Chapter 21 PROKARYOTES AND VIRUSES

Transcription

1 Chapter 21 PROKARYOTES AND VIRUSES

2 Bozeman Video classification of life 7RiE

3 Impacts, Issues: West Nile Virus Takes Off Alexander the Great, 336 B.C., conquered a vast empire It s speculated that his demise was due to West Nile encephalitis

4 Impacts, Issues: West Nile Virus Takes Off West Nile Virus is pathogenic, it invades its host and multiplies, causing disease It s a flavivirus, traveling inside mosquitoes which act as the transferring agent from host to host

5 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

6 The Prokaryotes Only two groups Archaebacteria and Eubacteria Arose before the eukaryotes

7 Prokaryotic Characteristics No membrane-bound nucleus Single chromosome Cell wall (in most species) Prokaryotic fission Metabolic diversity

8 Prokaryotic Body Plan DN A bacterial flagellum pilus capsule plasma membran e ribosomes in cytoplasm cell wall cytoplasm

9 Prokaryotic Body Plan cytoplasm, with ribosomes DNA, in nucleoid pilus bacterial flagellum outer capsule cell wall plasma membrane Fig. 21-2, p.334

10 Bacterial Shapes coccus bacillus spirillum p. 334

11 Bacterial Shapes Fig. 21-3b, p.335

12 Bacterial Shapes Fig. 21-3c, p.335

13 Bacterial Shapes sex pilus Fig. 21-3d, p.335

14 Metabolic Diversity Photoautotrophs Chemoautotrophs Chemoheterotrophs

15 Gram Stain Fig. 21-4, p.335

16 Gram Staining Video M6mxjY0

17 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

18 Prokaryotic Fission Fig. 21-5, p.335

19 Conjugation Transfer of plasmid Fig. 21-6, p.337

20 Prokaryotic Classification EUBACTERIA (Bacteria) ARCHAEBACTERIA (Archaea) EUKARYOTES (Eukarya) Traditionally classified by numerical taxonomy Now increased use of comparative biochemistry

21 Bozeman Videos Bacteria & Archaebacteria kpxtu

22 Eubacteria Includes most familiar bacteria Have fatty acids in plasma membrane Most have cell wall; always includes peptidoglycan Classification based largely on metabolism

23 Eubacterial Diversity Photoautotrophic Aerobic (Cyanobacteria) Anaerobic (Green bacteria) Chemoautotrophic Important in nitrogen cycle Chemoheterotrophic Largest group

24 Eubacterial Diversity Fig. 21-7b, p.338

25 Some Pathogenic Eubacteria Most are chemoheterotrophs E. coli strains Clostridium botulinum Clostridium tetanus Borrelia burgdorferi Rickettsia rickettsii

26 Bacterial Behavior Bacteria move toward nutrient-rich regions Aerobes move toward oxygen; anaerobes avoid it Photosynthetic types move toward light Magnetotactic bacteria swim downward Myobacteria show collective behavior

27 Archaebacteria Methanogens Extreme halophiles Extreme thermophiles

28 Methanogens Fig a, p.340

29 Extreme Halophiles Fig a, p.341

30 Extreme Thermophiles Fig b, p.341

31 Virus Noncellular infectious agent Protein wrapped around a nucleic acid core Cannot reproduce itself; can only be reproduced using a host cell

32 Bozeman Video--Viruses G_syI

33 Viral Body Plans Complex virus (bacteriophage) Genetic material is DNA or RNA Coat is protein Helical virus Polyhedral virus Fig , p.342

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36 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

37 Lytic Pathway Lysis of host cell is induced; infectious particles escape. Tail fibers and other parts are added to coats. Virus particles bind to wall of suitable host. Viral genetic material enters cell cytoplasm. Viral protein molecules are assembled into coats; DNA is packaged inside. Viral DNA directs host machinery to produce viral proteins and viral DNA. Stepped Art Fig Page 358

38 Lysogenic Pathway Viral DNA usually becomes integrated into the bacterial chromosome. Viral DNA is excised from chromosome and cell enters lytic pathway. Prior to prokaryotic fission, the chromosome and integrated viral DNA are replicated. After binary fission, each daughter cell will have recombinant DNA. Stepped Art Fig (2) Page 358

39 Bozeman Video Viral Replication YQIug

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41 New Threats Emerging Pathogens Ebola virus Monkeypox virus SARS virus Drug-resistant strains Food poisoning E. coli Salmonella

42 Viroids Smaller than viruses Strands or circles of RNA No protein-coding genes No protein coat Cause many plant diseases

43 Prions Small proteins Linked to human diseases Kuru Creutzfeldt-Jakob disease (CJD) Animal diseases Scrapie in sheep Bovine spongiform encephalopathy (mad cow disease)