Degradation of wheat straw and maize stem by a monocentric and a polycentric rumen fungi, alone or in association with rumen cellulolytic bacteria

Roger, V.; Bernalier, Annick; Grenet, Élisabeth; Fonty, Gérard; Jamot, Jacqueline; Gouet, Philippe

doi:10.1016/0377-8401(93)90024-e

Cited by 23 publications

(19 citation statements)

References 23 publications

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“…Most, but not all, strains of Ruminococcus albus, Ruminococcus flavefaciens, and Butyrivibrio fibrisolvens will inhibit the fungi in coculture; however, this was also found to vary between species of fungi (8,11,28,32,47,50). In contrast, the strongly cellulolytic species F. succinogenes has little if any effect on the fungi (8,11,28,50). This difference between species and strains appears to rule out fermentation products as the source of the inhibition.…”

Section: Discussionmentioning

confidence: 97%

“…In addition to some preliminary studies by Akin and Windham (4), which suggested that rumen bacteria could inhibit fungal growth and activity, investigators have noted that some species of fibrolytic rumen bacteria can strongly inhibit the fungi (47). Most, but not all, strains of Ruminococcus albus, Ruminococcus flavefaciens, and Butyrivibrio fibrisolvens will inhibit the fungi in coculture; however, this was also found to vary between species of fungi (8,11,28,32,47,50). In contrast, the strongly cellulolytic species F. succinogenes has little if any effect on the fungi (8,11,28,50).…”

Section: Discussionmentioning

confidence: 98%

“…In general, these cocultures produce an increased amount of fungal biomass (9) and exhibit an increase in both the rate and extent of cellulose degradation (7,10,33). On the other hand, when combined in coculture with the cellulolytic ruminococci, their cellulolytic activity appeared to be inhibited (11,28,50). In contrast, Fibrobacter succinogenes appears to have little if any effect on the activity of the fungi (11, 50).…”

mentioning

confidence: 99%

“…On the other hand, when combined in coculture with the cellulolytic ruminococci, their cellulolytic activity appeared to be inhibited (11,28,50). In contrast, Fibrobacter succinogenes appears to have little if any effect on the activity of the fungi (11,50). Coincubations of protozoa with fungi have shown that the protozoa are able to both ingest and digest fungi (47).…”

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confidence: 99%

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Antibiosis between Ruminal Bacteria and Ruminal Fungi

Dehority

Tirabasso

2000

Appl Environ Microbiol

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Cellulose digestion, bacterial numbers, and fungal numbers were monitored over time in vitro by using a purified cellulose medium with and without antibiotics (penicillin and streptomycin). All fermentations were inoculated with a 1:10 dilution of whole rumen contents (WRC). Without antibiotics, cellulose digestion was higher (P < 0.01) at 24, 30, 48, and 72 h; fungi had almost disappeared by 24 h, while bacterial concentrations increased over 100-fold in 24 h and then decreased gradually up to 72 h. In those fermentations with added antibiotics, fungal concentrations increased 4-fold by 30 h and up to 42-fold at 72 h; bacterial concentrations were markedly reduced by 24 h and remained low through 72 h. Similar results were obtained with ground alfalfa as a substrate. In further studies, the in vitro fermentation of purified cellulose without antibiotics was stopped after 18 to 20 h, and the microbial population was killed by autoclaving. Antibiotics were added to half of the tubes, and all tubes were reinoculated with WRC. After 72 h, extensive cellulose digestion had occurred in those tubes without antibiotics, as compared to very low cellulose digestion with added antibiotics. The extent of this inhibition was found to increase in proportion to the length of the initial fermentation period, suggesting the production of a heat-stable inhibitory factor or factors. The inhibitory activity was present in rumen fluid, could be extracted from lyophilized rumen fluid (LRF) with water, and was stable in response to proteolytic enzymes. In addition, the water-extracted residue of LRF was found to contain growth factor activity for rumen fungi in vitro.The flagellated microorganisms observed in rumen contents by Liebetanz in 1910 (36) and Braune in 1913 (13) were originally believed to be flagellate protozoa. However, in a series of classic studies, Orpin (39-45) determined that these organisms were actually flagellated zoospores of anaerobic fungi. Although concentrations of the fungi are relatively low in comparison to those of the bacteria and ciliate protozoa, they possess a wide range of enzymes which are capable of hydrolyzing most of the structural polysaccharides occurring in plant cell walls (21,26,35,48,53,55). The fungi also appear to be superior to the rumen bacteria in their ability to break down and degrade the structural barriers in plant material (2). They are able to weaken and partially or fully degrade the more recalcitrant plant tissues as well as penetrate the cuticle barrier (3, 5, 34). When fungi were removed from the rumen, both feed intake and fiber digestibility were decreased; however, total viable bacteria, cellulolytic bacteria, or ciliate protozoal concentrations were not affected (24). Based on in vitro studies with rumen fluid, using antibiotics and a fungicide to selectively culture either the bacteria or fungi, Akin and coworkers (1, 56) concluded that the bacteria were the most active fiberdigesting organisms, even though fungal numbers were increased in the antibiotic-treated cultur...

