Genome analysis of novel Apilactobacillus sp. isolate from butterfly (Pieris canidia) gut reveals occurrence of unique glucanogenic traits and probiotic potential.

This study was conducted with a perception that fructose-rich niches may inhabit novel species of lactic acid bacteria that are gaining importance as probiotics and for the production of exopolysaccharides that have applications in food and pharmaceuticals. Recently, some Lactobacillus species have been reclassified as fructophilic lactic acid bacteria due to their preference for fructose over glucose as a carbon source. These bacteria are likely to be found in fructose rich niches such as flower nectar and insects that feed on it. We explored the butterfly gut and acquired a new isolate, designated as F1, of fructophilic lactic acid bacteria, which produces a glucan-type exopolysaccharide. Whole genome sequencing and in silico analysis revealed that F1 has significantly lower average nucleotide identity and DNA-DNA hybridization values as compared to its closest Apilactobacillus neighbors in phylogenetic analysis. Therefore, we declare the isolate F1 as a novel Apilactobacillus species with the proposed name of Apilactobacillus iqraium F1. Genome mining further revealed that F1 harbors genes for exopolysaccharide synthesis and health-promoting attributes. To this end, F1 is the only Apilactobacillus species harboring three diverse α-glucan-synthesis genes that cluster with different types of dextransucrases in the dendrogram. Moreover, many nutritional marker genes, as well as genes for epithelial cell adhesion and antimicrobial synthesis, were also detected suggesting the probiotic attributes of F1. Overall analysis suggests A. iqraium sp. F1 be a potential candidate for various health beneficial and pharmaceutical applications.

Crystal structure of an inulosucrase from Halalkalicoccus jeotgali B3T, a halophilic archaeal strain.

Several archaea harbor genes that code for fructosyltransferase (FTF) enzymes. These enzymes have not been characterized yet at structure-function level, but are of extreme interest in view of their potential role in the synthesis of novel compounds for food, nutrition, and pharmaceutical applications. In this study, 3D structure of an inulin-type fructan producing enzyme, inulosucrase (InuHj), from the archaeon Halalkalicoccus jeotgali was resolved in its apo form and with bound substrate (sucrose) molecule and first transglycosylation product (1-kestose). This is the first crystal structure of an FTF from halophilic archaea. Its overall five-bladed ß-propeller fold is conserved with previously reported FTFs, but also shows some unique features. The InuHj structure is closer to those of Gram-negative bacteria, with exceptions such as residue E266, which is conserved in FTFs of Gram-positive bacteria and has possible role in fructan polymer synthesis in these bacteria as compared to fructooligosaccharide (FOS) production by FTFs of Gram-negative bacteria. Highly negative electrostatic surface potential of InuHj, due to a large amount of acidic residues, likely contributes to its halophilicity. The complex of InuHj with 1-kestose indicates that the residues D287 in the 4B-4C loop, Y330 in 4D-5A, and D361 in the unique α2 helix may interact with longer FOSs and facilitate the binding of longer FOS chains during synthesis. The outcome of this work will provide targets for future structure-function studies of FTF enzymes, particularly those from archaea.

Raman spectroscopy for the analysis of different exo-polysaccharides produced by bacteria.

In this study, Raman spectroscopy is employed for the characterization and comparison of two different classes of exo-polysaccharides including glucans and fructans which are produced by different bacteria. For this purpose, nine samples are used including five samples of glucans and four of fructans. Raman spectral results of all these polysaccharides show clear differences among various glucans as well as fructans showing the potential of this technique to identify the differences within the same class of the compounds. Moreover, these two classes are also compared on the basis of their Raman spectral data and can be differentiated on the basis of their unique Raman features. Multivariate data analysis techniques, Principle Component Analysis (PCA) is found very helpful for the comparison of the Raman spectral data of these classes of the carbohydrates.