Chapter 2: Observing the Microbial Cell
SIZE OF PROKARYOTES
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Prokaryotes are generally smaller then eukaryotes
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Small size allows nutrients to reach all parts of cell quickly
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Prokaryotic cells can be as small as 0.2μm.
The smallest eukaryotic cells are 2μm.
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Cocci- typically has diameter of 2 µm
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Some microbiologists have proposed that bacteria smaller than 0.2 μm exist in
nature, cells referred to as nanobacteria
•
If one considers the space needed to house all essential molecules of life, it is
unlikely they could exist within a volume available in a cell less than 0.1 μm.
•
Prokaryotic cells can have a wide variety of
cellular morphologies
, which are
often helpful in identification.
Bacterial Shapes
1.
Simplest shape is sphere
o
singular- coccus
o
plural- cocci
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Arrangement:
o
Coccus- single cells
o
Diplococcus- 2 cells
o
Streptococcus- chaings of more than 2 cells
o
Staphylococcus- grapelike clusters of cells
o
Tetrads- packets of 4 cells
2.
Most common shape is rods
o
Singular- bacillus
o
Plural- bacilli
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Can be very long & thin or short & fat
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Occur singly or in chains
3.
Spirals:
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Rigid spiral-shaped bacteria are called spirilla (singular-
spirillum)
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Flexible spiral-shaped bacteria are called spirochetes (flexible
corkscrew shaped cells with multiple curves)
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Vibrio – curved rods
Microscopy
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Simple microscopes
o
one lens
o
magnify 50X – 300X
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Compound microscopes
o
multiple lenses
o
Much higher magnification
Ones in 2051 lab magnify 1000X
Lens System of Compound Microscopes
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Condenser lens
o
located between light source and specimen
o
Focuses light rays up through specimen
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- Fall '07
- Brininstool
- Microbiology, cells, smallest eukaryotic cells, Dark- Field Microscopy o Cells, Bright- field Microscopy o Microscope, Coccus- single cells
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