Effects of Coumarin and Sparteine on Attachment to Cellulose and Cellulolysis by Neocallimastix frontalis RE1

Gut Microbiota and Their Role in Health and Metabolic Disease of Dairy Cow

Ruminants are mostly herbivorous animals that employ rumen fermentation for the digestion of feed materials, including dairy cows. Ruminants consume plant fibre as their regular diet, but lack the machinery for their digestion. For this reason, ruminants maintain a symbiotic relation with microorganisms that are capable of producing enzymes to degrade plant polymers. Various species of microflora including bacteria, protozoa, fungi, archaea, and bacteriophages are hosted at distinct concentrations for accomplishing complete digestion. The ingested feed is digested at a defined stratum. The polysaccharic plant fibrils are degraded by cellulolytic bacteria, and the substrate formed is acted upon by other bacteria. This sequential degradative mechanism forms the base of complete digestion as well as harvesting energy from the ingested feed. The composition of microbiota readily gets tuned to the changes in the feed habits of the dairy cow. The overall energy production as well as digestion is decided by the intactness of the resident communal flora. Disturbances in the homogeneity gastrointestinal microflora has severe effects on the digestive system and various other organs. This disharmony in communal relationship also causes various metabolic disorders. The dominance of methanogens sometimes lead to bloating, and high sugar feed culminates in ruminal acidosis. Likewise, disruptive microfloral constitution also ignites reticuloperitonitis, ulcers, diarrhoea, etc. The role of symbiotic microflora in the occurrence and progress of a few important metabolic diseases are discussed in this review. Future studies in multiomics provides platform to determine the physiological and phenotypical upgradation of dairy cow for milk production.

Dynamic role of single-celled fungi in ruminal microbial ecology and activities

In ruminants, high fermentation capacity is necessary to develop more efficient ruminant production systems. Greater level of production depends on the ability of the microbial ecosystem to convert organic matter into precursors of milk and meat. This has led to increased interest by animal nutritionists, biochemists and microbiologists in evaluating different strategies to manipulate the rumen biota to improve animal performance, production efficiency and animal health. One of such strategies is the use of natural feed additives such as single-celled fungi yeast. The main objectives of using yeasts as natural additives in ruminant diets include; (i) to prevent rumen microflora disorders, (ii) to improve and sustain higher production of milk and meat, (iii) to reduce rumen acidosis and bloat which adversely affect animal health and performance, (iv) to decrease the risk of ruminant-associated human pathogens and (v) to reduce the excretion of nitrogenous-based compounds, carbon dioxide and methane. Yeast, a natural feed additive, has the potential to enhance feed degradation by increasing the concentration of volatile fatty acids during fermentation processes. In addition, microbial growth in the rumen is enhanced in the presence of yeast leading to the delivery of a greater amount of microbial protein to the duodenum and high nitrogen retention. Single-celled fungi yeast has demonstrated its ability to increase fibre digestibility and lower faecal output of organic matter due to improved digestion of organic matter, which subsequently improves animal productivity. Yeast also has the ability to alter the fermentation process in the rumen in a way that reduces methane formation. Furthermore, yeast inclusion in ruminant diets has been reported to decrease toxins absorption such as mycotoxins and promote epithelial cell integrity. This review article provides information on the impact of single-celled fungi yeast as a feed supplement on ruminal microbiota and its function to improve the health and productive longevity of ruminants.

Fusarium graminearum growth inhibition due to glucose starvation caused by osthol

The effects of osthol, a plant coumarin, on morphology, sugar uptake and cell wall components of Fusarium graminearum were examined in vitro by electron microscopy,¹⁴C-labelling and enzyme activity detection. The results revealed that osthol could inhibit the hypha growth of F. graminearum by decreasing hyphal absorption to reducing sugar. After treatment with 100 μg·mL⁻¹ osthol for 24 h, many hyphal fragments of F. graminearum appeared. Microscopy observation showed that the cell walls of hyphal fragments blurred and the organelles of the cells degraded with the increasing vacuoles. The N-acetyl-D-glucosamine contents and chitinase activity both increased when hypha were treated with 100 μg·mL⁻¹ osthol, whereas the activity of β-1,6-glucanase remained unchanged. When F. graminearum fed with ¹⁴C glucose was treated with 100 μg·mL⁻¹osthol, glucose contents decreased to the lowest level, while the contents in non-osthol treated controls remained unchanged. These results suggested that chitinase activity might be related to glucose starvation under osthol treatment, and that the appearance of hyphae fragments maybe the results of the promoted chitinase activity which itself triggered chitin degradation.

Effects of esculin and esculetin on the survival of Escherichia coli O157 in human faecal slurries, continuous-flow simulations of the rumen and colon and in calves

The human pathogen Escherichia coli O157:H7 is thought to be spread by direct or indirect contact with infected animal or human faeces. The present study investigated the effects of the plant coumarin esculin and its aglycone esculetin on the survival of a strain of E. coli O157 under gut conditions. The addition of these compounds to human faecal slurries and in vitro continuous-flow fermenter models simulating conditions in the human colon and rumen caused marked decreases in the survival of an introduced strain of E. coli O157. When four calves were experimentally infected with E. coli O157 and fed esculin, the pathogen was detected in five of twenty-eight (18 %) of faecal samples examined post-inoculation, compared with thirteen of thirty-five (37 %) of faecal samples examined from five control calves not fed esculin. Coumarin compounds that occur naturally in dietary plants or when supplemented in the diet probably inhibit the survival of E. coli O157 in the gut.

Inhibitory activity of gut bacteria against Escherichia coli O157 mediated by dietary plant metabolites

Under both aerobic and anaerobic conditions, the growth of Escherichia coli O157 strain NCTC 12,900 was inhibited by the coumarins esculetin, umbelliferone and scopoletin, but not by the coumarin glycoside esculin. Esculin-hydrolysing bacteria from the rumen, the pig gut and the human gut inhibited growth of E. coli in an overlay-plate assay in the presence of esculin. The combined effect of esculetin and volatile fatty acids was greater than the effect of either factor alone suggesting that coumarin glycosides in the diet might reduce the growth or survival of E. coli O157 in the gut. Adding esculin to incubations of mixed rumen contents significantly reduced the survival of E. coli O157.