1. What are prokaryotic cells? Single-celled bacteria and archaeans No nucleus or membrane-bound organelles Smallest, most widely distributed, numerous, and metabolically diverse organisms –Autotrophs and heterotrophs Spheres (cocci), rods (bacilli), spirals (spirilla)

2. How does the structure look? Typical surface structures –Cell wall –Outermost protective capsule or slime layer –One or more flagella –Pili

3. How do Prokaryotes Reproduce? Only bacteria and archaeans reproduce by prokaryotic fission: –Replication of single, circular prokaryotic chromosome –Division of parent cell into two genetically equivalent daughter cells Horizontal gene transfers can move genes between prokaryotes Conjugation moves a plasmid and some chromosomal genes into another cell through a sex pilus

4. What are the bacteria? The most common and diverse prokaryotes –Some are pathogens (cause disease in a host)

5. Bacterial Diversity: Cyanobacteria Oxygen-releasing photoautotrophs –Chloroplasts probably evolved from ancient cyanobacteria by endosymbiosis

6. Bacterial diversity: proteobacteria The most diverse bacterial group –Include autotrophs and heterotrophs, free-living species, beneficial symbionts, and pathogens –Example: Thiomargarita namibiensis –Bacterial are divided into two classes or groups Gram Positive Gram negative

7. What are gram-positive bacteria ? Have thick walls –Endospores resist heat, boiling, irradiation, acids and disinfectants –Some are human pathogens Chlamydias

8. What are spirochetes? Spring-shaped –Live on their own or in hosts –Some are pathogens

9. What are the archaeans? Archaeans are prokaryotic, but like eukaryotic cells in certain features –Halophiles (salt lovers), extreme thermophiles, and methanogens (methane makers) Comparisons of structure, function, and genetic sequences put archaeans in a separate domain, between eukaryotes and bacteria Archaeans are more diverse and widely distributed than previously thought

10. What are the viruses? Viruses are noncellular infectious particles that cannot reproduce on their own Viruses infect a host cell; their genes and enzymes take over the host’s mechanisms of replication and protein synthesis Virus infections

11. Virus Structure A virus particle consists of a core of DNA or RNA and a protein coat In some viruses, the coat is enveloped in some of an infected cell’s plasma membrane –Outer envelope forms as each new virus particle is released by budding or lysis In bacteriophages and other complex viruses, the coat has a sheath and other structures

12. Viral Multiplication Pathways Multiplication pathways vary greatly Two are common among bacteriophages –Lytic pathway –Lysogenic pathway

13. Lytic Pathway New virus particles are released by lysis –Multiplication is rapid

14. Lysogenic Pathway Virus enters a latent state that extends the cycle –Host cell is not killed outright Viral nucleic acids integrate into host chromosome –All host cell’s descendants inherit genetic material –May be reactivated many generations later, causing cell to enter lytic pathway

15. What are prion infections? Prions are infectious misfolded versions of normal proteins

16. How do pathogens evolve? Pathogens evolve to not kill a host before they can infect other host individuals Use of antibiotics favors antibiotic-resistant bacteria Genes that convey drug resistance can arise by mutation, may spread among members of the same or different species by conjugation Diseases can be fatal –If an individual becomes host to multiple pathogens –If an individual has no coevolved defenses –If a pathogen mutates into a different form that can breach current defenses Two deadly emerging pathogens –Ebola and the H5N1 strain of bird flu