Microorganisms or microbes are microscopic living organisms that cannot be seen through our naked eyes. For example: bacteria, viruses, fungi, algae, etc.
Microorganisms are present everywhere. These are present in the soil, air, water, on our skin, inside our gut, on plants and other living organisms. You name it and you have them. These are also present in the hot springs, in cold water, on the mountains, in the deep sea vents and where not.
Microbes are unicellular or multicellular, prokaryotic or eukaryotic living organisms that may or may not have chlorophyll.
Let’s discuss the microorganisms in detail.
Bacteria (singular: bacterium) are unicellular, prokaryotic, microscopic living organisms. These are of different shapes and sizes. These may or may not possess flagella for locomotion. These reproduce by binary fission. These are classifies into different types depending upon their shape, presence or absence of flagella and on the basis of their mode of nutrition. On broader scale, bacteria are divided into two categories, archaebacteria and eubacteria.
Fungi (singular: fungus) are unicellular, eukaryotic, microscopic living organisms that reproduce asexually. These have saprophytic mode of nutrition and grow on dead and decaying matter. These are also parasitic and cause diseases in humans. Fungi are broadly classified into yeasts and molds.
Algae (singular: alga) are unicellular, eukaryotic, microscopic living organisms that contain chlorophyll. These have the ability to make their own food by photosynthesis and thus are autoprophs. These are present in aquatic environment and can be found in association with other organisms. Algae are classified on the basis of their color.
Viruses (singular: virus) are very minute infectious particles that contain either DNA or RNA and a protein coat. These can replicate only within a living host cell. Outside the host these behave as particles. Viruses cause infection in almost all organisms. These are classified depending upon the type of nucleic acid, capsid and envelope they possess.
Protozoa (singular: protozoan) are microscopic, unicellular, eukaryotic living organisms that lack a cell wall. These are free living and parasitic microorganisms. These are also found in close association with other animals. These are divided into different groups depending upon their mode of locomotion.
Microorganisms are both harmful and beneficial. In biotechnology, the beneficial aspect of microorganisms are exploited for the human welfare.