1. Bacteria: Single-celled prokaryotes (lacking a nucleus) with diverse shapes, sizes, and metabolic capabilities. They are found in all environments and play crucial roles in ecosystems and human health.

2. Archaea: Single-celled prokaryotes that are distinct from bacteria, often found in extreme environments like hot springs and salt lakes. They are also essential in various ecosystems and have potential applications in biotechnology.

3. Fungi: Eukaryotic organisms (with a nucleus) that include yeasts, molds, and mushrooms. They are important decomposers and play a role in food production and medicine.

4. Protozoa: Single-celled eukaryotic organisms with a wide range of forms and life cycles. They are diverse in their habitats and are involved in food chains and disease transmission.

5. Viruses: Non-living entities consisting of genetic material (DNA or RNA) enclosed in a protein coat. They require a host cell to replicate and can cause various diseases.

It's important to note that while these are the five main groups, there are other microorganisms such as algae (eukaryotic organisms that perform photosynthesis), prions (misfolded proteins that can cause disease), and viroids (small infectious RNA molecules). However, these are often not included in the "five basic groups" as they are less diverse or have more specialized roles compared to the five mentioned above.