Degradation of isolated grass mesophyll, epidermis and fibre cell walls in the rumen and by cellulolytic rumen bacteria in axenic culture

Abstract

T.P. 1986. Degradation of isolated grass mesophyll, epidermis and fibre cell walls in the rumen and by cellulolytic rumen bacteria in axenic culture. Journal of Applied Bacteriology 60, 321-336.The degradation of cell walls of mesophyll, epidermis and fibre cells isolated from leaves of perennial and Italian ryegrass within the sheep rumen or by selected strains of rumen bacteria in oitro, was followed by estimation of dry matter loss, or loss of neutral sugar residues. Primary cell walls (mesophyll and epidermis) were fully degraded within 12 h in the rumen, while the more heavily lignified fibre cell walls showed only a 40% loss of dry matter over the same period. Neutral sugar residues were lost at a common rate from walls of all three cell types. Incubation of cell walls with cellulolytic bacteria showed that the extent to which cell walls were attacked was constantly ordered (epidermis > mesophyll > fibre). The rate of degradation of cell walls was less in axenic culture than within the rumen. Greatest weight losses were produced by Ruminococcus albus, followed by Eacteroides succinogenes, with RuminococcusJlavefaciens effecting the least change, regardless of the nature of the cell wall provided as a substrate. Xylose was more readily lost from primary cell walls than glucose during the early stages of attack, but both were lost at a common rate from fibre cell walls. Dry matter losses produced by the hemicellulolytic strain, Eacteroides ruminocola, were limited even after extended incubation. Electron microscopy indicated that R. albus was less commonly attached to cell walls than were the other cellulolytic strains, although evidence of capsular material was present. Eacteroides succinogenes was seen with an extensive capsule which enveloped clusters of cells, forming micro-colonies in association with the plant cell wall. Vesicle-like structures, commonly associated with the cellulolytic bacteria R. albus and B. succinogenes, were found on comparatively few occasions in this study.

Leaf tissues proportion and chemical composition of Axonopus jesuiticus x A. scoparius as a function of pig slurry application

“…The epidermis content increase is desirable because the inner wall of this tissue offers no resistance to microbial digestion, since the composition of its cell wall is equal to the mesophyll (CHESSON et al, 1986). In addition, the increase on the non-lignifi ed vascular tissue and parenchyma proportion, which have high digestibility, and the reduction of the structural characteristics that limit forage breakdown, which are mainly the support tissue highly lignifi ed, like sclerenchyma and xylem (AKIN, 1989), showed an improvement of the anatomical attributes that infl uences the nutritive value of the grass.…”

Qualitative and anatomical characteristics of tree-shrub legumes in the Forest Zone in Pernambuco state, Brazil

“…According to Chesson et al (1986) the mesophyll cells are easily fragmented into small particles, being quickly and completely digested. This digestion starts in these cells up to the phloem, which has only a thin primary non-lignified wall (Hanna et al, 1973;Akin et al, 1973).…”

Características anatômicas e valor nutritivo de quatro gramíneas predominantes em pastagem natural de Viçosa, MG

“…microbiana, pois a composição de sua parede celular equivale à do mesofilo (Chesson et al, 1986). A digestão das células do mesofilo poderá ocorrer sem colonização prévia da parede celular (Akin et al, 1974), apesar de essas células em gramíneas tropicais se mostrarem densas e radialmente arranjadas.…”

“…A digestão das células do mesofilo poderá ocorrer sem colonização prévia da parede celular (Akin et al, 1974), apesar de essas células em gramíneas tropicais se mostrarem densas e radialmente arranjadas. A facilidade de digestão possibilita maior fragmentação da partícula e rápida digestão dos demais tecidos (Chesson et al, 1986), mas isso só será possível se a parede celular primária das partículas apresentar-se delgada e não-lignificada, pois as alterações químicas das células podem resultar em menor taxa de digestão e interferir no desaparecimento dos demais tecidos (Lempp et al, 1998).…”