Structure and Physiology of Square-shaped and Other Halophilic Bacteria from the Gavish Sabkha

The extremely halophilic bacteria described in the following two chapters occur in the zones of highest salinity in the Gavish Sabkha (see Chap. 9). When one of us (A. E. Walsby) visited the Gavish Sabkha (together with W. E. Krumbein in April 1979) he was mainly in search of gas-vacuolate halophilic bacteria. Samples of the pink salt and brine slush of the pools of the elevated central parts of the Gavish Sabkha, when investigated microscopically, revealed an exciting new group of bacteria. Floating ethereally among the microorganisms were diaphanous squares with glistening gas vacuoles attached to them. Further inspection revealed that many of the squares had just discernible thickness and were made up of subsidiary squares linked like postage stamps in a sheet. It transpired that each square was a bacterium of unprecedented form. After the first description of these unique bacteria from the Gavish Sabkha (Walsby 1980), W. Stoeckenius (see Chap. 11) and Y. Cohen isolated other bacteria of square shapes which turned out to contain bacteriorhodopsin and to be able to change from the square shape into the normal form of bacteria.