Prokaryotes

1. Prokaryotes The smallest and most common microorganisms are prokaryotes which are single-celled organisms that lack a nucleus.

2. Prokaryotes • Used to simply be called bacteria • Used to be placed in the kingdom Monera • Now classified into two Domains • Bacteria • Archaea

3. Bacteria – Contains one Kingdom: Eubacteria ribosome • Larger of the two Domains • Live almost anywhere • Their cell wall contains peptidoglycan peptidoglycan cell wall cell membrane DNA pili flagellum

4. Archaea – Contains one Kingdom: Archaebacteria • Cell wall lacks peptidoglycan • Their DNA is more like that of eukaryotes than eubacteria • They live in extremely harsh environments • Very salty = halophiles • Very hot or very cold = extremophiles • Oxygen free environments (thick mud, digestive tract of animals); produce methane = methanogens

5. Identifying prokaryotes • Prokaryotes are identified by their: • Shapes • Chemical nature of their cell walls • The way they move • The way they obtain energy

6. Bacilli (bacillus) = Rod-shaped prokaryotes

7. Cocci (coccus) =Sphericalprokaryotes

8. Spirilla (spirillum) = Spiral and corkscrew shaped prokaryotes

9. Cell Walls • A Gram stain is used to differentiate between cell wall composition.

10. Gram positive • Bacterial cells with one thick cell wall that contains peptidoglycan stain violet and are Gram positive

11. Gram negative • Bacterial cells with thinner walls with an outer layer of lipid stain pink or light red and are Gram negative

12. Movement • Flagella – whip structures • Lash, snake or spiral forward • Glide along a layer of slime they secrete • Do not move

13. How prokaryotes obtain energy • Prokaryotes that obtain energy in a similar manner to green plants are photoautotrophs. An example is cyanobacteria • Prokaryotes that obtain energy directly from inorganic molecules are chemoautotrophs

14. Energy continued • Prokaryotes that make their own food are autotrophs • Prokaryotes that obtain their food from an outside source are heterotrophs • Some heterotrophs can release toxins that are responsible for food poisoning

15. Heterotrophs • Chemoheterotrophs take in organic molecules for both energy and a supply of carbon • An interesting group are those that capture sunlight for energy but need organic compounds for their carbon source (nutrition). These are photoheterotrophs.

16. How prokaryotes metabolize or release energy from their food • Obligate aerobes – Require oxygen for cellular respiration • Obligate anaerobes – Oxygen is toxic; release energy through fermentation • Facultative anaerobes – Do not need oxygen, but are not killed by it. Can switch back and forth between cellular respiration and fermentation

17. Reproduction Prokaryotes exchange genetic material through conjugation Prokaryotes reproduce asexually through binary fission

18. Endospore • When growth conditions become unfavorable, bacteria can form spores called endospores. • These spores allow bacteria to stay dormant until conditions are favorable.

19. Importance of bacteria • Bacteria are important decomposers and help the ecosystem recycle nutrients • All organisms rely on bacteria for nitrogenfixation • However, bacteria are also pathogens and cause disease by either breaking down tissues or producing poisons

20. Human uses of bacteria • Food production (cheese, yogurt, sour cream, buttermilk, pickles, sauerkraut and vinegar). • Industry • digest petroleum (clean up oil spills) • remove waste products and poisons from water • mine minerals • genetic engineering for medicines and hormones

21. Methods of controlling bacteria • Antibiotics – drugs or natural compounds used to attack and destroy bacteria • Sterilization – destroy bacteria by heat or chemical action (disinfectants) • Refrigeration – cold temperature slows bacteria growth • Canning – heat food to a high temperature, place in sterile glass jars or metal cans • Chemically preserving foods – salt (salted meat), vinegar (pickled), sugar (jam), and human made preservatives