The bacterial cell wall is essential for viability and mechanical stability, and is, therefore, the main target in antibiotic treatment. A thorough investigation and fundamental understanding of the cell wall and its main component, the peptidoglycan mesh surrounding the cell that is responsible for mechanical stability, is of utmost importance. In this work, the authors investigated the cell wall of Staphylococcus aureus and Bacillus subtilis in their native state using living bacteria and the isolated peptidoglycan (sacculi). For this purpose, the authors used Bruker’s NanoWizard 3 AFM in QI mode and the Dimension FastScan Bio in the Tapping and PeakForce Tapping Modes.
The intact bacterial surface showed a disordered peptidoglycan gel with large, deep pores. Investigation of the inner surface using bacterial sacculi revealed that the inner cell wall is much denser and shows differences in the architecture of the two species, being either disordered or circular depending on the location and whether it is in the “cylinder” or the division septa.
This study provides high-resolution information on the molecular architecture of the bacterial inner and outer cell walls in liquid, as opposed to traditional methods that are usually restricted to dry conditions.