Atomic Force Microscopy of Bacillus subtilis

Abstract

Nanotechnology and especially nanobiotechnology are continuously growing fields. The investigation of living samples and biological processes provides new approaches for developing applications and devices in biology and health care. Working on a nanobiotechnological level is a very delicate issue, considering imaging and sample preparation techniques and one will soon reach the technical limits of nanotechnological investigation methods.<br />Within this thesis the Atomic Force Microscope proved to be a powerful tool for nanobiotechnological investigations on Bacillus subtilis.<br />Bacillus subtilis is a single- celled bacterium, which has the ability to sporulate and thereby survives extreme environmental conditions.<br />Bacillius subtilis is not harmful to human health and its spores, which are extremely resistant to environmental influences, serve as safe model organisms for pathogenic microorganisms in water hygiene. Bacillus subtilis is used to evaluate water disinfection devices using ultraviolet radiation. By inducing adverse environmental conditions to living Bacillus subtilis cells the sporulation process is successfully initiated and the different morphological stages are - for the first time ever - imaged using AFM techniques. Two different types of spores due to the different methods of inducing the sporulation are investigated. One type of spores is resistant to UV-radiation whereas the other type is very sensitive to UV-radiation. The different types are investigated by Force Mapping techniques using the AFM and the cell surface properties are finally compared. Our investigations revealed that UV-sensitive Bacillus subtilis spores are softer when measuring the indentation depth of the cantilever tip at a preset trigger force whereas the UV-resistant spores show a lower indentation depth compared to the UV-sensitive spores using the same force.<br />