Psychrotolerant hydrocarbon-degrading Rhodococcus strains isolated from polluted Antarctic soils

Abstract

Three hydrocarbon-degrading Rhodococcus strains isolated from polluted Antarctic soils proved to be closely related despite their different origins. Strains had a similar hydrocarbon degradation pattern and optimum growth temperature ranged between 25ºC and 30ºC, showing that strains are psychrotolerant but not psychrophiles. Specific growth rate on rich media ranged between 0.12 and 0.21 h−1, higher than those observed on hydrocarbons as carbon source. Results suggest that in Antarctic contaminated soils, closely related Rhodococcus strains are present and could play an important role in decontamination. Microcosm systems showed that, although the natural microflora respond significantly to the pollutants, bioaugmentation with Rhodococcus strain (ADH), improved biodegradation either alone or mixed with a hydrocarbon-degrading Acinetobacter strain. In comparison with microcosm where only ADH was inoculated, a non-significant decrease in hydrocarbon concentration was observed when ADH was inoculated as mixed culture with a previously tested strain. Pollutants dramatically reduced bacterial groups in soils resulting in a dominance of Pseudomonas. Microcosms showed that when natural microflora has no previous history of exposure to the pollutants, bioaugmentation with autochthonous strains improves degradation of the contaminants. The positive response of the native bacteria to the pollutants leaves the question open as to whether bioaugmentation is necessary when soils have a long previous exposure to hydrocarbons.

Mrakia psychrophila sp. nov., a new species isolated from Antarctic soil

“…Psychrophilic yeasts are very important due to their physiological adaptation and contributions to soil fertility, and they also have potential application in biotechnology. Ruberto et al(2005) isolated some Rhodococcus strains having the ability to degrade hydrocarbon at low temperature. Cold active enzymes from psychrophilic yeasts can be applied to the food industry, for clarification of fruit juice and other fields at low temperature.…”

Diversity of culturable marine bacteria on the coastline of the central area of San Jorge Gulf, Argentina

“…Other hydrocarbon degrading bacteria found were Rhodococcus, which have a greater capacity to survive in adverse conditions, are able to use different hydrocarbon and have catabolic versatility (Whyte et al 1999, Ruberto et al 2005. Besides, Rhodococcus is the most common genus of Nocardiacea recovered from marine sediment (Gontang et al 2007).…”

Diversidad de bacterias cultivables con capacidad de degradar hidrocarburos de la playa de Caleta Córdova, Argentina

“…Shewanella ha sido estudiada en la última década en los procesos de biorremediación por poseer un importante rol en el cometabolismo de compuestos halogenados y del petróleo, también por su capacidad de reducir el magnesio y el óxido de hierro, como por su habilidad de producir ácidos grasos poliinsaturados (Ron et al 2002), situación poco común en bacterias. Otro género encontrado fue Rhodococcus, que posee la capacidad de utilizar diversos hidrocarburos por su enorme versatilidad catabólica (Larkin et al 1999, Ruberto et al 2005, Seto et al 1995, Whyte et al 1999). …”