Jean-Pierre Chambost

Construction of a genomic library of Erwinia chrysanthemi and molecular cloning of cellulase gene

SummaryA genomic library of Erwinia chrysanthemi has been constructed using cosmid pMMB34 as the cloning vector. Among 1,500 clones many Erwinia markers have been found. One of the 9 recombinant cosmids carrying a structural gene for endo-β-1,4-glucanase, cel, was studied: after subcloning and restriction analysis, a physical map of the 10 kb insert is given and the location of the cel gene is proposed.

Characterization and partial purification of a branching enzyme from Escherichiacoli

Abstract Under conditions of growth limitation by either nitrogen or sulfur, Escherichia coli and Aerobacter aerogenes accumulate, in the presence of excess glucose, large intracellular amounts of a highly branched glycogen closely similar to animal and yeast glycogens ( Segel et al ., 1965 ; Sigal et al ., 1964 ). The (1 → 4) α-D-glycosidic linkages of this bacterial glycogen are formed in the presence of a primer by an ADP-glucose-transglucosylase which has only a very low activity with UDP-glucose as glucosyl donor ( Greenberg and Preiss, 1964 ). This finding is in agreement with the previous observation ( Sigal et al ., 1964 ) that normal or even larger amounts of glycogen are accumulated by UDPG-pyrophosphorylase negative mutants of E . coli . The present paper reports the isolation from E. coli and partial purification of a branching enzyme, or amylo-1,4 → 1,6-transglucosidase (systematic name: α-1,4 glucan: α-1,4 glucan, 6-glycosyl-transferase, EC 2.4.1.18). Found in plants, animal tissues and yeast, this enzyme had been little studied in bacteria, its presence being only reported in crude dialyzed extracts of Arthrobacter globiformis ( Zevenhuizen, 1964 ). The branching enzyme from E . coli is active with both amylose and amylopectin, and has been separated from an amylolytic enzyme producing reducing sugars from the same substrates.

Unprimed glucan biosynthesis by a particulate ADP-glucose-glucan glucosyl transferase from an Escherichia coli mutant and its stimulation by a protein factor

Summary A particulate fraction of an E. coli mutant catalyses the transfert of glucose from ADP-glucose to glycogen but also to a methanol-insoluble product in the absence of primer. The last reaction requires the presence of albumin and either high concentrations of salts or a protein factor. This factor is present in the 158,000 x g supernatant of DF 2000 mutant and in the extracts of mutants lacking glycogen synthase.

Light Effects on α-amylase Activity and Carbohydrate Content in Relation to Lipid Mobilization during the Seedling Growth of Sunflower

The changes in α-amylase activity and in starch and free sugar content were investigated in correlation with lipid mobilization inHelianthus annuus during the first 15 days of seedling growth in discontinuous light and in darkness. Throughout the seedling development α-amylase activity increased more significantly in light than in darkness. It was always lower in cotyledons than in other tissues of the embryo axis. In both culture conditions, most of the transitory carbohydrates accumulated in germinating cotyledons were very likely synthesized by gluconeogenesis from the stored lipid breakdown. Nevertheless, in light-grown cotyledons, photosynthesis contributes to increase the carbohydrate levels. The study of several soluble sugars indicates that 1) sucrose stored in cotyledons of mature seeds was used at the onset of seedling growth, more rapidly in light than in darkness, 2) galactose and xylose, both involved as precursors of some cell-wall polysaccharides, remained at a very low level throughout the 15 days and 3) glucose, fructose and maltose accumulated in old etiolated cotyledons in contrast to what occurred in the light.

Assimilation in Soft Rot Erwinias: Cellobiose Pathway

The main product of cellulose degradation by Erwinia chrysanthemi is a β-glucoside: cellobiose. In most organisms its utilization has been studied in conjunction with that of two aryl β-glucosides, arbutin and salicin, which share with cellobiose the peculiarity to yield glucose as the only sugar after hydrolysis. Since the endo- and exocellulases which break cellulose down are operating outside the cell, the produced cellobiose must be taken into the cell.