1. Bacteria

2. Bacteria Characteristics
Unicellular
Circular DNA
No organelles
1/10th the size of eukaryotic cells
Flagella-long hair-like structure used for movement
Reproduce asexually –Binary Fission 2 2

3. Bacterial Shapes 3 main shapes - coccus – sphere - bacillus – rods
- spirillum - spiral

4. Bacterial Characteristics
Metabolic diversity – Bacteria can produce energy in a variety of circumstances
autotroph – (self-feeding) – some bacteria can produce their own food
- some use photosynthesis – get energy from light
- some use chemosynthesis – get energy from
chemicals
Heterotroph - (other feeding) – many bacteria
are unable to produce their own food and are required to eat other things 4 4

5. Bacterial Characteristics: Metabolic diversity continued
obligate aerobe – like us these bacteria need oxygen
obligate anaerobe - these bacteria need to be in an oxygen free environment – human gut
facultative anaerobe – these bacteria can live in either an oxygen or oxygen free environment

6. Bacterial Structure cell wall cell membrane pilus chromosome nucleoid
capsule
ribosome
plasmid
cytoplasm
flagellum

7. Bacterial Structure: Cell Wall
Made of peptidoglycan – a combination of protein and polysaccharides
Some bacteria called Gram negative bacteria have an additional layer of membrane that contains lipopolysaccharide
- this extra layer inhibits the uptake of antibiotics – protecting
the bacteria
cell wall
cell
membrane
cell
membrane
lipopolysaccharide
cell wall
Outer membrane

8. Bacterial Structure continued
Pili – hairlike structures usually found
in Gram neg. bacteria. Help the bacteria stick to surfaces.
Also forms conjugation bridge
Chromosome – a single loop of DNA
that is folded on itself
- controls the cell’s function
Nucleoid – the region of the cytoplasm
where the DNA is found
Plasmid – an accessory loop of DNA – small contains only a few genes - can be responsible for: conjugation, antibiotic resistance, unique metabolic properties – like the ability to use hydrocarbons
Capsule – found outside some bacteria stores nutrients and protects the bacteria from changing environmental conditions

9. Reproduction - Binary Fission
Bacterial cells undergoing binary fission 9 9

10. Reproduction - Binary Fission
Asexual reproduction
- offspring are genetically
identical to parent – no
new genetic combinations
- under ideal conditions
can occur every 20 min
- creates large numbers
of bacteria in a short
time

11. Each spot represents
a single bacterial
cell that reproduced
by binary fission to
produce millions of
genetically identical
cells.
Genetically identical,
good or bad?

12. Exchanging Genetic Information
Bacterial cells need to be able to exchange genetic information
- creates new genetic combinations which increases the ability of the bacteria to survive
Bacteria have 3 methods for exchanging DNA
-Transduction – viruses carry DNA from one bacterial cell to another
-Transformation – bacteria can absorb “naked” DNA released by dead bacteria from the environment
- Conjugation – two bacteria join at a conjugation bridge, one bacteria passes on a copy of its plasmid or chromosome 12 12

13. Exchanging Genetic Information

14. Transduction – DNA is carried from one bacteria to another by a virus14 14

15. Transformation: Bacteria absorb “naked” DNA from the environment15 15

16. Conjugation 16 16

17. Conjugation- one cell passes a copy of its plasmid or chromosome to another
Recipient
Cell
Donor Cell
A special pilus forms
a connection called
a conjugation bridge
between 2 bacterial
cells
Plasmid
Conjugation bridge
The donor cell
copies its plasmid
or chromosome and
passes the copy
through the
conjugation bridge
Cells separate 17 17

18. Bacteria Play Important Roles in Ecosystems
Decomposers
– recycle dead organisms releasing their nutrients back to the environment for use by other organisms – SPONCH
Without decomposers,
the elements on earth
would have remained
locked up in dead organisms and life would have ceased

19. Bacterial Roles: Nitrogen Fixation
some bacteria contain enzymes which allow them to convert (or fix) nitrogen from the air into a useable form
- they are nitrogen fixing bacteria
- Why do living things use nitrogen?

20. Bacterial Roles: Producers
In some ecosystems
chemosynthetic and
photosynthetic bacteria
serve as the basis of
the food chain
– chemosynthetic bacteria in deep ocean vents convert hydrogen sulfide (H2S) gas into energy
- cyanobacteria are photosynthetic bacteria
which act as producers in many aquatic
ecosystems

21. Bacterial Roles: Symbiotic Bacteria
Many bacteria live in or on other organisms (including humans) and aid their host
- some live in the gut of herbivores helping to digest cellulose
- bacteria in the gut of humans
aid digestion and produce
vitamins
- bacteria on skin and in body
openings help prevent infection
by harmful organisms
Stomach bacteria help maintain stomach pH, produce B and K vitamins, studies show that babies given lactobacilius bacteria have less diarrhea 21

22. Bacterial Roles: Pathogenic Bacteria
Pathogens are organisms that cause disease
- only a small portion of bacteria are pathogens
- most bacteria diseases are caused by toxins
released by the bacteria
- these toxins:
- poison cells and damage tissue
- interfere with cell signaling
- over-stimulate cells causing them to malfunction

23. Pathogenic Bacteria: Biofilms
Some bacteria can form a biofilm – a matrix made of polysaccharide
- once formed, the matrix traps other bacteria
- the biofilm protects the bacteria, making it hard to kill them
Biofilms form on joint replacements, contact lenses, plaque on your teeth. 23

24. Antibiotics
Antibiotics are chemicals which either kill bacteria or prevent their growth and reproduction
Bacteria and other microbes produce antibiotics to reduce competition from other organisms
Penicillin was the first to be use to fight disease
- discovered accidently by Alexander Fleming in 1928
The discovery of antibiotics
revolutionized the treatment
of disease
Antibiotics which kill bacteria are bacteriacidal, the antibiotics which stop growth are referred to as bacteriastatic 24

25. Antibiotic Action
Antibiotics effect bacteria, but not eukaryotic cells
Antibiotics attack bacteria in 5 ways
- some damage the cell walls or prevent new cell wall from forming
- some damage the cell membrane
- some prevent protein synthesis
- some prevent DNA from being copied
- some interfere with bacterial metabolism
Bacterial ribosomes are 70S 50S and 30S subunits – antibiotics impact these subunits
Eukaryotic ribosomes are 80S 60S and 40S subunits – antibiotics don’t impact these 25

26. Antibiotic Resistance
Some bacteria have developed a resistance to the effect
of some antibiotics
- the number of resistant bacteria is growing
The problem is increased by overuse and misuse of antibiotics
- use of antibiotics to treat viral infections – antibiotics don’t effect viruses
- the use of antibiotics in livestock (cattle, chickens, pigs)
antibiotics show up in the meat and milk
- people take the antibiotics until they feel better, but stop before all of the bacteria are destroyed
- this kills the most susceptible bacteria, but leaves the more resistant bacteria 26

27. Black Plague-Yersinia pestis
Bacillus bacterium from flea bites that recently fed on infected rats. Flea regurgitates germs onto human open wound. Sign of infection is lymph nodes swellings called Buboes. Dried blood under the skin turns black, hence the name Black Death. Spread is slow from person to person. Mortality is very high (75%) for untreated cases. Now early treatment with antibiotics is very effective. 27 27

28. Vocabulary autotroph pili heterotroph nucleoid peptidoglycan capsule
plasmid conjugation bridge
Gram - obligate aerobe
Gram + obligate anaerobe
binary fission facultative anaerobe
conjugation nitrogen fixing bacteria
transduction cyanobacteria
transformation pathogens
biofilm 28 28