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Section: Discussionmentioning

confidence: 97%

Section: Discussionmentioning

confidence: 98%

mentioning

confidence: 99%

mentioning

confidence: 99%

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Antibiosis between Ruminal Bacteria and Ruminal Fungi

Dehority

Tirabasso

2000

Appl Environ Microbiol

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“…Many relationships are known to exist among microorganisms in the rumen. Various workers have shown that anaerobic fungi interact with hydrogen-utilizing bacteria (3,4,12,15,16,17,21,24,33). In the presence of hydrogen-utilizing bacteria such as methanogens, anaerobic fungi are more effective at degrading cellulose.…”

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confidence: 99%

Relative Contributions of Bacteria, Protozoa, and Fungi to In Vitro Degradation of Orchard Grass Cell Walls and Their Interactions

Lee

Cheng

2000

Appl Environ Microbiol

144

121

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To assess the relative contributions of microbial groups (bacteria, protozoa, and fungi) in rumen fluids to the overall process of plant cell wall digestion in the rumen, representatives of these groups were selected by physical and chemical treatments of whole rumen fluid and used to construct an artificial rumen ecosystem. Physical treatments involved homogenization, centrifugation, filtration, and heat sterilization. Chemical treatments involved the addition of antibiotics and various chemicals to rumen fluid. To evaluate the potential activity and relative contribution to degradation of cell walls by specific microbial groups, the following fractions were prepared: a positive system (whole ruminal fluid), a bacterial (B) system, a protozoal (P) system, a fungal (F) system, and a negative system (cell-free rumen fluid). To assess the interactions between specific microbial fractions, mixed cultures (B؉P, B؉F, and P؉F systems) were also assigned. Patterns of degradation due to the various treatments resulted in three distinct groups of data based on the degradation rate of cell wall material and on cell wall-degrading enzyme activities. The order of degradation was as follows: positive and F systems > B system > negative and P systems. Therefore, fungal activity was responsible for most of the cell wall degradation. Cell wall degradation by the anaerobic bacterial fraction was significantly less than by the fungal fraction, and the protozoal fraction failed to grow under the conditions used. In general, in the mixed culture systems the coculture systems demonstrated a decrease in cellulolysis compared with that of the monoculture systems. When one microbial fraction was associated with another microbial fraction, two types of results were obtained. The protozoal fraction inhibited cellulolysis of cell wall material by both the bacterial and the fungal fractions, while in the coculture between the bacterial fraction and the fungal fraction a synergistic interaction was detected.Bacteria, protozoa, and fungi have been shown to be the microorganisms involved in plant cell wall digestion in the rumen. However, due to the difficulty of separating each microbial group in the rumen, to difficulties in measuring fungal biomass, and to the complex nature of the rumen ecosystem, the precise role and overall contribution of each microbial group to the degradation and fermentation of plant cell wall material is not understood. In spite of complicated interrelationships among the microorganisms (e.g., bacteria, protozoa, and fungi) in the rumen ecosystem, bacteria are believed to play a major role because of their numerical predominance and metabolic diversity (7). However, protozoa have been shown to digest from 25 to 30% of total fiber. The extent of the involvement of fungi, however, has not yet been estimated. Interaction effects between microorganisms can range from synergism to antagonism and depend on the microbial groups and species involved and the type of substrate used. In vitro examinations to estimate the role...

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