Prokaryotes and Viruses - Biological Principles - Lecture Slides, Slides of Biology

Download Prokaryotes and Viruses - Biological Principles - Lecture Slides and more Slides Biology in PDF only on Docsity! Prokaryotes and Viruses Chapter 21 Docsity.com Microorganisms • Single-celled organisms that are too small to be seen without a microscope • Bacteria are the smallest living organisms • Viruses are smaller but are not alive Docsity.com Metabolic Diversity • Photoautotrophs • Chemoautotrophs • Chemoheterotrophs Docsity.com Bacterial Genes • Bacteria have a single chromosome – Circular molecule of DNA • Many bacteria also have plasmids – Self-replicating circle of DNA that has a few genes – Can be passed from one cell to another Docsity.com Conjugation nicked plasmid in donor cell conjugation tube to recipient cell Transfer of plasmid Figure 21.8 Page 351 Docsity.com Eubacteria • Includes most familiar bacteria • Have fatty acids in plasma membrane • Most have cell wall; always includes peptidoglycan • Classification based largely on metabolism Docsity.com Eubacterial Diversity • Photoautotrophic – Aerobic (Cyanobacteria) – Anaerobic (Green bacteria) • Chemoautotrophic – Important in nitrogen cycle • Chemoheterotrophic – Largest group Docsity.com Some Pathogenic Eubacteria • Most are chemoheterotrophs – E. coli strains – Clostridium botulinum – Clostridium tetanus – Borrelia burgdorferi – Rickettsia rickettsii Docsity.com Viral Body Plans • Genetic material is DNA or RNA • Coat is protein Complex virus (bacteriophage) Polyhedral virus Helical virus Fig. 21.18 Page 356 Docsity.com Viral Multiplication - Basic Steps • Attach to host cell • Enter host (virus or just genetic material) • Direct host to make viral genetic material and protein • Assemble viral nucleic acids and proteins • Release new viral particles Docsity.com Lytic Pathway Stepped Art Fig. 21.20 Virus particles bind to wall of suitable host. Viral genetic material enters cell cytoplasm. Viral DNA directs host machinery to produce viral proteins and viral DNA. Viral protein molecules are assembled into coats; DNA is packaged inside. Tail fibers and other parts are added to coats. Lysis of host cell is induced; infectious particles escape. Docsity.com Prions • Small proteins • Linked to human diseases – Kuru – Creutzfeldt-Jakob disease (CJD) • Animal diseases – Scrapie in sheep – Bovine spongiform encephalopathy (mad cow disease) Docsity.com Nature of Disease • Contagious disease pathogens must directly contact a new host • Epidemic • Pandemic (AIDS) • Sporadic • Endemic Docsity.com Evolution and Disease • Host and pathogen are coevolving • If a pathogen kills too quickly, it might disappear along with the individual host • Most dangerous if pathogen – Is overwhelming in numbers – Is in a novel host – Is a mutant strain Docsity.com