Prokaryotes (Archaea and Bacteria) Chapter 28. 2 The First Cells Microfossils are fossilized forms...
-
Upload
magdalene-short -
Category
Documents
-
view
216 -
download
3
Transcript of Prokaryotes (Archaea and Bacteria) Chapter 28. 2 The First Cells Microfossils are fossilized forms...
Prokaryotes (Archaea and Bacteria)
Chapter 28
2
The First CellsMicrofossils are fossilized forms of microscopic life
-Oldest are 3.5 billion years old -Isotopic analysis and concentration of carbon-12 in fossils
suggests that carbon fixation was active as much as 3.8 BYACarbon-12 is found in higher concentrations in living vs. nonliving
things
3
The Cyanobacteria
Stromatolites are mats of cyanobacterial cells that trap mineral deposits-Oldest are 2.7 billion years old
-Lipids were found in ancient rocks
4
5
Flagella, spin like propellers Composed of the protein flagellin
6
Prokaryotic FeaturesMetabolic diversity
-Two types of PHOTOSYNTHESIS
-Oxygenic = Produces oxygen (make O
by oxidizing H20)
-Anoxygenic = Nonoxygen producing
(e.g.make S by oxidizing H2S... purple sulfur bacteria)
-Chemolithotrophic prokaryotes derive energy from inorganic molecules (e.g. oxidize ammonia making nitrate, taken up by plants)
7
Bacteria vs. Archaea
Plasma membrane
-Bacterial-Connected to glycerol by ester linkages
as seen in Eukarya
-Archaeal-Connected to glycerol by ether linkages
• Cell wall– All prokaryotes have cell walls– Bacteria have peptidoglycan– Archaea lack peptidoglycan
• DNA replication– Both have single replication origin– Archaeal DNA replication is more similar to
that of eukaryotes
• Gene Expression– Archaeal transcription and translation are
more similar to those of eukaryotes
8
Bacteria vs. Archaea
Molecular Classification
1. Amino acid sequences of key proteins
2. Percent guanine–cytosine content
3. Nucleic acid hybridization– Closely related species will have more base
pairing
4. Gene and RNA sequencing– Especially rRNA
5. Whole-genome sequencing
9
10
Most prokaryotes have one of 3 basic shapes
-Bacillus = Rod-shaped
-Coccus = Spherical
-Spirillum = Helical-shaped
Prokaryotic Shapes
11
Maintains shape and protects the cell from swelling and rupturing
Consists of peptidoglycan
-Polysaccharides cross-linked with peptides
Cell wall is the basis of the Gram stain
The Bacterial Cell Wall
12
Two main types
-Gram-positive bacteria
-Thick peptidoglycan
-Teichoic and lipoteichoic acids
-Gram-negative bacteria
-Thin peptidoglycan
-Have an outer membrane
-Contains lipopolysaccharide
The Bacterial Cell Wall
13
The Bacterial Cell Wall
14
The Bacterial Cell Wall
15
Internal Structure
Internal membranes
-Invaginated cell membrane
-For respiration or photosynthesis
Endospores
-Highly-resistant structures
-Released upon cell lysis
-Can germinate back to normal cell
16
Prokaryotic Genetics
Prokaryotes do not reproduce sexually
However, they undergo horizontal gene transfer, which is of three types
-Conjugation = Cell-to-cell contact
-Transduction = By bacteriophages
-Transformation = From the environment
17
ConjugationTransfer of the F plasmid occurs through the
conjugation bridge
The end result is two F+ cells
-R (antibiotic resistance) plasmids
-Virulence plasmids (E. coli O157:H7 strain)
18
Transduction
Viruses package bacterial DNA and transfer it in a subsequent infection
19
Transformation
Natural transformation
-DNA that is released from a dead cell is picked up by another live cell...Horizontal gene transfer (no cell fusion so not sexual !!)
20
Prokaryotic Metabolism
Acquisition of Carbon
-Autotrophs = From inorganic CO2
-Heterotrophs = From organic molecules
Acquisition of Energy
-Chemolithotrophs = From inorganic chemicals
-Phototrophs = From sunlight
21
Prokaryotic MetabolismPhotoautotrophs
-Cyanobacteria (light to reduce Carbon--using C02 via oxidation of H20). Similar to plants and
algae.Chemolithoautotrophs
-Nitrifiers FOR energy (e.g. ammonia to nitrite). Can make reduced organic molecules from CO2
Photoheterotrophs -Purple and green Nonsulfur Bacteria
(e.g. light to oxidize Hydrogen. C source not from CO2)Chemoheterotrophs
-Majority of prokaryotes-Use organic molecules for C and energy
(oxidize organic carbon to C02 for energy. Aren’t anabolic from a CO2 starting point)
22
Prokaryotic Metabolism
Type III secretion system
-Found in many Gram-negative bacteria
-Used to transfer virulence proteins directly into host cells
-Yersinia pestis – Bubonic plague
-Pseudomonads – Plant pathogens
-Blights, soft rot, wilts
23
Human Bacterial Disease
Tuberculosis
-Mycobacterium tuberculosis
-Afflicts the respiratory system
-Mutidrug-resistant (MDR) strains are very alarming
24
Human Bacterial Disease
Dental caries (tooth decay)
-Plaque consists of bacterial biofilms
-Streptococcus ferments sugar to lactic acid
-Tooth enamel degenerates
Peptic ulcers
-Helicobacter pylori is the main cause
-Treated with antibiotics
25
Gonorrhea
-Neisseria gonorrhoeae
-Can pass from mom to baby via birth canal
-Can cause pelvic inflammatory disease (PID)
Chlamydia
-Chlamydia trachomatis
-Can cause PID and heart disease
Sexually transmitted diseases (STDs)
26
Beneficial Prokaryotes
Prokaryotes are crucial to chemical cycles
-Decomposers release a dead organism’s atoms to the environment
-Photosynthesizers fix carbon into sugars
-Nitrogen fixers reduce N2 to NH3 (ammonia)
27
Beneficial Prokaryotes
Bacteria are used for bioremediation
-Remove pollutants from water, air and soil
-Exxon Valdez oil spill