Invisible to our eyes, but found everywhere. Need microscope to observe individual cells. Some bacteria can divide very rapidly, with generation times as short as 20 minutes. Some bacteria motile, some not Almost all bacteria become dormant when starved, start to grow again very quickly once nutrients are available.
Some bacteria have specialized dormancy structure, the endospore .
Endospores can survive boiling for up to several hours , can be revived after decades of dormancy. One recent report suggests reviving dormant endospores from insect gut trapped in million year old amber. Human gut bacteria which are living in an anaerobic environment, but capable of living and growing aerobically, such as on food. Clean up oil spills Ferment sugars to lactic acid. Milk yogurt, cheese, sour cream, buttermilk, etc.