola sp. nov. two marine bacteria isolated from an agar-degrading co-culture.

Two novel Gram-stain-negative, aerobic, and non-motile strains, designated FZY0004T and YYF002T, were isolated from an agar-degrading co-culture, which was obtained from seawater of the intertidal zone of Yancheng City, the Yellow Sea of China. Strain FZY0004T optimally grew at 28°C, pH 7.0, and 2-6% NaCl, while strain YYF002T optimally grew at 28°C, pH 7.5, and 2-4% NaCl. Strain FZY0004T possessed Q-9 as the major respiratory quinone, and its major fatty acids (> 10%) were summed feature 8 (C18:1 ω7c), C16:0, and summed feature 3 (C16:1 ω7c/C16:1 ω6c). The polar lipids identified in strain FZY0004T were phosphatidylethanolamine (PE), phosphatidylglycerol (PG), and several unidentified phospholipids (PL) and lipids (L). On the other hand, strain YYF002T had MK-6 as the predominant respiratory quinone and its major fatty acids consisted of iso-C15:0, iso-C15:1 G, and iso-C15:0 3-OH. The polar lipids identified in strain YYF002T were aminolipid (AL), PE, and several unidentified lipids. Strain FZY0004T shared 99.5% 16S rRNA gene sequence similarity and 90.1% average nucleotide identity (ANI) with T. povalilytica Zumi 95T, and strain YYF002T shared 99.2% 16S rRNA gene sequence similarity and 88.2% ANI with W. poriferorum JCM 12885T. The genomic DNA G + C contents of strains FZY0004T and YYF002T were 54.5% and 33.5%, respectively. The phylogenetic, phenotypic, and physiological characteristics permitted the distinction of the two strains from their neighbors, and we thus propose the names Thalassospira aquimaris sp. nov. (type strain FZY0004T = JCM 35895T = MCCC 1K08380T) and Winogradskyella marincola sp. nov. (type strain YYF002T = JCM 35950T = MCCC 1K08382T).

Probing the energy landscape of the lipid interactions of the serotonin1A receptor

G protein-coupled receptors (GPCRs) are lipid-regulated transmembrane proteins that play a central role in cell signaling and pharmacology. Although the role of membrane lipids in GPCR function is well established, the underlying GPCR-lipid interactions have not been thermodynamically characterized due to the complexity of these interactions. In this work, we estimate the energetics and dynamics of lipid association from coarse-grain simulations of the serotonin1A receptor embedded in a complex membrane. We show that lipids bind to the receptor with varying energetics of 1–4 kT, and timescales of 1–10 μs. The most favorable energetics and longest residence times are observed for cholesterol, glycosphingolipid GM1, phosphatidylethanolamine (PE) and phosphatidylserine (PS) lipids. Multi-exponential fitting of the contact probability suggests distinct dynamic regimes, corresponding to ps, ns and μs timescales, that we correlate with the annular, intermediate and non-annular lipid sites. The timescales of lipid binding correspond to high barrier heights, despite their relatively weaker energetics. Our results highlight that GPCR-lipid interactions are driven by both thermodynamic interactions and the dynamical features of lipid binding.

Mesobacterium hydrothermale sp. nov., isolated from shallow-sea hydrothermal systems off Kueishantao Island.

A Gram-negative, rod-shaped, non-motile, aerobic bacterium, designated as strain TK19101T, was isolated from the intermediate seawater of yellow vent in the shallow-sea hydrothermal system located near Kueishantao Island. The strain was found to grow at 10-40°C (optimum, 35°C), at pH 6.0-8.0 (optimum, 7.0), and in 0-5% (w/v) NaCl (optimum, 1%). Strain TK19101T was catalase-positive and oxidase-positive. The predominant fatty acids (> 10%) in strain TK19101T cells were C16:0, summed feature 8 (C18:1 ω6c and/or C18:1 ω7c), and C18:0. The predominant isoprenoid quinone of strain TK19101T was ubiquinone-10. The polar lipids of strain TK19101T comprised phosphatidylcholine, phosphatidylethanolamine, phosphatidylglycerol, phospholipid, and unknown polar lipid. Phylogenetic analysis based on 16S rRNA gene sequences showed that strain TK19101T belonged to the genus Mesobacterium. Strain TK19101T exhibited highest 16S rRNA gene sequence similarity value to Mesobacterium pallidum MCCC M24557T (97.48%). The estimated average nucleotide identity and digital DNA-DNA hybridization values between strain TK19101T and the closest related species Mesobacterium pallidum MCCC M24557T were 74.88% and 20.30%, respectively. The DNA G + C content was 63.49mol%. On the basis of the analysis of 16S rRNA gene sequences, genotypic and phylogenetic data, strain TK19101T has a unique phylogenetic status and represents a novel species of genus Mesobacterium, for which the name Mesobacterium hydrothermale sp. nov. is proposed. The type strain is TK19101T (= MCCC 1K08936T = KCTC 8354T).

