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with a Nikon CoolPix 990

Light and Epifluorescence Microscopy
on a Zeiss Axioskop

© 2001 Dr. Frank Jochem

    We mounted a Nikon CoolPix 990 digital camera to a Zeiss Axioskop epifluorescence microscope for both light and fluorescence microscopy. The camera was attached to the c-mount phototube of the Axioskop by a metal sleeve. The metal sleeve fits over the standard Zeiss c-mount and possesses a thread at the upper end that fits the lense threat of the CoolPix. The camera is operated using a net adapter because the batteries' life time is too short for routine use of the camera on the microscope. Microphotographs are usually taken at the highest camera photo quality (Fine), but pictures posted here were taken at intermediate quality.

    The coccoid cyanoabacterium Synechococcus spp. under green light excitation. The phycoerythrin in the cells produces a deep red autofluorescence. Size of cells ca. 1.8 Ám. Cells occur single or in doublets. Common phytoplankton in (sub)tropical oceans.

    Size comparison between the coccoid cyanobacterium Synechococcus sp. (yellow), heterotrophic bacteria (green), and Prochlorococcus sp. Prochlorococcus does not contain phycoerythrin and exhibits a plain red autofluorescence. Bacteria stained with SYBR Green I (Molecular Probes, Eugene, OR ).

    What a grazer can eat -- This picture shows a heterotrophic organism that has ingested several eukaryotic algal cells and heterotrophic bacteria. The outer cell membrane of the grazer can be seen as a dim shadow (marked by stemless arrows; difficult to see on some computer screen resolution and color settings.). The nucleus of the grazer can be seen in dim green in the center of the cell, visible by SYBR Green I staining of the DNA. SYBR Green I staining also produces green fluorescence in the bacteria. The orange cell inside the grazer is probably not a Synechococcus but also a eukaryotic alga that is already further digested. The chlorophyll autofluorescence of ingested algae is known to turn to orange upon increasing chlorophyll digestion by the grazer cell. Some grazers retain captured chloroplasts from ingested algae for a variable period of time and utilize the photosynthesis these chloroplast can still perform. Such grazers are called mixotrophs, i.e. their nutrition stems partly from ingesting other organisms and partly from the photosynthesis of the retained chloroplasts.

    The heterotrophic dinoflagellate Pfiesteria piscicida. Left: bright field microscopy, Pfiestiera marked by black arrows, algal prey (the cryptomonad Rhodomonas) marked by orange arrows. Right: Autofluorescence and DNA staining by YoYo-1 (Molecular Probes, Eugene OR). The cell shape is seen by a faint green fluorescence; the nucleus (N) is brightly stained by YoYo; ingested prey (the cryptomonad Rhodomonas) can be seen inside the cell (Ch = prey chloroplast with red chlorophyll autofluorescence, N(P) = prey nucleus, stained by YoYo).

    Gram Staining of Bacteria Gram-staining of bacteria isolated on general nutrient agar plates for the Gulf Stream off the South Florida coast. Long gram-positive rods in chains appear violet, gram-negative rods red. 100× oil immersion objective.

These photographs demonstrate that reasonable microphotography is possible with a Nikon CoolPix digital camera. Although the quality of photographs might not reach that of professional microphotography systems, simple digital cameras present an affordable alternative for routine photodocumentation. Professional microphotography systems offered by the microscope manufacterers and specialized companies run easily at $10,000-$20,000. Digital cameras allow photodocumentation for private or hobby microscopy for less than a few hundred dollars (excl. the microscope).

The here presented work was performed at the Marine Science Institute at The University of Texas at Austin. The Zeiss Axioskop microscope was funded by German Research Coucil grant DFG Jo 192/5-1. A triple tube C-mount and the Nikon Cooplix were funded by the Nancy Lee and Perry R. Bass Endowment to the University of Texas at Austin.