Application of Mach-Zehnder transmitted light interference microscopy in biology

Application of Mach-Zehnder transmitted light interference microscopy in biology

 Dr. Joachim Jahnke, Prof. Dr. Ursula B. Priefer

In the beginning of 2006 Daniel Mahlmann (Dipl.-Phys.) from the Institute for Technologies of Optical Systems at RWTH Aachen University developed the concept of an automatic Mach-Zehnder microscope-interferometer. Since 2007 the Unit of Soil Ecology is user of a partly computerised automatic Mach-Zehnder interference microscope for transmitted light on basis of an instrument made by LEITZ in the 19sixties. The adapted documentation and evaluation software was continuously be optimized.

An absolute advantage of this method is the possibility to show the distribution of optical density in selected single, living cells of many e. g. algal species. That can be done rapidly without staining the cells. The cellular dry mass can be calculated within a few minutes. Changes of mass density distribution or cellular dry weight of single, living cells dependent on e. g. environmental factors can be followed over a long lasting time span.

The actual emphases of our research using the interference microscopy are

1. The analysis of biomass distribution within algal dominated biofilms growing on soil surfaces.

2. The dependence of biomass (calculated as cellular dry weight unit biovolume) of single, living algal cells on specific growth conditions (temperature, light, nutrient limitation, soil properties etc).

Figures taken with the Mach-Zehnder microscope show 1. Brightfield: a natural biofilm build up on a slide showing bundles of cyanobacterial trichomes (Microcoleus) within their own EPS (single trichoms are ca 6 µm in diameter. 2. The same object shown in figure 1 adjusted to a homogeneous field of interference.3. Brightfield images of phytoplankton species and the corresponding plotted images. Values of dry weight (dw) per unit biovolume are given.