Chapter 27: Prokaryotes

1. Chapter 27: Prokaryotes

2. The total biomass of the prokaryotes is 10 times greater than that of all the eukaryotes!! • Bacteria are UBIQUITOUS due to their adaptability. • Huge genetic diversity as demonstrated by sequencing their DNA

3. Classification Use to be only by shape, motility and Gram staining Now we use molecular systematics (comparing genes) ~ 4,500 identified today Formerly 1 Kingdom Monera Domain – Bacteria – Kingdom Eubacteria– Largest Kingdom Domain – Archaea– Kingdom Archaebacteria All Extremophiles Thermophiles – like it hot!! Sulfolobus in hot springs (90`C) and Pyrolobus in the Mid-Atlantic Ridge (113`C) Halophiles – Dead Sea and Great Salt Lake Methanogens – Use CO2 to oxidize H2 and produce methane. Found in swamps, marshes, clay soil and your intestines

4. Two Domains Bacteria Archaea Kingdom – Eubacteria Archaebacteria Largest kingdom Extremophiles Have Peptidoglycan call walls Lack Peptidoglycan

5. Classification Scheme • No longer a 5 kingdom system as designed by Cornell’s Robert H Whittaker. • Now use Carl Woese’s 3 Domain classification based on small subunit rRNA as a marker for evolutionary relationships. • Split Monera into the two Prokaryotic kingdoms • Showed that Eukaryotes were derived from Archaebacteria

7. Characteristics • Prokaryotic cells • Unicellular or colonial • Average diameter/length 1 – 5 um • 3 basic shapes: Bacillus– Rod shaped Bacillus anthracis E. coli Coccus- Spherical Streptococcus pyogenes Spirillum – Spiral Borreliaburgdorferi Treponemapallidum

8. Structure Cell Wall – • determines shape of bacteria • Prevents bursting in hypotonic environments • Eubacteria made up of a unique compound called Peptidoglycan (sugar & polypeptide) • (lacking in Archael cells) • Determines staining properties • Gram + has a thick layer of peptidoglycan • Gram – has a thin layer of peptidoglycan

9. Gram Staining Procedure Gram negative Gram positive

11. So why does peptidoglycan matter? • Antibiotics interfere with the production of peptidoglycan. • Gram staining is a tool to determine the identification and the cell wall structure of a bacterium • Gram + have a thicker wall of peptidoglycan and respond better to antibiotics • Gram – bacteria with their thin peptidoglycan walls are not easily destroyed by antibiotics Listing Pseudomonas aerugenosa

12. Extracellular Structures • Some bacteria have a Capsule (polysaccharides or proteins) to adhere to host cell & other cells in a colony • Fimbriae & Piliare hairlike structures for attachment to host cells and mucous membranes • Sex pilus for conjugation

14. Movement • Flagella for movement • 50 um/second! • Can be one (polar) or all over (peritrichous) • Taxis • Is a movement in response to a stimulus (chemical, oxygen, nutrients and even each other

15. Intracellular • One long circular DNA with 1/1000th the # of genes as a eukaryotic cell • DNA found in the nucleoid region • May be plasmids • Have ribosomes • All have a cell membrane

16. Reproduction • Binary Fission – E. coli doubling time is 20 minutes • Endospores – (Bacillus & Clostridium genera) Resistant cells produced during adverse environmental conditions (low oxygen, nutrients, crowding, moisture, extreme temperatures • Replicates DNA • Surrounds DNA with a thickened wall • Dehydrates • To kill them, need 121`C for 15 minutes (autoclave) • Conjugation

17. Nutrient: To Eat or not to Eat? What makes them so successful is their adaptability to any environmental conditions • Photoautotrophs– Photosynthesize (Cyanobacteria, plants, algae & some protists) Energy source – Sun Carbon source – CO2 • Chemoautotrophs – unique to bacteria Energy source – Oxidized inorganics like H2S, NH3, Fe2+ Carbon source – CO2 Nitrosomonasoxidizes NH3 to nitrites (NO2−). • Photoheterotrophs- Some marine species & Heliobacteria Energy source – light Carbon source – Organic source • Chemoheterotrophs – Us, bacteria on us, fungus and plants Energy source and Carbon source are Organic Compounds

18. Respiration • Obligate Aerobes – need O2 such as the ones in your respiratory tract Streptococcus, Pseudomonas aeruginosa and Mycobacterium tuberculosis • Facultative Anaerobes – use O2 if present or got through fermentation Staphylococcus, E. coli and Listeria • Obligate Anaerobes – die in the presence of O2. Strictly go through fermentation Clostridium (botulism and tetanus)

19. Nitrogen Fixation • Rhizobium– Cyanobacteria that convert atomspheric N2 to NH3. • “Fixed” nitrogen is converted to Amino Acids and other organic compounds • Need light, CO2, N2, H2O and some minerals to fix nitrogen • Found in root nodules of legumes

20. Colonialism: A few billion is better than 1 • Living together in a group or colony • Allows the colony to utilize resources more efficiently • Anabaena (filamentous cCanobacterium) has Photosynthesis and Nitrogen fixing genes but can’t do them both at the same time (Photosynthesis releases O2 which interferes with N-fixing • Most of the cells go through photosynthesis and a few will do the N-fixing (Heterocysts) • Form a surface coating called a biofilm

21. Role in the Biosphere • Decomposers (Chemoautotrophs) • Symbiosis – Mutualistic with the E.coli in our intestines • Pathogens - 2-3 million die of TB/year, 2million die of diarrheal disease! Here is your song Exotoxins – proteins released by live bacteria – Cholera Endotoxins – lipopolysaccharides released following death - Salmonella

23. Biotechnology – Plasmids and recombinant DNA • Bioremediation– Uses organisms to remove pollutants from soil, air and water. 6. Mining gold (1 million kg Au concentrate/day in Ghana), ores such as Copper (30 billion kg/year) from Copper Sulfides 7. Food production – by fermentation – yogurt, sour cream, pickles, soy sauce, kimchi, sauerkraut, buttermilk, wine…