No abstract
Glucose uptake by Bacteroides suceinogenes S85 was measured under conditions that maintained anaerobiosis and osmotic stability. Uptake was inhibited by compounds which interfere with electron transport systems, maintenance of proton or metal ion gradients, or ATP synthesis. The most potent inhibitors were proton and metal ionophores. Oxygen strongly inhibited glucose uptake. Na+ and Li+, but not K+, stimulated glucose uptake. A variety of sugars, including atmethylglucoside, did not inhibit glucose uptake. Only cellobiose and 2-deoxy-D-glucose were inhibitory, but neither behaved as a competitive inhibitor. Metabolism of both sugars appeared to be responsible for the inhibition. Cells grown in celloblose medium transported glucose at one-half the rate of glucose-grown cells. Spheroplasts transported glucose as well as whole cells, indicating glucose uptake is not dependent on a periplasmic glucose-binding protein. Differences in glucose uptake patterns were detected in cells harvested during the transition from the lag to the log phase of growth compared with cells obtained during the log phase. These differences were not due to different mechanisms for glucose uptake in the cell types. Based on the results of this study, B. succinogenes cohtains a highly specific, active transport system for glucose. Evidence of a phosphoenolpyruvate-glucose phosphotransferase system was not found.
Cellobiose transport by the cellulolytic ruminal anaerobe Fibrobacter (Bacteroides) succinogenes was measured using randomly tritiated cellobiose. When assayed at the same concentration (1 mM), total cellobiose uptake was one-fourth to one-third that of total glucose uptake. The abilities of F. succinogenes to transport cellobiose or glucose were not affected by the sugar on which the cells were grown. Aspects of the simultaneous transport of [14C(U)]glucose and [3H(G)]cellobiose, the failure of high concentrations of cold glucose to compete with hypothetical [3H(G)]glucose (derived externally from [3H(G)]cellobiose), and differential metal-ion stimulation of cellobiose transport indicate a cellobiose permease, rather than cellobiase plus glucose permease, was responsible for cellobiose transport. Glucose (10-fold molar excess) partially inhibited cellobiose transport. This was enhanced by prior incubation of the cells with glucose, suggesting subsequent metabolism of the glucose was responsible for the inhibition. Compounds interfering with electron transport or maintenance of transmembrane ion gradients inhibited cellobiose uptake, indicating that active transport rather than a phosphoenolpyruvate:phosphotransferase system catalyzed cellobiose transport. Na+, but not Li+, stimulated cellobiose transport.
Guanosine 5'-diphosphate :3-diphosphate (ppGpp) an(d gctanosine 5'-triphosphate 3-diphosphate (pppGpp) were detected in foirnic acid extracts of airexposed cultures of Bacteroa'(ls thetaiotaomicron. he irleintification of ppGpp and pppGpp in B. thetaiotaomicron was base(d On the following results: (i) cochrormatographv of P-labeledl hNperphosphor-vlatedl nucleotides in two different two-dimensional solvent systemis with authenitic pI)pGpp) anrlc pppGpp; (ii) incorporation of [ H]guanosine into the putative ppGp p andl ppjpGIpp (iii) alkalinie lability; and (iv) iesistance, to periodate oxidatioi. 1iheie was a imaikecl increase in the concentiation of ppGpp anrd pppGpp) after shift fiomn anaerobic to aerobic coinditions, andi accumulation of both ppG)pp ani(l pppGipp was blocked unrlcet these conditions by plrett'eatmient of the cultuie with rifampin oI tetiacycline. Growth and incorpotation of [ H]guanosine, [ H]thvmidine, [C Isutccinate, and L-[:;S]nmethiorline iInto nmac-romIolecules were inhibited immediately uI)pon exposure to air. The accumulation of ppGpp and pppGpp in thetaiotaonmicron upon exposure to air-may replresent a novel signal for synthesis (f these conipoundls. Meiimbers of the genus Bacteroides ate strictly anaerobic, gram-negative, non-sp)oreforming bacilli which constitute a large percentage of the total cultivable fecal microflora of animals including humans (12). Several studies have rethe cultUres Was m11eaISUre(l tusinig either a Klett-Sttntmersoni colorimeter (re(d filter) or a Bausch ani(d Lomb Spectronic 20 (660 nn10) LIsing test tubes 1:3 by 196 tnt))i.Radiolabeling of ppGpp and pppGpp. To label cultures of B. thetaiota(omticron undem atlaerohiC ((0t)-(litiorls, 2)))) /Wi of carrier-free [;'2 lorthophosphate (specific ra(lioactivity, 100 Ci/mg) was adcledi to culttore tcheS (1:3 by0 166 m) anI(d (rliecd uic(ler a streattl 950 on July 31, 2020 by guest
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