Metabolic Diversity and Flexibility for Hydrocarbon Biodegradation by Rhodococcus

ALVAREZ HM; SILVA RA

Actinobacteria Application in Bioremediation and Production of Industrial Enzymes

CRC Press Taylor & Francis Group

Lugar: Boca Ratón; Año: 2012; p. 241 - 273

Rhodococcus are metabolically versatile actinobacteria frequently found in the environment. These microorganisms have been considered excellent candidates for bioremediation of contaminated environments for different reasons. The metabolism of rhodococci has evolved to adapt to a wide diversity of carbon sources. The large genomes of diverse Rhodococcus species contain a multiplicity of catabolic genes, which reflects the wide degradation capabilities of these microorganisms. Members of this genus are able to degrade lineal and branched alkanes, monaromatic and polyaromatic hydrocarbons, nitrogenated and chlorinated compounds, among others. In addition, they are endowed with a robust, diverse and flexible metabolism, which is necessary for metabolically adapting to environments with fluctuating nutritional conditions. In general, Rhodococcus bacteria seems to have a low energy life style showing a relative slow growth even when nutrients are available. They seem to posses the ability to conserve metabolic useful energy during catabolism of substrates, thus, a part of the resulting energy can be used for growth and division, and the surplus is channeled into energy storage pathways. In this context, most Rhodococcus are able to accumulate variable amounts of triacylglycerols (TAG). Starvation experiments demonstrated that some Rhodococcus strains possess specialized mechanisms for turning metabolism down when nutrients are in short supply or when cells are subjected to other stress conditions that normally occur in arid soils. During nitrogen starvation and high C:N rates, as occur during an oil spill in arid soil, cells are able to reduce their metabolic activity and their ability of mineralize the carbon source, but increase significantly the biosynthesis and accumulation of TAG. This process permits a continuous degradation of the carbon sources (environmental pollutants) still under unbalanced nutritional conditions as are found in the environment. This article aims to discuss the metabolic diversity of rhodococci for degrading a wide range of pollutants and the metabolic flexibility for degrading pollutants under nutritional fluctuating conditions.