Rhodococcus sp. A5, a UV-resistant actinobacterium isolated from High-Altitude Andean Lakes able to accumulate storage lipids

ALBARRACÍN V.H.; BEQUER-URBANO S.; ALVAREZ H.M.; GÄRTNER W.; FARIAS M.E.

Puerto Vallarta

Simposio; 16TH INTERNATIONAL SYMPOSIUM ON THE BIOLOGY OF ACTINOMYCETES; 2011

ISBA Board

The genus Rhodococcus comprises a group of non-motile, non-sporulating, aerobic Gram-positive filamentous rods within the Actinobacteria Class with potential applications in bioremediation and as microbial biocatalyst. Nevertheless, there is little information on the biology of Rhodococcus strains isolated from extreme environments which, otherwise, hide an important biotechnological potential. In the course of sampling expeditions, we have isolated a highly UV-B resistant actinobacterium strain belonging to the genus Rhodococcus from the extreme ecosystem of High-Altitude Andean Lakes (HAAL, between 3,000 and 6,000 m asl) at the northwest part of Argentina; its complete description, UV-resistance profile and ability to accumulate storage lipids, are herein presented. Strain A5, previously isolated from freshwater of Lake Azul (4,560 m asl), was subjected to taxonomical identification using phenotypic and genotypic data. 16S rDNA sequencing revealed a 99.4% of identity with the corresponding sequence of Rhodococcus corynebacterioides DSM 20151(T). This strain was further used for comparison. UV-resistance assays made in agar and liquid media exposing the strains to increasing doses of UV-B irradiation showed that DSM 20151(T) was more sensitive to UV than the HAAL strain which was able to grow even after 60 min of continuous irradiation. Strains A5 and DSM 20151(T) were both able to synthesize and accumulate triacylglycerols (TAG) during cultivation of cells on glucose and hexadecane under nitrogen-starvation conditions. For strain A5, TAG amounted up to 17% and 32% (CDW) whereas cells of strain DSM 20151(T) accumulated 9% and 18% (CDW) of TAG after cultivation on glucose and hexadecane, respectively. The ability of UV- resistant Rhodococcus sp. A5 to accumulate storage lipids may permit cells to rapidly respond to nutritional stress and to maintain active its metabolism under fluctuating conditions as the ones impairing at the HAAL.