A cellulolytic bacterium, identified as belonging to the genus Cellulumonas, produced two classes of cellulases when grown in the presence of cellulose. One class comprised enzymes which were tightly bound to cellulose, and the other, enzymes which were found free in the culture supernatant fluid. The cellulose-bound activity reached a maximum at the beginning of the stationary phase and then decreased, whereas the soluble activity increased to a plateau late in the stationary phase. The production of both classes of enzyme was repressed by adding cellobiose or glycerol to the cellulose. Deprivation of carbon sources did not induce cellulolytic activity. Cellobiose and sophorose showed only weak inducing activity in the absence of cellulose. I N T R O D U C T I O NThe macromolecular and insoluble nature of cellulose suggests that it is degraded extracellularly by micro-organisms. The regulation of cellulase production by cellulolytic organisms must, therefore, occur without direct interaction between the substrate and intracellular effector molecules. Furthermore, the production of cellulases may be controlled at the level of secretion besides the more orthodox methods of control. Such control has been reported for Cellvibrio fulvus (Berg, In the present work, a bacterium identified as a member of the genus Cellulomonas was found to produce two groups of extracellular cellulases, one group binding to cellulose and the other remaining free in the culture supernatant fluid. The production and regulation of production of these cellulases has been investigated by testing the effects of cellulose powder (a macromolecular substrate), cellobiose (a disaccharide derived from cellulose). glycerol (a readily-assimilated substrate, not related to cellulose) and acetate (a substrate * Present address :I
Sixty-four ampicillin-resistant strains of Escherichia coli were studied. Six characters were examined: (i) resistance to ampicillin, cephalothin, and carbenicillin, (ii) synergy between ampicillin and cloxacillin, (iii) level of,-lactamase activity after osmotic shock, (iv) transferability of ampicillin resistance, (v) immunological characterization of the enzyme, and (vi) determination of substrate profiles. One class of strains was found in which synthesis of ,B-lactamase is inferred to be plasmid mediated; these strains are highly resistant to ampicillin and carbenicillin, sensitive to cephalothin, do not show synergism between ampicillin and cloxacillin, and reveal a high enzymatic activity after osmotic shock. A second class is formed by strains for which ,-lactamase synthesis is inferred to be chromosomal; these strains present a low resistance level to ampicillin, are sensitive to carbenicillin and resistant to cephalothin, show a synergism between ampicillin and cloxacillin, and reveal a very low enzymatic activity after osmotic shock. These characters may be used to differentiate periplasmic and cell-bound /-lactamases.
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