Prokaryotes

1. Prokaryotes Or 100 Trillion Friends That You Didn’t Know You Had

2. The Human Microbiome • We are actually a giant ecosystem of microbes • Prokaryotes comprise between 1-3% of the mass of a human body - up to 6lbs of a 200 lb person can be microbes

3. Classification: Some Old, Some New • Biologists have typically classified living things into 5 large groups called kingdoms - Monera, Protista, Fungi, Plantae & Animalia • Then biologists discovered organisms called Archea – they are prokaryotic organisms but aren’t bacteria. - What to do?

4. The Challenge of Archea • Archea present a problem, they a are prokaryotes – They have no nucleus or organelles • They also share traits with eukaryotes - similarities in DNA and synthesis • They have traits unique to themselves - cell membrane lipids, ability to survive extremely high temperature

5. Enter the Domain System of Classification • Scientists divided living things into 3 Supergroups called domains these consist of Bacteria, Archea and Eukarya

6. Archea can be Extremophiles • Some species of archea can be found in environments so extreme, that nothing else lives there- extreme temps, extreme pH, extremely salty etc…

7. Bacteria Earth’s oldest life forms – between 3.5 and 3.8 billion years old Most abundant life form – up to 2.5 billion individual bacteria in 1 gram of fertile soil Very adaptable – found in all of Earth’s ecosystems

8. Bacteria Characteristics Unicellular Circular DNA No organelles 1/10th the size of eukaryotic cells Flagella-long hair-like structure used for movement Reproduce asexually –Binary Fission

9. Bacterial Shapes • 3 main shapes - coccus – sphere - bacillus – rods - spirillum - spiral

10. Bacterial Characteristics Metabolic diversity – Bacteria can produce energy in a variety of circumstances autotroph – (self-feeding) – some bacteria can produce their own food - some use photosynthesis – get energy from light - some use chemosynthesis – get energy from chemicals Heterotroph - (other feeding) – many bacteria are unable to produce their own food and are required to eat other things

11. Bacterial Characteristics:Metabolic diversity continued obligate aerobe – like us these bacteria need oxygen obligate anaerobe - these bacteria need to be in an oxygen free environment – human gut facultative anaerobe – these bacteria can live in either an oxygen or oxygen free environment

12. Bacterial Structure Cell Wall Cell Membrane Pilus chromosome nucleoid capsule ribosome plasmid cytoplasm flagellum

13. Bacterial Structure: Cell Wall • Made of peptidoglycan – a combination of protein and polysaccharides • Some bacteria called Gram negative bacteria have an additional layer of membrane that contains lipopolysaccharide - this extra layer inhibits the uptake of antibiotics – protecting the bacteria cellwall cell membrane cell membrane lipopolysaccharide cellwall Outer membrane

14. Gram + vs. Gram - The type of cell wall is used by doctors to help diagnose disease The bacteria are stained with a special stain called Gram stain Absorb stain appear purple Bacteria without the extramembrane, appear purple. These are Gram positive (Gram +) bacteria Bacteria with the extra membrane appear pink. These are Gram negative ( Gram -) bacteria Don’t absorb stain appear pink

15. Bacterial Structure continued • Pili – hairlike structures usually found in Gram neg. bacteria. Help the bacteria stick to surfaces. Also forms conjugation bridge • Chromosome – a single loop of DNA that is folded on itself - controls the cell’s function • Nucleoid – the region of the cytoplasm where the DNA is found • Plasmid – an accessory loop of DNA – small contains only a few genes - can be responsible for: conjugation, antibiotic resistance, unique metabolic properties – like the ability to use hydrocarbons • Capsule – found outside some bacteria stores nutrients and protects the bacteria from changing environmental conditions

16. Reproduction - Binary Fission Bacterial cells undergoing binary fission

17. Reproduction - Binary Fission • Asexual reproduction - offspring are genetically identical to parent – no new genetic combinations - under ideal conditions can occur every 20 min - creates large numbers of bacteria in a short time

18. Each spot represents a single bacterial cell that reproduced by binary fission to produce millions of genetically identical cells. • Genetically identical, good or bad?

