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Microbiology
| Bacteria are Prokaryotes; in the Kingdom Monera |
| The Bacteria can be divided
into two different groups. The Eubacteria
and the Archaebacteria. Eubacteria are probably the more common, but the Archaebacteria have been found in thousands of environments, many of them very strange by our standards |
Extreme bacteria - The Archaebacteria are generally found in environmental extremes (as far as we're concerned) in that they exist in hot springs at 100 degrees C (boiling water!), in the bottom of the ocean at ~110C and in water the density of lead, in saturated salt ponds and other environments that would seem to be inimitable to life. They can metabolize unusual substances for energy like methane, sulfur, and hydrogen gas. Their origin and relationship to Eubacteria and eukaryotes is currently being hotly debated among microbiologists. However, some of their biochemical characteristics resemble eukaryotes more than they do Eubacteria. Fortunately, there are no reports of any pathogenic Archaebacteria.
| Required reading -> Extreme bacteria - and you thought the X-games were extreme! |
Eubacteria
- There are an enormous number of Eubacteria species, with a bazillion
new ones being discovered every time someone looks.
The size, shape and arrangement of the bacteria, is one method of identifying the many types. This characteristic is called their morphology. Bacteria come in a bewildering and exciting variety of morphologies.
The most common bacterial shapes are rods, round, and spiral-shaped |
Shape offers many advantages to the bacterium. The cocci shape is more resistant to drying than the rod, the rod has more surface area for nutrient absorption and the spirillum structure provides less resistance to movement. These shape differences are only superficial and mask many more important differences inside.
The Bacilli are rod-shaped (yellowish-green or light blue in the image above). The rods of the bacilli may be long, short, thick, thin, have rounded or pointed ends, or they may be thicker at one end than the other etc. The bacilli may be found mainly as single cells or as groups such as chains,
The Cocci
are round. Cocci
may be large, small, round or oval shaped to various degrees. Cocci also
are found as individuals or in various groups. Diplococci
are round bacteria that are found in twos (see the Cocci in the
image above).
Staphylococci are Cocci, typically arranged in clumps or grape-like
clusters (Staph is Greek for a bunch of grapes).
Streptococci
are Cocci who remain joined after binary fission and form long "strings"
of bacteria, as in the image above. The
Spirilli are
spiral-shaped (corkscrew)
bacteria. These may be found as fat, thin, loose spirals or
very tight spirals.
Within each of these groups are hundreds of variations as the bacteria
occur as single cells or common grouping such as chains, uneven clusters,
pairs, tetrads, octads and other packets. They may exist as masses embedded
within a capsule or form spores. There are square bacteria, star-shaped
bacteria, stalked bacteria, budding bacteria, and bacteria that grow in
netlike arrangements. The morphology of bacteria isn't really a very good
tool for distinguishing between the very large number of bacterial species.
If you really want to know what type of bacteria it is, you have to look
at its Biochemistry or Genetics.
| Summary -There are many different types of bacteria. The can be classified by the environment in which they live; e.g. Archaebacteria which live in extreme environments, or by their shape. There are three primary shapes of Eubacteria: Cocci: round, Bacilli; rod-shaped, and Spirilli; spiral. The ultimate method for classifying bacterial is Biochemical. |
Virus Structure 
Antibiotics Attack - HHMI, a tutorial designed to give any student background information on antibiotics, their function, and their targets. This multimedia presentation includes five major chapters that cover bacteria, antibiotic structure, pathways of attack, penicillin, and antibiotic resistance. |
