Comparable antibacterial effects and action mechanisms of ethyl cyanoacrylate nanoparticles on Bacillus subtilis and Escherichia coli evaluated by transcriptome and morphological changes

We previously demonstrated that ethyl cyanoacrylate nanoparticles (ECA-NPs) inhibit the growth specific rate of B. subtilis and E. coli under culture conditions, indicating their antibacterial effect. Exposure to ECA-NPs increased levels of reactive oxygen species (ROS), which induced oxidative stress, resulting in cellular dysfunction. Here, we report a possible mechanism by which ECA-NPs act on the response of both bacteria to ECA-NPs by evaluating their transcriptome and morphological changes. The results revealed that B. subtilis and E. coli responded to ECA-NPs using different mechanisms. Unlike wild-type (WT) strains, E. coli strains lacking RecA, an essential protein for SOS response, exhibited less sensitivity to ECA-NPs. Moreover, as oxidative damage worsened, a loss of cell membrane integrity is triggered, accompanied by phosphatidylserine (PS) externalization that resembles the hallmarks of eukaryotic apoptosis. Taken together, apoptosis-like death (ALD) is induced in E. coli by ROS generation through the presence of ECA-NPs. Meanwhile, ECA-NP-treated B. subtilis cells undergo necrosis rather than apoptosis, which is further supported by the results of annexin V/propidium iodide (PI) analysis.