An anti-biofilm material: polysaccharides prevent the precipitation reaction of silver ions and chloride ions and lead to the synthesis of nano silver chloride.

The formation of biofilm is one of the causes of bacterial pathogenicity and drug resistance. Recent studies have reported a variety of anti-biofilm materials and achieved good results. However, it is still very important to develop some materials with wider application scenarios or higher biofilm resistance. In this study, a new method to rapidly synthesize nano silver chloride with anti-biofilm activity is proposed. It is a generalizable method in which bacterial extracellular polysaccharides are used to adsorb silver ions, thereby inhibiting the formation of white large-size silver chloride precipitates, and then ultraviolet light is used to induce the synthesis of small-sized nano silver chloride. A variety of polysaccharides can be utilized in the synthesis of nano silver chloride particles. The generated complex was characterized by XRD, UV-vis, EDX, FTIR and TEM methods. Further, the novel complex was found to show highly effective anti-biofilm and bactericidal activity within the biosafety concentration. In view of the high stability of nano sliver chloride, we propose that the novel nano material has the potential as a long-term antibacterial material.

Synthesis of globotriose-modified peptides for the preparation of a colorimetric biosensor to detect Shiga toxins.

Globotriose (Gal-α1, 4-Gal-ß1, 4-Glc) is involved in binding with Shiga toxins (Stxs) produced by Shigella dysenteriae and certain pathogenic Escherichia coli strains which could cause severe gastroenteritis and hemolytic uremic syndrome (HUS). Thus, this trisaccharide group and its derivatives provide potentials in the development of carbohydrate-based diagnostic and therapeutic reagents against bacterial infection. Instead of the tedious chemical synthesis of globotriose or its glycoconjugates, we reported a multi-step (step-wise) enzymatic synthesis system containing glucosyltransferase (ApNGT, E.C. 4.3.3.5), ß-1, 4-galactosyltransferase (LgtB, E.C. 2.4.1.22) and α-1, 4-galactosyltransferase (LgtC, E.C. 2.4.1.44) to produce globotriose-containing glycopeptides. In addition, based on the specific binding between Stxs and globotriose, a cost-efficient, convenient, ultra-sensitive and specific colorimetric biosensor was further constructed to detect Stxs using glycoconjugated Au@Fe-TFPA-COP (globotriose@Au@Fe-TFPA-COP) as a nanoenzyme catalyst. We estimate that this method conveniently applied in the detection of Stx-producing bacteria and associated infectious diseases.

Identification microbial glycans substructure associate with disease and species.

The microbial glycans mediate many significant biological acts, such as pathogen survival, host-microbe interactions, and immune evasion. The systematic study of microbial glycans structure remains challenging because of its high complexity and variability. In this study, we screened all the microbial glycans structures in the CSDB (Carbohydrate Structure Database), disassembled them into substructures, and calculated all the substructures' numbers. The results showed that a large number of glycan substructures are shared among different microorganisms. Further analysis showed that the glycan substructures appeared in specific bacterial groups may be related to the species and pathogenicity of microorganisms. Broadly, these findings provided an alternative approach or clue to discover the hidden information and the biological functions of glycans. The results can be used to detect broad-scope pathogen or prepare broad-spectrum vaccines.

Substrate specificity of the galactokinase from the human gut symbiont Akkermansia muciniphila ATCC BAA-835.

Galactokinases, which catalyze the phosphorylation of galactose and possible other monosaccharides, can provide an activated sugar donor to synthesize sugar-containing molecules. In this study, a novel galactokinase from human gut symbiont Akkermansia muciniphila ATCC BAA-835 (GalKAmu) was expressed and characterized. GalKAmu displayed broad substrate tolerance, with catalytic activity towards Gal (100 %), GalN (100 %), GalA (20.2 %), Glc (52.5 %), GlcNAc (15.5 %), Xyl (<5%), ManNAc (58 %), ManF (37.4 %) and l-Glc (80 %). Most interestingly, this was the first GalK isoform which can tolerate ManNAc. Thus, our characterization of GalKAmu broadens the substrate selection of galactokinases.

Probing peptide substrate specificities of N-glycosyltranferase isoforms from different bacterial species.

N-glycosyltransferase (NGT) is responsible for transferring hexose monosaccharides to the asparagine side chain of proteins and polypeptides in the consensus sequon (N-(X≠P)-T/S) with nucleotide-activated sugars as donor substrates. Here, we expressed and purified four different N-glycosyltransferases derived from diverse bacteria, including Actinobacillus pleuropneumoniae, Aggregatibacter aphrophilus, Kingella kingae and Bibersteinia trehalosi, and measured their catalytic activities of four synthesized peptides via in vitro glycosylation assays. RP-HPLC and mass spectrometry were used to identify and quantify the glycopeptide formation by distinct NGT isoforms. We then analyzed and compared the glycosylation efficiencies of different peptides for these four NGT isoforms, which showed distinct substrate selectivities. We sought to probe peptide specificities among various NGT isoforms, which could broaden the application of NGT-catalyzed N-glycosylation of a variety of therapeutic proteins.