Antibacterial and cytotoxicity studies of pyrrolo-based organic scaffolds and their binding interaction with bovine serum albumin.

Two pyrrolo-based compounds, 1H-pyrrolo[3,2-b]pyridine-3-carboxylic acid (L1) and 1H-pyrrolo[3,2-c]pyridine-4-carboxylic acid (L2), were employed for the detection of bovine serum albumin (BSA) by UV-Vis and fluorescence spectroscopic methods in phosphate buffer solution (pH = 7). In the presence of L1 and L2, the fluorescence emission of BSA at 340 nm was quenched and concomitantly a red-shifted emission band appeared at 420 nm (L1)/450 nm (L2). The fluorescence spectral changes indicate the protein-ligand complex formation between BSA and L1/L2. An isothermal titration calorimetry (ITC) experiment was conducted to determine the binding ability between BSA and L1/L2. The binding constants are found to be 4.45 ± 0.22 × 104 M-1 for L1 and 2.29 ± 0.11 × 104 M-1 for L2, respectively. The thermodynamic parameters were calculated from ITC measurements (i.e. ∆rH = -40 ± 2 kcal/mol, ∆rG = -4.57 ± 0.22 kcal/mol and -T∆rS = 35.4 ± 1.77 kcal/mol), which indicated that the protein-ligand complex formation between L1/L2 with BSA is mainly due to the electrostatic interactions. The protein-ligand interactions were studied by performing molecular docking. Further, the antibacterial assay of L1 and L2 was conducted against gram-positive and gram-negative bacterial strains in an effort to address the difficulties caused by the co-occurrence of antimicrobial and multidrug-resistant bacteria. E. coli and S. aureus were significantly inhibited by L1 and L2. The L1 exhibits 13, 12 and 15 mm, whereas L2 exhibits a 2, 3 and 5 mm zone of inhibition against S. aureus, S. pyogenes and E. coli, respectively. In silico molecular docking of L1 and L2 was performed with bacterial DNA gyrase to establish the intermolecular interactions. Finally, the in vitro cytotoxicity activities of the ligands L1 and L2 have been carried out using drosophila.

Genome-based reclassification of Streptococcus ursoris as a later heterotypic synonym of Streptococcus ratti.

Among the species of genus Streptococcus two members namely Streptococcus ratti and Streptococcus ursoris were isolated from oral cavity of rat and bear, respectively. Type strain of these members shows a 16S rRNA gene sequence similarity of 98.9%. Based on systematic phylo-taxonogenomics investigations, we could deduce the taxonomic assignment of the members of these species. Genome similarity assessment among the type strain of these members using average nucleotide identity (orthoANI and fastANI), digital DNA-DNA hybridization and average amino acid identity (AAI) were 98.5, 98.3, 88, and 98.3% respectively. All these values exceed the species delineation cutoffs suggesting a unified species. Phylogenetic tree obtained using 16S rRNA gene sequence also indicates the monophyletic nature of the member strains. Such monophyletic taxonomic positioning of the strains was further complemented with the whole genome-based phylogenomic tree. Based on these evidences, we propose S. ursoris should be reclassified as a later heterotypic synonym of S. ratti.