Melibiose

About: Melibiose is a research topic. Over the lifetime, 1002 publications have been published within this topic receiving 27300 citations. The topic is also known as: Melibiose.

Studies on Induction and Repression in Activated Sludge Systems.

Abstract: Both repression and induction of substrate utilization have been the subject of many basic research investigations employing pure cultures. In this investigation these effects were studied using heterogeneous microbial populations prevalent in such biological treatment processes as activated sludge systems. Diauxic substrate removal by activated sludge was observed in a multicomponent medium consisting of glucose and sorbitol. The sludge was acclimated solely to sorbitol; however, the presence of glucose blocked sorbitol removal until glucose was completely utilized. Both diphasic and triphasic oxygen utilization was shown for activated sludges metabolizing multicomponent synthetic wastes consisting of glucose, melibiose, and lactose. It appears from these studies that melibiose utilization was suppressed by the presence of glucose and, although melibiose induced acclimation to lactose, the presence of melibose suppressed lactose utilization. Studies were also conducted using glycogen and starch systems in which it was found that acclimation to either compound conferred immediate acclimation to the other. It was also found that loss of acclimation to lactose was a passive phenomenon and its kinetics could be predicted on the basis of simple diluting out of the enzyme(s) responsible for such acclimation.

Transgalactosylation Catalyzed by α-Galactosidase from Candida guilliermondii H-404

Abstract: The thermostable α-galactosidase from Candida guilliermondii H-404 synthesized self-transfer products in the absence of a suitable acceptor. The main self-transfer product, using melibiose as a donor substrate, was O-α-D-galactosyl-(1,6)-O-α-D-galactosyl-(1,6)-D-glucose. This enzyme had a wide acceptor specificity. D-Glucose, D-galactose, maltose, maltitol, and 1,4-butandiol were the most effective acceptors in the transgalactosylation catalyzed by this enzyme. The enzyme could also transfer α-galactosyl residues to pentoses (L-arabinose, D-xylose, and D-ribose) and methyl pentoses (D-fucose and L-rhamnose). The main transfer products to lactose, maltose, and sucrose as acceptors were identified as O-α-D-galactosyl-(1,6)-O-β-D-galactosyl-(1,4)-D-glucose, O-α-D-galactosyl-(1,6)-O-α-D-glucosyl-(1,4)-D-glucose, and O-α-D-galactosyl-(1,6)-O-α-D-glucosyl-(1,2)-β-D-fructoside (raffinose), respectively.

Lactobacillus hordniae, a New Species from the Leafhopper (Hordnia circellata)

Abstract: A gram-positive, rod-shaped bacterium, originally thought by Auger (1974) to be the agent of Pierce's disease of grapevines, is commonly associated with Hordnia circellata, one of the leafhopper vectors of the disease. The bacterium has the following colonial and cellular characteristics: smooth, glistening white, or chalky colonies, 0.4 to 0.5 mm in diameter with entire margins; gram positive becoming gram variable after 5 days in culture; nonmotile and nonsporeforming; grows between 15 and 37°C with an optimum between 28 and 30°C and no growth at 9 or 45°C; optimum growth occurs at pH 6.5, with growth observed at pH 4.5 and pH 9.0. The bacterium does not survive after 5 to 7 days of growth and must be maintained on fresh medium. It is rod-shaped (0.6 by 1.5 to 2.0 μm), growing in short chains of three to four cells each, and possesses mesosomes and a cell wall of uniform thickness (28 to 35 nm) that consists of an electrondense outer layer and an inner layer resembling unit-membrane structure. The organism is a facultative anaerobe which reacts negatively in tests for cytochrome oxidase, catalase, “gelatinase,” urease, tryptophanase, and nitrate and disulfide reductase activities. No dextran or levan is produced from sucrose. It produces L-(+)-lactic acid but not D-(—)-lactic acid from glucose and sucrose fermentation, acetylmethylcarbinol, or arginine deaminase. Glucose, sucrose, galactose, maltose, fructose, trehalose, salicin, inulin, and cellobiose, but not gluconate, lactose, mannose, mannitol, sorbitol, melibiose, or raffinose, were utilized as carbon sources. Its chromosome has an average guanine-plus-cytosine content of 32.75 mol%. Based on these features, the bacterium appears to be a hitherto unrecognized species of the genus Lactobacillus, for which the name Lactobacillus hordniae sp. nov. is proposed. The type strain is HC-1 (= ATCC 29071).

Cloning and expression of the multiple sugar metabolism (msm) operon of Streptococcus mutans in heterologous streptococcal hosts.

Abstract: The multiple sugar metabolism (msm) operon of Streptococcus mutans is responsible for the uptake and metabolism of a variety of sugars. In order to further characterize the substrate specificities of the transport system, a 12-kb region of DNA containing the entire msm operon was cloned, via a novel two-step integration strategy, into the chromosomes of two heterologous streptococcal strains, Streptococcus gordonii Challis and Streptococcus anginosus Is57, as well as the chromosome of a natural isolate of S. mutans with a deletion of the msm region. These strains are unable to transport or ferment melibiose, raffinose, or isomaltosaccharides, but the newly constructed recombinants gained the ability to ferment all of these sugars. The S. gordonii Challis construct containing msm was shown to transport radiolabelled melibiose, raffinose, isomaltotriose, and isomaltotetraose, and the transport function was also subjected to induction by raffinose, an inducer of the msm operon in S. mutans. The results confirm the role of the msm operon in the transport and metabolism of melibiose, raffinose, and isomaltosaccharides.