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Some archaea look like little rods or tiny balls, and some even get around like bacteria, using long hair- or whip-like appendages called flagella that stick out of their cell walls and act like a microscopic outboard motor to get them where they are going.
Like bacteria, archaea lack a true nucleus. Both bacteria and archaea usually have one DNA molecule suspended in the cell's cytoplasm contained within a cell membrane. Most, but not all, have a tough, rigid outer cell wall.