Study on phospholipids in diverse Rhodococcus species

PELICON P; SILVA RA; ALVAREZ HM

Mar del Plata

Congreso; VIII Congreso Argentino de Microbiologia General (SAMIGE); 2012

Sociedad Argentina de Microbiología General (SAMIGE)

Rhodococcus bacteria are able to accumulate significant amounts of triacylglycerols (TAG). This process has been extensively studied in rhodococci during last years. Although phospholipids (PL) share common biosynthesis pathways with TAG, very little is known about such lipids in the genus. Variations of PL residues permit cells to control the fluidity and functionality of cellular membranes under different environmental conditions. The aim of this study was to characterize the major PL species occurring in different Rhodococcus species, and to analyze the modification of PL composition when the temperature for cell incubation is decreased. A detailed bioinformatic analysis using the available genomic databases was performed. PL species were analyzed by diverse mono- and bidimensional chromatographic techniques, using different supports, developers and standards. Specific reactions to determine sugars and phosphorous were performed. Bioinformatic analyses of complete genome sequences of five Rhodococcus species showed high redundancy and inter-specie variability of genes involved in TAG metabolism, in contrast to that observed for PL metabolism genes. All rhododoccal strains grew at 5 °C but showed retarded growth compared with R. erythropolis, which grew quickly. Chemical analyses of lipid extracts revealed, in general, similar composition of PL species in cells of R. jostii, R. opacus, R. fascians and R. erythropolis during cultivation on gluconate at 28 °C. Phosphatidylglycerol was the main PL in all strains, whereas phosphatidylethanolamine, cardiolipin, phosphatidylinositol and a variety of phosphatidylserines were also observed. PL profiles did not change significantly when the incubation temperature was decreased to 10 °C, although a slight decrease of phosphatidylglycerol in most strains was detected. This effect was particularly observed in R. erythropolis DSM43060. This strain produced at low temperatures high amounts of a compound identified as a glycodiacylglycerol (Rf 0.8), composed by 1,3-diacylglycerol and glucose molecules. Results showed that PL biosynthesis pathways are conserved among rhodococci, with low variability and redundancy of involved genes. Only slight variations of PL species occur in rhodococcal cells when the incubation temperature was decreased from 28 to 10 °C. The biosynthesis of glycodiacylglycerols, which may stabilize lipid membranes, could contribute to the rapid adaptation of R. erythropolis to low temperatures.