Photoactive Pigments in Halobacteria from the Gavish Sabkha

Abstract

The Gavish Dabkha in late summer and early fall typically shows a large area covered with a salt crust and a residual small and shallow, crescent-shaped brine pool with a strong orange-red color. The color is due to the presence of halobacteria at a cell density of ~ 10⁷ cells ml. The population of the unicellular algae (Dunaliella),more abundant earlier in the year, has almost disappeared at this stage and in addition to the halobacteria only a few, small unidentified flagellates are seen upon microscopic examination of the brine. The color of the brine is due to a high concentration of carotenoid pigments present in the cell membranes of these bacteria, mainly the C₅₀ carotenoid bacterioruberin. The distribution of microorganisms in the Gavish Sabkha is described in Chapters 11, 12 and 14. The physiological aspects of research on halobacteria are dealt with in Chapter 12. Ecological considerations are presented in Chapter 11. In this chapter, we deal mainly with the relations of halobacteria to light.