About 5000 different kinds of bacteria
are currently recognized, but there are doubtless
many thousands more awaiting proper identification (figure
34.2). Every place microbiologists look, new species are
being discovered, in some cases altering the way we think
about bacteria. In the 1970s and 80s a new type of bacterium
was analyzed that eventually lead to the classification
of a new prokaryotic cell type, the archeabacteria (or
Archaea). Even when viewed with an electron microscope,
the structural differences between different bacteria are
minor compared to other groups of organisms. Because the
structural differences are so slight, bacteria are classified
based primarily upon their metabolic and genetic characteristics.
Bacteria can be characterized properly only when
they are grown on a defined medium because the characteristics
of these organisms often change, depending on
their growth conditions.
About 5000 different kinds of bacteriaare currently recognized, but there are doubtlessmany thousands more awaiting proper identification (figure34.2). Every place microbiologists look, new species arebeing discovered, in some cases altering the way we thinkabout bacteria. In the 1970s and 80s a new type of bacteriumwas analyzed that eventually lead to the classificationof a new prokaryotic cell type, the archeabacteria (orArchaea). Even when viewed with an electron microscope,the structural differences between different bacteria areminor compared to other groups of organisms. Because thestructural differences are so slight, bacteria are classifiedbased primarily upon their metabolic and genetic characteristics.Bacteria can be characterized properly only whenthey are grown on a defined medium because the characteristicsof these organisms often change, depending ontheir growth conditions.
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