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Microbial life is defined as
organisms that exist and are nearly impossible to
see with the "naked eye". There are several
instruments that help to see microorganisms and
they include: light microscope, scanning
microscope, phase-contrast microscope and electron
micrscope. Life is an arbitrary term that is used
in many different contexts. To help simplify the
term in biology, there has been a set of
characteristics established.
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Since all living organisms share
many biological characteristics, there must be a
way to further classify them for organization
purposes. The first method of organization was
developed by Carl Linnaeus, and was based upon
taxonomy or external features. This led to the
development of the five kingdoms; Monera, Protista,
Fungi, Plantae and Animalia. Of the five kingdoms,
all except Monera were eukaryotes. The prokaryotes
were thought to be the most primitive of all
organisms. However, a new method by
molecular
systemists was used to
analyze relationship amongst organisms. This method
employed the use of rRNA (ribosomal ribonucleic
acid) and through the proximity of rRNA, a
relationship between organisms was established.
Closely related organisms are likely to have
similar ribosomal RNA's, while distantly related
organisms are expected to have ribosomal RNA's that
are less similar.
The idea that has now evolved is
the idea of three
domains, whether than
five kingdoms. The three domains is presently
acknowledging that there was a single common
ancestor, which then evolved into present day
prokaryotes and eukaryotes. The new classification
system also now breaks down the prokaryotes into
two groups; the Archaea and Eubacteria.
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