Prokaryotes like bacteria and archea make up the human microbiome, comprising 1-3% of the human body mass. Bacteria are some of Earth's oldest life forms and come in various shapes. They have diverse metabolic functions and can live in extreme environments. Some bacteria engage in symbiotic relationships with humans and support functions like digestion. While many bacteria are beneficial, certain pathogens can cause diseases. Advances like antibiotics revolutionized medicine but their overuse led to increased antibiotic resistance in bacteria.

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

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

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

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

5. Enter the Domain System ofEnter the Domain System of
ClassificationClassification
 Scientists divided living things into 3Scientists divided living things into 3
Supergroups called domains these consist ofSupergroups called domains these consist of
Bacteria, Archea and EukaryaBacteria, Archea and Eukarya

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

7. BacteriaBacteria
 EarthEarth’s oldest life forms’s oldest life forms
–– between 3.5 and 3.8 billion years oldbetween 3.5 and 3.8 billion years old
 Most abundant life form – up to 2.5 billionMost abundant life form – up to 2.5 billion
individual bacteria in 1 gram of fertile soilindividual bacteria in 1 gram of fertile soil
 Very adaptable – found in all of EarthVery adaptable – found in all of Earth’s’s
ecosystemsecosystems

8. Bacteria CharacteristicsBacteria Characteristics
 UnicellularUnicellular
 Circular DNACircular DNA
 No organellesNo organelles
 1/101/10thth
the size of eukaryotic cellsthe size of eukaryotic cells
 Flagella-long hair-like structure used forFlagella-long hair-like structure used for
movementmovement
 Reproduce asexually –Binary FissionReproduce asexually –Binary Fission

9. Bacterial ShapesBacterial Shapes
 3 main shapes3 main shapes
- coccus – sphere- coccus – sphere
- bacillus – rods- bacillus – rods
- spirillum - spiral- spirillum - spiral

10. Bacterial CharacteristicsBacterial Characteristics
 Metabolic diversity –Metabolic diversity – Bacteria can produceBacteria can produce
energy in a variety of circumstancesenergy in a variety of circumstances
autotrophautotroph – (self-feeding) – some bacteria can– (self-feeding) – some bacteria can
produce their own foodproduce their own food
- some use photosynthesis – get energy from- some use photosynthesis – get energy from
lightlight
- some use chemosynthesis – get energy from- some use chemosynthesis – get energy from
chemicalschemicals
HeterotrophHeterotroph - (other feeding) – many bacteria- (other feeding) – many bacteria
are unable to produce their ownare unable to produce their own
food and are required to eat otherfood and are required to eat other
thingsthings

11. Bacterial Characteristics:Bacterial Characteristics:
Metabolic diversity continuedMetabolic diversity continued
obligate aerobeobligate aerobe – like us these bacteria need oxygen– like us these bacteria need oxygen
obligate anaerobeobligate anaerobe - these bacteria need to be in an oxygen- these bacteria need to be in an oxygen
free environment – human gutfree environment – human gut
facultative anaerobefacultative anaerobe – these bacteria can live in either an– these bacteria can live in either an
oxygen or oxygen free environmentoxygen or oxygen free environment

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

13. Bacterial Structure: Cell WallBacterial Structure: Cell Wall
 Made ofMade of peptidoglycanpeptidoglycan – a combination of protein and– a combination of protein and
polysaccharidespolysaccharides
 Some bacteria calledSome bacteria called Gram negative bacteriaGram negative bacteria have an additionalhave an additional
layer of membrane that contains lipopolysaccharidelayer of membrane that contains lipopolysaccharide
- this extra layer inhibits the uptake of antibiotics – protecting- this extra layer inhibits the uptake of antibiotics – protecting
the bacteriathe bacteria
cell
membrane
cell wall
cell
membrane
Outer membrane
lipopolysaccharide
cell wall

14. Gram + vs. Gram -Gram + vs. Gram -
Absorb stain appear purple
Don’t absorb stain appear
pink
The type of cell wall is used by
doctors to help diagnose disease
The bacteria are stained with a
special stain called Gram stain
Bacteria without the extra membrane,
appear purple. These are Gram positive
(Gram +) bacteria
Bacteria with the extra membrane
appear pink. These are Gram negative
( Gram -) bacteria