Crenobacter oryzisoli sp. nov., a novel phosphate-solubilizing bacterium isolated from the paddy soil.

Two Gram-staining-negative, facultative anaerobic, rod-shaped and phosphate-solubilizing strains designated SG2303T and SG2305, were isolated from paddy soil in China. Phylogenetic analysis based on 16S rRNA gene sequences indicated that SG2303T and SG2305 represented a member of the genus Crenobacter within the family Neisseriaceae of the phylum Pseudomonadota. Strain SG2303T displayed higher 16S rRNA gene sequence similarities with members of the genus Crenobacter ranging from 93.5 to 94.0%. Strains C. luteus YIM 78141T and C. cavernae K1W11S-77T were closest related to the isolated strains and were considered as type strains. Growth of strain SG2303T occurred at 10-55°C (optimum 37°C), pH 5.0-9.0 (optimum pH 6.0-7.0) and 0-1% (w/v) NaCl (optimum 0%). The average nucleotide identity (ANI) and digital DNA-DNA hybridization (dDDH) values between strain SG2303T and its closely related taxa were 76.1-78.2% and 20.5-22.1%, respectively. The genomic DNA G + C content was 62.2%. The quinone of strain SG2303T was Q-8. The major fatty acids (> 10%) of strain SG2303T were C16:0 (30.6%), summed feature 3 (C16:1ω7c and/or C16:1ω6c) (26.0%) and C12:0 3OH (12.1%). The polar lipids were phosphatidylglycerol (PG), diphosphatidylglycerol (DPG), phosphatidylethanolamine (PE), phospholipids (PL), glycolipid (GL) and unidentified lipids (UL). Based on the results of the phylogenetic, physiological, biochemical, and morphological analysis, strain SG2303T is recognized as a novel species of the genus Crenobacter, for which the name Crenobacter oryzisoli sp. nov. is proposed. The type strain is SG2303T (= GDMCC 1.3970T = JCM 36468T). In addition, SG2303T was also able of phosphorus solubilization and promoting the growth of rice seeds. Strain SG2303T exhibited a relatively high dissolvable phosphorus content of 2.52µg·mL- 1.

ToF-SIMS imaging reveals changes in tumor cell lipids during metastatic progression of melanoma.

Most melanomas progress from radial to vertical growth phase before spreading locoregionally and distally. Much is still unknown about the metabolic changes in the tumor cells and their microenvironment during this metastatic progression. We aimed to gain new insight into the molecular characteristics of melanoma in regard to spatial lipidomics to deliver new knowledge regarding tumor metastatic progression. We included 10 fresh tumor samples from 10 patients including two insitu melanomas, two invasive primary melanomas, and six metastatic melanomas (four in-transit metastases and two distant metastases). In addition, we analyzed four healthy skin controls from the same patients. Time-of-flight imaging secondary ion mass spectrometry (ToF-SIMS) enabled detailed spatial-lipidomics that could be directly correlated with conventional histopathological analysis of consecutive H&E-stained tissue sections. Significant differences in the lipid profiles were found in primary compared to metastatic melanomas, notably an increase in phosphatidylethanolamine lipids relative to phosphatidylinositol lipids and an increase in GM3 gangliosides in the metastatic samples. Furthermore, analysis of the data from in transit versus distant metastases samples highlighted that specific phospholipids, and a difference in the long versus shorter chain GM3 gangliosides, discriminated the metastatic routes. Further studies are warranted to verify these preliminary findings. Lipidomic changes could serve as a novel biomarker for tumor progression and even serve as a target for novel treatments. Furthermore, analyzing the lipid profiles could help to differentiate between primary and metastatic melanomas in challenging cases.

Structure and Activity of Reconstructed Pseudo-Ancestral Cyclotides.

