Chapter 21 PROKARYOTES AND VIRUSES

Chapter 21 PROKARYOTES AND VIRUSES

Bozeman Video classification of life http://www.youtube.com/watch?v=tyl_8gv 7RiE

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

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

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

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

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

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

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

Bacterial Shapes coccus bacillus spirillum p. 334

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

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

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

Metabolic Diversity Photoautotrophs Chemoautotrophs Chemoheterotrophs

Gram Stain Fig. 21-4, p.335

Gram Staining Video http://www.youtube.com/watch?v=oogg M6mxjY0

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

Prokaryotic Fission Fig. 21-5, p.335

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

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

Bozeman Videos Bacteria & Archaebacteria http://www.youtube.com/watch?v=h-z9-9oowc4 http://www.youtube.com/watch?v=w25ni9 kpxtu

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

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

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

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

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

Archaebacteria Methanogens Extreme halophiles Extreme thermophiles

Methanogens Fig. 21-11a, p.340

Extreme Halophiles Fig. 21-12a, p.341

Extreme Thermophiles Fig. 21-12b, p.341

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

Bozeman Video--Viruses http://www.youtube.com/watch?v=l8ohs7 G_syI

Viral Body Plans Complex virus (bacteriophage) Genetic material is DNA or RNA Coat is protein Helical virus Polyhedral virus Fig. 21-13, p.342

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

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. 21.20 Page 358

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 21.20 (2) Page 358

Bozeman Video Viral Replication http://www.youtube.com/watch?v=eqk1cy YQIug

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

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

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