Host-Bifidobacterium interactions in the axenic mouse: partial characterization of bifidogenic factors in the intestinal contents

Growth factors for Bifidobacterium bifidum were detected in faeces of axenic mice strain C3H. Most of these factors were found in the nondialyzable fraction obtained after aqueous extraction and dialysis. SDS-PAGE and filtration chromatography on Sepharose 4B revealed that many glycosylated components harbored a bifidigenic activity. Intestinal colinization of mice by B. bifidum involved the utilization and eventually the disappearance of the intestinal bifidigenic factors. There was no change in the protein concentration in fecal extracts, but the total hexose concentration was lower. Comparison of electrophoretic PAGE profiles after periodic acid Schiff coloration showed that bacteria used up the glycosylated fractions of many glycopeptides, particularly those of mucins and four glycoproteins. There was no correlation between the hexose concentration detected in every active fraction and the degree of in vivo degradation of bifidigenic factors. The attack on active glycopeptides having a molecular mass greater than 670 kDa thus revealed hexose sites that were not detectable previously by the phenol - sulfuric acid method. However, the amount of bifidigenic factors detected in vitro allowed us to measure the importance of the degradation of a component by B. bifidum in vivo.     

Inoculation of the digestive tract of axenic mice with the autochthonous bacteria of mineral water

Summary The autochthonous bacteria present in mineral water from Vittel Grande Source were not able to establish themselves, i.e. to multiply and subsist in a great number in the digestive tract of axenic mice.The inocula of these bacteria ingested by the animals were either completely or only partly destroyed during their transit through the digestive tract of the animals.The autochthonous bacteria of the water, ingested in a very high amount or injected intraperitoneally, have never brought about detectable pathological disorders in the animals.     

beta-Aspartylglycine, a substance unique to caecal contents of germ-free and antibiotic-treated mice.

The caecal supernatants from germ-free, antibiotic-treated and control mice were compared with respect to their content of low-molecular-weight substances (less than 3500 mol. wt.). The supernatants contained about the same amount of free amino acids. After acid hydrolysis, the caecal supernatants of germ-free and antibiotic-treated mice showed a 2.9-fold increase in free amino acids, whereas a similar treatment of the supernatant from control mice resulted in a 2.6-fold increase. By gel filtration on Sephadex G-25, and high-voltage paper electrophoresis at pH 3.5 of the fractions eluted after the void volume, it was found that the caecal supernatants of germ-free and antibiotic-treated mice contained a substance more acidic than aspartic acid. Preparative high-voltage electrophoresis, dansylation, amino acid analysis and a specific colour reaction showed the substance to be beta-aspartylglycine. After a minimal 36 h of treatment with neomycin and bacitracin, a high concentration of beta-aspartylglycine was found, and no enterococci and aerobic Gram-negative rods could be cultured from the caecal contents. The possibility that in one mouse the appearance of beta-aspartylglycine was related to a decrease in Gram-negative rods was ruled out by selective elimination of aerobic Gram-negative rods by using polymyxin B. This suggests that other bacteria concomitantly eliminated with the enterococci and aerobic Gram-negative rods, directly or indirectly, could play a role in the accumulation of beta-aspartylglycine.     

Gas exchanges by Phymatotrichum omnivorum in a closed,axenic system

Gas exchanges byPhymatotrichum omnivorum were studied in a closed, axenic system. The fungus liberated CO₂ and ethylene, and appeared to utilize N₂. Over a 44-day test period, CO₂ increased from 0.1 to 312.8 ml/liter. Oxygen decreased from 211 to 17.8 ml/liter and N₂ decreased from 789 to 669.5 ml/liter during the same period. The combined uptake of N₂ and O₂ was equal to the release of CO₂ in the ambient gas.A rapid increase in ethylene was observed 14 to 28 days after the flasks were inoculated (15 to 160 nliter/liter). Mycelial strands and sclerotial initials formed on the flask sides, but mature sclerotia did not develop.Supported in part by Cooperative Agreement 70-178 from Cotton Incorporated. A contribution of the Texas Agricultural Experiment Station.     

Trophic niche similarities of sympatric Turdus thrushes determined by fecal contents,stable isotopes,and bipartite network approaches

An ecological niche has been defined as an n‐dimensional hypervolume formed by conditions and resources that species need to survive, grow, and reproduce. In practice, such niche dimensions are measurable and describe how species share resources, which has been thought to be a crucial mechanism for coexistence and a major driver of broad biodiversity patterns. Here, we investigate resource partitioning and trophic interactions of three sympatric, phylogenetically related and morphologically similar species of thrushes (Turdus spp.). Based on one year of data collected in southern Brazil, we investigated niche partitioning using three approaches: diet and trophic niche assessed by fecal analysis, diet and niche estimated by stable isotopes in blood and mixing models, and bipartite network analysis derived from direct diet and mixing model outputs. Approaches revealed that the three sympatric thrushes are generalists that feed on similar diets, demonstrating high niche overlap. Fruits from C3 plants were one of the most important food items in their networks, with wide links connecting the three thrush species. Turdus amaurochalinus and T. albicollis had the greatest trophic and isotopic niche overlap, with 90% and 20% overlap, respectively. There was partitioning of key resources between these two species, with a shared preference for fig tree fruits—Ficus cestrifolia (T. amaurochalinus PSIRI% = 11.3 and T. albicollis = 11.5), which was not present in the diet of T. rufiventris. Results added a new approach to the network analysis based on values from the stable isotope mixing models, allowing comparisons between traditional dietary analysis and diet inferred by isotopic mixing models, which reflects food items effectively assimilated in consumer tissues. Both are visualized in bipartite networks and show food‐consumers link strengths. This approach could be useful to other studies using stable isotopes coupled to network analysis, particularly useful in sympatric species with similar niches.     

