AP Biology

Ch. 23 Bacteria

Intro to BacteriaAnton van LeeuwenhoekPathogenDecomposer, recycler, producers, agriculture

ProkaryotesArchaeabacteriaEubacteriaSmaller than eukaryote

Exception = Epulopiscium fishelsoni

Most unicellularSome colonies/filaments

Bacteria on Pin

Shapes of BacteriaSpherical =

Twos – Long chains – Bunches –

Rod-shaped =Single rods or chains

Helical – Short helix =Rigid, longer helix =Flexible, longer helix =

Fig. 27-2

(a) Spherical (cocci)

1 µm

(b) Rod-shaped (bacilli)

2 µm

(c) Spiral

5 µm

Lack membrane-bound organellesNo nuclei, mitochondria, chloroplasts, ER, Golgi, lysosome

Cytoplasm – ribosomes and storage granulesMetabolic enzymesPlasma membrane may be infolded

Bacterial Cell WallSupport, shapeHypotonicHypertonic

High sugar/salt (jams, salted fish)

Bacterial Cell Wall continuedEubacteria – peptidoglycan

Peptidoglycan = complex polymer consisting of amino sugars linked with short polypeptides

Gram StainingGram +

Thick cell wall – mostly peptidoglycanAbsorb and retain crystal violet dye

Gram –2 layers = thin peptidoglycan +thick outer membrane

Do not retain crystal violet dye when rinsed with alcohol

Fig. 27-3

Cellwall

Peptidoglycanlayer

Plasma membrane

Protein

Gram-positivebacteria

(a) Gram-positive: peptidoglycan traps crystal violet.

Gram-negativebacteria

(b) Gram-negative: crystal violet is easily rinsed away, revealing red dye.

20 µm

Cellwall

Plasma membrane

Protein

Carbohydrate portionof lipopolysaccharide

Outermembrane

Peptidoglycanlayer

Fig. 27-3a

Cellwall

Peptidoglycanlayer

Plasma membrane

Protein

(a) Gram-positive: peptidoglycan traps crystal violet.

Fig. 27-3b

Cellwall Peptidoglycan

layerPlasma membrane

Protein

(b) Gram-negative: crystal violet is easily rinsed away, revealing red dye.

Outermembrane

Carbohydrate portionof lipopolysaccharide

Fig. 27-3c

Gram-positivebacteria

Gram-negativebacteria

20 µm

Gram-Positive Bacteria

• Gram-positive bacteria include –Actinomycetes–Bacillus anthracis–Clostridium botulinum–Some Staphylococcus and Streptococcus–Mycoplasms, the smallest known cells

Fig. 27-18m

Streptomyces, the source of manyantibiotics (colorized SEM)

5 µ

m

Fig. 27-18n

1 µ

m

Hundreds of mycoplasmascovering a human fibroblastcell (colorized SEM)

The Bacterial GlycocalyxAround cell wallSome bacteriaFree-living

Add protection against phagocytosis by microorganisms

Disease-causingProtect against phagocytosis by WBCsEx: Streptococcus pneumoniae

AttachmentRocks, plant roots, human teeth

Fig. 27-4

Capsule

200 nm

Bacterial Pili (Pilus)ProteinAdhere Transmission of DNA between bacteria

Fig. 27-5

Fimbriae

200 nm

Motile BacteriaWater = viscous Flagella rotate

# and location – classify3 parts

1. basal body – motor; anchors flagellum

2. hook – curved; connects basal body to long, hollow filament

3. single filament

Bacterial FlagellumBasal Body motor

ATP energy -pump protons out of cell

Diffusion of protons back powers motor –spins flagellum like a propeller

Rotary motion pushing the cell

Fig. 27-6

Flagellum

Filament

Hook

Basal apparatus

Cell wall

Plasmamembrane

50 nm

Fig. 27-6a

Cell wall

Filament

Hook

Basal apparatus

Plasmamembrane

Fig. 27-6b

Prokaryotic flagellum (TEM)

50 nm

Bacterial Flagella

Genetic material in bacteriaSingle circular DNA molecule

CytoplasmLittle protein

PlasmidsSmall circular fragment of DNACan replicate independently of genomic DNA

Become integrated in genomic DNA

Fig. 27-8

Chromosome Plasmids

1 µm

Reproduction in Bacteria - Asexual

Binary fission1 cell 2 cells1st – circular bacterial DNA replicated

2nd – transverse wall is formedFast<20min.

Soon – lack of food, accumulation of waste products

Reproduction continuedBudding

Bulge (bud)Bud enlarges, matures, separates

FragmentationWalls develop within cell separates into several new cells

No Sexual Reproduction – INSTEAD: Genetic Exchange of Material1. Transformation –

2. Transduction –

3. Conjugation – E. coli – donor cells (“male” cells)Plasmids can be transmitted to recipient

“female” cellsPilus on donor recognizes recipient cell and

makes the 1st contactCytoplasmic bridge forms btw. 2 cells and

DNA is transferred from donor to recipient

Fig. 27-11-1

Donorcell

A+ B+

A+ B+

Phage DNA

Fig. 27-11-2

A+

Donorcell

A+ B+

A+ B+

Phage DNA

Fig. 27-11-3

Recipientcell

B–

A+

A–

Recombination

A+

Donorcell

A+ B+

A+ B+

Phage DNA

Fig. 27-11-4

Recombinant cell

Recipientcell

A+ B–

B–

A+

A–

Recombination

A+

Donorcell

A+ B+

A+ B+

Phage DNA

Fig. 27-12

Sex pilus 1 µm

Fig. 27-13-1

F plasmid

F+ cell

F– cell

Matingbridge

Bacterial chromosome

Bacterialchromosome

(a) Conjugation and transfer of an F plasmid

Fig. 27-13-2

F plasmid

F+ cell

F– cell

Matingbridge

Bacterial chromosome

Bacterialchromosome

(a) Conjugation and transfer of an F plasmid

Fig. 27-13-3

F plasmid

F+ cell

F– cell

Matingbridge

Bacterial chromosome

Bacterialchromosome

(a) Conjugation and transfer of an F plasmid

F+ cell

F+ cell

The F Factor in the Chromosome

• A cell with the F factor built into its chromosomes functions as a donor during conjugation

