ABSTRACT
Staphylococcus aureus is a public health threat due to the prevalence of antibiotic resistance and the capacity of this organism to infect numerous organs in vertebrates. To generate energy needed to proliferate within tissues, S. aureus transitions between aerobic respiration and fermentation. Fermentation results in a distinct colony morphology called the small-colony variant (SCV) due to decreased membrane potential and ATP production. These traits promote increased resistance to aminoglycoside antibiotics. Consequently, SCVs are associated with persistent infections. We hypothesize that dedicated physiological pathways support fermentative growth of S. aureus that represent potential targets for treatment of resistant infections. Lipoteichoic acid (LTA) is an essential component of the Gram-positive cell envelope that functions to maintain ion homeostasis, resist osmotic stress, and regulate autolytic activity. Previous studies revealed that perturbation of LTA reduces viability of metabolically restricted S. aureus, but the mechanism by which LTA supports S. aureus metabolic versatility is unknown. Though LTA is essential, the enzyme that synthesizes the modified lipid anchor, YpfP, is dispensable. However, ypfP mutants produce altered LTA, leading to elongation of the polymer and decreased cell association. We demonstrate that viability of ypfP mutants is significantly reduced upon environmental and genetic induction of fermentation. This anaerobic viability defect correlates with decreased membrane potential and is restored upon cation supplementation. Additionally, ypfP suppressor mutants exhibiting restored anaerobic viability harbor compensatory mutations in the LTA biosynthetic pathway that restore membrane potential. Overall, these results demonstrate that LTA maintains membrane potential during fermentative proliferation and promotes S. aureus metabolic versatility.
Subject(s)
Staphylococcal Infections , Staphylococcus aureus , Animals , Staphylococcus aureus/metabolism , Lipopolysaccharides/metabolism , Mutation , Teichoic Acids , Drug Resistance, MicrobialABSTRACT
Glycolipids constitute the majority of membrane components in oxygenic photosynthetic organisms, whereas they are minor lipids in other organisms. In cyanobacteria, three glycolipids comprise ~90 mol% of the total lipids in thylakoid membranes, where photosynthetic electron transport occurs. Among these glycolipids, 80 mol% are galactolipids (monogalactosyldiacylglycerol and digalactosyldiacylglycerol). Galactolipids are well conserved in oxygenic photosynthetic organisms and are believed to be essential for the integrity of the membrane system. It remains unclear, however, which part(s) of the galactolipid structure is the key factor for their function, e.g., the sugar moiety and/or the anomeric configuration. To address this issue, several bacterial membrane glycolipid synthase genes have been introduced into cyanobacteria to test for complementation of knocked-out genes involved in galactolipid biosynthesis. In this review, we summarize recent advances in the analyses of sugar species and configurations of glycolipids heterologously synthesized in the thylakoid membrane and discuss their functional importance.
Subject(s)
Cyanobacteria/genetics , Glycolipids/chemistry , Thylakoids/chemistry , Bacterial Proteins/genetics , Bacterial Proteins/metabolism , Biosynthetic Pathways , Cyanobacteria/metabolism , Molecular StructureABSTRACT
AIM: To study the effect of Yupingfeng Powder(YPFP) on rat's allergic rhinitis induced by stimulating ovalbumin.and reveal the influence on Th1,Th2 and Th1/Th2 proportion. METHODS: 8-week-old BALB/c mice were sensitized by means of intranasal and systemic intraperitoneal injection application of OVA,6 subjects were administered including 2,500 mg/kg extracts of YPFP for 7 days in early stage(interference group);6 mice were administered YPFP in after challenge(therapy group);the placebo group were given saline.After 7 days,Th1 and Th2 in splenocyte were detected by flow cytometry(FCM) and nasobuccal mucosa pathology were observed. RESULTS: When compared with Th2 of animal model group(9.86?1.40),there was a significant decrease expressing Th2 after PFP treatment(3.41?0.72,P