BIOL 2051 Chapter : Chapter 2
In library on first floor at reserve desk:
MICROBIOLOGY: An Evolving Science- call number is RX52
Circulates 2hrs BUILDING USE ONLY
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 0.2μm. The smallest eukaryotic cells are 2μm.
• Cocci- sphere shaped bacteria- typically have 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 (shape), 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- chains of more than 2 cells
o Staphylococcus- grapelike cluster of cells
o Tetrads- packets of 4 cells
2. Most common shape is rods
o Singular- bacillus
o Plural- bacilli
• Can be very long & thin or short & fat
• Occur singly or in chains
3. Spirals:
• Rigid spiral-shaped bacteria are called spirilla (singular-spirllum)
• Flexible spiral-shaped bacteria are called spirochetes with multiple curves
• Vibrio – curved rods
Microscopy
• Simple microscopes
o one lens
o magnify 50 – 300X
• Compound microscopes
o multiple lenses
o Much higher magnification
▪ Ones in 2051 lab magnify up to 1000x
Document Summary
In library on first floor at reserve desk: Microbiology: an evolving science- call number is rx52. 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 m. The smallest eukaryotic cells are 2 m: cocci- sphere shaped bacteria- typically have diameter of 2 m, some microbiologists have proposed that bacteria smaller than 0. 2 m exist in nature, cells referred to as nanobacteria. Microscopy: simple microscopes, one lens, magnify 50 300x, compound microscopes, multiple lenses, much higher magnification, ones in 2051 lab magnify up to 1000x. Lens system of compound microscopes: condenser lens located between light source and specimen focuses light rays up through specimen, objective lens system, closest to specimen, typical scope has 10, 40, & 100x objective lenses. In each objective are multiple lenses: ocular lens system, closest to the eye, typically magnify 10x, each ocular has multiple lenses.
