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Escherichia coli cannot grow on L-lyxose, a pentose analog of the 6-deoxyhexose L-rhamnose, which supports the growth of this and other enteric bacteria. L-Rhamnose is metabolized in E. coli by a system that consists of a rhamnose permease, rhamnose isomerase, rhamnulose kinase, and rhamnulose-1-phosphate aldolase, which yields the degradation products(More)
Methylammonium is a substrate for the ammonium transport system of Azotobacter vinelandii. During cellular uptake methylammonium is rapidly converted to a less polar metabolite (E. M. Barnes, Jr., and P. Zimniak, J. Bacteriol. 146:512-516, 1981). This metabolite has been isolated from A. vinelandii and identified as gamma-glutamylmethylamide by mass(More)
Ammonium and methylammonium are rapidly taken up by cultures of Azotobacter vinelandii respiring in the presence of succinate. The rate of methylamine uptake increased with external pH from 5.5 to 7.5 but increasing the pH further to 8.5 had little effect on activity, indicating that methylammonium cation rather than uncharged methylamine is the permeant(More)
The effect of exogenous unsaturated fatty acids on the fatty acid composition of phospholipids of a mutant of E. coli has been examined. These exogenous acids serve as growth factors for an auxotroph requiring unsaturated fatty acids. When each member of a structurally homologous series of cis-unsaturated fatty acids serves as a growth factor, the(More)
The energetics of ammonium ion transport by Escherichia coli have been studied using [14C]methylammonium as a substrate. Rapid assays for uptake allowed kinetic parameters (CH3NH3+ Km = 36 microM; Vmax = 4 nmol X s-1 X mg-1 to be determined in the absence of CH3NH3+ metabolism. Cells cultured in media containing 1 mM NH4+ failed to express CH3NH3+ transport(More)
Thirty-two different types of anaerobic bacteria isolated from chickens have been tested for anti-salmonella activity in vitro. Under the conditions of the test only Bacteroides hypermegas and a Bifidobacterium sp. were shown to inhibit the salmonellas and this was attributed to the production of volatile fatty acids (VFA's) coupled with a low pH. When(More)
1. gamma-Aminobutyric acid (GABA) (10-500 microM) was applied to cultured chick cerebral neurons by pressure ejection, and the resulting currents (IGABA) were recorded using standard whole-cell voltage-clamp techniques. Plots of the peak IGABA as a function of membrane potential were nonlinear with an outwardly rectifying appearance. 2. IGABA decayed during(More)
  • E M Barnes
  • 1996
Prolonged occupancy of GABAA receptors by ligands, including GABA and benzodiazepine agonists, sets in motion a series of mechanisms that can be termed use-dependent regulation. These mechanisms can be subdivided into two distinct pathways, one for GABAA receptor downregulation and another for upregulation. Treatment of cortical neurons with GABA or(More)