Light microscopy

Light microscopy

In order to visualize small structures and samples of biological specimens at a cellular und subcellular level, light microscopy is a fundamental and versatile technique to answer our biogeochemical research questions. Our laboratories are equipped with several light microscopes, namely Olympus BX-61 and Zeiss Axiovert 40 CFL.

Beside conventional bright-field light microscopy, we are able to apply a set of contrast-enhancing techniques to image living cells and their fine structures with high magnification.

Phase contrast microscopy is a valuable tool to examine suspension culture cells, which barely absorb light and hence cannot be seen in bright-field or dark-field mode by the human eye. Minor phase shifts of the light passing through the specimen are converted into a change in the light intensity. By using phase contrast microscopy, we are able to observe e.g. physiological changes of plant cells upon exposure to potentially toxic metals and radionuclides.[1,2]

By using differential interference contrast microscopy (DIC), transparent biological objects appear as a shadow-cast or relief-like image to the observer. Two closely spaced parallel rays are generated and made to interfere after passing through an unstained sample, giving rise to high resolution images of the specimen.

Another often-employed microscopic technique is fluorescence microscopy, which allows the specific and sensitive staining of membranes, proteins or other molecules of interest. It helps us e.g. to differentiate between cellular compartments, between dead and alive cells (bacteria and archaea) and the presence or absence of stressors such as reactive oxygen species (ROS).

In dark-field illumination mode, direct light is bypassing the objective. Only light scattered by the specimen enters the objective, resulting in a dark background with bright objects of interest. In our laboratories, this illumination is commonly used to observe morphology and physiology of biological specimens.

All this enables us to use microscopic techniques to contribute to a molecular understanding of biogeochemical processes.

1. John, W. A., Lückel, B., Matschiavelli, N., Hübner, R., Matschi, S., Hoehenwarter, W., & Sachs, S. (2022) "Endocytosis is a significant contributor to uranium(VI) uptake in tobacco (Nicotiana tabacum) BY-2 cells in phosphate-deficient culture" Science of The Total Environment, 823, 153700. https://doi.org/10.1016/J.SCITOTENV.2022.153700
2. Klotzsche, M., Vogel, M., Sachs, S., Raff, J., Stumpf, T., Drobot, B., & Steudtner, R. (2023). "How tobacco (Nicotiana tabacum) BY-2 cells cope with Eu(III) – A microspectroscopic study" Analyst. https://doi.org/10.1039/D3AN00741C