The building block of the Kharaa, and the key to ever unraveling their mystery and inner-workings, is the bacteria-like life form that first appears on a ship or base. How it appears is one question we would desperately like to answer.
As near as we can tell, trace amounts of the bacteria begin to collect in areas containing water or heat sources. The bacteria reproduce, slowly forming a mat, visible to the naked eye. It also seems to direct airborne streams down the hallways and passageways, and anywhere it finds another source of energy (water or heat) it forms another mat, from which it sends out more streams, etcetera. It is safe to assume that every square inch of a facility is rapidly infiltrated with at least trace amounts of bacteria, anchored at source points that become potential hive locations (so far, we have never seen more than three). All of these bacteria are in contact with one another, sharing data on their environment, and triggering responses to stimuli (like energy sources, or danger). They form a network, called the Bacterium.