The smallest and most plentiful microorganisms in our food—and in the world—are bacteria. Even though you can’t see them without a microscope, bacteria are everywhere.
What are bacteria?
So what are these microscopic life-forms? Unlike plants and animals, bacteria are made of a single cell. You can see a typical bacterium below and take a look inside its cell. Bacteria often live in large clumps called colonies. They multiply constantly by dividing their cells.
Most bacteria are shaped like rods,but many are round. Others are bent or shaped like spirals. Bacteria also vary in size, but most measure between 1 and 4 micrometers across.
Whatever shape bacteria are, the insides of their cells hold the same basic parts. On the outside, some bacteria have pili to hold onto the cells of their food source. The larger hairs are flagella, which many bacteria use to move around.
Hungry bacteria
Bacteria need food to survive. Mostly they live on organic matter—food that comes from living things—just like we do. As bacteria digest food, they change the food they are eating.
Living in milk
Milk contains bacteria called lactobacilli that live on lactose, the sugar in milk. When milk goes sour, it’s because lactobacilli are producing a sour substance called lactic acid as they feed. Nobody wants to drink sour milk, but we can use the bacteria in milk to make food we do like. Next you will see how bacteria and fungi together help make some of our favorite foods!
Bacterial Names
Scientists use the term bacilli to describe rodshaped bacteria and cocci for bacteria shaped like spheres. These bacteria shapes are common in milk. Lacto means milk, so some milk bacteria are named lactobacilli and others are lactococci.
