The World of Microbes - Classification of Microorganisms

Microorganisms are tiny organisms that cannot be seen with the naked eye and are classified into four major groups: Bacteria, Fungi, Protozoa, and some Algae.

Bacteria are single-celled prokaryotic organisms that vary in shape (spherical, rod-shaped, spiral) and size, typically ranging from $0.2 \mu m$ to $100 \mu m$.

Fungi are eukaryotic organisms that can be unicellular like Yeast or multicellular like $Penicillium$. They are non-green and follow saprophytic or parasitic modes of nutrition.

Protozoa are unicellular eukaryotic organisms, such as $Amoeba$ and $Paramecium$, which are mostly aquatic and can be free-living or parasitic.

Algae are plant-like organisms that contain chlorophyll and perform photosynthesis. Examples include $Chlamydomonas$ and $Spirogyra$.

Viruses are microscopic entities that are different from other microbes because they reproduce only inside the cells of the host organism (plant, animal, or bacteria).

Measurement of microbes is usually done in micrometers ($1 \mu m = 10^{-6} m$) or nanometers ($1 nm = 10^{-9} m$).

Fermentation is the biological process where microbes like Yeast convert sugar into alcohol and carbon dioxide: $C_{6}H_{12}O_{6} \rightarrow 2C_{2}H_{5}OH + 2CO_{2}$.