The key lethal effect existed in the antibacterial behavior of short, medium, and long chain fatty acid monoglycerides on Escherichia coli

Abstract

Monoglyceride is an amphiphilic molecule with promising antimicrobial activity for bacteria; however, the key lethal effect in its antibacterial behavior was still unknown. In the study, monobutyrate (MB), monolaurate (ML), monomyristate (MM) were selected to represent the short, medium, and long chain monoglycerides to compare their inhibitory effect against Escherichia coli, and a new dose-dependent inhibitory mechanism was proposed by the key lethal effect. The minimal inhibitory concentration and antibacterial curve showed a huge diversity existed in biology activity of MB, ML and MM. The results in scanning electron microscopy and flow cytometry assay indicated that the interference level of MB on cell membrane was obviously weaker than that of ML and MM, while the latter two had similar performance in increasing cell permeability at low doses. The results presented in UV-Vis spectroscopy, cell cycle and biomacromolecules synthesis inhibition assay showed that the cell cycle of Escherichia coli was obviously affected by three monoglycerides at doses near MIC, which was therefore regarded as the key lethal effect. The reason for the better biological activity of MM than ML was the stronger interference ability on bacterial cell cycle. In addition, an expanded antibacterial mode was raised that cell permeability increase at low doses was antimicrobial basis, cell cycle arrest at medium doses played the key lethal effect, and cell lysis at high doses was the result of combined action.