Factors determining the development of algal and bacterial blooms in the Dead Sea: a study of simulation experiments in outdoor ponds

A halophilic bacterium was isolated from bottom sediment from the Dead Sea. The organism possessed the properties of the halobacteria, but differed from the known species in two important respects, 1) the cells were disc shaped and often cupped when grown under optimum conditions, 2) the optimum requirements for sodium chloride was in the range 1.7--2.5 molar which is about half of that generally reported for the halobacteria. The organism was assigned to the genus Halobacterium and described as Halobacterium volcanni spec. rov. The optimum sodium chloride concentration for growth was close to that found in the Dead Sea. The tolerance for magnesium chloride was very high; the organism grew well in media containing magnesium chloride in the concentrations found in the Dead Sea. Halobacterium volcanii is therefore remarkably well fitted for life in the Dead Sea.

The extremely halophilic rod-shaped bacterium, strain R-4, has features very different from other known Halobacterium species. As do all other extreme halophiles, the organism possesses a high excess of acidic over basic amino acids in its proteins, a cell wall lacking peptidoglycan, and ether-linked diphytanyl lipids. It differs from the "classic" halobacteria in several important ways: it can use many different compounds as sole sources of carbon and energy. It is strongly amylolytic and lipolytic (against different Tweens), and does not produce H(2)S. The cell envelope of R-4 is much thicker than that of other halobacteria. The proportions of polar lipids in the envelope are different, and a new glycolipid sulfate is present in this strain. The envelope has a relatively low protein content, although a glycoprotein similar to the one of Halobacterium salinarium was detected. The G + C content (60%) is lower than that of other halobacteria. It is suggested that R-4 be designated a new species, Halobacterium mediterranei. Copyright © 1983 Gustav Fischer Verlag, Stuttgart/New York. Published by Elsevier GmbH.. All rights reserved.