Cyclotides are cyclic peptides that are promising scaffolds for the design of drug candidates and chemical tools. However, despite there being hundreds of reported cyclotides, drug design studies have commonly focussed on a select few prototypic examples. Here, we explored whether ancestral sequence reconstruction could be used to generate new cyclotides for further optimization. We show that the reconstructed 'pseudo-ancestral' sequences, named Ancy-m (for the ancestral cyclotide of the Möbius sub-family) and Ancy-b (for the bracelet sub-family), have well-defined structures like their extant members, comprising the core structural feature of a cyclic cystine knot. This motif underpins efforts to re-engineer cyclotides for agrochemical and therapeutic applications. We further show that the reconstructed sequences are resistant to temperatures approaching boiling, bind to phosphatidyl-ethanolamine lipid bilayers at micromolar affinity, and inhibit the growth of insect cells at inhibitory concentrations in the micromolar range. Interestingly, the Ancy-b cyclotide had a higher oxidative folding yield than its comparator cyclotide cyO2, which belongs to the bracelet cyclotide subfamily known to be notoriously difficult to fold. Overall, this study provides new cyclotide sequences not yet found naturally that could be valuable starting points for the understanding of cyclotide evolution and for further optimization as drug leads.

Optical and molecular features of negatively curved surfaces created by POPE lipids: A crucial role of the initial conditions

Membrane fusion is closely related to plasma membrane domains rich in cone-shaped phosphatidylethanolamine (PE) lipids that can reverse membrane curvature under certain conditions. The phase transition of PE-based lipid membranes from the lamellar fluid phase (Lα) to the inverse hexagonal phase (HII) is commonly taken as a general model in reconstructing the membrane fusion pathway, and whose structural features have been mostly described so far using structural and microscopic techniques. The aim of this paper is to decipher the optical and molecular features of Lβ → Lα and especially of Lα → HII transition of 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphoethanolamine (POPE) lipids at pH = 7.0 when they are initially prepared in the form of both multi- and unilamellar liposomes (MLVs and LUVs). The distinction between optical properties of MLS- and LUVs-derived HII phase, provided from turbidity-sensitive temperature-dependent UV–Vis spectra, was attributed to different formation mechanisms of HII phase. Most importantly, from FTIR spectroscopic data of POPE lipids in Lβ (15 °C), Lα (50 °C) and HII (85 °C) phases we identified the changes in molecular features of POPE lipids during phase transitions. Among the latter, by far the most significant is different hydration pattern of POPE lipids in MLVs- and LUVs-derived HII phase which extends from the polar-apolar interface all the way to the terminal amino group of the POPE lipid, along with the changes in the conformation of glycerol backbone as evidenced by the signature of α-methylene groups. Molecular dynamics simulations confirmed higher water penetration in HII phase and provided insight into hydrogen bonding patterns.

Ottowia cancrivicina sp. nov., isolated from human stomach.

A Gram-negative, facultative anaerobic, non-motile and rod-shaped bacterium, designated 10c7w1T, was isolated from a human gastrointestinal tract. Colonies on agar plates were small, circular, smooth and beige. The optimal growth conditions were determined to be 37 °C, pH 7.0-7.5 and 0 % (w/v) NaCl. Comparative analysis of complete 16S rRNA gene sequences revealed that strain 10c7w1T showed the highest sequence similarity of 95.8 % to Ottowia beijingensis MCCC 1A01410T, followed by Ottowia thiooxydans (95.2 %) JCM 11629T. The average amino acid identity values between 10c7w1T and O. beijingensis MCCC 1A01410T and O. thiooxydans JCM 11629T were above 60 % (71.4 and 69.5 %). The average nucleotide identity values between strain 10c7w1T and O. beijingensis MCCC 1A01410T and O. thiooxydans JCM 11629T were 76.9 and 72.5 %, respectively. The dominant fatty acids (≥10 %) were straight chain ones, with summed feature 3 (C16 : 1 ω7c/C16 : 1 ω6c), summed feature 8 (C18 : 1 ω7c/C18 : 1 ω6c) and C16 : 00 being the most abundant. Q-8 was the only respiratory quinone. The major polar lipids of strain 10c7w1T were phosphatidylethanolamine, diphosphatidylglycerol and unknown lipids. The DNA G+C content of strain 10c7w1T was 63.6 mol%. On the basis of phylogenetic, phenotypic and chemotaxonomic data, strain 10c7w1T is considered to represent a novel species within the genus Ottowia, for which the name Ottowia cancrivicina sp. nov. is proposed. The type strain is 10c7w1T (=MCCC 1H01399T=KCTC 92200T).

