Colonizers are the base unit for bacteria. They have mediocre starting stats, and are not particularly fast or large. Colonizers are most classified as a support unit, however their main ability, colonizing enzyme, can turn the tide of a battle.
Colonizers are mostly used to create semi permanent buffer zones to keep enemies from getting close to your units or resources. However aspiring players could try and colonize the entire map, or create a mobile wall generator to keep enemies contained. The colonizing enzyme they produce also synergizes with several other units abilities.