Contrasting responses of marine bacterial strains exposed to carboxylated single-walled carbon nanotubes.

•The potential toxic effects of functionalized (COOH) single-walled carbon nanotubes (SWNTs) were investigated on the cell growth and viability of several Gram-negative marine bacterial strains.•Different sensitivity levels of marine bacterial strains toward SWNT-COOH exposure.•Higher toxicity of SWNT-COOH toward dispersed bacteria cells.•The relative expression of some functional genes involved in stress responses suggests that the oxidative stress response is the main toxicity mechanism of SWNT-COOH.