Effect of single-walled carbon nanotubes on Bacillus anthracis cell growth, sporulation, and spore germination

In this study, the effect of single-walled carbon nanotubes (SWCNTs) on B. anthracis cell growth, spore formation, and spore germination was studied. We found that SWCNTs at a concentration of 100 microg/ml exhibited obvious antimicrobial activity on 10(6) cfu/ml B. anthracis cells. At 300 microg/ml, 1 h of SWCNTs treatment could inactivate B. anthracis cells by approximately 2 log viable cell reduction. The SWCNT treatment did not induce spore formation. We also found that SWCNTs were not effective in the inactivation of B. anthracis spores at concentrations from 50 microg/ml up to 300 microg/ml. Fluorescence microscopy and scanning electron microscopy were used to examine the interactions between SWCNTs and B. anthracis cells/spores. Analysis of these microscopic images suggested that the direct contact between SWCNTs and B. anthracis cells lead to cell membrane damage and the inactivation of cells, whereas the lack of tight direct contact between SWCNTs and spores was the reason accounting for its ineffectiveness in inactivating spores.