In the old Whittaker five kingdom classification scheme; prokaryotes (“pre-nucleus”) such as bacteria
are in a single kingdom, Monera. Currently, taxonomist place organisms in one of three domains. In
this classification scheme, prokaryotes are placed in either the domain Bacteria or Archaea. The
prokaryotes that you will examine in this laboratory are classified in the domain Bacteria and kingdom
Bacteria.
Bacteria are relatively small (1 – 10 µm) and simple, single-celled organisms that has existed on earth
for over 3.5 billion years. These prokaryotes are most-likely has the greatest distribution of all
organisms. They are found almost everywhere from the soil to the air and even water. In these
various environments, bacteria can even withstand extreme temperatures and chemically harsh
environments.
Bacteria have developed numerous modes of nutrition. They can generally be classified as either an
autotroph or a heterotroph. These two nutritional modes can be further subcategorized based upon
whether they use light, inorganic or organic compounds. Most prokaryotes, however, are
heterotrophic, where they obtain nutrients from their surrounding environment.