Bacteria
Look at this full stop. About a quarter of a million bacteria could fit on it. This gives you an idea of how small bacteria are. Despite their tiny size many can do tremendous good while a few can do dreadful harm.

If you climbed a hill and looked out across the countryside you might see woods and fields. If you stayed there all year you would see the trees come into leaf in the spring and turn the countryside green through the summer. In the autumn you would see the leaves turn brown and fall to the ground. At this time of year you would also see many plants die and leave their yellow stalks and flower heads behind.

While you watched the plants in the countryside over a year the animals would have been busy too. Plant eating animals such as deer would have nibbled away at the leaves in a wood and left their droppings behind. Owls would have caught mice and swallowed them. Later the owl would regurgitate the mouse bones and fur in a cigar- shaped object called an owl pellet. Sadly some animals crossing roads would have been killed by cars and their bodies left by the side of the road.

You may think that as large numbers of plants and animals die every year, and as animals make droppings and many trees shed their leaves you could expect to find the countryside full of plant and animal remains. However, if you take a walk through the countryside you will find some leaves and maybe a few animal droppings and even a few bones but you will not find many.

The reason for this is the billions of bacteria in the soil. The animal wastes, the leaves and dead bodies of plants and animals that fall on the soil are food for the bacteria. The bacteria cover the surfaces of their food and release juices onto it. In the juices are chemicals called enzymes. The enzymes break down the food until it dissolves in the juice. The bacteria then take in the dissolved food in the juice and use it to grow and breed. As the bacteria grow and breed they also are eaten by other microbes, which, when they die, are eaten by more bacteria and so the feeding frenzy continues throughout the year every year.

Although we may think that the bacteria merely help to tidy up the countryside they do a far more important job. As bacteria feed, minerals are released from the wastes and bodies. The minerals enter the soil and form nourishment or nutrients for plants. The plants take up the minerals and use them to grow and to breed. When an animal feeds on a plant it takes in some of the minerals and uses them in its own body. If the animal is then eaten by another animal, the minerals are passed on. When an animal makes droppings some minerals are lost and return to the soil. When plants and animals die their minerals also return to the soil with the help of bacteria. The bacteria that live in the soil and the minerals are the main recyclers.

While many kinds of bacteria are helping life survive on the planet by recycling minerals some bacteria feed in a different way. They attack living bodies and cause damage inside them. The damage results in disease. If the damage is great and the plant or animal cannot defend itself against attack then death will result. Unfortunately, when people think about bacteria, they think about those which are harmful germs but they should also think about the billions which are harmless and helping to keep the soil fertile so that plants can grow healthily in it.

Are bacteria found only in the soil?
No, they are found almost everywhere. They coat your body and cover everything you are looking at. They cover plants and animals too. Bacteria are found in water and also in the air.

Are all these bacteria feeding?
No. A bacterium has a resting stage in its life cycle called a spore. This is like a microscopic armour-plated case in which the bacterium can survive without feeding. In the spore stage a bacterium can float through the air and land on any surface. It will not break out of its spore unless it detects the right conditions for feeding. Your keyboard may be covered in bacterial spores but they will not burst into life because the conditions are dry and bacteria cannot feed on the plastic.

What happens when a spore lands in suitable conditions for the bacterium?
The bacterium breaks out and starts to feed. When it reaches a certain size it divides in two. Later, after the new bacteria have fed and become fully grown they breed too.

How fast can bacteria grow and breed?
It has been found that in ideal conditions some kinds of bacteria can breed every twenty minutes. This means that if you had one bacterium at the beginning of an hour you would have two after twenty minutes, four after forty minutes and eight at the end of the hour. You may think that the bacterium would produce eight new individuals in an hour but they breed much faster than this. In the second hour the number of bacteria would reach sixteen after twenty minutes, thirty-two after forty minutes and sixty-four at the end of the second hour. If the conditions remained the same the numbers of bacteria would greatly increase. In fact, someone once calculated that if a bacterium was allowed to breed in ideal conditions there would be so many bacteria after twenty five hours that they would fill a room twenty metres long, ten metres wide and five metres high.

If bacteria can breed so fast why is the world not full of them?
Bacteria very rarely land in a place where conditions are ideal. This means that they grow and breed at a much slower rate. Bacteria are also eaten by other microbes so this helps to keep their numbers down.

Do all bacteria look alike?
No. They are divided into three groups according to their body shape. Some bacteria are rod-shaped and they are called bacilli (singular: bacillus). Other bacteria are ball-shaped and they are called cocci (singular: coccus). A third group are corkscrew-shaped and they are called spirilla (singular: spirillum).

Are these strange sounding names ever used?
Yes, some of them are. You may hear a doctor or a nurse talk about a staphylococcus infection. This means that the infection is caused by ball-shaped bacteria, which are clustered together like a bunch of grapes. An infection may be a streptococcus infection. This means that it is caused by ball-shaped bacteria, which are joined together in a line and look like beads in a necklace.

What would happen if all the bacteria were removed from the soil?
There would be no recycling of animal wastes, leaves or the bodies of dead plants and animals. They would simply lie on the ground. In time the plants would use up all the minerals in the soil. When this had happened, the plants would die. The animals that fed on the plants would die and the predators would die. Plant and animal life on earth would cease.

Do we have minerals in our bodies?
Yes, you do. For example, you use calcium to make strong bones and teeth. You use iron to make red blood cells. These minerals come from your food.

Are the minerals in our bodies recycled?
Yes, they are. Countless times. For example, some of the calcium in your bones has been passing between plant and animal and bacteria since before the times of the dinosaurs. The chances are that some of the calcium in your bones once formed the bone of a dinosaur.