The endogenous respiration of Pseudomonas aeruginosa

A study of the endogenous respiration of the aerobic bacterium Pseudomonas aeruginosa was undertaken with a view to establishing the nature of the endogenous substrate and the relationship, if any, of the endogenous respiration to the oxidation of exogenous substrate. It was shown that the only end-products accumulating during endogenous respiration were ammonia and carbon dioxide. There were no detectable changes in the carbohydrate, lipid, nucleic acid or protein content of the cells during endogenous respiration. Inhibitor studies showed that protein was an endogenous substrate, and this was confirmed by the fact that after endogenous respiration succinate-grown cells required a slight induction period for succinate oxidation. Since keto-acids did not accumulate during endogenous respiration, the amino acids produced by protein degradation were probably oxidized to completion. Calculations based on this assumption showed that the ammonia production could account for all of the oxygen consumed. In the presence of an oxidizable substrate there was no production of ammonia. Manometric data showed that the endogenous respiration was not suppressed during the oxidation of an exogenous substrate. Inhibitor studies showed that oxidative assimilation involved the reassimilation of the ammonia produced by the endogenous respiration.Science, Faculty ofMicrobiology and Immunology, Department ofGraduat

Domains in microbial β-1,4-glycanases : sequence conservation, function and enzyme families

International audienc

The identification of the catalytic nucleophiles of two β-galactosidases from glycoside hydrolase family 35

International audienceThe beta-galactosidases from Xanthomonas manihotis (beta-Gal Xmn) and Bacillus circulans (beta-Gal-3 Bcir) are retaining glycosidases that hydrolyze glycosidic bonds through a double displacement mechanism involving a covalent glycosyl-enzyme intermediate. The mechanism-based inactivator 2,4-dinitrophenyl 2-deoxy-2-fluoro-beta-D-galactopyranoside was shown to inactivate beta-Gal Xmn and beta-Gal-3 Bcir through the accumulation of 2-deoxy-2-fluorogalactosyl enzyme intermediates with half lives of 40 and 625 h, respectively. Peptic digestion of these labeled enzymes and analysis by LC-MS identified Glu(260) and Glu(233) as the catalytic nucleophiles involved in the formation of the glycosyl-enzyme intermediate during catalysis by beta-Gal Xmn and beta-Gal-3 Bcir, respectively. These findings confirm the previous prediction of the position of these residues based on primary sequence similarities to other members of the glycoside hydrolase family 35

Visualization of the adsoption of a bacterial endo-β-1-4-glucanase and its isolated cellulose-binding domain to crystalline cellulose

International audienc

The adsorption of a bacterial cellulase and its two isolated domains to crystalline cellulose

International audienc

Isolation and characterization of Escherichia coli clones expressing cellulase genes from Cellulomonas fimi

NRC publication: Ye