BacteriaBacteria Earth’s oldest life forms (PROKARYOTES)Earth’s oldest life forms (PROKARYOTES)

– – 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 Most abundant life form – up to 2.5

billion individual bacteria in 1 gram of billion individual bacteria in 1 gram of fertile soilfertile soil

Very adaptable – found in all of Earth’s Very adaptable – found in all of Earth’s

ecosystemsecosystems

Bacteria CharacteristicsBacteria Characteristics UnicellularUnicellular Circular DNA Circular DNA No organellesNo organelles 1/101/10thth the size of eukaryotic cells the size of eukaryotic cells Flagella-long hair-like structure used Flagella-long hair-like structure used

for movementfor movement Reproduce asexually –Binary FissionReproduce asexually –Binary Fission

Bacterial ShapesBacterial Shapes

3 main shapes3 main shapes

- coccus – sphere- coccus – sphere

- bacillus – rods- bacillus – rods

- spirillum - spiral - spirillum - spiral

Bacterial CharacteristicsBacterial Characteristics Metabolic diversity – Metabolic diversity – Bacteria can produce Bacteria 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 food produce their own food

- some use photosynthesis – get energy from - some use photosynthesis – get energy from light light

- some use chemosynthesis – get energy - some use chemosynthesis – get energy fromfrom

chemicalschemicals

Heterotroph Heterotroph - (other feeding) – many bacteria - (other feeding) – many bacteria

are unable to produce their own are unable to produce their own food and are required to eat food and are required to eat

other other things things

Bacterial Characteristics:Bacterial Characteristics: Metabolic diversity continuedMetabolic diversity continued

obligate aerobe obligate aerobe – like us these bacteria need oxygen– like us these bacteria need oxygen

obligate anaerobe obligate anaerobe - these bacteria need to be in an - these bacteria need to be in an oxygen oxygen free environment – human free environment – human gutgut

facultative anaerobe facultative anaerobe – these bacteria can live in either – these bacteria can live in either an an oxygen or oxygen free oxygen or oxygen free environmentenvironment

Bacterial StructureBacterial Structure

Cell WallCell Membrane

Pilus

chromosome

plasmid

flagellum

nucleoid

ribosomecytoplasm

capsule

Bacterial Structure: Cell Bacterial Structure: Cell WallWall

Made of Made of peptidoglycanpeptidoglycan – a combination of protein and – a combination of protein and polysaccharidespolysaccharides

Some bacteria called Some bacteria called Gram negative bacteriaGram negative bacteria have an have an additional layer of membrane that contains additional layer of membrane that contains lipopolysaccharide lipopolysaccharide

- this extra layer inhibits the uptake of antibiotics – - this extra layer inhibits the uptake of antibiotics – protectingprotecting

the bacteriathe bacteria

cellmembrane

cell wall

cellmembrane

Outer membrane

lipopolysaccharide

cell wall

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 aspecial stain called Gram stain

Bacteria without the extra

membrane, appear purple. These are Gram positive (Gram +) bacteriaBacteria with the extra membrane appear pink. These are Gram negative ( Gram -) bacteria

Bacterial Structure Bacterial Structure continuedcontinued

PiliPili – hairlike structures usually found – hairlike structures usually found

in Gram neg. bacteria. Help thein Gram neg. bacteria. Help thebacteria stick to surfaces. bacteria stick to surfaces.

Also forms Also forms conjugation bridge conjugation bridge ChromosomeChromosome – a single loop of DNA – a single loop of DNA

that is folded on itselfthat is folded on itself

- controls the cell’s function- controls the cell’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 – an accessory loop of DNA – small contains only a

few few genes - can be responsible for: conjugation, genes - can be responsible for: conjugation, antibiotic antibiotic resistance, unique metabolic properties – resistance, unique metabolic properties – like the ability to like the ability to use hydrocarbons use hydrocarbons

CapsuleCapsule – found outside some bacteria stores nutrients and – found outside some bacteria stores nutrients and protects protects the bacteria from changing the bacteria from changing environmental conditionsenvironmental conditions

Reproduction - Binary Reproduction - Binary FissionFission

Bacterial cells undergoing binary fissionBacterial cells undergoing binary fission

Reproduction - Binary Reproduction - Binary FissionFission

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

Each spot represents Each spot represents

a single bacteriala single bacterial

cell that reproduced cell 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?

