Types of microorganisms
Fungi are a
large and diverse group of eukaryotic, non-photosynthetic,
spore-forming organisms. They have rigid cell walls.
Respiration takes place in bodies called mitochondria
in the cytoplasm. Fungal cells have an elaborate
arrangement of internal membranes. Fungi can be
divided into two broad groups: filamentous fungi
(including moulds and macrofungi) and yeasts.
a large group of eukaryotic, single celled organisms,
which lack a rigid cell wall and usually chloroplasts.
They vary widely in size, cell structure and form,
ranging from Amoeba with its very fluid shape and
simple internal organization and few specialised
organelles through to Paramecium with its fixed
shape, complex internal organisation and many specialised
Algae are a
diverse group of eukaryotic organisms that contain
chlorophyll and carry out photosynthesis. Some contain
other photosynthetic pigments which gives them their
characteristic colour - most algae are green, but
some are red. They occur in a wide range of forms
from microscopic to macroscopic e.g. seaweeds, some
of which are up to 30 metres long and are not considered
to be micro-organisms. Microscopic algae exist either
as single cells e.g. chlorella, in colonies e.g.
Volvox or in filaments e.g. Spirogyra.
in size from 0.1 to 15 micron, with some "giants"
that may reach half a millimeter. They make up the
most metabolically diverse group of living organisms.
Although some are parasitic to animals and plants,
the majority of bacteria are free-living, having
either a neutral or beneficial relationship with
humans and other animals and plants. Their metabolic
versatility is incredible; while most are heterotrophs,
using either light or chemical energy. One of their
most remarkable characteristics is their ability
to multiply rapidly, with generation times usually
ranging between minutes to hours. Bacteria also
include cyanobacteria, a specific group of microorganisms
capable of oxygenic photosynthesis.
have a wide range of shapes: spheres, rods, spirals,
lobed, flat rectangular or irregular. Some exist
as single cells, other form filaments or clusters.
Some are motile. They are often called extremophiles
because they are found in extreme conditions in
the environment, such as in hot springs, or salt
crystallizing pans the depths of the ocean.
very small, ranging between 0.01 and 0.03 ?m, and
only we visualized under electron microscope. They
cannot live independently, and only multiply inside
the cells of other organisms. However, their demand
for a host is fairly specific. For example, it is
unlikely that a crustacean virus will attack humans
or fish. Viruses are also the simplest of all organisms
and are made of nucleic acid (either DNA or RNA),
frequently coated with a protein layer.