Some microorganisms are harmful to us, so if it is on the food, how do we know that and if we eat that, will it be harmful to us?

Microorganisms are invisible and hence one cannot visibly distinguish them as good microbes and bad microbes.

A microorganism is an organism that is so small and invisible to the naked eye. Some examples of microbes include bacteria, fungi, protozoa, viruses, etc. Some microorganisms are beneficial, while others are pathogenic, i.e. they cause diseases in humans and animals.

Microorganisms are omnipresent. They can be either unicellular, i.e. contain a single cell, or multicellular, i.e. made up of many cells. The human body is home to millions of microorganisms.

Every human cell has more than 10 microbes, and these serve various purposes like digestion, production of vitamins, detoxification, boosting immunity, etc. So, they are categorized as good microbes, as they help humans in leading a healthy life.

In contrast, some microbes use the host cellular machinery for their own purposes like replication and survival and cause an unhealthy state, such as a disease onset in a human being. Such microbes are termed as germs or pathogens or bad microbes.

These pathogens or bad microbes cause diseases and infections like chickenpox, typhoid, tetanus, tuberculosis and hence are referred to as harmful microorganisms or germs.