Bacteroides ruminicola did not take up 14C from exogenous "C-labeled L-proline or 14C-labeled L-glutamic acid and took up very little 14C from exogenous 4C-labeled L-valine. Growing cultures of B. ruminicola rapidly took up 14C from "4C-prolinelabeled peptides of molecular weights up to 2,000 and incorporated it into trichloroacetic acid-insoluble cell material. Uptake and incorporation did not occur at 0 C and were reduced or eliminated in glucose-starved cells, depending upon the length of time the cells were starved. The initial rate of uptake of peptides seemed to exhibit saturation kinetics, but it was impossible to establish this conclusively. The initial uptake of 14C from peptides was not affected by chloramphenicol but the incorporation of it into trichloroacetic acid-insoluble cell material was virtually eliminated. Only moderate amounts of trichloroacetic acid-extractable, labeled material were present in cells during peptide uptake, whether or not chloramphenicol was present. "4C-proline was rapidly released from labeled peptides during uptake, whether or not chloramphenicol was present. The amount of "IC fixed into trichloroacetic acid-insoluble cell material was directly related to the size of peptides originally supplied in the medium. It is concluded that B. ruminicola possesses a general system for the uptake of peptides, that peptides are rapidly hydrolyzed during or after uptake, and that oligopeptides function only to supply amino acids in a form available to the organism.
It is well established that large quantities of volatile fatty acids (\'FA) are produced within the rumen by microbial action on cellulose. starch and protein. One of the first requirements for an understanding of the biochemistry of ruminant metabolism is a knowledge of quantities and proportions of the \'FA produced and absorbed and the form in which these rumen substances enter the blood of the host animal. Sumerous technics have been devised to gain a measure of these values; however. these methods have measured only one part of this system. i.e., either production or absorption ( 1 ) . That variable results have been obtained is not unespected in view of the dynamic nature of this system where production and absorption occur continuously and simultaneously. Rumen perfusion was selected as a technic for measuring simultaneouslq-both total production and absorption of \'FA.The rumina of 2 mature goats weighing approximately 60 lb were perfused with heparinized blood by use of pump-oxygenator apparatus similar to one used previously in this laboratory ( 2 ) . These animals had been fed a diet of mixed hay and concentrate ad lib. for 6 weeks prior to the perfusion studies. Labeled substrates were added to rumen contents immediately prior to perfusion, 50 pc of n-butyrate-l-C14Na being used for perfusion 40 and 50 pc of propionate-l-Ci4 N a in perfusion 42. The 2 perfusions. 30 and 42, were conducted for SO and 115 minutes respectively. Organic acids in blood and rumen fluid were measured by modification of the chromatographic technic of Wiseman and Trvin ( 3 ) . Blood glucose was determined by the method of Somogyi(4). Analysis for to-3lcthods.tal acetone bodies in blood was performed by procedure of Weichselbaum and Somogyi ( 5 ) . Acetoacetic acid was isolated by method of Cavallini and Frontali ( 6 ) . Measurements of radioactivity were made with a windowless flow tube used in the Geiger region. Osazones were prepared for estimating activity in blood glucose. The carboxyl carbon of P-hydroxybutyrate was removed by oxidation and counted as barium carbonate.Rates of blood flow through the isolated rumina were 65 ml/minute in perfusion 40 and 150 ml/minute in perfusion 42. These values are equivalent to 25 to 50% of the estimated in vivo rate (7).Quantitative results for perfusion 40 are presented in Table T. The total increase in organic acids in the isolated system amounted to 2392 mg of which 31% is represented by increase in blood. Similarity in molar per cent of the organic acids in rumen fluid at beginning and end of perfusion, is indicative of maintenance of a nearly normal physiological state. Comparison of increases of individual acids in blood with increases in rumen fluid shows that, with the exception of formate and lactate, the increases in blood were a reflection of production of these acids.The perfused rumen utilized glucose, blood concentration decreasing from 43.8 to 29.3 mg % during experiment. No change occurred in level of acetone bodies in the blood.The quantitative results from perfusion 4...
Hybridization of deoxyribonucleic acid (DNA) from Lactobacillus bulgaricus (ATCC 11842) with DNA of L. lactis (ATCC 12315), L. helveticus (ATCC 15009), and L. jugurt (ATCC 521) showed 86.0% reassociation with L. lactis , 4.8% with L. helveticus , and none with L. jugurt .
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