BIOL2051_Ch.2

BIOL2051_Ch.2 - Chapter 2: Observing the Microbial Cell...

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Chapter 2: Observing the Microbial Cell SIZE OF PROKARYOTES Prokaryotes are generally smaller than eukaryotes Small size allows nutrients to reach all parts of the cell quickly Prokaryotic cells can be as small as 0.2μm. The smallest eukaryotic cells are 2μm. Figure 2.4 Cocci shaped bacteria typically have a diameter of 2 µm 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 Arrangement: o Coccus- single cells o Diplococcus- 2 cells o Streptococcus- chain of more than 2 cells o Staphylococcus- grape-like clusters of cells o Tetrads- packets of 4 cells stuck together 2. Most common shape is rods o Singular- bacillus o Plural- bacilli Can be very long & thin or short & fat
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Occur singly or in chains 3. Spirals: Rigid spiral-shaped bacteria are called spirilla (singular- spirillum) Flexible spiral-shaped bacteria are called spirochetes Vibrio – curved rods (looks similar to sickle-cell) Microscopy Simple microscopes o one lens o magnify 50 – 300 X Compound microscopes o multiple lenses o Much higher magnification Ones in 2051 lab magnify 100X Lens System of Compound Microscopes Condenser lens focuses light rays up o Located between light source and specimen o Focus light rays up through specimen
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This note was uploaded on 05/07/2011 for the course BIOL 2153 taught by Professor Larkin during the Spring '03 term at LSU.

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BIOL2051_Ch.2 - Chapter 2: Observing the Microbial Cell...

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