ap biology ch. 23 bacteria. intro to bacteriabacteria anton van leeuwenhoek pathogen decomposer,...
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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