The amoeba is remarkable for its very large genome. The species Amoeba proteus has 290 billion (10^9) base pairs in its genome, while the related Polychaos dubium (formerly known as Amoeba dubia) has 670 billion base pairs. The human genome is small by contrast, with its count of 2.9 billion bases.

Like most cells, amoebae are adversely affected by excessive osmotic pressurecaused by extremely saline or dilute water. Amoebae will prevent theinflux of salt in saline water, resulting in a net loss of water as thecell becomes isotonic with the environment, causing the cell to shrink. Placed into fresh water, amoebae will also attempt to match the concentration of the surrounding water, causing the cell to swell and sometimes burst .

In environments which are potentially lethal to the cell, an amoeba maybecome dormant by forming itself into a ball and secreting a protectivemembrane to become a microbial cyst. The cell remains in this state until it encounters more favourable conditions. While in cyst form the amoeba will not replicate and may die if unable to emerge for a lengthy period of time.