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2. What are bacteria?
 Bacteria are among the smallest
living organisms.
 They usually band together in
colonies.
 Bacteria can be autotrophic, E. Coli O157:H7
can make you
make their own food
very sick.
or
heterotrophic, feed off of other
organisms.
This E. coli helps you digest
food.

3. Characteristics of Bacteria
 Three basic shapes
 Rod shaped called bacilli (buh-sill-eye)
 Round shaped called cocci (cox-eye)
Bacilli
 Spiral shaped
Spiral
Cocci

4. Structure of Bacteria
 Bacteria have these features:
 Cell wall
 resists osmotic pressure
 Flagella
 movement
 Pili
 Attachment
 Capsule
 protection and biofilms

5. Structure of Bacteria

6. Structure of Bacteria
 Cell Wall made of Peptidoglycan
 May have a sticky coating called the Capsule for attachment to host or
other bacteria
 Have small rings of DNA called Plasmids Unicellular
 Small in size (0.5 to 2μm)

7. Structure of Bacteria
Capsule
 Some bacteria (often pathogens) are surrounded by a
thick polysaccharide capsule.
 This is a loose jelly-like or mucus-like layer.
 It helps prevent immune system cells from reaching the
bacteria, and it forms part of biofilms.

8. Structure of Bacteria
 Pili are hairs projecting from the surface. They are
composed of pilin protein.
 There are several types:
 DNA can be transferred between bacteria by
conjugation, which is initiated when sex pili on the donor
cell attach to and draw in the recipient cell.
 Fimbriae are pili used to attach the bacteria to target cells
(in infection) or to surfaces, where they form a biofilm.

9. Structure of Bacteria
Flagella
 Flagella are long hairs used to propel the cells.
They are composed of flagellin protein.
 At the base of each flagellum is a motor embedded in
the membrane and cell wall.
 The suffix “-trichous” is used to describe the
placement of flagella: e.g. lophotrichous = several
flagella all clustered at one end

10. Structure of Bacteria
 Chemotaxis: Bacteria move toward the source of
nutrients by swimming up the chemical gradient.
 When moving up the gradient, bacteria rarely tumble,
but when moving across it, or in the opposite direction,
tumbling is frequent.
 This produces a net motion in the proper direction.

11. Structure of Bacteria
Spores
 Some bacteria can form very tough spores, which are
metabolically inactive and can survive a long time under very
harsh conditions.
 Allegedly, some bacterial spores that were embedded in
amber.
 Panspermia: the idea that life got started on Earth due
to bacterial spores that drifted in from another solar.
 Spores survive very high or low temperatures.

12. Movement and feeding
 Bacteria get around in
many ways.
 Some bacteria move using
flagella.
 Others have a slimy layer to
grip surfaces.
 Some are carried by the
movement of air or liquids.
.

13. Movement and feeding
 Photosynthetic bacteria can
make their own food from
sunlight and carbon dioxide, just
like plants.
 Bacteria that break down dead
organisms get their food by
absorbing it.
These blue green
bacteria use sunlight to
make food.

14. The importance of bacteria
 Bacteria are useful in many
areas of industry.
 Yogurt and cheese are made
with certain types of bacteria.
 Bacteria break down waste
products in sewage.
 Bacteria can help clean up oil
spills.

15. The importance of bacteria
 Bacteria are an
important part of
the nutrient cycles
that all life depends
upon.

16. The importance of bacteria
 Bacteria are “nature’s recyclers.”

17. Harmful effects of bacteria
 Certain bacteria act as pathogens and cause tetanus,
typhoid fever, pneumonia, syphilis, cholera,
food-borne illness and tuberculosis.
 Streptococcus bacteria may cause small infections
like strep throat and some serious diseases like
pneumonia.
 Some of the stomach bacteria enter the body through
the mouth, and they can survive in the acidic conditions
in the stomach.

18. Harmful effects of bacteria
Acidic condition
Typhoid fever

19. Harmful effects of bacteria
 Campylobacter is a group of bacteria that can create
illnesses in humans and is a common cause of food
poisoning.
 Harmful bacteria in food cause botulism, which can
cause paralysis or even death if even one-millionth of
the bacterium is ingested.
 Yersinia pestis or bubonic plague, is a rod-shaped
type of bacterium which is well-known for its harmful
nature.

20. Harmful effects of bacteria
 Bacteria-carrying fleas
found on animals such as
rats and mice transmit the
bacteria that are believed to
have caused the deaths of
millions of people in human
history.
 Antibiotics are widely used
to kill harmful bacteria.

21. Where do you get a pathogen ?
 Contact with people who are sick
 Direct or indirect
 Food, Water, or other Surfaces that are contaminated
Foods that could be
contaminated Direct contact Indirect contact

22. Where do you get a pathogen?
Direct
Contact
Indirect
Contact
Foods and water
may be
contaminated

23. How can I avoid pathogens?
 Wash your hands often so you won’t transfer
bacteria to your mouth or food
 Warm water with soap for 20 seconds, rub hard
between fingers and nails
• Cook food thoroughly to kill any pathogens that may be
in your food
• Store food properly to limit pathogen growth
– Cold temperatures (40F)

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