Interactions Between Rumen Anaerobic Fungi And Rumen Bacteria Of Goats During In Vitro Fermentation

Rumen is a complex micro-ecosystem where bacteria, protozoa and anaerobic fungi are the three major microorganism groups. Many relationships are known to exist among rumen microorganisms. The interactions among microorganisms can lead to changes in microbial composition and structure in the rumen, and consequently affect the rumen fermentation. Therefore, further investigating the interactions among rumen microorganisms may help manipulate rumen metabolism. The aim of this thesis was to investigate the interactions between rumen anaerobic fungi and bacteria from the goats by comparing in vitro pure cultures and cocultures. This thesis was described in the following four sections.In the first section, cellulolytic bacteria were isolated from goat rumen using anaerobic roll-tube techniques. In vitro fermentation characteristics of these bacteria on filter paper and rice straw were investigated. The results showed that both mixed cellulolytic bacteria and single cellulolytic bacterium exhibited high ability of degrading rice straw and filter paper. For mixed cellulolytic bacteria, the apparent dry matter losses on rice straw and filter paper after 96 h fermentation were 59.59% and 36.12%, the CMCase activities in the culture supernatants were 0.26 U and 0.15 U, respectively. For single cellulolytic bacterium, the apparent dry matter losses on rice straw and filter paper after 96 h fermentation were 55.26% and 32.29%, and the CMCase activities in the culture supernatants were 0.27 U and 0.18 U, respectively. For both mixed cellulolytic bacteria and single cellulolytic bacterium, the apparent dry matter losses and CMCase activity on filter paper were much higher than those on rice straw.In the second section, effects of culture supernatant of rumen anaerobic fungi from different growth stages on in vitro fermentation of rumen bacteria of the goat were investigated and the effects of different processes of supernatants were also analyzed. As compared with the control, treatments with supernatants from cultures after 6, 12 and 24 h fermentation, could significantly decrease apparent dry matter losses and CMCase activities. With 72 h fermentation supernatant, however, the apparent dry matter losses and CMCase activites increased significantly as compared with the control. The supernatant of fungal cultures after 72 h fermentation were treated by three methods: i ) autoclaving at 115 Cfor 20 min; ii ) sterililzed by passing through a 0.22-m-pore-diameter polysulfone membrane filter; iii) frozen at -20C for 24 h. As compared with the control, the treatment with autoclaved anaerobic fungal culture supernatant showed a significant decrease in apparent dry matter losses and CMCase activities. With frozen fermentation supernatant, however, the apparent dry matter loss and CMCase activites increased significantly.In the third section, fermentation profiles on rice straw from cocultures with rumen fungi and rumen bacteria were compared with rumen fungal cultures and rumen bacterial cultures. The results showed that, during the first 24 h fermentation, the cocultures degraded smaller amount of substrate, with DM loss (5.85%) significantly lower than that in bacterial cultures (10.49%). The TVFA and acetate concentrations in cocultures were significantly lower than those in bacterial cultures. However, by the end of 48, 72 and 96 h fermentation, apparent DM losses in the cocultures (24.37%, 29.04% and 30.81%) were significantly higher than in their corresponding bacterial cultures (21.69%, 26.41% and 27.34%). Furthermore, by the end of 72 h fermentation, the propionate and butyrate concentrations in cocultures were higher than in bacterial cultures. The apparent dry matter losses in cocultures after 72 h and 96 h fermentation were lower than those in rumen fungal cultures. During the whole fermentation, the population densities of rumen bacteria in cocultures were lower than that in bacterial cultures. The population densities of anaerobic fungi in cocultures were also lower than that in fungal cultures and no live fungi w...