Microbiology, study of microorganisms, or microbes, a diverse group of minute,
simple life forms that include bacteria, archaea, algae, fungi, protozoa, and viruses.
Types of microorganisms
The major groups of microorganisms—namely
bacteria, archaea, fungi (yeasts and molds), algae, protozoa, and viruses.
1. Bacteria (eubacteria and
archaea)
Microbiology came into being largely through studies of bacteria. The experiments of Louis Pasteur in France, Robert Koch in Germany, and others in the late 1800s
established the importance of microbes to humans. As stated in the Historical
background section, the research of these scientists provided proof for the
germ theory of disease and the germ theory of fermentation.
The organisms that
constitute the microbial world are characterized as either prokaryotes or eukaryotes; all bacteria are
prokaryotic—that is, single-celled organisms without a membrane-bound nucleus.
2. Algae
Unlike bacteria, algae are eukaryotes and, like plants, contain the
green pigment chlorophyll, carry out photosynthesis, and have rigid cell walls.
They normally occur in moist soil and aquatic environments. These eukaryotes
may be unicellular and microscopic in size or multicellular and up to 120
metres (nearly 400 feet) in length. Algae as a group also exhibit a variety of
shapes. Single-celled species may be spherical, rod-shaped, club-shaped, or
spindle-shaped.
3. Fungi
4. Protozoa
Protozoa, or
protozoans, are single-celled, eukaryotic microorganisms. Some protozoa are
oval or spherical, others elongated. Still others have different shapes at
different stages of the life cycle. Like animal cells, protozoa lack cell
walls, are able to move at some stage of their life cycle, and ingest particles
of food; however, some phytoflagellate protozoa are plantlike, obtaining their energy via
photosynthesis. Protozoan cells
contain the typical internal structures of an animal cell.
The amoebas (also amoebae) do not swim, but they can
creep along surfaces by extending a portion of themselves as a pseudopod and
then allowing the rest of the cell to flow into this extension.
5. Viruses
Viruses,
agents considered on the borderline of living organisms, are also included in
the science of microbiology, come in several shapes, and are widely distributed
in nature, infecting animal cells, plant cells, and microorganisms. The field
of study in which they are investigated is called virology.
All viruses are obligate parasites; that is, they lack metabolic machinery of their own to
generate energy or to synthesize proteins, so they depend on host cells to
carry out these vital functions.
6. Lichens
Lichens represent a form of symbiosis, namely, an association of two different
organisms wherein each benefits. A lichen consists of a photosynthetic microbe
(an alga or a cyanobacterium) growing in an intimate association with a fungus.
Lichens play
an important role ecologically; among other activities they are capable of
transforming rock to soil.
The phrase "small is powerful" is true and microorganisms are live examples of it & really, the wonders of life are always hidden in small things.