Microbial mats are macroscopically visible communities of microorganisms, which play an important role for the interaction of microorganisms with their environment [1]. Important examples are mats dominated by Fe(II)-oxidizing bacteria, which are typically found in wet, Fe(II)-rich environments such as lake sediments and mine tunnels [2,3].
The microscopic constituents of microbial mats can be analyzed using 2D microscopy approaches such as SEM. Other properties such as the microbial community and elemental composition are accessible using bulk analytical methods [e.g. 3]. However, little is known about the 3-dimensional structure of these mats.
Samples of two microbial mats from an abandoned mine tunnel were analyzed by FIB/SEM tomography using a Zeiss Auriga CrossBeam instrument. The samples were embedded in resin. Metal ions and minerals within the sample were responsible for contrast generation. The voxel size was 30 x 30 x 30 nm³. The resulting 3D reconstructions show the original arrangement of the microscopic constituents in great detail (Fig. 1,2). The two mats were dominated by different types of Fe(II)-oxidizing bacteria, which formed characteristic structures that were visible in the two respective volumes. A large part of both volumes appeared void.
The results of this analysis provide explanations for a series of macroscopically observed effects, such as the physical stability of the mats, high water content, efficient interaction with the feeding water, and the creation of a habitat for a variety of different microbial species. In addition, the results represent a valuable reference for the detection of microfossils in sedimentary rocks.
References
[1] WE Krumbein et al. (2003), in Fossil and recent biofilms. Springer Netherlands, pp. 1-27
[2] EJ Fleming et al. (2014), ISME J 8, pp. 804-815
[3] C Heim et al. (2015), Front Earth Sci 3
Figures:
Figure 1: Volume reconstruction of microbial mat A; field of view 61 x 37 x 17 μm³
Figure 2: Volume reconstruction of microbial mat B; field of view 61 x 36 x 17 μm³
To cite this abstract:
Fabian Zeitvogel, Martin Obst, Birgit Schroeppel, Claus J. Burkhardt; Revealing the internal structure of microbial mats by FIB/SEM tomography. The 16th European Microscopy Congress, Lyon, France. https://emc-proceedings.com/abstract/revealing-the-internal-structure-of-microbial-mats-by-fibsem-tomography/. Accessed: December 4, 2023« Back to The 16th European Microscopy Congress 2016
EMC Abstracts - https://emc-proceedings.com/abstract/revealing-the-internal-structure-of-microbial-mats-by-fibsem-tomography/