Flavobacterium acetivorans sp. nov. and Flavobacterium galactosidilyticum sp. nov., psychrotolerant flavobacteria isolated from cultivated fish.

Two yellow-coloured strains, F-29T and F-340T, were isolated from fish farms in Antalya and Mugla in 2015 and 2017 during surveillance studies. The 16S rRNA gene sequence analysis showed that both strains belong to the genus Flavobacterium. A polyphasic approach involving a comprehensive genome analysis was employed to ascertain the taxonomic provenance of the strains. The overall genome-relatedness indices of digital DNA-DNA hybridization (dDDH) and average nucleotide identity (ANI) between the strains and the other members of the genus Flavobacterium were found to be well below the established thresholds of 70 and 95 %, respectively. The whole-genome-based phylogenetic analysis revealed that strain F-29T is closely related to Flavobacterium granuli (dDDH 39.3 % and ANI 89.4 %), while strain F-340T has a close relationship with the type strain of Flavobacterium pygoscelis (dDDH 25.6 % and ANI 81.5 %). Both strains were psychrotolerant with an optimum growth temperature of 25 °C. The chemotaxonomic characteristics of the strains were typical of the genus Flavobacterium. Both strains had phosphatidylethanolamine, aminolipids and unidentified lipids in their polar lipid profile and MK-6 as the isoprenoid quinone. The major fatty acids were iso-C15 : 0 and anteiso-C15 : 0. The genome size of the strains was 3.5 Mb, while G+C contents were 35.3 mol% for strain F-29T and 33.4 mol% for strain F-340T. Overall, the characterizations confirmed that both strains are representatives of two novel species within the genus Flavobacterium, for which the names Flavobacterium acetivorans sp. nov. and Flavobacterium galactosidilyticum sp. nov. are proposed, with F-29T (JCM 34193T=KCTC 82253T) and F-340T (JCM 34203T=KCTC 82263T) as the type strains, respectively.

Roseibium algicola sp. nov. and Roseibium porphyridii sp. nov., isolated from marine red algae.

Two Gram-stain-negative, strictly aerobic rods, designated as RMAR6-6T and KMA01T, exhibiting catalase- and oxidase-positive activities, were isolated from marine red algae in the Republic of Korea. Cells of strain RMAR6-6T exhibited flagellar motility, while those of strain KMA01T were non-motile. Strain RMAR6-6T exhibited optimal growth at 30-35°C and pH 7.0-8.0 with 4.0-6.0 % (w/v) NaCl, while strain KMA01T grew optimally at 30-35 °C, pH 7.0-8.0 and 2.0-5.0% NaCl. Both strains shared common major respiratory isoprenoid quinone (ubiquinone-10), cellular fatty acids (C18 : 0, C18: 1 ω7c 11-methyl, C20 : 1 ω7c and summed feature 8) and polar lipids (phosphatidylglycerol, phosphatidylmonomethylethanolamine, diphosphatidylglycerol, phosphatidylethanolamine, phosphatidylcholine and sulphoquinovosyldiacylglycerol). The genomic DNA G+C contents were 59.0 and 55.0 mol% for strains RMAR6-6T and KMA01T, respectively. With 98.5 % 16S rRNA gene similarity, 75.2 % average nucleotide identity (ANI) and 19.8 % digital DNA-DNA hybridization (dDDH) values, strains RMAR6-6T and KMA01T were identified as representing distinct species. Phylogenetic analyses based on both 16S rRNA gene and genome sequences revealed that strains RMAR6-6T and KMA01T formed distinct phylogenic lineages within the genus Roseibium, most closely related to Roseibium aggregatum IAM 12614T and Roseibium album CECT 5094T, respectively. The ANI and dDDH values between strain RMAR6-6T and R. aggregatum IAM 12614T were 87.5 and 33.3 %, respectively. Similarly, the values between KMA01T and R. album CECT 5094T were 74.2 % (ANI) and 19.3 % (dDDH). Based on phenotypic, chemotaxonomic and molecular characteristics, strains RMAR6-6T and KMA01T represent two novel species of the genus Roseibium, for which the names R. algicola sp. nov. (RMAR6-6T=KACC 22482T=JCM 34977T) and R. porphyridii sp. nov. (KMA01T=KACC 22479T=JCM 34597T) are proposed, respectively.

Three-step docking by WIPI2, ATG16L1, and ATG3 delivers LC3 to the phagophore.