• The recipient becomes a recombinant bacterium, with DNA from two different cells

• It is assumed that horizontal gene transfer is also important in archaea

R Plasmids and Antibiotic Resistance

• R plasmids carry genes for antibiotic resistance

• Antibiotics select for bacteria with genes that are resistant to the antibiotics

• Antibiotic resistant strains of bacteria are becoming more common

EndosporesUnfavorable environmentSome bacteria

Endospores1 endospore/original cellCan survive extreme conditionsFavorable conditions

Endospores continuedMedical importance – Clostridium tetani – tetanusBacillus anthracis - anthrax

Fig. 27-9

Endospore

0.3 µm

Metabolic diversityHeterotrophs

Must obtain organic compounds from other organisms

Most free-living saprotrophsAutotrophs

Can make own organic molecules from simple raw materials

Photosynthetic autotrophs (photoautotrophs)

Chemosynthetic autotrophs (chemoautotrophs)

Table 27-1

Aerobes Vs. AnaerobesAerobic – Anaerobic

Facultative anaerobes –

Obligate anaerobes –

Certain bacteria killed by low O2 level

ArchaeaProduce methane gas from simple C

Extreme environmentsNo peptidoglycanMethanogens, halophiles, thermophiles

Methanogens

O2 free environmentsStrict anaerobesProduce methane gasImportant in recycling organic products of organisms in swamps

Extreme HalophilesHeterotrophsSaturated brine solutionsSome – capture energy of light with a purple pigment (bacteriorhododpsin) similar to pigment rhodopsin involved in animal visionDifferent from photosynthesis

Halophile Salt Ponds

Extreme ThermophilesHot, acidic environmentsSulfur springs – YellowstoneVolcanoes under seaDeep sea vents

Fig. 27-17

EubacteriaEcological importance

Photosynthesis – Soil – Mutualism –

Agriculture:Roots of legumesFixing nitrogen

Fig. 27-18c

Rhizobium (arrows) inside a rootcell of a legume (TEM)

2.5

µm

Eubacteria continuedCausing disease

Normal microbiota Prevent harmful bacteriaHuman intestine – Vit. K, some B vitamins

Opportunistic bacteria –

Robert Koch – showed bacteria cause infectious disease

Koch’s postulates1. pathogen must be present in every individual with the disease

2. sample of the microorganism taken from the diseased host can be grown in pure culture

3. when a sample of pure culture is injected into a healthy host, it causes the same disease

4. microorganism can be recovered from the experimentally infected host

PathogensEnter by food, dust, droplets, wounds, bites

To cause disease adhere to specific cell type, multiply, produce toxin

Fig. 27-18h

Helicobacter pylori (colorized TEM)

2 µ

m

Cause Stomach Ulcers

Fig. 27-18j

2.5

µm

Chlamydia (arrows) inside ananimal cell (colorized TEM)

•Parasites in animal cells•Causes blindness and nongonococcal urethritis by sexual transmission

Fig. 27-18k

Leptospira, a spirochete(colorized TEM)

5 µ

m

•helical heterotrophs•Some, such as Treponema pallidum, which causes syphilis, and Borrelia burgdorferi, which causes Lyme disease, are parasites

Fig. 27-21

5 µm

Exotoxins= strong poisons either secreted from the cell or leak out when the bacterial cell is destroyed

Ex: Diphtheria – toxin kills cells/causes inflammation

Botulism – food poisoning – paralysis/death

Destroyed by heat

Commercial Uses of BacteriaFermentation – Tasty Bacteria

Lactic acid bacteria – cheese, salami, vinegar, soy sauce

AntibioticsSoil bacteriaG-bacillusMolds

Commercial uses continuedReproduction rates high

Make biomoleculesGenetic engineering

Vaccines, HGH, insulin, insect resistance

Sewage treatmentLandfill – break down solid wasteBioremediation

Fig. 27-22

(a)

(b)

(c)

Fig. 27-18e

Thiomargarita namibiensiscontaining sulfur wastes (LM)

0.5

µm

Endotoxins Not secreted; components of cell walls of most G-

Affect host when released from dead bacteria

Bind to macrophages and stimulate them to release substances causing fever/other symptoms

Not destroyed by heating

CyanobacteriaPhotosynthesize1st oxygen

Antibiotics2 classes

Inhibit protein biosynthesis

Inhibit cell wall biosynthesis

Resistance

You should now be able to:

1. Distinguish between the cell walls of gram-positive and gram-negative bacteria

2. State the function of the following features: capsule, sex pilus, nucleoid, plasmid, and endospore

3. Explain how plasmids are important in genetics

4. Distinguish among the following sets of terms: photoautotrophs, chemoautotrophs, photoheterotrophs, and chemoheterotrophs; obligate aerobe, facultative anaerobe, and obligate anaerobe; exotoxins and endotoxins