15. Bacterial Structure continuedBacterial Structure continued
 PiliPili – hairlike structures usually found– hairlike structures usually found
in Gram neg. bacteria. Help thein Gram neg. bacteria. Help the
bacteria stick to surfaces.bacteria stick to surfaces.
Also formsAlso forms conjugation bridgeconjugation bridge
 ChromosomeChromosome – a single loop of DNA– a single loop of DNA
that is folded on itselfthat is folded on itself
- controls the cell- controls the cell’s function’s function
 NucleoidNucleoid – the region of the cytoplasm– the region of the cytoplasm
where the DNA is foundwhere the DNA is found
 PlasmidPlasmid – an accessory loop of DNA – small contains only a few– an accessory loop of DNA – small contains only a few
genes - can be responsible for: conjugation, antibioticgenes - can be responsible for: conjugation, antibiotic
resistance, unique metabolic properties – like the ability toresistance, unique metabolic properties – like the ability to
use hydrocarbonsuse hydrocarbons
 CapsuleCapsule – found outside some bacteria stores nutrients and protects– found outside some bacteria stores nutrients and protects
the bacteria from changing environmental conditionsthe bacteria from changing environmental conditions

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

17. Reproduction - Binary FissionReproduction - Binary Fission
 Asexual reproductionAsexual reproduction
- offspring are genetically- offspring are genetically
identical to parent – noidentical to parent – no
new genetic combinationsnew genetic combinations
- under ideal conditions- under ideal conditions
can occur every 20 mincan occur every 20 min
- creates large numbers- creates large numbers
of bacteria in a shortof bacteria in a short
timetime

18.  Each spot representsEach spot represents
a single bacteriala single bacterial
cell that reproducedcell that reproduced
by binary fission toby binary fission to
produce millions ofproduce millions of
genetically identicalgenetically identical
cells.cells.
 Genetically identical,Genetically identical,
good or bad?good or bad?

19. Exchanging Genetic InformationExchanging Genetic Information
 Bacterial cells need to be able to exchange geneticBacterial cells need to be able to exchange genetic
informationinformation
- creates new genetic combinations which increases the- creates new genetic combinations which increases the
ability of the bacteria to surviveability of the bacteria to survive
 Bacteria have 3 methods for exchanging DNABacteria have 3 methods for exchanging DNA
-Transduction-Transduction – viruses carry DNA from one bacterial– viruses carry DNA from one bacterial
cell to anothercell to another
-Transformation-Transformation – bacteria can absorb– bacteria can absorb “naked” DNA“naked” DNA
released by dead bacteria fromreleased by dead bacteria from
thethe environmentenvironment
-- ConjugationConjugation – two bacteria join at a conjugation– two bacteria join at a conjugation
bridge, one bacteria passes on abridge, one bacteria passes on a
copy of its plasmid or chromosomecopy of its plasmid or chromosome

20. Exchanging Genetic InformationExchanging Genetic Information

21. TransductionTransduction –– DNA is carried fromDNA is carried from
one bacteria to another by a virusone bacteria to another by a virus

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

23. ConjugationConjugation

24. Conjugation-Conjugation- one cell passes a copy ofone cell passes a copy of
its plasmid or chromosome to anotherits plasmid or chromosome to another
Donor Cell
Recipient
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

25. Bacteria Play Important Roles inBacteria Play Important Roles in
EcosystemsEcosystems
 DecomposersDecomposers
–– recycle dead organisms releasing theirrecycle dead organisms releasing their
nutrients back to the environment fornutrients back to the environment for
use by other organisms –use by other organisms – SPONCHSPONCH
Without decomposers,Without decomposers,
the elements on earththe elements on earth
would have remainedwould have remained
locked up in deadlocked up in dead
organisms and lifeorganisms and life
would have ceasedwould have ceased

