Diversity, adaptation and activity of the bacterial flora in saline environments

• Published in: Biology and fertility of soils Vol. 25; no. 3; pp. 211 - 223
• Main Author: Zahran, H.H
• Format: Journal Article
• Language: English
• Published: Berlin Springer 01.09.1997
• Subjects: adaptation; Agronomy. Soil science and plant productions; anatomy and morphology; Animal, plant and microbial ecology; Biochemistry and biology; biodiversity; biogeochemical cycles; Biological and medical sciences; cell structures; Chemical, physicochemical, biochemical and biological properties; communities; ecosystems; environment; Fundamental and applied biological sciences. Psychology; halophytic bacteria; literature reviews; microbial activity; Microbial ecology; Microbiology; osmoregulation; Physics, chemistry, biochemistry and biology of agricultural and forest soils; saline soils; salt marshes; salt tolerance; salt-affected soils; Soil; soil bacteria; Soil science; World; Microbial activity; Microbiology; Taxonomy; Cultivated soil; Environmental factor; Microflora; Review; Biodiversity; Saline soil; Salt marsh; Salt affected soil; Nitrogen fixation; Bacteria; Soil science; Diazotrophy; Adaptation; Halotolerance; Economic importance; Osmoregulation; Ecology; Sodium chloride; Bacteriology; Salinity; Edaphic factor; Soil biology
• ISSN: 0178-2762; 1432-0789
• DOI: 10.1007/s003740050306

Saline environments have a natural bacterial flora, which may play a significant role in the economy of these habitats. The natural saline environments (usually containing salinity equivalent to 4-30% NaCl) are aquatic (e.g. salt marshes) or terrestrial (e.g. saline lands). Saline environments include an increasing area of salt-affected cultivated soils throughout the world. These environments contain various ions which may interfere with uptake of water and which may be toxic to a large number of organisms. Saline environments harbour taxonomically diverse bacterial groups, which exhibit modified physiological and structural characteristics under the prevailing saline conditions. The majority of these bacteria can osmoregulate by synthesizing specific compatible organic osmolytes such as glutamine, proline and glycine betaine and a few of them accumulate inorganic solutes such as Na(+), K(+) and Mg(2+). The morphology of the bacteria is usually modified, cells are usually elongated, swollen and showing shrinkage, in addition to changes in the cell and cytoplasmic volume. The chemical composition of membranes may also occasionally be modified, and the synthesis pattern of proteins, lipids, fatty acids and polysaccharides may change with a moderate increase in salinity. However, ultrastructural alterations in cells of halophilic bacteria have not been reported, and profound changes in cellular properties of these bacteria only occur at concentrations above 2M NaCl. Evidence has accumulated that the bacteria are essential elements in the saline environment because of their activity such as degradation of plant remains, nitrogen fixation and production of active metabolites.