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In this article we will discuss about the survival of halophiles under halophilic conditions.
The halophiles have developed a number of peculiar modifications to adapt themselves to high salty conditions. The halophilic green alga Dunaliella devoid of rigid cell wall builds up high intracellular glycerol concentration to maintain osmotic balance. The obligately halophilic Halobacterium maintain osmotic balance with high intracellular concentration of potassium chloride (KCl).
It is interesting enough that Halo bacterium cannot live under low salinities and requires a minimum of 3.0M NaCl for growing. Typical extreme halophiles are Halo bacterium, Halococcus, Natronobacterium, anoxyphotorophic bacterium Ectothiorhodospira and the green alga Dunaliella. It has been seen that isocitrate by are from Haloferax mediterranei required high KCL concentrations and optimal activity was at 1.5 – 3 M potassium chloride at 7.0 pH.
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Some species belonging to halophilic archaea have evolved a unique mechanism of photosynthesis based on the presence of bacteriorhodopsin a wonderful protein pigment in their cytoplasmic membranes e.g. in Halo bacterium (Fig. 6.6). The purple 568 nm mediates light driven proton pump which drives ATP synthesis. Bacteriorhodopsin is localized as zisolated patches within the cytoplasmic membrane of Halo bacterium.
Halophilic archaea Halo bacterium develops chloride pumps which are based on halorho dopsin to transport chloride in the fall to maintain osmotic balance and to meet out the deficiency of chloride ions which leave the all when protons are expelled, (see Fig. 6.7.) The ribosomes of Halo bacterium need high concentrations of potassium ions to remain stable. The enzymes of this bacterium also need high concentrations of salt to maintain their active configuration and function, and get inactivated at low salinity.
Halo bacterium which is a unique heterotrophic aerobic archaeaon is devoid of murein and its all well seems to require sodium ions for stability. Some strains of Halo bacterium possess bacteriorhodopsin bilayer membrane components, which serve as light-driven proton pumps. They use light energy to pump protons out of the all, hence generate an electron an electrochemical potential. This all leads to ATP synthesis. Thus Halo bacterium has adapted to live in highly saline, often saturated brine environmental conditions.
