Groups of microorganisms - SS2 Biology Lesson Note

Microorganisms are a diverse group of living organisms that are too small to be seen with the naked eye. They play vital roles in various ecosystems, contributing to nutrient cycling, decomposition, disease-causing pathogens, and even industrial processes. Microorganisms can be broadly classified into four main groups based on their cellular structure: bacteria, archaea, fungi, and protists.

1.       Bacteria: Bacteria are single-celled microorganisms that can be found in almost every habitat on Earth. They are prokaryotic, meaning they lack a nucleus and other membrane-bound organelles. Bacteria are incredibly diverse and exhibit a wide range of shapes, including spheres (cocci), rods (bacilli), and spirals (spirilla). They can be classified based on their oxygen requirements, such as aerobic (require oxygen) and anaerobic (live without oxygen). Bacteria play crucial roles in nutrient recycling, decomposition, nitrogen fixation, and some can be beneficial or harmful to human health.

2.       Archaea: Archaea are also single-celled microorganisms that were once classified as bacteria but are now recognized as a separate domain of life. Like bacteria, archaea are prokaryotic and have diverse shapes and habitats. Archaea are known for their ability to survive in extreme environments, such as hot springs, salt pans, and deep-sea hydrothermal vents. They have unique biochemical and genetic characteristics, distinct from bacteria and eukaryotes. Archaea play important ecological roles in extreme environments and contribute to global biogeochemical cycles.

3.       Fungi: Fungi are eukaryotic microorganisms that include a vast range of organisms, such as mushrooms, molds, and yeasts. They have complex cellular structures and are distinct from plants and animals. Fungi obtain nutrients by breaking down organic matter and are considered nature's decomposers. They play crucial roles in nutrient cycling, soil formation, mycorrhizal associations with plant roots, and food production (e.g., fermentation). Fungi can also cause plant diseases and infections in animals and humans.

4.       Protists: Protists are a diverse group of eukaryotic microorganisms that do not fit into the other major groups (bacteria, archaea, or fungi). They are typically unicellular but can also exist as colonies or multicellular organisms. Protists encompass a wide range of organisms, including algae, amoebas, ciliates, and flagellates. They can be found in various aquatic and terrestrial environments and play important roles as primary producers, predators, or parasites. Some protists are responsible for harmful algal blooms, while others are essential components of food chains and marine ecosystems.