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Beneficial Lactic Acid Bacteria
Published in K. Balamurugan, U. Prithika, Pocket Guide to Bacterial Infections, 2019
Besides the aforementioned compounds, LAB are sources of many other substances: bacteriocins, vitamins, enzymes, exopolysaccharides, and sweeteners. A wide range of LAB are able to produce capsular or extracellular polysaccharides with various chemical composition and properties. The term exopolysaccharide (EPS) often denotes all forms of polysaccharides located outside of the microbial cell wall. Polysaccharides are divided into two groups: homopolysaccharides composed of only one type of monosaccharide and heteropolysaccharides containing two or more types of sugars. Two pathways for biosynthesis of exocellular polysaccharides have been described for LAB: the Wzy-dependent pathway and the extracellular glycosyltransferase pathway for synthesis of glucans and fructans. Genes encoding Wzy-dependent proteins in LAB are typically organized in a cluster with an operon structure and can be chromosomal as well as plasmid-borne. These gene clusters are extremely diverse, and their nucleotide sequences are among the most variable sequences in LAB genomes. Genes in the operon can be categorized into several groups: modulatory genes, polysaccharide assembly machinery genes, genes encoding glycosyltransferase involved in the assembly of the repeating units, and genes required for the synthesis of activated sugar precursors and modification of the sugar residues. Clusters are usually 15–20 Kb in size and comprise less than 30 genes. Genes of LAB have the same orientation and are transcribed as a single mRNA. Extracellular glycosyltransferase pathway is a simple biochemical route employing a specific glucansucrase or fructansucrase and an extracellular sugar donor for the synthesis of glucans or fructans (Zeidan et al. 2017). All EPS-producing bifidobacteria appear to synthesize EPS through internal heteropolysaccharide pathways. Their EPS biosynthesis is concentrated in the 25.6 Kb region composed of 20 genes, 18 of which are positioned in oppositely directed but adjacent transcriptional loci. Regulatory genes have not been identified in Bifidobacterium spp. to date (Ryan et al. 2015).
Potential oral probiotic Lactobacillus pentosus MJM60383 inhibits Streptococcus mutans biofilm formation by inhibiting sucrose decomposition
Published in Journal of Oral Microbiology, 2023
Mingkun Gu, Joo-Hyung Cho, Joo-Won Suh, Jinhua Cheng
S. mutans can secrete glucansucrase (also known as glucosyltransferase), an extracellular enzyme, to split sucrose and utilize the resulting glucose molecules to build exopolysaccharide, thereby contributing to the pathogenesis of dental caries [46]. We found that sucrose decomposition was reduced by the treatment of L. pentosus MJM60383 supernatant throughout the time course. This result suggested that the L. pentosus MJM60383 supernatant may inhibit the enzyme activities of glucansucrases or their expression. Ahn, Ki Bum et al. reported [26] that lipoteichoic acid of L. plantarum KCTC10887BP, a cell-wall component of gram-positive bacteria, reduced the biofilm formation of S. mutans by interfering with sucrose decomposition and resulted in the reduction of exopolysaccharide synthesis. However, to the best of our knowledge, this is the first report that Lactobacillus culture supernatant decreased S. mutans biofilm formation by inhibiting sucrose decomposition.
Prioritization and characterization of validated biofilm blockers targeting glucosyltransferase C of Streptococcus mutans
Published in Artificial Cells, Nanomedicine, and Biotechnology, 2021
Hazza A. Alhobeira, Mohammed Al Mogbel, Saif Khan, Mahvish Khan, Shafiul Haque, Pallavi Somvanshi, Mohd Wahid, Raju K. Mandal
The structural coordinates of GtfC was retrieved from RCSB-PDB (3AIC). This .pdb file represents the crystal structure of Glucansucrase from Streptococcus mutans in complex with D-Acarbose [19]. This structure was deciphered by x-ray diffraction @3.11 Å resolution. The native state of GtfC is known to be a monomer [19]. A GtfC monomer complexed with alpha D-Acarbose, 2-(n-morpholino)-ethanesulfonic acid and calcium was selected from the crystallised octamer .pdb file. The target structure was free of ligands (D-Acarbose and 2-(n-morpholino)-ethanesulfonic acid) but include the water molecules found to be linked with the crystal structure. The target GtfC monomer was prepared according to the protein preparation protocol of BIOVIA Discovery Studio. The input parameters have been given in the Supplementary Information (SI) file. The target protein monomer was typed with CHARMM36 force field [32]. The active site was defined based on pdb site record (Figure 2). Includes Glu515, Asp477, Asp588, Arg475, His587, Tyr916, Tyr430, Leu433, Asn481, and Trp517.