chapter 2

chapter 2 - Chapter 2 Thursday, January 15, 2009 10:05 AM...

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Chapter 2 Thursday, January 15, 2009 10:05 AM Chapter 2: Observing the Microbial Cell SIZE OF PROKARYOTES Prokaryotes are generally smaller than eukaryotes Small size allows nutrients to reach all parts of cell quickly Prokaryotic cells can be as small as 0.2 μ m. The smallest eukaryotic cells are 2 μ m. Figure 2.4 Cocci shaped bacteria- typically has diameter of 2 μm Some microbiologists have proposed that bacteria smaller than 0.2 μ m 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 μ m. Prokaryotic cells can have a wide variety of cellular morphologies, which are often helpful in identification. Bacterial Shapes Simplest shape is sphere singular- coccus plural- cocci Arrangement: Coccus- single cells Diplococcus- 2 cells Streptococcus- chains of more than 2 cells Staphylococcus- grape-like clusters of cells Tetrads- packets of 4 cells stuck together Staphylococcus aureas is an organism which grows as staphylococci How do you know if its talking about an organism or a shape? Italicized capitalized Most common shape is rods Singular- bacillus
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Plural- bacilli Occur singly or in chains Spirals: Rigid spiral-shaped bacteria are called spirilla (singular- spirillum) Flexible spiral-shaped bacteria are called spirochetes Vibrio – curved rods (kinda looks like sickle-cell) Figure 2.6 Microscopy Simple microscopes one lens magnify 50 – 300 X Compound microscopes multiple lenses Much higher magnification Ones in 2051 lab magnify 100x Lens System of Compound Microscopes
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chapter 2 - Chapter 2 Thursday, January 15, 2009 10:05 AM...

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