It’s true. In fact, without bacteria there would be no life as we know it, no plants, no animals, not even a protists could live on this planet.

Most bacteria live in soil and water where they multiplying to staggering numbers providing their living requirements are met. A single drop of pond water can contain millions, a water sample taken near some decomposing aquatic vegetation--billions.

Rods swimming up nutrient gradient.

Filamentous bacteria

The ecology of planet earth relies on these tiny organisms. They convert atmospheric nitrogen into compounds plants require, they create vitamins and other products for their animal hosts, and they are the maintenance crew that breaks down dead bodies, cast off parts, and animal wastes.

Decomposers at work

Decomposers at work

Bacterial decomposition allows the nutrient molecules, that would otherwise remain locked up in dead bodies, to be recycled in the living world. Our video/DVD program, Viruses and Bacteria shows motile bacteria homing in on their food source using adaptive behavior.

Biologists know only a small percentage of these organisms--maybe less than 10%. 90% of the bacteria found in nature are waiting to be discovered and we can only imagine the vital roles they play in the maintenance of life on earth.

Spiral bacteria showing flagell

One line of bacteria has a special claim to fame, for without them we would not be breathing. In fact, we would not even be here. The Cyanobacteria (once known as blue-green algae) developed the chemistry needed to split water into hydrogen and oxygen sometime around two billion years ago. They were the first organisms to release the oxygen into the atmosphere and begin the evolution of aerobic life forms: protists, plants, animals and fungi.

Anabaena, a common cyanobacterium

Bacteria have played central roles in this evolutionary drama. They were among the first cells to appear on earth. Long filamentous bacteria, similar to those above, left their imprints in two billion year old rocks, and indirect evidence of bacterial life goes back to around 3.8 billion years, about a billion years after the planet formed.

Paramecia aggregate feeding on a clump of bacteria

As more complex nucleated cells evolved, bacteria not only became a ready food source, some moved right in with the diners, becoming permanent guests. A number of the cellular organelles found in plants, animals, and protists began in just this way. Check out the mitochondria below. These organelles originated as symbiotic bacteria. They contain some of their original bacterial DNA, and reproduce themselves. As you can see, mitochondria even look like bacteria. Mitochondria from the ciliated protists, Opisthonecta, seen in a membrane bubble. All of the pictures above are of living bacteria featured in our program: BRANCHES ON THE TREE OF LIFE: Viruses and Bacteria.

Mitochondria from the ciliated protists, Opisthonecta, seen in a membrane bubble.