Prior to the implementation of any new technology, possible environmental and health repercussions first must be researched. Fullerenes are to be produced soon on an industrial scale, with applications quickly following. To investigate the possible environmental impact of fullerenes, a C60-water suspension (nano-C60) was synthesized and then evaluated for cell-association and toxicity, using the bacteria Escherichia coli and Bacillus subtilis as indicator species. In a defined low-salts medium, nano-C60 associated with both the Gram-negative E. coli and the Gram-positive B. subtilis, albeit more strongly with the former. Nano-C60 also displayed antimicrobial properties against both E. coli and B. subtilis, with minimal inhibitory concentrations of 0.5 to 1 mg/L and 1.5 to 3.0 mg/L, respectively. Media with higher salt contents result in the nano-C60 particles aggregating and falling out of suspension; thus, higher salt solutions reduced or eliminated the antimicrobial properties of nano-C60.