Transport of lipopolysaccharide to the Gram-negative bacterial cell surface

Zhang

et al. 2018

Adv Funct Materials

Microorganisms are widely used as the biotemplates for producing micro/ nanomaterials owing to their unique features, such as exquisite morphology, renewable, and environmentally friendly. However, mass intracellular synthesis of uniformly dispersed nanoparticles (NPs) inside microorganisms is still challenging, especially in a predictable and controllable manner. Here, a facile and efficiency strategy is proposed to controllably produce highly dispersed and surfactant-free Pd@Ag core-shell NPs within the Spirulina platensis (Sp.) cells. In this approach, the Sp. cells' permeability is enhanced by the hydrochloric acid treatment first, which enables the Pd NPs penetrate the cell envelope and distribute uniformly inside the cells, and then they can work as the catalytic seeds for the following electroless silver deposition, resulting in the intracellular fabrication of Pd@Ag core-shell NPs with no agglomeration. The Pd@Ag NPs show excellent catalytic activity (turnover frequency is up to 2893 h −1 for the 6.32 nm Pd@Ag NPs), good stability, and recyclability toward the 4-nitrophenol reductions. The excellent properties are attributed to the asymmetrical core-shell structure, small size, and good dispersion of Pd@Ag NPs. Due to its facility, cost-effectiveness, and versatility, this method can be expanded to other microorganisms, so it opens tremendous opportunities for various metallic nanoparticles intracellular synthesis as well as the practical application.

Section: Resultsmentioning

confidence: 86%

Facile Fabrication of Highly Dispersed Pd@Ag Core–Shell Nanoparticles Embedded in Spirulina platensis by Electroless Deposition and Their Catalytic Properties

Zhang

et al. 2018

Adv Funct Materials

“…The und-PP-linked O-units are then polymerized on the periplasmic leaflet of the inner membrane by the Wzy polymerase that allows the formation of the complete O-chain. The O-chain is finally ligated to the core oligosaccharide by the WaaL ligase forming a complete LPS that is then translocated to the bacterial surface by the Lpt-system45. In group I and IV capsules, the O-units, assembled by the Wzx/Wzy-dependent pathway, are translocated to the bacterial surface by the coordinated action of the Wza, Wzb and Wzc proteins46.…”

mentioning

confidence: 99%

Evidence for a LOS and a capsular polysaccharide in Capnocytophaga canimorsus

Renzi

Ittig

Sadovskaya

et al. 2016

Sci Rep

Capnocytophaga canimorsus is a dog’s and cat’s oral commensal which can cause fatal human infections upon bites or scratches. Infections mainly start with flu-like symptoms but can rapidly evolve in fatal septicaemia with a mortality as high as 40%. Here we present the discovery of a polysaccharide capsule (CPS) at the surface of C. canimorsus 5 (Cc5), a strain isolated from a fulminant septicaemia. We provide genetic and chemical data showing that this capsule is related to the lipooligosaccharide (LOS) and probably composed of the same polysaccharide units. A CPS was also found in nine out of nine other strains of C. canimorsus. In addition, the genomes of three of these strains, sequenced previously, contain genes similar to those encoding CPS biosynthesis in Cc5. Thus, the presence of a CPS is likely to be a common property of C. canimorsus. The CPS and not the LOS confers protection against the bactericidal effect of human serum and phagocytosis by macrophages. An antiserum raised against the capsule increased the killing of C. canimorsus by human serum thus showing that anti-capsule antibodies have a protective role. These findings provide a new major element in the understanding of the pathogenesis of C. canimorsus.

“…LptD and other 6 proteins – LptA, B, C, E, F and G – constitute a trans-membrane complex responsible for transporting lipopolysaccharide (LPS)222324. Through interaction with the lipoprotein component LptE, which adopts a roll-like structure embedded in the LptD barrel, LptD mediates the final translocation of fully synthesized LPS from periplasm to the outer leaflet of the outer membrane252627282930. LPS, a glycolipid consisting of several fatty acyl chains and perhaps hundreds of sugars, is synthesized in the cytoplasm and finally assembled in inner membrane.…”

mentioning

confidence: 99%

LptD is a promising vaccine antigen and potential immunotherapeutic target for protection against Vibrio species infection

Zha

et al. 2016

Sci Rep

Outer membrane proteins (OMPs) are unique to Gram-negative bacteria. Several features, including surface exposure, conservation among strains and ability to induce immune responses, make OMPs attractive targets for using as vaccine antigens and immunotherapeutics. LptD is an essential OMP that mediates the final transport of lipopolysaccharide (LPS) to outer leaflet. The protein in Vibrio parahaemolyticus was identified to have immunogenicity in our previous report. In this study, broad distribution, high conservation and similar surface-epitopes of LptD were found among the major Vibrio species. LptD was further revealed to be associated with immune responses, and it has a strong ability to stimulate antibody response. More importantly, it conferred 100% immune protection against lethal challenge by V. parahaemolyticus in mice when the mice were vaccinated with LptD, and this finding was consistent with the observation of efficient clearance of bacteria in vaccination mice. Strikingly, targeting of bacteria by the LptD antibody caused significant decreases in both the growth and LPS level and an increase in susceptibility to hydrophobic antibiotics. These findings were consistent with those previously obtained in lptD-deletion bacteria. These data demonstrated LptD is a promising vaccine antigens and a potential target for antibody-based therapy to protect against Vibrio infections.