Transcriptomic analysis of the dual response of Rhodococcus aetherivorans BCP1 to inorganic arsenic oxyanions

Bacterial strains belonging to the genus Rhodococcus are capable to degrade various toxic organic compounds and tolerate high concentrations of metal(loid)s. We have previously shown that R. aetherivorans BCP1 is resistant to various levels of the two arsenic inorganic species, arsenite [As(III)] and arsenate [As(V)]. However, while arsenite showed toxic effects as early as 5 mM, arsenate at 30 mM even boosted the growth rate of BCP1 cells and was only toxic at concentrations > 100 mM. Since such behavior could be linked to peculiar aspects of its metabolism, the transcriptomic analysis of BCP1 cells exposed to 5 mM As(III) and 30 mM As(V), was performed in this work. The aim was to clarify the mechanisms underlying the arsenic stress response of the two growth phenotypes in the presence of the two different oxyanions. The results revealed that As(III) induced higher activity of ROS-scavenging enzymes as compared to As(V) in relation with the expression of enzymes involved in cellular damage recovery and redox buffers/cofactors (ergothioneine, mycofactocin and mycothiol). Further, As(III) downregulated pathways related to cell division while both oxyanions downregulated genes involved in glycolysis. Notably, As(V) induced the expression of enzymes participating in the synthesis of metallophores and rearranged the central and energetic metabolism, also inducing alternative pathways for ATP synthesis and glucose consumption. This study, in providing the transcriptomic data on R. aetherivorans exposed to arsenic oxyanions, sheds some light on the plasticity of rhodococcal response to arsenic stress, which may be important for the improvement of biotechnological applications.