Physiological cellular responses and adaptations of Rhodococcus erythropolis IBBPo1 to toxic organic solvents.

A new Gram-positive bacterium, Rhodococcus erythropolis IBBPo1 (KF059972.1) was isolated from a crude oil-contaminated soil sample by enrichment culture method. R. erythropolis IBBPo1 was able to tolerate a wide range of toxic compounds, such as antibiotics (800-1000μg/mL), synthetic surfactants (50-200μg/mL), and organic solvents (40%-100%). R. erythropolis IBBPo1 showed good tolerance to both alkanes (cyclohexane, n-hexane, n-decane) and aromatics (toluene, styrene, ethylbenzene) with logPOW (logarithm of the partition coefficient of the solvent in octanol-water mixture) values between 2.64 and 5.98. However, alkanes were less toxic for R. erythropolis IBBPo1 cells, compared with aromatics. The high organic solvent tolerance of R. erythropolis IBBPo1 could be due to the presence in their large genome of some catabolic (alkB, alkB1, todC1, todM, xylM), transporter (HAE1) and trehalose-6-phosphate synthase (otsA1, KF059973.1) genes. Numerous and complex physiological cellular responses and adaptations involved in organic solvent tolerance were revealed in R. erythropolis IBBPo1 cells exposed 1 and 24hr to 1% organic solvents. R. erythropolis IBBPo1 cells adapt to 1% organic solvents by changing surface hydrophobicity, morphology and their metabolic fingerprinting. Considerable modifications in otsA1 gene sequence were also observed in cells exposed to organic solvents (except ethylbenzene).