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  1. Microorganism - Wikipedia

    A microorganism, or microbe, [a] is an organism of microscopic size, which may exist in its single-celled form or as a colony of cells. The possible existence of unseen microbial life was suspected from …

  2. Microbiology | Definition, History, & Microorganisms | Britannica

    Dec 4, 2025 · Microorganisms are of incalculable value to Earth’s ecology, disintegrating animal and plant remains and converting them to simpler substances that can be recycled in other organisms. …

  3. Microorganism – Definition, Types, Importance, Examples

    Mar 28, 2024 · What is Microorganism? Microorganisms, often referred to as microbes, constitute a diverse and pervasive group of life forms characterized by their microscopic dimensions, typically …

  4. MICROORGANISM Definition & Meaning - Merriam-Webster

    The meaning of MICROORGANISM is an organism (such as a bacterium or protozoan) of microscopic or ultramicroscopic size.

  5. The Five Major Types of Microorganisms

    Aug 4, 2025 · Each type of microorganism—bacteria, viruses, fungi, protozoa, and algae—occupies a unique niche in Earth’s ecosystems. Yet they do not exist in isolation.

  6. 1.4: Types of Microorganisms - Biology LibreTexts

    Microorganisms differ from each other not only in size, but also in structure, habitat, metabolism, and many other characteristics. While we typically think of microorganisms as being unicellular, there are …

  7. Microorganisms Definition - Microbiology Key Term | Fiveable

    Microorganisms, also known as microbes, are tiny living organisms that are invisible to the naked eye. They include a diverse group of microscopic life forms such as bacteria, archaea, fungi, protists, and …

  8. Microorganism - Ask Microbiology

    A microorganism is a living entity that is too small to be seen unaided. This term encompasses bacteria, archaea, microscopic fungi, algae, and protozoa; viruses and prions, although not truly living, are …

  9. Microorganism - New World Encyclopedia

    A microorganism, or microbe, is an organism (form of life) that is microscopic (too small to be seen by the unaided human eye). Microorganisms can be bacteria, fungi, archaea, or protists, but not viruses …

  10. In brief: What are microbes? - InformedHealth.org - NCBI Bookshelf

    Apr 5, 2022 · Microbes are tiny living things that are found all around us. Also known as microorganisms, they are too small to be seen by the naked eye. They live in water, soil, and in the air. The human …