Unicellular organisms: Good or bad?

Oh no, I will be all alone this Valentine’s day. But Philip, you are never really alone. There are trillions and trillions of bacteria inside of you at all times. What?! But I’m not sick!

Don’t bacteria make you sick? Well, you’re partly right Philip — some bacteria can be quite harmful, and make you very unwell. But there are actually a lot of bacteria that help you survive. Bacteria are organisms made up of one cell, unicellular organisms. Like Philip, we often think of bacteria as harmful.

But in fact, our digestive systems wouldn’t function properly without bacteria. Bacteria help us absorb many nutrients. The same goes for animals. Cows, for instance, need bacteria in their gut to be able to digest grass. Our gut bacteria protect us from diseases, too, and help us stay healthy.

Scientists think that our gut bacteria often act as instructors for the cells involved in our immune system. For example, it is often bacteria which instruct these cells that new types of food you try are good, rather than bad for you. Some bacteria are really important for food production as well. Have you ever wondered why it says on some yogurt packaging that the yogurt contains ‘living cultures’? This is because living bacteria are used in the process of making yogurt!

But it’s not just bacteria. There are other unicellular organisms used to produce food too. If you’ve ever made your own bread, you’ve probably used a unicellular organism — yeast! Yeast makes bread rise, and makes the bread airy and soft! Another type of yeast is used in brewing, to make many different kinds of alcoholic beverages.

So, unicellular organisms do lots of things. One type of unicellular organism — phytoplankton — is food for many living things in seas or lakes. Phytoplankton are at the start of nearly every food chain in the sea. Without them most ocean life would not exist. Not only that, but phytoplankton produce about half of all the oxygen on Earth!

Though of course, not all unicellular organisms are good for us, for plants or animals. There are harmful types of phytoplankton, yeasts and bacteria, that can cause very serious, even deadly diseases. Phytoplankton can grow out of control when there are too many nutrients in the water. The phytoplankton become an algal bloom. Algal blooms can be extremely dangerous, as they produce toxic substances that harm other living things, such as fish, plants and even people.

And different types of yeast can cause infections — in the mouth, the gut or the vagina. They can be unpleasant, but are treatable. Finally, as Philip pointed out, bacteria cause many diseases that affect humans. Luckily most of them can be treated with antibiotics. But Philip, if you’re still looking for something to do on Valentine’s day, you could help me clean my bathroom to get rid of all the bad bacteria?