Viability and phenotypic heterogeneity of Rhodococcus Rhodochrous CNMN-AC-05 in the presence of fullerene C60

Abstract

Introduction. In recent years, due to wide applications of nanotechnologies in various fields, the safety of nanomaterials has become a pressing issue. Fullerene C₆₀ is not an exception. Research on the activity of microorganisms and their interaction with nanoparticles is of major importance, both for microorganisms and for the ecosystem as a whole.

Material and methods. Fullerene C₆₀powder was purchased from Sigma-Aldrich. The object of study was R. rhodochrous CNMN-Ac-05 strain. The number of viable bacterial cells was estimated by colony-forming units (CFU). The morphological features of the rhodococci colonies have been described according to the usual microbiological method.

Results. It was established that fullerene C₆₀ in concentrations of 1-25 mg/L fullerene C₆₀ stimulated the growth of R. rhodochrous by 2.4-2.8 times. As the concentration of fullerene C₆₀ increased up to 50-100 mg/L, the multiplication and growth of rhodococci decreased by 29.5% and 38% respectively. In the presence of 1-10 mg/L fullerene C₆₀ the rhodococci population remained homogeneous, being composed of 100% S type colonies. The increase of fullerene C₆₀ concentration led both to the decrease in the CFU number and to the appearance of R type colonies, up to 1.3% of population.

Conclusions. Fullerene C₆₀ in concentrations 1-100 mg/L had no obvious toxic effect on the rhodococci strain. The optimum concentration is 10 mg/L. The concentrations higher than 25 mg/L led to the dissociation of rhodococcal population and diminution in the CFU counts, but not to the total inhibition.