Concept Notes: Classification of Microorganisms & Commercial Roles
Microorganisms populate virtually every ecological niche on Earth, from boiling hydrothermal vents to polar ice caps.
1. The Four Primary Microbial Groups
- Bacteria: Single-celled prokaryotes lacking a membrane-bound nucleus (e.g., Lactobacillus, Rhizobium).
- Fungi: Heterotrophic, non-green spore-producers possessing chitinous walls (e.g., Bread mould, Yeast, Aspergillus).
- Protozoa: Animal-like unicellular eukaryotes, largely motile and heterotrophic (e.g., Amoeba, Paramecium, Plasmodium).
- Algae: Aquatic autotrophs containing photosynthetic chlorophyll (e.g., Chlamydomonas, Spirogyra).
2. The Unique Nature of Viruses
- Acellular nucleoprotein particles incapable of autonomous metabolism.
- Active and reproductive strictly inside living host cells; inert crystals outside.
3. Commercial and Household Utility
- Lactobacillus in Dairy: Converts lactose sugar into lactic acid, curdling milk proteins.
- Yeast in Fermentation & Baking: Converts sugars into ethyl alcohol ($C_2H_5OH$) and releases $\text{CO}_2$ gas, inflating bread dough with soft, spongy pores.
- Environmental Cleansers: Decompose organic dead biomass into harmless humus, recycling vital soil nutrients.