Precipitation and bacteria
				Confocal laser scanning microscope images (clic to enlarge)
		A novel method using excision and fixation in Nanoplast, a hydrophilic embedding resin, allows confocal imaging of natural microbial communities and their extracellular polymeric secretions (EPS) while in situ. Prestaining with fluorescent probes permits the observation of specific cellular and extracellular components. Marine stromatolites sediments were examined using this method. Optical sectioning using confocal laser scanning microscopy (CLSM) permitted high-resolution imaging through sediments (see above). Delicate arrangements of the EPS that are associated with sedimentary microbial biofilms were imaged using a fluorescein isothiocyanate (FITC)-labeled lectin (convanavalin-A) probe. Close microspatial associations of heterotrophic bacteria cells and autotrophic cyanobateria cells were also observed. The nanoplast resin produces no detectable autofluorescence. Further coupling of multi-photon scanning laser microscopy (2P-LSM) with a conventional single photon CLSM allowed concurrent imaging of DAPI-labeled microbial cells, FITC-labeled EPS and autofluorescent carbonate sand grains. The multi-photon infrared laser permits deep (approximately 1mm) penetration of samples and the excitation of DAPI, which normally requires UV-excitation with minimal disturbance to the samples. The unique combination of Nanoplast with fluorescent probes, CLSM and 2P-LSM allows for the preservation and imaging of natural microbial communities in their in situ state, a method easily adapted for examinations of other microbial systems.
		For more information see Decho and Kawaguchi (1999)