Rate Of Cell Wall Degradation Research Articles

Relationships between chemical composition and in vitro gas production parameters of maize leaves and stems.

This study investigated the chemical composition (proximate and Van Soest analysis) and in vitro gas production parameters of maize leaves and stems separately, and related the in vitro gas production parameters with the chemical composition, of thirteen maize cultivars. After harvest in September 2016, all plants were separated into two morphological fractions: leaves and stems. The crude protein (CP) content was greater, and the ratio of acid detergent lignin (ADL) to potentially rumen degradable fibre (calculated as the difference between neutral detergent fibre and ADL; ADL:pRDF) was lower in the leaves than in the stems in all 13 cultivars. For the leaves, the cumulative gas production between 3 and 20 hr (A2), representing cell wall fermentation in the rumen fluid, and the cumulative 72‐hr gas production (GP72), representing total organic matter (OM) degradation, were moderately to weakly correlated with the chemical composition, including hemicellulose, cellulose, ADL and CP content (R 2 < 0.40), whilst the best relationship between the half‐time value (B2), representing the rate of cell wall degradation, and chemical composition had an R 2 of 0.63. For the stems, the best relationship between A2, B2 and GP72 with chemical composition was greater (R 2 ≥ 0.74) and the best relationship included hemicellulose (A2 only), cellulose and ADL (GP72 and A2 only) contents. In conclusion, maize leaves and stems differed in chemical composition, in particular CP content and ADL:pRDF. The A2 and GP72 of the stems, but not of the leaves, were highly correlated with the chemical composition, indicating that the cell wall and OM degradation of maize stems can be better predicted by its chemical composition.

Evaluation of arid region browse species from north eastern Nigeria using pen fed goats

Four 18–26 months old castrated Borno white×Sokoto Red goats were used in a 4×4 Latin square design to measure the dry matter intake (DMI), daily body weight change and dry matter digestibility (DMD) of four native Nigerian browse species, ( Ziziphus spinochrist, Wild., Acacia albida, Del., Sterculia satigera, Guill. and Anogeissus licocarpus, Guill.) native to the semi-arid regions. The mean DMI of Z. spinochrist, Wild. and A. albida, Del. were similar but higher than for S. satigera, Guill. and A. licocarpus, Guill. The DMD of A. licocarpus,Guill. was lower ( p<0.05) than for Z. spinochrist, Wild., Acacia licocarpus, Del. or S. satigera, Guill. The lowest body weight gain recorded was for A. licocarpus, Guill.; this was attributed to the larger amount of fibre in the forage resulting in a slow rate of cell wall degradation and rumen digestibility. Goats showed no visual signs of toxicosis. This study suggests that A. albida, Del. has the highest forage value for goats followed by Z. spinochrist, Wild., S. satigera, Guill. and A. licocarpus, Guill. Potentially the species examined can provide feed for goats as well as for other small ruminants during long dry periods when other feed is unavailable.

Ruminal digestion characteristics and effective degradability of cell wall of browse species from northeastern Mexico

Foliage from 15 shrub species was used to estimate the extent and rate of cell wall (CW) degradation in the rumen of fistulated Pelibuey sheep. Branches from the browse species: Acacia berlandieri, Acacia farnesiana, Acacia greggii, Acacia rigidula, Celtis pallida, Cercidium macrum, Condalia obovata, Cordia boisieri, Desmanthus virgathus, Leucaena leucocephala, Leucophyllum texanum, Opuntia lindehimieri, Porlieria angustifolia, Prosopis glandulosa, and Ziziphus obtusifolia, were collected during the spring of 1993 in Marı́n, County, Nuevo León, México. Medicago sativa hay was used for comparison. Twelve ruminally cannulated male sheep (45 kg BW) were used (four sheep per plant) to incubate nylon bags (5 × 10 cm and 53 μm pore size); containing 4 g of ground material (1 mm screen) of each plant. Bags were incubated at 0, 4, 8, 12, 24 and 48 h. The rate of CW degradation ( c, %) was highest ( P < 0.001) in O. lindehimieri (9.8) and lowest in A. rigidula (2.8). Only O. lindehimieri and C. pallida (8.5) had higher CW degradation rates than M. sativa (7.1). Effective degradability of CW (EDCW), at outflow rates of 2%, 5% and 8% h −1 values were higher in C. pallida (74.3, 62.9 and 56.6), C. obovata (54.5, 45.8 and 39.7), L. leucocephala (54.7, 45.1 and 39.8) and O. lindehimieri (67.8, 56.6 and 50.6) than in M. sativa (54.1, 44.9 and 39.5). High levels of lignin and condensed tannins affected the EDCW in some plants. Species such as C. pallida, C. obovata, L. Leucocephala and O. lindehimieri may be considered as good available forages for grazing ruminants in northern Mexico.

