title: Accumulation of reserve carbohydrate by rumen protozoa and bacteria in competition for glucose.
abstract: The aim of this study was to determine if rumen protozoa could form large amounts of reserve carbohydrate compared to the amounts formed by bacteria when competing for glucose in batch cultures. We separated large protozoa and small bacteria from rumen fluid by filtration and centrifugation, recombined equal protein masses of each group into one mixture, and subsequently harvested (reseparated) these groups at intervals after glucose dosing. This method allowed us to monitor reserve carbohydrate accumulation of protozoa and bacteria individually. When mixtures were dosed with a moderate concentration of glucose (4.62 or 5 mM) (n = 2 each), protozoa accumulated large amounts of reserve carbohydrate; 58.7% (standard error of the mean [SEM], 2.2%) glucose carbon was recovered from protozoal reserve carbohydrate at time of peak reserve carbohydrate concentrations. Only 1.7% (SEM, 2.2%) was recovered in bacterial reserve carbohydrate, which was less than that for protozoa (P < 0.001). When provided a high concentration of glucose (20 mM) (n = 4 each), 24.1% (SEM, 2.2%) of glucose carbon was recovered from protozoal reserve carbohydrate, which was still higher (P = 0.001) than the 5.0% (SEM, 2.2%) glucose carbon recovered from bacterial reserve carbohydrate. Our novel competition experiments directly demonstrate that mixed protozoa can sequester sugar away from bacteria by accumulating reserve carbohydrate, giving protozoa a competitive advantage and stabilizing fermentation in the rumen. Similar experiments could be used to investigate the importance of starch sequestration.
authors.affiliation: Department of Animal Sciences, The Ohio State University, Columbus, Ohio, USA.
authors.forename: Bethany L
authors.initials: BL
authors.lastname: Denton
authors.affiliation: Department of Animal Sciences, The Ohio State University, Columbus, Ohio, USA.
authors.forename: Leanne E
authors.initials: LE
authors.lastname: Diese
authors.affiliation: Department of Animal Sciences, The Ohio State University, Columbus, Ohio, USA The Ohio State Interdisciplinary Ph.D. Program in Nutrition, The Ohio State University, Columbus, Ohio, USA.
authors.forename: Jeffrey L
authors.initials: JL
authors.lastname: Firkins
authors.affiliation: The Ohio State Interdisciplinary Ph.D. Program in Nutrition, The Ohio State University, Columbus, Ohio, USA thackmann@ufl.edu.
authors.forename: Timothy J
authors.initials: TJ
authors.lastname: Hackmann
mesh_terms: D000818:Animals; D001419:Bacteria / Q000737:chemistry / Q000378:metabolism*; D050260:Carbohydrate Metabolism; D002241:Carbohydrates / Q000032:analysis; D002417:Cattle; D016798:Ciliophora / Q000737:chemistry / Q000378:metabolism*; D005947:Glucose / Q000378:metabolism; D012417:Rumen / Q000382:microbiology* / Q000469:parasitology*
chemical_list: D002241:Carbohydrates; D005947:Glucose