1. Prokaryotes
Or 100 Trillion Friends That
You Didn’t Know You Had

2. The Human Microbiome We are actually a giant ecosystem of microbes
Prokaryotes comprise between 1-3% of the mass of a human body
- up to 6lbs of a 200 lb person can be microbes

3. Classification: Some Old, Some New
Biologists have typically classified living things into 5 large groups called kingdoms
- Monera, Protista, Fungi, Plantae & Animalia
Then biologists discovered organisms called Archea – they are prokaryotic organisms but aren’t bacteria.
- What to do?

4. The Challenge of Archea
Archea present a problem, they a are prokaryotes
– They have no nucleus or organelles
They also share traits with eukaryotes
- similarities in DNA and synthesis
They have traits unique to themselves
- cell membrane lipids, ability to
survive extremely high temperature

5. Enter the Domain System of Classification
Scientists divided living things into 3 Supergroups called domains these consist of Bacteria, Archea and Eukarya

6. Archea can be Extremophiles
Some species of archea can be found in environments so extreme, that nothing else lives there- extreme temps, extreme pH, extremely salty etc…

7. Bacteria Earth’s oldest life forms
– between 3.5 and 3.8 billion years old
Most abundant life form – up to 2.5 billion individual bacteria in 1 gram of fertile soil
Very adaptable – found in all of Earth’s
ecosystems 7

8. 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 8

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

10. 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 10

11. 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

12. Bacterial Structure Cell Wall Cell Membrane Pilus chromosome nucleoid
capsule
ribosome
plasmid
cytoplasm
flagellum

13. 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

14. Gram + vs. Gram -
The type of cell wall is used by doctors to help diagnose disease
The bacteria are stained with a
special stain called Gram stain
Absorb stain appear purple
Bacteria without the extra membrane, appear purple. These are Gram positive (Gram +) bacteria
Named after Danish Scientist Hans Christian Gram – No Joke Gram was working on Pneumonia and discovered that different organisms took up stain differently. The process stains the both types of cells with crystal violet, and then they are treated with alcohol which
Bacteria with the extra membrane appear pink. These are Gram negative ( Gram -) bacteria
Don’t absorb stain appear
pink 14

15. 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

16. Reproduction - Binary Fission
Bacterial cells undergoing binary fission 16

17. 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

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

19. 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 19

20. Exchanging Genetic Information

21. Transduction – DNA is carried from one bacteria to another by a virus21

22. Transformation: Bacteria absorb “naked” DNA from the environment22

23. Conjugation 23

24. 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 24

25. 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

26. 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?

27. 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

28. 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

29. 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

30. 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.

31. 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
Two scientists Walter Florey and Ernst Chain determined
how to use penicillin to
treat disease in 1939.
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

32. 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

33. 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

34. 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. 34

35. Syphilis--Treponema pallidum/Bacterial
Causes an ulcer at the site of infection. 4 stages of life. Treatment now with Penicillin. 35

36. Mycobacterium leprae/Bacteria
Rod like Bacteria-spread through coughing and sneezing. In old days they thought it was genetic and they isolated people-Leprae colonies. Now (1940)there is antibiotic treatment to clear up the symptoms in 6-12 months. 36

37. Clostridium perfringes/Bacteria
Gram positive bacillus. Can cause gas gangrene. Often caused from fecal contamination of a wound Usually in the buttocks, thighs, and perineum. Infection may proceed up to 10cm per hour. Often produces large amounts of CO2 and hydrogen . 37

38. Vocabulary Microbiome Archea 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 38