The rate and extent of cell-wall degradation in vitro for 40 silages varying in composition and digestibility

The rate and extent of cell-wall degradation was recorded in 40 silages in order to explore the variation between silages and provide material and results to use in the search for a lower cost method. The method used in the present study was selected from four compared previously (Wilman et al., 1996. Anim. Feed Sci. Technol., 63, 99–109). Freeze-dried, milled silage was incubated in buffered rumen fluid in sealed tubes for 0, 3, 8, 16, 24, 45 or 72 h and then boiled with neutral detergent. The constants a, b and c in the equation p = a + b(1 − e − ct ) (Ørskov and McDonald, 1979. J. Agric. Sci. Cambridge, 92: 499–503.) (where p is the percentage of cell wall degraded after t hours of incubation) were calculated for each silage. The rate of cell-wall degradation in the early stages of fermentation was much higher in a lucerne silage than in the grass and forage maize silages. Mixtures of lucerne and forage maize were intermediate in rate of cell-wall degradation. Among 28 grass silages, ‘ c’ varied from 0.029 to 0.066, indicating wide variation in rate of cell-wall degradation; ‘ c’ was negatively correlated with the cell-wall content of the silage ( r = − 0.81), suggesting that the cell wall from the younger, leafier crops was degraded more quickly than that from more mature crops. The cell-wall degradation curve from 3 to 72 h of incubation was well described by the equation p = ( a + b)(1 − e − c( t − t o ) ), where t o is the lage period before rapid degradation began. In the case of the 28 grass silages there were strong correlations between ‘( a + b)’ and cell-wall degradation after 72 h ( r = +0.92) and between ‘ c’ and cell-wall degradation after 24 h as a percentage of cell-wall degradation after 72 h ( r = +0.95), suggesting that, for some purposes, it may be sufficient to have only 0, 24 and 72 h of incubation.

Effect of high temperature on cell wall modifications associated with tomato fruit ripening

Abstract Tomato fruit (cv. ‘Sunny’) were harvested at the mature green stage and kept for 4 days at either 21°C or 40°C, then subsequently stored at 21°C. Red color development was inhibited in heated fruit, as was softening. Fourteen days after treatment, heat-stressed fruit were twice as firm as the controls. The cell wall uronide content increased in heat-exposed fruit while remaining unchanged in samples stored constantly at 21°C. Heat treatment inhibited ripening-associated cell wall modification so that 14 days after treatment, stressed fruit contained only one-third the amount of soluble polyuronides that was present in the control fruit. Furthermore, the rate of loss of cell wall galactose and arabinose was reduced in heat-stressed tomatoes. Postharvest exposure of unripe tomato fruit to high temperature appears to reduce the rate of cell wall degradation, while the synthesis of polyuronide components continues normally.

Triggering of autolytic cell wall degradation in Escherichia coli by beta-lactam antibiotics.

A biochemical method was developed to quantitatively compare the effectiveness of beta-lactams in triggering murein degradation (autolysin activity) in Escherichia coli. Bacteria prelabeled in their cell walls with radioactive diaminopimelic acid in growth medium were exposed for 10 min to the antibiotics at the appropriate minimal growth inhibitory concentrations and at multiples of these values, and the rate of cell wall degradation was followed during subsequent penicillin-binding protein (PBP)-1 were the most effective triggers of autolytic wall degradation; beta-lactams selective for PBP-2 were the poorest; and antibiotics preferentially binding to PBP-3 showed intermediate activities. The relative effectiveness of beta-lactams in autolysin triggering was found to parallel the effectiveness of the same drugs in causing rapid loss of viability, culture lysis, and spheroplast formation. Autolysin triggering was suppressed by inhibitors of protein and ribonucleic acid biosynthesis but not by inhibitors of deoxyribonucleic acid synthesis. The beta-lactam-induced cell wall degradation did not seem to involve a direct stimulation of enzyme activity or synthesis of new enzyme molecules, and murein sacculi isolated from cells that had been preexposed to a triggering dose of beta-lactam treatment exhibited the same sensitivity to crude, homologous autolysins as sacculi prepared from untreated control bacteria. On the basis of these observations, mechanisms are considered for the triggering of E. coli autolysins and for the role of autolytic activity in bacterial spheroplast formation, lysis, and death.

DISTRIBUTION OF RADIOACTIVITY IN AUTOLYZED CELL WALL OF BACILLUS CEREUS DURING SPHEROPLAST FORMATION.

Kronish, Donald P. (Warner-Lambert Research Institute, Morris Plains, N.J.), Raam R. Mohan, and Benjamin S. Schwartz. Distribution of radioactivity in autolyzed cell wall of Bacillus cereus during spheroplast formation. J. Bacteriol. 87:581-587. 1964.-Spheroplasts of Bacillus cereus strain T were produced from cells grown in the presence of uniformly labeled C(14)-glucose. At regular intervals during spheroplast formation, enzymatically degraded cell wall was isolated by a new procedure. Radioactivity of solubilized cell wall in cell-free material increased from 2.5 to 42% of the total incorporated label during spheroplast formation. The rate of cell-wall degradation as measured by increase in radioactivity was biphasic with relative slopes of 2.0 and 5.0. During autolytic depolymerization of B. cereus cell wall, two major components were solubilized at different rates. Chemical fractionation revealed these to be a peptide and a mucopeptide. The possibility of two enzymes being involved in spheroplast formation and cell-wall degradation is discussed.