microorganismen

Microorganismen, or microbes, are microscopic living organisms or biological entities that often cannot be seen with the naked eye. They range from simple single-celled organisms to clusters of cells and, in some classifications, include acellular infectious particles such as viruses. Despite their small size, they display a wide variety of shapes, metabolisms, and life cycles.

The major groups commonly recognized are bacteria, archaea, fungi (including yeasts and molds), algae, and protozoa. Viruses are also studied within microbiology and, although not cellular, they are typically treated as microorganisms due to their ecological and medical relevance. Microorganisms can live independently or as part of complex communities.

They inhabit nearly every environment on Earth, from soil and freshwater to oceans and the air, as well as the surfaces and internal tissues of plants and animals. They drive essential processes such as decomposition, nutrient cycling, and primary production through photosynthesis. Many microorganisms are beneficial, aiding digestion, producing nutrients, or used in food fermentation and biotechnology. Others can cause diseases in humans, animals, or plants, and require public health measures to control their spread.

Study and manipulation of microorganisms rely on microscopy, culture in selective media, and molecular techniques such as DNA sequencing and metagenomics. Model organisms like Escherichia coli and Saccharomyces cerevisiae play key roles in research, while advances in genomics have expanded understanding of microbial diversity and function. Size and diversity among microorganisms span a wide range, from about 0.2 micrometers to several tens of micrometers for cellular forms, with viruses generally smaller.