Evidence for the phosphorylation of a proenkephalin-derived peptide, peptide B

The potential phosphorylation of a proenkephalin-derived peptide, Peptide B, was investigated in primary cultures of bovine adrenal chromaffin cells and fresh adrenal medullary tissue. Cultures were labeled with [32P]phosphate for 24 h and extracts subjected to immunoprecipitation using affinity-purified anti-serum directed against the carboxyl terminus of Peptide B. A 4.6-kDa-labeled peptide was observed in autoradiograms of immunoprecipitates separated by sodium dodecyl sulfate-polyacrylamide electrophoresis; this peptide was not observed when excess antigen was present during the immunoprecipitation. Radioimmunoassay of extracts prepared from adrenal medullary tissue and separated by isoelectric focusing revealed the presence of four isoelectric forms of Peptide B-immunoreactive peptides; these peptides also exhibited Met-enkephalin-Arg-Phe immunoreactivity. The isoelectric points of these peptides (4.5, 4.3, 4.1, and 3.9) were consistent with the predicted pI values for phosphorylated derivatives of Peptide B. Treatment of samples with alkaline phosphatase prior to isoelectric focusing resulted in the conversion of the more acidic forms to the least acidic form. The presence of phosphate in the more acidic peaks was additionally verified by isoelectric focusing of 32P-labeled immunoprecipitates; the pI values of the radioactive peptides corresponded precisely to the peaks of immunoreactivity. In adrenal medullary tissue, the relative contributions of the various phosphorylated species to the total Peptide B immunoreactivity were as follows: unphosphorylated form, 13%; singly phosphorylated, 31%; doubly phosphorylated, 37%; and triply phosphorylated, 17%. Thus more than 85% of the Peptide B molecules present in the bovine adrenal medulla are phosphorylated.     

beta-Lactotensin, a neurotensin agonist peptide derived from bovine beta-lactoglobulin, enhances memory consolidation in mice

beta-Lactotensin (His-Ile-Arg-Leu) is an ileum-contracting tetrapeptide isolated from bovine beta-lactoglobulin. We previously reported that a neurotensin agonist beta-lactotensin shows antinociceptive effect through neurotensin NT(2) receptor. We found that centrally or orally administered beta-lactotensin at a dose of 60nmol/mouse or 300-500mg/kg, respectively, increased memory consolidation in the step-through-type inhibitory avoidance test in mice. The memory-enhancing activity of beta-lactotensin was inhibited by the dopamine D(2) receptor antagonist raclopride but not the D(1) receptor antagonist SCH23390. Taken together, beta-lactotensin might improve memory consolidation through activating the dopamine D(2) receptor.     

Development of a new technique for obtaining axenic meat

Summary A new technique for obtaining axenic meat is described. The procedure is based on the use of a liquid peracetic acid lock united with two isolators, permanently connected together. After immersion in a 3% solution of peracetic acid for 2 min, the surfaces of muscles obtained from pig, horse and cattle were shown to be completely decontaminated. Such meats appeared perfectly fit for gnotobiotic studies in the field of meat microbiology.     

Transfer of a gene containing the Arg-Gly-Asp peptide prolongs the bleeding time of mice

Peptides containing Arg-Gly-Asp (RGD) have been used to decrease thrombosis by competitive inhibition of the integrin glycoprotein, alphaIIb/beta3a, in platelets. However, they have a short half-life in vivo. A naked plasmid, pCMV-RGD, was transferred into the skeletal muscle of mice and RGD gene expression was observed by RT-PCR. The bleeding time between control mice and RGD-transferred mice was prolonged from the 10th day to the 80th day after gene transfer while the blood glucose and serum insulin-like proteins remained at normal levels. These results provided a convenient and effective approach to relieve patients from thrombi in a single step over a relatively long period.     

Effect of high contents of dietary animal-derived protein or carbohydrates on canine fecal microbiota

ABSTRACT: BACKGROUND: Considerable evidence suggests that food impacts both the gastro-intestinal (GI) function and the microbial ecology of the canine GI tract. The aim of this study was to evaluate the influence of high-carbohydrate (HC), high-protein (HP) and dry commercial (DC) diets on the canine colonic microbiota in Beagle dogs. Diets were allocated according to the Graeco-Latin square design. For this purpose, microbial DNA was isolated from faecal samples and separated by density gradient centrifugation, resulting in specific profiling based on the guanine-cytosine content (%G+C). In addition, 16S rRNA gene amplicons were obtained from the most abundant %G+C peaks and analysed by sequence analysis, producing a total of 720 non-redundant sequences (240 sequences per diet). RESULTS: The DC diet sample showed high abundance of representatives of the orders Clostridiales, Lactobacillales, Coriobacteriales and Bacteroidales. Sequence diversity was highest for DC diet samples and included representatives of the orders Lactobacillales and Bacteroidales, which were not detected in samples from the HP and HC diets. These latter two diets also had reduced levels of representatives of the family Lachnospiraceae, specifically Clostridial cluster XIVa. The HC diet favoured representatives of the order Erysipelotrichales, more specifically the Clostridial cluster XVIII, while the HP diet favoured representatives of the order Fusobacteriales. CONCLUSIONS: This study detected Coriobacteriales in dog faeces, possibly due to the non-selective nature of the %G+C profiling method used in combination with sequencing. Moreover, our work demonstrates that the effect of diet on faecal microbiota can be explained based on the metabolic properties of the detected microbial taxa.