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Slide 1

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Microbes & Disease…read more

Slide 2

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Culturing Bacteria
Commercial biotechnology
Bacterial Disease
Viral Disease
Protection Against Disease…read more

Slide 3

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A microbe is any organism that is not visible with the naked
The unaided resolution of the eye is about 0.1mm
Bacteria are classified according to their shape:
1) Cocci: spherical bacteria
- Cocci ­ smallest bacteria, occur as single spheres
- Diplococci ­ pairs of spheres, e.g. pneumonia
- Staphylococci ­ clusters of spheres, e.g. food poisoning
- Streptococci ­ chains of spheres, e.g. sore throat
2) Bacilli: rod-shaped bacteria:
- Individual rods ­ e.g. typhoid fever
- Chains of rods ­ e.g. anthrax
3) Spirilla ­ large, spiral-shaped bacteria - e.g. syphilis
4) Vibrio ­ crescent-shaped bacteria - e.g. cholera…read more

Slide 4

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Reproduction of Bacteria
Cell elongation results in the synthesis of additional cytoplasm
& nuclear material
DNA replication takes place (there is no mitotic spindle), & the
nuclear material attaches to the plasma membrane or
A septum begins to develop, & the nuclear material is
distributed to both sides
The septum is completed, & a cell wall develops to divide the
cell into two
The two daughter cells grow to a critical size, & then repeat
this process…read more

Slide 5

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Culturing Bacteria
New genetic material can be inserted into a bacterium in three
main ways:
1) Conjugation: bacteria link together by their pili. Donor
passes a plasmid called the F-factor (fertility) to the recipient
cell. The F-factor may be in a plasmid (replicating
independently), or incorporated into the main bacterial
2) Transformation: one bacterium releases DNA which is
absorbed by a second bacterium, allowing it to acquire new
3) Transduction: new genes can be inserted into the bacterial
chromosome by a bacteria phage (a virus acting as a vector)…read more

Slide 6

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Culturing Bacteria
The bacterial population growth curve occurs in four main
1) Lag phase: cells are active, but there is little increase in
number. The cells accommodate to the new conditions, take in
water & synthesise ribosomes & enzymes
2) Log phase: Nutrients & space are in plentiful supply, so
there is little competition, & the bacteria multiply at their
maximum rate…read more

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