The covalent attachment of ubiquitin-like LC3 proteins (microtubule-associated proteins 1A/1B light chain 3) prepares the autophagic membrane for cargo recruitment. We resolve key steps in LC3 lipidation by combining molecular dynamics simulations and experiments in vitro and in cellulo. We show how the E3-like ligaseautophagy-related 12 (ATG12)-ATG5-ATG16L1 in complex with the E2-like conjugase ATG3 docks LC3 onto the membrane in three steps by (i) the phosphatidylinositol 3-phosphate effector protein WD repeat domain phosphoinositide-interacting protein 2 (WIPI2), (ii) helix α2 of ATG16L1, and (iii) a membrane-interacting surface of ATG3. Phosphatidylethanolamine (PE) lipids concentrate in a region around the thioester bond between ATG3 and LC3, highlighting residues with a possible role in the catalytic transfer of LC3 to PE, including two conserved histidines. In a near-complete pathway from the initial membrane recruitment to the LC3 lipidation reaction, the three-step targeting of the ATG12-ATG5-ATG16L1 machinery establishes a high level of regulatory control.

Lipidomics based on UHPLC/Q-TOF-MS to characterize lipid metabolic profiling in patients with newly diagnosed type 2 diabetes mellitus with dyslipidemia

Dyslipidemia often accompanies type 2 diabetes mellitus (T2DM). Elevated blood glucose in patients commonly leads to high levels of lipids. Lipid molecules can play a crucial role in early detection, treatment, and prognosis of T2DM with dyslipidemia. Previous lipid studies on T2DM mainly focused on Western diabetic populations with elevated blood glucose. In this research, we investigate both high blood sugar and high lipid levels to better understand changes in plasma lipid metabolism in newly diagnosed Chinese T2DM patients with dyslipidemia (NDDD). We used a plasma lipid analysis method based on ultra-high performance liquid chromatography coupled with mass spectrometry technology (UHPLC-MS) and statistical analysis to characterize lipid profiles and identify potential biomarkers in NDDD patients compared to healthy control (HC) subjects. Additionally, we examined the differences in lipid profiles between hyperlipidemia (HL) patients and HC subjects. We found significant changes in 15 and 23 lipid molecules, including lysophosphatidylcholine (LysoPC), phosphatidylcholine (PC), phosphatidylethanolamine (PE), sphingomyelin (SM), and ceramide (Cer), in the NDDD and HL groups compared to the HC group. These altered lipid molecules are associated with five metabolic pathways, with sphingolipid metabolism and glycerophospholipid metabolism being the most relevant to glucose and lipid metabolism changes. These lipid biomarkers are strongly correlated with traditional markers of glucose and lipid metabolism. Notably, Cer(d18:1/24:0), SM(d18:1/24:0), SM(d18:1/16:1), SM(d18:1/24:1), and SM(d18:2/24:1) were identified as essential potential biomarkers closely linked to clinical parameters through synthetic analysis of receiver operating characteristic curves, random forest analysis, and Pearson matrix correlation. These lipid biomarkers can enhance the risk prediction for the development of T2DM in individuals with dyslipidemia but no clinical signs of high blood sugar. Furthermore, they offer insights into the pathological mechanisms of T2DM with dyslipidemia.

Curvature sensing lipid dynamics in a mitochondrial inner membrane model

Membrane curvature is essential for many cellular structures and processes, and factors such as leaflet asymmetry, lipid composition, and proteins all play important roles. Cardiolipin is the signature lipid of mitochondrial membranes and is essential for maintaining the highly curved shapes of the inner mitochondrial membrane (IMM) and the spatial arrangement of membrane proteins. In this study, we investigate the partitioning behavior of various lipids present in the IMM using coarse-grained molecular dynamics simulations. This study explores curved bilayer systems containing phosphatidylcholine (PC), phosphatidylethanolamine (PE), and cardiolipin (CDL) in binary and ternary component mixtures. Curvature properties such as mean and Gaussian curvatures, as well as the distribution of lipids into the various curved regions of the cristae models, are quantified. Overall, this work represents an advance beyond previous studies on lipid curvature sensing by simulating these systems in a geometry that has the morphological features and scales of curvature consistent with regions of the IMM. We find that CDL has a stronger preference for accumulating in regions of negative curvature than PE lipids, in agreement with previous results. Furthermore, we find lipid partitioning propensity is dominated by sensitivity to mean curvature, while there is a weaker correlation with Gaussian curvature.