BacteriaBacteria

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 for Flagella-long hair-like structure used for movementmovement

• 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 from- some use chemosynthesis – get energy from

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 other food and are required to eat 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 oxygen - these bacteria need to be in an oxygen free environment – human gut free environment – human gut

facultative anaerobe facultative anaerobe – these bacteria can live in either an – these bacteria can live in either 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 WallBacterial Structure: Cell Wall• 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 additional have an additional

layer of membrane that contains lipopolysaccharide layer 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

cellmembrane

cell wall

cellmembrane

Outer membrane

lipopolysaccharide

cell wall

Bacterial Structure continuedBacterial Structure continued• 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 few – an accessory loop of DNA – small contains only a few

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

to to use hydrocarbons use hydrocarbons• CapsuleCapsule – found outside some bacteria stores nutrients and protects – found outside some bacteria stores nutrients and protects

the bacteria from changing environmental conditions the bacteria from changing environmental conditions

Reproduction - Binary FissionReproduction - Binary Fission

Bacterial cells undergoing binary fissionBacterial cells undergoing binary fission

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

• 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 ability - creates new genetic combinations which increases the ability of the bacteria to surviveof 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 cell to anotherto 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, bridge, one bacteria passes on a one bacteria passes on a copy of its plasmid or copy of its plasmid or

chromosomechromosome

Exchanging Genetic InformationExchanging Genetic Information

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

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

environmentenvironment

ConjugationConjugation

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

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 Roles in Bacteria Play Important Roles in Ecosystems 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 use by other organisms – 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 FixationBacterial Roles: Nitrogen Fixation• some bacteria contain enzymes which allow them to some 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?

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 convert chemosynthetic bacteria in deep ocean vents convert hydrogen sulfide (Hhydrogen 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 BacteriaSymbiotic Bacteria

Many 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 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 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 BacteriaPathogenic Bacteria

• 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 malfunctionmalfunction

Pathogenic Bacteria: BiofilmsPathogenic Bacteria: Biofilms

• Some bacteria can form a Some 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

AntibioticsAntibiotics

• Antibiotics are chemicals which either kill bacteria or prevent their growth Antibiotics are chemicals which either kill bacteria or prevent their growth and reproductionand reproduction

• Bacteria and other microbes produce antibiotics to reduce competition Bacteria and other microbes produce antibiotics to reduce competition from other organismsfrom 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 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

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 of The problem is increased by overuse and misuse of

antibioticsantibiotics

- use of antibiotics to treat viral infections – antibiotics don’t effect - use of antibiotics to treat viral infections – antibiotics don’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 of - people take the antibiotics until they feel better, but stop before all of the bacteria are destroyedthe bacteria are destroyed

- this kills the most susceptible bacteria, but leaves the more resistant - this kills the most susceptible bacteria, but leaves the more resistant bacteriabacteria

Black Plague-Black Plague-YersiniaYersinia pestispestis

VocabularyVocabularyautotrophautotroph pili pili

heterotroph heterotroph nucleoidnucleoid

peptidoglycanpeptidoglycan capsule capsule

plasmidplasmid conjugation bridge conjugation 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