Revealing the Compact Structure of Lactic Acid Bacterial Heteroexopolysaccharides by SAXS and DLS

Molecular structures of exopolysaccharides are required to understand their functions and the relationships between the structure and physical and rheological properties. Small-angle X-ray scattering and dynamic light scattering were used in conjunction with molecular modeling to characterize solution structures of three lactic acid bacterial heteroexopolysaccharides (HePS-1, HePS-2, and HePS-3). Values of radius of gyration <i>R</i>_G, cross-sectional radius of gyration <i>R</i>_XS, approximate length <i>L</i>, and hydrodynamic diameter were not directly proportional to the molar mass and indicated the HePSs adopted a compact coil-like rather than an extended conformation. Constrained molecular modeling of 15000 randomized HePS-1 conformers resulted in five best-fit structures with <i>R</i> factor of 3.9−4.6% revealing random coil-like structure. Φ and Ψ angle analysis of glycosidic linkages in HePS-1 structures suggests Gal<i>f</i> residues significantly influence the conformation. Ab initio scattering modeling of HePS-2 and HePS-3 gave excellent curve fittings with χ² of 0.43 and 0.34 for best-fit models, respectively, compatible with coil-like conformation. The findings disclose solution behavior of HePS relevant for their interactions with biomacromolecules, for example, milk proteins

Interaction between structurally different heteroexopolysaccharides and β-lactoglobulin studied by solution scattering and analytical ultracentrifugation

Predmet ovog rada je Lean proizvodnja-korak ka uspjehu. Lean proizvodnje naglašava minimiziranje količine resursa koji se koriste u raznim aktivnostima kompanije i uključuje identificiranje i eliminiranje aktivnosti koje ne donosi vrijednost. Filozofija Lean proizvodnje uključuje principe i praksu smanjivanja troškova kroz uklanjanje "otpada" i kroz pojednostavljenje svih aktivnosti kompanije. Postoji sedam vrsta tradicionalnih otpada u aktivnostima kompanije i više od desetak alata za njihovo uklanjanje. U postizanju filozofije Lean proizvodnje pet je glavnih koraka koji označavaju životni ciklus racionalne proizvodnje. Lean proizvodnja i filozofija racionalnog poslovanja omogućava kompanijama da budu bolje, brže, njihovi proizvodi i/ili usluge jeftinije, a one same privlačnije kupcima.The subject of this paper is Lean production-step to success. Lean Production highlights the minimization of the amount of resources used in the company's various activities and involves identifying and eliminating activities that do not bring value. The Lean manufacturing philosophy includes the principles and practice of reducing costs through the removal of "waste" and simplifying all company activities. There are seven types of traditional waste in the company's activities and more than a dozen tools for their removal. In achieving the Lean production philosophy, five major steps are to be found that indicate the life cycle of rational production. Lean manufacturing and the philosophy of rational business enable companies to be better, faster, their products and/or services cheaper, and those more attractive to customers

Phosphorus-31 and deuterium solid-state nuclear magnetic resonance studies of the headgroup conformation of phosphonolipids in biological and model membranes.

Solid-state nuclear magnetic resonance (NMR) techniques were applied to the study of the phase behavior and to the determination of the headgroup conformation of phosphonolipids, both natural and synthetic. The results are compared with those for analogous phospholipids in biological and model membranes. \sp{31}P NMR was used to characterize the phase behavior of phospho- and phosphonolipids present in polar and total lipid extracts of the protozoa Tetrahymena thermophila. The \sp{31}P NMR spectra of aqueous dispersions of polar and total lipids consist in the partial superposition of two powder patterns, one for each phosphorus-containing lipid class. At low temperature, both lipid extracts give rise to lineshapes characteristic of the lamellar structure. Spectra of the polar lipids show that between 15 and 40\sp\circC, a broad, reversible transition from bilayer to hexagonal phase takes place. On the other hand, the phase behavior for total lipids is different: no hexagonal phase is formed, the lipids remain in the bilayer phase at a higher temperature, and a transition to an isotropic phase occurs between 35 and 40\sp\circC, which is not easily reversible. A large proportion of ethanolamine-containing lipids, both phosphate and phosphonate analogs, is responsible for the hexagonal phase formation observed with the polar lipids. When neutral lipids are present with the polar lipids, the bilayer is stabilized up to a higher temperature. One of the neutral lipid components, tetrahymanol, a pentacyclic triterpenoid, is believed to be responsible for this stabilization. The results show that the conformation of the headgroup up to the phosphorus atom is very similar in phospho- and phosphonolipids, i.e. the C2-C3-O-P torsion angle is nearly trans and the C3-O-P-C1 angle variable over the range of values investigated, with a bend at the phosphorus atom. Contrary to the phosphodiester moiety in analogous phospholipids which adopts a gauche-gauche conformation, two solutions for the next torsion angle O-P-C1-C2 were found around 100 and 130\sp\circ. The last segment P-C1-C2-N is nearly trans, whereas the corresponding O-C1-C2-N segment in phospholipids is gauche. Despite the differences in the torsion angle values, the overall appearance of the headgroup is similar for both phospho- and phosphonolipids. The headgroup first extends out of the bilayer plane, bending at the phosphorus atom and the terminal portion lies nearly parallel to the membrane surface. (Abstract shortened by UMI.

