ABSTRACT
A bacterial strain, designated TMd3a3T, was isolated from a freshwater sample collected from the Tamagawa River in Japan. The cells of strain TMd3a3T were facultatively anaerobic, Gram-stain-negative, non-spore-forming rods that showed gliding motility. This strain was capable of denitrification and anaerobic growth with nitrate. Cloned 16S rRNA gene sequences of strain TMd3a3T yielded three different sequences (similarity between the three sequences: 98.9-99.7 %). The 16S rRNA gene sequences of strain TMd3a3T showed high similarity to those of Flavobacterium tructae 435-08T (97.2-97.4 % similarity), F. resistens BD-b365T (96.7-97.4 %), F. maotaiense T9T (97.0-97.3 %), F. limicola ST-82T (96.5-97.3 %), F. aquidurense WB 1.1-56T (96.9-97.2 %), F. spartansii T16T (96.9-97.2 %) and F. psychrolimnae LMG 22018T (96.4-97.0 %). Strain TMd3a3T contained menaquinone 6 as the sole respiratory quinone. The major cellular fatty acids were iso-C15 : 0 and summed feature 3 (C16 : 1ω7c and/or C16 : 1ω6c). The polar lipids were phosphatidylethanolamine, five unidentified aminolipids and five unidentified polar lipids. The DNA G+C content was 36.5 mol %. The DNA-DNA relatedness values of strain TMd3a3Twith F. tructae CCUG 60100T, F. resistens DSM 19382T, F. maotaiense JCM 19927T, F. limicola DSM 15094T, F. aquidurense DSM 18293T, F. spartansii ATCC BAA-2541T and F. psychrolimnae DSM 16141T were below 13 %. From the chemotaxonomic and physiological data and the levels of DNA-DNA relatedness, strain TMd3a3T should be classified as the representative of a novel species of the genus Flavobacterium, for which the name Flavobacterium aquicola sp. nov. (type strain TMd3a3T=JCM 30987T=DSM 100880T) is proposed.
Subject(s)
Flavobacterium/classification , Phylogeny , Rivers/microbiology , Bacterial Typing Techniques , Base Composition , DNA, Bacterial/genetics , Fatty Acids/chemistry , Flavobacterium/genetics , Flavobacterium/isolation & purification , Japan , Nucleic Acid Hybridization , Phosphatidylethanolamines/chemistry , RNA, Ribosomal, 16S/genetics , Sequence Analysis, DNA , Vitamin K 2/analogs & derivatives , Vitamin K 2/chemistryABSTRACT
Within the secreted phospholipase A2(sPLA2) family, group X sPLA2(sPLA2-X) has the highest capacity to hydrolyze cellular membranes and has long been thought to promote inflammation by releasing arachidonic acid, a precursor of pro-inflammatory eicosanoids. Unexpectedly, we found that transgenic mice globally overexpressing human sPLA2-X (PLA2G10-Tg) displayed striking immunosuppressive and lean phenotypes with lymphopenia and increased M2-like macrophages, accompanied by marked elevation of free ω3 polyunsaturated fatty acids (PUFAs) and their metabolites. Studies usingPla2g10-deficient mice revealed that endogenous sPLA2-X, which is highly expressed in the colon epithelium and spermatozoa, mobilized ω3 PUFAs or their metabolites to protect against dextran sulfate-induced colitis and to promote fertilization, respectively. In colitis, sPLA2-X deficiency increased colorectal expression of Th17 cytokines, and ω3 PUFAs attenuated their production by lamina propria cells partly through the fatty acid receptor GPR120. In comparison, cytosolic phospholipase A2(cPLA2α) protects from colitis by mobilizing ω6 arachidonic acid metabolites, including prostaglandin E2 Thus, our results underscore a previously unrecognized role of sPLA2-X as an ω3 PUFA mobilizerin vivo, segregated mobilization of ω3 and ω6 PUFA metabolites by sPLA2-X and cPLA2α, respectively, in protection against colitis, and the novel role of a particular sPLA2-X-driven PUFA in fertilization.
Subject(s)
Colitis/genetics , Colon/enzymology , Fatty Acids, Omega-3/biosynthesis , Fertility/genetics , Group X Phospholipases A2/genetics , Spermatozoa/enzymology , Animals , Arachidonic Acid/antagonists & inhibitors , Arachidonic Acid/biosynthesis , Colitis/chemically induced , Colitis/enzymology , Colitis/therapy , Colon/pathology , Dextran Sulfate , Fatty Acids, Omega-3/metabolism , Fatty Acids, Omega-6/biosynthesis , Fatty Acids, Omega-6/metabolism , Gene Expression , Gene Expression Profiling , Group X Phospholipases A2/metabolism , Humans , Interleukin-17/biosynthesis , Male , Mice , Mice, Transgenic , Phospholipases A2/genetics , Phospholipases A2/metabolism , Receptors, G-Protein-Coupled/genetics , Receptors, G-Protein-Coupled/metabolism , Sperm Count , Sperm Motility , Spermatozoa/pathology , Th17 Cells/metabolism , Th17 Cells/pathology , TransgenesABSTRACT
Metabolic disorders, including obesity and insulin resistance, have their basis in dysregulated lipid metabolism and low-grade inflammation. In a microarray search of unique lipase-related genes whose expressions are associated with obesity, we found that two secreted phospholipase A2s (sPLA2s), PLA2G5 and PLA2G2E, were robustly induced in adipocytes of obese mice. Analyses of Pla2g5(-/-) and Pla2g2e(-/-) mice revealed distinct roles of these sPLA2s in diet-induced obesity. PLA2G5 hydrolyzed phosphatidylcholine in fat-overladen low-density lipoprotein to release unsaturated fatty acids, which prevented palmitate-induced M1 macrophage polarization. As such, PLA2G5 tipped the immune balance toward an M2 state, thereby counteracting adipose tissue inflammation, insulin resistance, hyperlipidemia, and obesity. PLA2G2E altered minor lipoprotein phospholipids, phosphatidylserine and phosphatidylethanolamine, and moderately facilitated lipid accumulation in adipose tissue and liver. Collectively, the identification of "metabolic sPLA2s" adds this gene family to a growing list of lipolytic enzymes that act as metabolic coordinators.
