MICROBES WITHIN DEAD SEA SEDIMENTS: THEIR CHEMICAL SIGNATURES AND MODES OF FOSSILIZATION

The Dead Sea, an evaporite basin, contains a halophilic, prokaryote fauna that is rich in numbers, but limited in generic diversity. A JEOL 6340F field emission scanning electron microscope (FE-SEM), IXRF energy dispersive x-ray spectrometer (EDS), and a Phillips XL30 environmental electron microscope (ESEM) are used to analyze benthic detrital and evaporite deposits from waters less than 2 meters deep. We are interested in identifying the chemical signatures of the microbial representatives inhabiting both detrital and evaporite surfaces, including their possible methods of fossilization. Clay and silt sized detrital samples are frequently pitted with many of them containing halite crystals. Halite crystals can also occur as relatively pure aggregates. Sand sized particles indicate pitting with secondary clay formation and magnesium deposits. ESEM analysis indicates the presence of rods (785 nm to 3.62 micrometers), and coccoid to irregular coccoid shapes (828 nm to 1.65 micrometers) within the microbial size range. FE-SEM indicates the presence of elliptically shaped mineralized microbes. Some contain cytoplasmic extensions. All of the mineralized microbes possess calcium ion signatures, a metallic ion that can be associated with microbial activity. Biofilm development is apparently limited within our samples, as even freshly collected material does not possess thick accumulations similar to Bahamian saline lakes. Dead Sea deposits contain a variety of microbial forms with limited biofilm development. Fossilized forms are represented by elliptical to rod-shaped forms with the absence of fossilized coccoid shapes. This is significant as there are coccoid forms present, but apparently fossilization is marginal to nonexistent. Acknowledgments: M. Nelman, for her excellent contributions with the ESEM.