Tiny microorganisms have a huge world around us. Microorganisms can be unicellular i.e single-celled or they may also be multicellular. They include everything from Bacteria, Fungi, Protozoa, Algae. Microorganisms have a purpose in their lives: to survive and multiply. For their survival, they need food, air, water, an environment to live in and a way to dispose of waste. Some of these microorganisms make their own food through photosynthesis just like plants do whereas other microorganisms use other substances for food.


Good Microbes

We often hear about ‘germs’ and how they are bad, how they can cause diseases and how you should protect yourself from them. But not all microorganisms are bad; in fact, there are multiple ways which these microorganisms are useful and beneficial to us.

Here are a few examples of how microbes can be useful to us (Why not All Microbes are Harmful):

1. Most people associate microbes with diseases, but the number of microorganisms that are harmful to us is vastly outnumbered by the ones that harm us. It is very important to note that several antibiotics like penicillin and also vaccines are made possible due to microbes. Microbes are also used to produce substances like Insulin that are used by diabetic patients.

2. Microbes play a very integral role in the food industry. In the dairy industry, microorganisms are used to process milk into cheese, yoghurt, buttermilk, paneer etc. Various large dairy companies maintain their specific microorganism cultures very carefully. You may have noticed that the curd and yoghurt that the tastes different from the one made at home and also varies from brand to brand, that is because they all use different cultures (Each brand has a well kept secret culture strain!).Yeast is also used for fermentation of the dough to make bread.

3. Not just in food preparation, microbes can also be used as food sources themselves! Mushrooms are the major class of microbes that are used as food directly. Truffles are another kind of fungi that are also eaten as food. Not all varieties of mushrooms are edible and many are poisonous too.

4. Sewage water that is generated needs to be treated before it is sent back into water bodies such as rivers or seas. In the various steps of this treatment process, microorganisms are used. Microorganisms help to reduce the level of oxygen consumption due to organic matter in the water. In the final steps of sewage water treatment, microorganisms also help clear the other microbes, so that treated water can be released.

5. In the wake of the increasing climate crisis, it is of a better choice to go back to using natural products, especially in agriculture and farming. Many species of microbes that have a symbiotic relationship with leguminous plants are used to capture nitrogen into the soil. This technique is used instead of using artificial fertilizers and are known as biofertilizers.

6. Microorganisms such as yeast are used in the alcohol industry for the fermentation process to make various alcohol products such as wine and beer.


Bad microbes 

Now, before we take a look at how these microorganisms can be harmful to us, let us take another look at them. Let us remember, that these ‘harmful’ microbes are in constant search for food, space to live in and means to multiply.

Here are a few examples of how microorganisms are harmful to us

1. Amoebiasis caused by Entamoeba histolytica results in gastrointestinal infections causing diarrhoea which may include blood and mucous.

2. Malaria is caused by the protist Plasmodium that results in recurring fever, headache and can even lead to death if untreated. The plasmodium parasite needs to enter the blood, mature through its various stages including the host’s liver before completing its life cycle.

3. Typhoid is caused by Salmonella typhi and results in high fever

4. Different types of diseases are also spread by viruses including the common flu by the influenza virus, dengue by the dengue virus and even deadly diseases like ebola through the ebola virus.

5. Viruses also infect other animal species- you may have heard of bird flu and other diseases caused by viruses.

6. Microorganisms also cause spoilage of food. If bacteria find a suitable food source, they start breaking it down for consumption and in the process produce waste products such as various acid. These acids may be harmful to health, even if the microorganisms itself may not be harmful. A bacteria called Clostridium perfingens targets meat and poultry products and render them unsuitable for consumption whereas another bacteria Bacillus cereus targets milk products.

7. Fungi also spoil food- you may have seen the layer of bread mould form on a piece of bread lying around attended for a few days


The number of microorganisms that can be harmful to us is far outnumbered by the ones that are useful to us or are not harmful. The damage done by the harmful microorganisms can of course be disastrous and hence it is always beneficial to take preventive measures. 





Stark, L. A. (2010). Beneficial microorganisms: countering Microbephobia. CBE—Life Sciences Education9(4), 387-389.


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About Author

Saunri Dhodi Lobo is pursuing M.Sc in Life Sciences with specialization in Neurobiology. Her interests include writing poetry, going for nature walks and swimming. Currently she is involved in research on Alzheimer’s Disease in fruit flies.

Read all Articles by Saunri Dhodi Lobo

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