Effects of cell structure of gram-positive and gram-negative bacteria based on their dielectric properties

Current procedures for the identification and characterization of microorganisms are based on complex and time-consuming protocols. Here, we hypothesize that the distinct cellular composition of microorganisms could be identified by dielectric spectroscopy. Gram-positive and Gram-negative bacterial strain permittivity measurement was performed using a network analyzer and a coaxial probe in the frequency range from 50 MHz to 300 MHz. All bacterial strains in suspension demonstrated correlation between cell count and permittivity values during the growth phase. When determining isolated cell pellets, a clear discrimination between Gram-positive and Gram-negative strains was possible in a frequency range between 50 MHz and 100 MHz. Our data clearly show that dielectric spectroscopy is able to obsess the growth kinetics and to identify the Gram-status of bacterial strains. In future this simple method could be used for biomedical diagnostics of infections.