Submitted to: Systematic and Applied Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/20/2002
Publication Date: 10/1/2002
Citation: ZIEMER, C.J., SHARP, R., STERN, M.D., COTTA, M.A., WHITEHEAD, T.R., STAHL, D.A. PERSISTENCE AND FUNCTIONAL IMPACT OF A MICROBIAL INOCULANT ON NATIVE MICROBIAL COMMUNITY STRUCTURE, NUTRIENT DIGESTION, AND FERMENTATION CHARACTERISTICS IN A RUMEN MODEL. SYSTEMATIC AND APPLIED MICROBIOLOGY. 2002. V. 25. P. 416-422. Interpretive Summary: Microbial fermentation in the forestomach (rumen) of ruminant livestock (sheep, cattle, goats, etc.) enables these animals to live on diets composed largely of fibrous plant materials. Although this confers an advantage to these animals and allows them to convert inexpensive feeds into high quality animal products, the use of plant components is often incomplete. As a result, higher quality and more costly feeds are added t diets to meet the nutrient demands required by modern livestock production systems. Efforts to improve the use of the fiber portion of animal diets has centered on physical and chemical treatments of feed materials. An alternative to this approach would be to modify the activities of the microorganisms themselves to increase their capacity for digestion of these materials. The bacterium, Bacteroides thetaiotaomicron strain BTX, was developed for this purpose. Strain BTX produces high levels of the digestive enzyme xylanase that may help breakdown plants. The current studies were conducted to test whether strain BTX could survive in rumen-like cultures in the laboratory and improve the digestion of plant fiber. In our experiments, we were able to use specific molecular probes to measure strain BTX and determine whether it was able to survive and compete with the normal rumen microbes present in these model cultures. Our results demonstrated strain BTX could survive and grow under rumen simulating conditions. Furthermore, the addition of strain BTX enhanced the digestion of plant fiber fed to these cultures. The information obtained demonstrates the potential for production of beneficial rumen inocula and will be helpful to the further development of this strain and others as rumen additives.
Technical Abstract: Small sub-unit (SSU) rRNA-targeted oligonucleotide probes were used to monitor the persistence of a genetically engineered bacterium inoculated in model rumens. Eight dual flow continuous culture fermenters were operated with either standard artificial saliva buffer or buffer with chondroitin sulfate (0.5 g l**-1) added. After 168 h of operation, fermenters were inoculated with Bacteroides thetaiotaomicron BTX (BTX), at approximately 1 of total bacteria (assuming 5 x 10**9 CFU ml**-1). B. thetaiotaomicron was quantified using a species-specific probe and shown to persist in fermenters 144 h after inoculation (relative abundance 0.48% and 1.42% of total SSU rRNA with standard and chondroitin sulfate buffers, respectively). No B. thetaiotaomicron SSU rRNA was detected in fermenter samples prior to inoculation with strain BTX. Relative abundances of Bacteria, Eucarya, and Archaea were not affected by either inoculation or buffer type. Chondroitin sulfate addition to the buffer increased bacterial nitrogen flow in fermenters but did not alter nutrient digestion. Fiber digestion, in particular the hemicellulose fraction, increased after strain BTX addition. Total short chain fatty acid (VFA) concentrations were not altered by either buffer or inoculum, but proportions of individual VFA differed. B. thetaiotaomicron BTX has the potential to increase ruminal fiber digestion, but further study is needed to determine effects on other fiber-digesting bacteria.