China
Africa
Explore chapters and articles related to this topic
Marine Polysaccharides from Algae
Published in Se-Kwon Kim, Marine Biochemistry, 2023
Wen-Yu Lu, Hui-Jing Li, Yan-Chao Wu
Immunomodulation is a therapeutic method that regulate the balance of cytokines in the human body by limiting inflammation and controlling immune response or by stimulating the defective immune system. Macrophages are immune cells of the innate immune system. They play an important role in maintaining homeostasis by changing their functions according to tissues. In addition, macrophages are the main source of pro-inflammatory factors (Wijesekara et al., 2011). A variety of cytokines regulate the activation, development, proliferation, killing of natural killer cells (NK cells) and chemotaxis. Raulet’s study showed that interleukin-2 and IL-15 can stimulate the proliferation of NK cells and the secretion of a variety of cytokines (Raulet, 2006). In fact, activated NK cells can secrete soluble cytokines such as IFN and tumor necrosis factor (TNF) to enhance the body’s immune response. Some polysaccharides and glycosides obtained from natural sources are considered as biological response regulators, which can enhance various immune responses. They can maintain homeostasis by regulating T/B lymphocytes, NK cells (Figure 4.3), macrophages (Figure 4.4) and complement system (Huang et al., 2019).
Phytomedicines Targeting Antibiotic Resistance through Quorum Sensing and Biofilm Formation Associated with Acne Vulgaris
Published in Namrita Lall, Medicinal Plants for Cosmetics, Health and Diseases, 2022
Isa A. Lambrechts, Namrita Lall
Gram-positive bacteria use a two-component communication system. First, an adenosine triphosphate (ATP)-binding cassette known as ABC exporter protein transports processed AL molecules from the bacteria to the extracellular matrix. Once the peptide-signaling molecules reach a threshold concentration, the secreted peptide signals bind to a histidine kinase sensor protein on the bacterial membrane. Bassler (1999, pp. 582–587) reports that “autophosphorylation occurs on a conserved histidine residue, transferring the phosphoryl group to a cognate response regulator on a conserved aspartate residue.” Following that, the phosphorylated response regulator binds to the lux promoters, suppressing or activating gene transcription (Figure 3.2) (Bassler, 1999).
Cell-Cell Communication in Lactic Acid Bacteria
Published in Marcela Albuquerque Cavalcanti de Albuquerque, Alejandra de Moreno de LeBlanc, Jean Guy LeBlanc, Raquel Bedani, Lactic Acid Bacteria, 2020
Emília Maria França Lima, Beatriz Ximena Valencia Quecán, Luciana Rodrigues da Cunha, Bernadette Dora Gombossy de Melo Franco, Uelinton Manoel Pinto
In other bacteria, bacteriocin production has also been shown to be induced by QS. For instance, plantaricin production in Lactobacillus (L.) plantarum happens at high population density in a coordinated way, using specific autoinducing signaling peptides (AIPs) that are often post-translationally modified and exported by dedicated transport systems, similar to the mechanism described for nisin. The AIP often involves a two-component regulatory system, comprising the histidine protein kinase (HPK) that monitors environmental factors, and the cytoplasmic response regulator (RR) that regulates gene expression, as previously described (Sturme et al. 2007). The secreted pheromone plantaricin A (PlnA) is used as a measure of bacterial cell density: PlnA triggers phosphorylation reactions of HPK and RR. Thus, phosphorylated RR binds to the promoters of the bacteriocin regulon and activates the genes involved in its biosynthesis. The antimicrobial activity of PlnA can be explained by its interaction with membrane lipids, changing the PlnA conformation. The interaction with the cell membrane also allows PlnA to bind the receptor which mediates the autoinducing effect (Kristiansen et al. 2005, Sturme et al. 2007, Di Cagno et al. 2010).
Quorum quenching enzymes and their effects on virulence, biofilm, and microbiomes: a review of recent advances
Published in Expert Review of Anti-infective Therapy, 2020
AIPs (Figure 1(b)) are short cyclical peptides involved in QS found in Gram-positive bacteria [21]. AIPs are synthesized in the cytosol as pro-AIPs which are processed to form mature AIPs either in the intracellular [22] or the extracellular [23] environment depending on the species. Due to their inability to passively diffuse across the cell membrane, AIPs are chaperoned by specialized membrane transporters [24]. AIPs are detected and bound by transmembrane histidine kinases when their extracellular concentration reaches the QS threshold [25]. This binding results in phosphorylation of a downstream response regulator, which regulates the expression of target genes for pathogenic phenotypes such as competence, DNA uptake, sporulation, virulence initiation [26]. AIP-based QS systems are well characterized in Staphylococcus aureus [27], Enterococcus faecalis [28], Bacillus subtilis [29], Listeria monocytogenes [30], and Clostridium perfringens [31].
Molecules involved in motility regulation in Escherichia coli cells: a review
Published in Biofouling, 2020
Fazlurrahman Khan, Nazia Tabassum, Dung Thuy Nguyen Pham, Sandra Folarin Oloketuyi, Young-Mog Kim
RcsCDB phosphorelay is a signaling system that is found only in Enterobacterales, including E. coli. This system is important for the regulation of capsular polysaccharide colanic acid synthesis, cell division, cell wall maintenance, stationary-phase sigma factor σS, motility, and virulence (Wang et al. 2007). The RcsCDB system has been shown to negatively regulate flagellar activity and virulence by recruiting RcsA and RcsB response regulators, RcsC membrane sensor kinase, and membrane-bound RcsD phosphotransfer protein (Majdalani and Gottesman 2005). Formation of a heterodimer consisting of RcsB and RcsA is required for binding to the flhD promoter, which then allows inhibition of flagellar gene synthesis (Francez-Charlot et al. 2003). The RcsCDB system also downregulates the expression of curli gene csgD in E. coli (Ferrières and Clarke 2003). Apart from the negative regulatory role in the flagella synthesis, the RcsCDB system is also involved in colanic acid synthesis, which contributes to biofilm maturation as an extracellular polymeric substance (Gottesman et al. 1985). RcsB homodimer is also responsible for the positive regulation of transcription of colonic acid synthesis gene wza (Trisler and Gottesman 1984).
Circumventing antimicrobial-resistance and preventing its development in novel, bacterial infection-control strategies
Published in Expert Opinion on Drug Delivery, 2020
Tianrong Yu, Guimei Jiang, Ruifang Gao, Gaojian Chen, Yijin Ren, Jian Liu, Henny C. van der Mei, Henk J. Busscher
Whereas bacterial cell wall membranes themselves present already effective barriers toward antibiotic uptake [107], bacterial membranes can also possess proteinaceous structures to pump out antibiotics that have entered a cell. Accordingly, efflux pumps have been recognized as a major mechanism applied by bacterial strains to prevent killing by antibiotics [108]. Depending on the family of efflux pumps they belong to [109–113], efflux pumps can be activated by chemical or mechanical stresses. In the presence of nisin, the intra-membrane located nisin sensor NsaS in S. aureus donates phosphate groups to an intra-cellularly located response-regulator NsaR to modulate efflux of the antibiotic [114]. Efflux was demonstrated to be more efficient when the intra-membrane sensor received not only a chemical stimulus but also a mechanical one due to adhesion to a surface (Figure 5(b)) [115], as in a biofilm.