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

Abstract

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.