Prokaryotes (Archaea and Bacteria) Chapter 28

2 The First Cells Microfossils 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 BYA Carbon-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

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5 Flagella, spin like propellers Composed of the protein flagellin

6 Prokaryotic Features Metabolic 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 Conjugation Transfer 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 CO 2 -Heterotrophs = From organic molecules Acquisition of Energy -Chemolithotrophs = From inorganic chemicals -Phototrophs = From sunlight

21 Prokaryotic Metabolism Photoautotrophs -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 N 2 to NH 3 (ammonia)

27 Beneficial Prokaryotes Bacteria are used for bioremediation -Remove pollutants from water, air and soil -Exxon Valdez oil spill