19. Exchanging Genetic Information Bacterial cells need to be able to exchange genetic information - creates new genetic combinations which increases the ability of the bacteria to survive Bacteria have 3 methods for exchanging DNA -Transduction – viruses carry DNA from one bacterial cell to another -Transformation – bacteria can absorb “naked” DNA released by dead bacteria from the environment - Conjugation – two bacteria join at a conjugation bridge, one bacteria passes on a copy of its plasmid or chromosome

20. Exchanging Genetic Information

21. Transduction – DNA is carried from one bacteria to another by a virus

22. Transformation: Bacteria absorb “naked” DNA from the environment

23. Conjugation

24. Conjugation- one cell passes a copy of its plasmid or chromosome to another Recipient Cell Donor Cell A special pilus forms a connection called a conjugation bridge between 2 bacterial cells Plasmid Conjugation bridge The donor cell copies its plasmid or chromosome and passes the copy through the conjugation bridge Cells separate

25. Bacteria Play Important Roles in Ecosystems • Decomposers – recycle dead organisms releasing their nutrients back to the environment for use by other organisms – SPONCH Without decomposers, the elements on earth would have remained locked up in dead organisms and life would have ceased

26. Bacterial Roles: Nitrogen Fixation • some bacteria contain enzymes which allow them to convert (or fix) nitrogen from the air into a useable form - they are nitrogen fixing bacteria - Why do living things use nitrogen?

27. Bacterial Roles: Producers • In some ecosystems chemosynthetic and photosynthetic bacteria serve as the basis of the food chain – chemosynthetic bacteria in deep ocean vents convert hydrogen sulfide (H2S) gas into energy - cyanobacteria are photosynthetic bacteria which act as producers in many aquatic ecosystems

28. Bacterial Roles: Symbiotic Bacteria Many bacteria live in or on other organisms (including humans) and aid their host - some live in the gut of herbivores helping to digest cellulose - bacteria in the gut of humans aid digestion and produce vitamins - bacteria on skin and in body openings help prevent infection by harmful organisms

29. Bacterial Roles: Pathogenic Bacteria • Pathogens are organisms that cause disease - only a small portion of bacteria are pathogens - most bacteria diseases are caused by toxins released by the bacteria - these toxins: - poison cells and damage tissue - interfere with cell signaling - over-stimulate cells causing them to malfunction

30. Pathogenic Bacteria: Biofilms • Some bacteria can form a biofilm – a matrix made of polysaccharide - once formed, the matrix traps other bacteria - the biofilm protects the bacteria, making it hard to kill them

31. Antibiotics • Antibiotics are chemicals which either kill bacteria or prevent their growth and reproduction • Bacteria and other microbes produce antibiotics to reduce competition from other organisms • Penicillin was the first to be use to fight disease - discovered accidently by Alexander Fleming in 1928 • Two scientists Walter Florey and Ernst Chain determined how to use penicillin to treat disease in 1939. • The discovery of antibiotics revolutionized the treatment of disease

32. Antibiotic Action • Antibiotics effect bacteria, but not eukaryotic cells • Antibiotics attack bacteria in 5 ways - some damage the cell walls or prevent new cell wall from forming - some damage the cell membrane - some prevent protein synthesis - some prevent DNA from being copied - some interfere with bacterial metabolism

33. Antibiotic Resistance • Some bacteria have developed a resistance to the effect of some antibiotics - the number of resistant bacteria is growing • The problem is increased by overuse and misuse of antibiotics - use of antibiotics to treat viral infections – antibiotics don’t effect viruses - the use of antibiotics in livestock (cattle, chickens, pigs) antibiotics show up in the meat and milk - people take the antibiotics until they feel better, but stop before all of the bacteria are destroyed - this kills the most susceptible bacteria, but leaves the more resistant bacteria

34. Black Plague-Yersiniapestis

35. Syphilis--Treponemapallidum/Bacterial

36. Mycobacteriumleprae/Bacteria

37. Clostridiumperfringes/Bacteria

38. Vocabulary Microbiome Archea autotroph pili heterotroph nucleoid peptidoglycan capsule plasmid conjugation bridge Gram - obligate aerobe Gram + obligate anaerobe binary fission facultative anaerobe conjugation nitrogen fixing bacteria transduction cyanobacteria transformation pathogens biofilm