Exchanging Genetic InformationExchanging Genetic Information Bacterial cells need to be able to exchange genetic Bacterial cells need to be able to exchange genetic

information information

- 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 another cell to another

-Transformation-Transformation – bacteria can absorb “naked” DNA – bacteria can absorb “naked” DNA released by dead bacteria from released by dead bacteria from the the

environmentenvironment

- - ConjugationConjugation – two bacteria join at a conjugation – two bacteria join at a conjugation bridge, one bacteria passes on a bridge, one bacteria passes on a copy of its copy of its

plasmid or chromosomeplasmid or chromosome

Exchanging Genetic Exchanging Genetic InformationInformation

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

Transformation: Bacteria Transformation: Bacteria absorb “naked” DNA from absorb “naked” DNA from

the environmentthe environment

ConjugationConjugation

Conjugation- Conjugation- one cell passes a one cell passes a copy of its plasmid or chromosome to copy of its plasmid or chromosome to anotheranother

Donor CellRecipient Cell

A special pilus formsa connection calleda conjugation bridgebetween 2 bacterialcells

Plasmid Conjugation bridge

The donor cell copies its plasmidor chromosome andpasses the copy through the conjugation bridge

Cells separate

Bacteria Play Important Bacteria Play Important Roles in Ecosystems Roles in Ecosystems Decomposers Decomposers

– – recycle dead organisms releasing their recycle dead organisms releasing their nutrients back to the environment for nutrients 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 remained would have remained

locked up in dead locked up in dead organisms and life organisms and life would have ceased would have ceased

Bacterial Roles: Nitrogen Bacterial Roles: Nitrogen FixationFixation

some bacteria contain enzymes which allow them some bacteria contain enzymes which allow them to convert (or fix) nitrogen from the air into a to convert (or fix) nitrogen from the air into a useable formuseable form

- they are - they are nitrogen fixing bacterianitrogen fixing bacteria

- - Why do living things use nitrogen?Why do living things use nitrogen?

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 chain the food chain

– – chemosynthetic bacteria in deep ocean vents chemosynthetic bacteria in deep ocean vents convert hydrogen sulfide (Hconvert hydrogen sulfide (H22S) gas into energyS) gas into energy

- - cyanobacteriacyanobacteria are photosynthetic bacteria are photosynthetic bacteria

which act as producers in many aquaticwhich act as producers in many aquatic

ecosystemsecosystems

Bacterial Roles: Bacterial Roles: Symbiotic Symbiotic BacteriaBacteriaMany bacteria live in or on other organisms Many 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 - some live in the gut of herbivores helping to digest celluloseto digest cellulose

- bacteria in the gut of humans - bacteria in the gut of humans

aid digestion and produce aid digestion and produce

vitaminsvitamins

- bacteria on skin and in body - bacteria on skin and in body

openings help prevent infection openings help prevent infection

by harmful organismsby harmful organisms

Bacterial Roles: Bacterial Roles: Pathogenic Pathogenic BacteriaBacteria PathogensPathogens are organisms that cause disease are 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 malfunction malfunction

AntibioticsAntibiotics Antibiotics are chemicals which either kill bacteria or prevent Antibiotics are chemicals which either kill bacteria or prevent

their growth and reproductiontheir growth and reproduction Bacteria and other microbes produce antibiotics to reduce Bacteria and other microbes produce antibiotics to reduce

competition from other organismscompetition 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 The discovery of antibioticsThe discovery of antibiotics

revolutionized the treatmentrevolutionized the treatment

of diseaseof disease

Antibiotic ActionAntibiotic Action Antibiotics effect bacteria, but not eukaryotic cells Antibiotics 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 - some damage the cell walls or prevent new cell wall from formingforming

- 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

Antibiotic ActionAntibiotic Action

Agar plates were seeded with Agar plates were seeded with Pseudomonas aeruginosa and Pseudomonas aeruginosa and Staphylococcus aureus. Staphylococcus aureus.

Four antibiotic disks were dispensed on Four antibiotic disks were dispensed on each plate. each plate.

The disks contained 30 µg of tetracycline The disks contained 30 µg of tetracycline (top left), 30 µg of vancomycin (top right), (top left), 30 µg of vancomycin (top right), 10 µg of ampicillin (bottom left), and 30 10 µg of ampicillin (bottom left), and 30 µg of chloramphenicol (bottom right). µg of chloramphenicol (bottom right).

Antibiotic ActionAntibiotic Action

Both plates were incubated at 30°C Both plates were incubated at 30°C overnight. The diameter of each overnight. The diameter of each zone was measured in millimeters zone was measured in millimeters and evaluated for susceptibility or and evaluated for susceptibility or resistance using the comparative resistance using the comparative standard method. Antibiotic standard method. Antibiotic susceptibility was compared between susceptibility was compared between the two strains of bacteria.the two strains of bacteria.

30 µ

g o

f tetra

cycline 3

0 µ

g o

f vanco

myci

n

10 µg o

f am

picill

in

30 µg of chloramphenicol

10 µg of ampicillin 30 µg of t

etracy

cline

30 µg of chloramphenicol

30 µg of vancomycin

Antibiotic ResistanceAntibiotic Resistance Some bacteria have developed a resistance to the Some bacteria have developed a resistance to the

effecteffect

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 of The problem is increased by overuse and misuse of

antibioticsantibiotics - use of antibiotics to treat viral infections – antibiotics don’t - use of antibiotics to treat viral infections – antibiotics don’t

effect viruseseffect viruses

- 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 - people take the antibiotics until they feel better, but stop before all of the bacteria are destroyedbefore all of 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

Black Plague-Black Plague-YersiniaYersinia pestispestis

Pseudomonas aeruginosa infection

Staphylococcus aureus Staphylococcus aureus infectioninfection