Background Lactobacillus rhamnosus GG (LGG) is the most widely used probiotic, but the mechanisms underlying its beneficial effects remain unresolved. Previous studies typically inoculated LGG in hosts with established gut microbiota, limiting the understanding of specific impacts of LGG on host due to numerous interactions among LGG, commensal microbes, and the host. There has been a scarcity of studies that used gnotobiotic animals to elucidate LGG-host interaction, in particular for gaining specific insights about how it modifies the metabolome. To evaluate whether LGG affects the metabolite output of pathobionts, we inoculated with LGG gnotobiotic mice containing Propionibacterium acnes, Turicibacter sanguinis, and Staphylococcus aureus (PTS). Results 16S rRNA sequencing of fecal samples by Ion Torrent and MinION platforms showed colonization of germ-free mice by PTS or by PTS plus LGG (LTS). Although the body weights and feeding rates of mice remained similar between PTS and LTS groups, co-associating LGG with PTS led to a pronounced reduction in abundance of P. acnes in the gut. Addition of LGG or its secretome inhibited P. acnes growth in culture. After optimizing procedures for fecal metabolite extraction and metabolomic liquid chromatography-mass spectrometry analysis, unsupervised and supervised multivariate analyses revealed a distinct separation among fecal metabolites of PTS, LTS, and germ-free groups. Variables-important-in-projection scores showed that LGG colonization robustly diminished guanine, ornitihine, and sorbitol while significantly elevating acetylated amino acids, ribitol, indolelactic acid, and histamine. In addition, carnitine, betaine, and glutamate increased while thymidine, quinic acid and biotin were reduced in both PTS and LTS groups. Furthermore, LGG association reduced intestinal mucosal expression levels of inflammatory cytokines, such as IL-1α, IL-1β and TNF-α. Conclusions LGG co-association had a negative impact on colonization of P. acnes, and markedly altered the metabolic output and inflammatory response elicited by pathobionts.
Barium titanate, barium zirconate, and barium hafnate are essential components of the electroceramic industry. Barium titanate is essentially used as multi-layered ceramic capacitors in computers, aerospace, and communication technologies. Barium zirconate is one of the most inert, stable, and corrosion-resistant perovskite employed in superconducting applications. Barium hafnate is used as a component of hybrid ceramic structures for high-temperature applications. The goal of this research was to apply a more environmentally benign synthesis design to the production of barium-based perovskites. The catecholate method, originally applied to the synthesis of barium titanate, was utilized as the approach for the synthesis of barium zirconate and barium hafnate. This developmental process consumed naturally occurring isomorphic forms of metal oxides and no post-sintering treatment was necessary. It resulted in the absence of by-products in most steps while achieving superior stoichiometric control over the barium-to-X (X 0Ti, Zr, Hf) molar ratio compared to previous methods.
Barium titanate is one of the most thoroughly studied members of the perovskite family due to its prominent place in the electroceramic industry. To be used as a capacitor at room temperature, a high-dielectric constant is needed which is achieved through doping. The focus of this research was to develop a more environmentally benign alternative to the doping of barium titanate. The barium source was barium titanyl catecholate, Ba[Ti(cat) 3 ] (aq) and the doping sources were strontium oxalate (SrC 2 O 4 ) and strontium carbonate (SrCO 3 ). The doping strategies included a solid-state synthetic pathway as well as microwave-and centrifuge-assisted methods which both employed water as the only solvent. The last two benign by design methods were tested with respect to their thermodynamic control over barium-to-strontium stoichiometric ratios. These methods of doping proved to be more environmentally friendly and economical while combining green chemistry and materials science.
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