Metabolisme carbone et energetique des Pseudomonas spp fluorescents saprophytes oxydase positive

Abstract

Saprophytic fluorescent Pseudomonas spp constitute an oxidase-positive group, including the species P chlororaphis, P fluorescens and P putida, which are common in the environment. Among these three species, some strains improve the plant growth and health and consequently are useful in agriculture. These beneficial effects are ascribed to the production of secondary metabolites (antibiotics, siderophores, phytohormones) and their synthesis is affected by the basal metabolism of the bacteria. Fluorescent pseudomonads are also implicated in the conservation of the environment. Their carbon and energy metabolism is indeed responsible for nitrate dissimilation and the degradation of xenobiotic compounds. The catabolic pathways of the main sugars, organic acids and amino acids, as well as the respiratory pathways twined to this catabolism, are presented in the present review. The use of carbohydrates is characterized by the extracellular oxidation of glucose and the prevalence of the Entner-Doudoroff pathway. The catabolism of organic and amino acids is linked to the cycles of Krebs and of the glyoxylate which play a major role in the metabolism of the bacteria. Except for arginine, the utilization of the studied compounds is only possible in the presence of oxygen or nitrogen oxides. The metabolic diversity of fluorescent Pseudomonas spp gives to these bacteria a great ability to adapt to various environments, such as the soil and the rhizosphere.