Effect of exopolysaccharides on phage-host interactions in lactococcus lactis

In this study, we report that Lactococcus lactis strains producing exopolysaccharides (EPS) are sensitive to virulent phages. Eight distinct lytic phages (Q61 to Q68) specifically infecting Eps strains were isolated in 47 buttermilk samples obtained from 13 North American factories. The eight phages were classified within the 936 species by the multiplex PCR method, indicating that these phages are not fundamentally distinct from those infecting Eps L. lactis strains. The host range of these phages was determined with 19 Lactococcus strains, including 7 Eps and 12 Eps cultures. Three phages (Q62, Q63, and Q64) attacked only the Eps strain SMQ-419, where as the five other phages (Q61, Q65, Q66, Q67, and Q68) infected only the Eps strain SMQ-420. The five other Eps strains (H414, MLT2, MLT3, SMQ-461, and SMQ-575) as well as the 12 Eps strains were insensitive to these phages. The monosaccharide composition of the polymer produced by theseven Eps strains was determined. The EPS produced by strains MLT3, SMQ-419, and SMQ-575 contained glucose, galactose, and rhamnose. The EPS fabricated by H414 contained only galactose. The EPS made byMLT2, SMQ-420, and SMQ-461 contained glucose and galactose. These findings indicate that the sugar composition of the EPS has no effect on phage sensitivity. The plasmid encoding the eps operon was cured from the two phage-sensitive strains. The cured derivatives were still phage sensitive, which indicates that EPS are not necessary for phage infection. Phage adsorption assays showed that the production of EPS does not confer a significant phage resistance phenotype

Effect of Exopolysaccharides on Phage-Host Interactions in Lactococcus lactis

In this study, we report that Lactococcus lactis strains producing exopolysaccharides (EPS) are sensitive to virulent phages. Eight distinct lytic phages (Q61 to Q68) specifically infecting Eps(+) strains were isolated in 47 buttermilk samples obtained from 13 North American factories. The eight phages were classified within the 936 species by the multiplex PCR method, indicating that these phages are not fundamentally distinct from those infecting Eps(−) L. lactis strains. The host range of these phages was determined with 19 Lactococcus strains, including 7 Eps(+) and 12 Eps(−) cultures. Three phages (Q62, Q63, and Q64) attacked only the Eps(+) strain SMQ-419, whereas the five other phages (Q61, Q65, Q66, Q67, and Q68) infected only the Eps(+) strain SMQ-420. The five other Eps(+) strains (H414, MLT2, MLT3, SMQ-461, and SMQ-575) as well as the 12 Eps(−) strains were insensitive to these phages. The monosaccharide composition of the polymer produced by the seven Eps(+) strains was determined. The EPS produced by strains MLT3, SMQ-419, and SMQ-575 contained glucose, galactose, and rhamnose. The EPS fabricated by H414 contained only galactose. The EPS made by MLT2, SMQ-420, and SMQ-461 contained glucose and galactose. These findings indicate that the sugar composition of the EPS has no effect on phage sensitivity. The plasmid encoding the eps operon was cured from the two phage-sensitive strains. The cured derivatives were still phage sensitive, which indicates that EPS are not necessary for phage infection. Phage adsorption assays showed that the production of EPS does not confer a significant phage resistance phenotype

Capsular Sialyltransferase Specificity Mediates Different Phenotypes in Streptococcus suis and Group B Streptococcus

The capsular polysaccharide (CPS) represents a key virulence factor for most encapsulated streptococci. Streptococcus suis and Group B Streptococcus (GBS) are both well-encapsulated pathogens of clinical importance in veterinary and/or human medicine and responsible for invasive systemic diseases. S. suis and GBS are the only Gram-positive bacteria which express a sialylated CPS at their surface. An important difference between these two sialylated CPSs is the linkage between the side-chain terminal galactose and sialic acid, being α-2,6 for S. suis but α-2,3 for GBS. It is still unclear how sialic acid may affect CPS production and, consequently, the pathogenesis of the disease caused by these two bacterial pathogens. Here, we investigated the role of sialic acid and the putative effect of sialic acid linkage modification in CPS synthesis using inter-species allelic exchange mutagenesis. To this aim, a new molecular biogenetic approach to express CPS with modified sialic acid linkage was developed. We showed that sialic acid (and its α-2,6 linkage) is crucial for S. suis CPS synthesis, whereas for GBS, CPS synthesis may occur in presence of an α-2,6 sialyltransferase or in absence of sialic acid moiety. To evaluate the effect of the CPS composition/structure on sialyltransferase activity, two distinct capsular serotypes within each bacterial species were compared (S. suis serotypes 2 and 14 and GBS serotypes III and V). It was demonstrated that the observed differences in sialyltransferase activity and specificity between S. suis and GBS were serotype unrestricted. This is the first time that a study investigates the interspecies exchange of capsular sialyltransferase genes in Gram-positive bacteria. The obtained mutants represent novel tools that could be used to further investigate the immunomodulatory properties of sialylated CPSs. Finally, in spite of common CPS structural characteristics and similarities in the cps loci, sialic acid exerts differential control of CPS expression by S. suis and GBS