Viruses & Prokaryotes: Morphology, Reproduction, & Significance, Slides of Biology

Download Viruses & Prokaryotes: Morphology, Reproduction, & Significance and more Slides Biology in PDF only on Docsity! Chapter 24 Viruses And Prokaryotes Docsity.com Summary - Viruses • What are viruses and why are scientists interested in them? • Morphology • Life cycles - reproduction • Virus diversity Docsity.com Why are Biologists Interested in Viruses? • Cause disease in just about every living organism, although many do not cause disease. • Pandemics/Epidemics – “Spanish flu” – killed up to 50 million people – HIV/AIDS • AIDS has already killed 28 million people worldwide. • There are about 39.5 million HIV-infected people worldwide; an additional 4.4 million people are infected each year. Docsity.com Studying Viruses • Why? – Produce vaccines – Develop antiviral drugs – Used as vectors for molecular biology experiments – recombinant DNA studies. Docsity.com Studying Viruses • Morphology – Genome – – Capsid – – Envelope – some have a phospholipid/ protein protective covering in addition to their capsid. Part viral part host in composition. Docsity.com Virus Reproduction • General Replication cycle – requires a host cell: Docsity.com Virus Reproduction • 2 types of replication cycles: – Lytic – following entry, replication and assembly, new virus particles exit the cell by rupturing the host cell membrane, often destroying the host cell, Figure 24-2. Docsity.com Studying Viruses • 2 Replication cycles cont’d – Lysogenic • Following entry, the viral genome is incorporated into the host cell genome. • As the host cell replicates its own genome the viral genome also is replicated and is passed on to daughter cells. • This phase may last years. • Usually some “trigger” will cause the host cell to enter a lytic phase. Docsity.com How do viruses enter cells? • In general, viruses without envelopes empty only their genome into cell while viruses with envelopes incorporate genome and capsid into cell (endocytosis). • HIV life cycle: cellsalive.com\hiv0.htm Docsity.com How Do Viruses Copy Their Genome? • DNA viruses often have their own DNA polymerase and use the host cell’s nucleotides to replicate. • Most RNA viruses use RNA replicase that synthesizes new RNA from the RNA template. • Retroviruses (other RNA viruses) use reverse transcriptase to make a cDNA. These cDNAs are incorporated into host’s genome and are replicated with the host’s genome. • **Mutations Docsity.com How Do Viruses Make New Proteins? • Transcription and translation: – Using viral DNA or cDNA, mRNA is transcribed and used to direct assembly of new proteins on ribosomes. – **Requires host cell’s amino acids. Docsity.com Virus Diversity • No phylogeny that includes all of the viruses. • Phylogenies for specific viruses, example HIV. Docsity.com Virus Diversity • Characteristics used to classify – ***Mutations in genome/proteins. Docsity.com Emerging Viruses and Host Expansion • Viruses jump from one host to another and mutate. Examples: – SIV and HIV – “Bird flu” and human influenza – Hanta, Ebola, SARS Docsity.com Summary - Prokaryotes • How are Bacteria and Archaea related? • Importance of prokaryotes • How prokaryotes are studied – Bacteria vs. Archaea – Prokaryotes cell surface features • Genetic variation • Metabolism • Key Lineages Docsity.com Introduction • Approximately 5000 species of bacteria and archaea have been identified, there are probably 10’s of millions of species on Earth. – 400 different species live in your GI tract, 500 in your mouth. – Abundance: There are 1012 bacteria on your skin; and billions in a tsp of soil. Docsity.com Why do Biologists Study Bacteria and Archaea? • The Bad – Bacteria cause diseases (are pathogenic) in plants and animals - spread by air, water, food, insects. • Louis Pasteur – food spoilage • Robert Koch – human disease – Cause tooth decay. – Bioweapons - anthrax Docsity.com Why do Biologist Study Bacteria and Archaea? • The Good – Used in the production of insulin, enzymes, vitamins, and antibiotics. – Used in bioremediation: sewage treatment, oil spill and chemical clean-up. – Used in fermentation – cheese, yogurt, vinegar. Docsity.com How are Bacteria/Archaea Studied? • Cultures – liquid or solid “mediums” with specific fuel sources and subjected to specific conditions. Docsity.com Bacteria and Archaea • Similarities: Docsity.com Gram Staining Distinguishes Two Types of Cell Walls in Bacteria Gram-positive cells retain Gram stain more than Gram-negative cells do. Gram-positive cells Gram-negative cells Docsity.com Prokaryotic Cell Surface • Many have thin rigid flagella, anchored to the cell wall that act like propellers. • Some prokaryotes have pili, shorter thinner hair-like extensions that help bacteria attach to surfaces. • Many prokaryotes form endospores, thick walls around nucleoid region. Why? • Biofilms Docsity.com Prokaryotic Variation • Mutation = errors in DNA replication; very frequent in prokaryotes; increased by radiation, UV, chemicals (drugs). • Recombination – transfer of genes by: – Transduction = – Conjugation = – Transformation = Docsity.com Diversity • Different types of metabolism • Different morphology – especially on the cell surface • Different hosts • Different genes Docsity.com Key Lineages - Bacteria • Firmicutes (low GC Gram Positive) – Rods or spheres, – Lactobacillus ferments milk, some fix N2. – Cause anthrax, botulism, tetanus, etc. Docsity.com Key Lineages Bacteria • Spirochaetes (spirochetes) – Corkscrew shape with flagella – Most use fermentation to produce ATP. – A few can fix N2 – Others cause syphilis, lyme disease. Docsity.com Key Lineages Bacteria • Chlamydiales – Spherical. – Chlamydia infections in eyes and urogenital tract (PID, sterility) Docsity.com Key Lineages Bacteria • Proteobacteria – Rods, spheres, spirals. – Fix N2, fermentation – vinegar – Others cause Legionnaire’s disease, cholera, food poisoning, dysentery, ulcers, etc. Docsity.com Key Lineages Archaea • Crenarchaeota – live in very hot or cold conditions, under high pressure, etc. • Euryarchaeota – live everywhere, incl. in high salt and high pH environments. Includes methanogens that live in mammalian guts. • Nanoarchaeota – small thermophile. Docsity.com