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

27. Bacterial Roles: ProducersBacterial Roles: Producers
 In some ecosystemsIn some ecosystems
chemosynthetic andchemosynthetic and
photosynthetic bacteriaphotosynthetic bacteria
serve as the basis ofserve as the basis of
the food chainthe food chain
–– chemosynthetic bacteria in deep ocean ventschemosynthetic bacteria in deep ocean vents
convert hydrogen sulfide (Hconvert hydrogen sulfide (H22S) gas into energyS) gas into energy
-- cyanobacteriacyanobacteria are photosynthetic bacteriaare photosynthetic bacteria
which act as producers in many aquaticwhich act as producers in many aquatic
ecosystemsecosystems

28. Bacterial Roles:Bacterial Roles: Symbiotic BacteriaSymbiotic Bacteria
Many bacteria live in or on other organismsMany bacteria live in or on other organisms
(including humans) and aid their host(including humans) and aid their host
- some live in the gut of herbivores helping to- some live in the gut of herbivores helping to
digest cellulosedigest cellulose
- bacteria in the gut of humans- bacteria in the gut of humans
aid digestion and produceaid digestion and produce
vitaminsvitamins
- bacteria on skin and in body- bacteria on skin and in body
openings help prevent infectionopenings help prevent infection
by harmful organismsby harmful organisms

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

30. Pathogenic Bacteria: BiofilmsPathogenic Bacteria: Biofilms
 Some bacteria can form aSome bacteria can form a biofilmbiofilm – a matrix– a matrix
made of polysaccharidemade of polysaccharide
- once formed, the matrix traps other bacteria- once formed, the matrix traps other bacteria
- the biofilm protects the bacteria, making it hard- the biofilm protects the bacteria, making it hard
to kill themto kill them

31. AntibioticsAntibiotics
 Antibiotics are chemicals which either kill bacteria orAntibiotics are chemicals which either kill bacteria or
prevent their growth and reproductionprevent their growth and reproduction
 Bacteria and other microbes produce antibiotics toBacteria and other microbes produce antibiotics to
reduce competition from other organismsreduce competition from other organisms
 Penicillin was the first to be use to fight diseasePenicillin was the first to be use to fight disease
- discovered accidently by Alexander Fleming in 1928- discovered accidently by Alexander Fleming in 1928
 Two scientists Walter Florey and Ernst Chain determinedTwo scientists Walter Florey and Ernst Chain determined
how to use penicillin tohow to use penicillin to
treat disease in 1939.treat disease in 1939.
 The discovery ofThe discovery of
antibiotics revolutionizedantibiotics revolutionized
the treatmentthe treatment
of disease

32. Antibiotic ActionAntibiotic Action
 Antibiotics effect bacteria, but not eukaryotic cellsAntibiotics effect bacteria, but not eukaryotic cells
 Antibiotics attack bacteria in 5 waysAntibiotics attack bacteria in 5 ways
- some damage the cell walls or prevent new cell wall from forming- some damage the cell walls or prevent new cell wall from forming
- some damage the cell membrane- some damage the cell membrane
- some prevent protein synthesis- some prevent protein synthesis
- some prevent DNA from being copied- some prevent DNA from being copied
- some interfere with bacterial metabolism- some interfere with bacterial metabolism

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

34. Black Plague-Black Plague-YersiniaYersinia pestispestis

35. Syphilis--Syphilis--TreponemaTreponema
pallidumpallidum/Bacterial/Bacterial

36. MycobacteriumMycobacterium lepraeleprae/Bacteria/Bacteria

37. ClostridiumClostridium perfringesperfringes/Bacteria/Bacteria

38. VocabularyVocabulary
Microbiome ArcheaMicrobiome Archea
autotrophautotroph pilipili
heterotrophheterotroph nucleoidnucleoid
peptidoglycanpeptidoglycan capsulecapsule
plasmidplasmid conjugation bridgeconjugation bridge
Gram -Gram - obligate aerobeobligate aerobe
Gram +Gram + obligate anaerobeobligate anaerobe
binary fissionbinary fission facultative anaerobefacultative anaerobe
conjugationconjugation nitrogen fixing bacterianitrogen fixing bacteria
transductiontransduction cyanobacteriacyanobacteria
transformationtransformation pathogenspathogens
biofilmbiofilm