Chapter 19 Viruses and Bacteria

Viruses Viruses are NOT cells! A virus is made up of: 1.Nucleic acid (RNA or DNA) 2. Protein coat

What is a virus? Made of nucleic acid (DNA OR RNA), protein coat (capsid) and sometimes lipids MUST enter living cells in order to reproduce Very small Range from a few to 100s of genes Bacteriophage = virus that infects bacteria

Viruses: Living or Non-living? No cell membrane or other living cell components Host cells required for reproduction Do not metabolize or respond to stimuli BUT, they do have genetic info and can change over time

Virus Infection: Lytic vs. Lysogenic Cycles Lytic Cycle: virus enters cell, makes copies of itself, and causes the cell to “lyse” or burst Lysogenic Cycle: virus integrates into host cell DNA and viral genetic info is copied along with host cell’s DNA

Lytic Cycle The viral infection that rapidly kills the host cell is the lytic cycle.

Lytic Cycle of a Cold or Influenza Virus The cold or flu virus infects cells lining of the nose and throat, reproducing more cold viruses and destroying body cells.

Review Lytic and Lysogenic Cycles… Handouts from book!

Retrovirus A virus that contains RNA instead of DNA Human Immunodeficiency Virus (HIV) is a retrovirus HIV causes AIDS ENVELOPE RNA CAPSID

HIV Virus and Immune System The thymus gland by the heart and the bone marrow produce the white blood cells that protect us from infection. HIV attacks the T cell of the immune system.

Retroviruses When enter cells, produce DNA copy of RNA then integrate into host cell Can remain dormant until replicate and burst open cell “Retro” because genetic info is copied backwards RNA => DNA

Destroys helper T cells –Makes getting other diseases really easy Transmitted by blood, breast feeding, sexually, and other bodily fluids Can happen to anyone! Mouth sores common to AIDS patients

Viruses as Parasites Take advantage of host cell’s respiration, nutrition and other cellular functions Depends entirely on another organism for its existence

Types of Viral Diseases Must know – Names – Symptoms – Transmission

West Nile Symptoms –Fever –Headache –Body ache Transmitted by –infected mosquitoes

Chicken Pox Symptoms –Fever and weakness –Red, itchy rash Transmitted by –Direct contact –Droplet inhalation

Common Cold Symptoms –Sneezing –Sore throat –Fever –Muscle and headaches Transmitted by –Direct contact –Droplet inhalation

Warts/HPV Symptoms –Noncancerous growths on skin; can become cancerous Transmitted by –Direct contact –Sex

Hepatitis Symptoms –Jaundice –Fatigue –Abdominal pain –Diarrhea and nausea Transmitted by –Human waste, contaminated food and water (Hep A) –Contact w/ bodily fluids (B & C)

Herpes Symptoms –Blister like sores (can actually be on any part of the body) –Fever –Fatigue Transmitted by –Direct contact –Sex

Measles Symptoms –High fever –Sore throat –Rash –Swollen eyelids Transmitted by –Droplet inhalation

Polio Symptoms –Fever –Headache –Muscle weakness –Difficulty swallowing Transmitted by –Droplet inhalation

Smallpox Symptoms –High fever –Fatigue –Rash Transmitted by –Contact –Droplet inhalation

Virus Prevention (No treatments!) Vaccination –Injection of weakened or dead pathogen Hygiene –Wash your hands! Safe sex –Use condoms or other prophylactic contraceptives Abstinence –Only method that is 100% effective against transmission of sexually transmitted viruses

Bacteria Bacteria are small PROKARYOTIC cells. They have a cell wall and DNA. Some bacteria are beneficial and some are pathogenic. *Pathogenic = disease causing

Bacteria Used as a common name to describe prokaryotes Usually range from 1-5 micrometers! Divided into two kingdoms: eubacteria and archaebacteria Staphylococcus epidermidis

Eubacteria Largest bacterial Kingdom Wide range; many lifestyles, live almost anywhere Usually have cell wall for shape and protection - cell wall contains peptidoglycan Have cell membrane- sometimes an extra membrane outside of it as well Escherichia coli

Archaebacteria Look similar to eubacteria under microscope but chemically different No peptidoglycan & different membrane lipids DNA more like eukaryotes (Share a more recent common ancestor) Live in extreme/harsh environments

How Are Bacteria Identified? Identified by: –Shape –Movement techniques –Way of obtaining energy –Oxygen Needs –Mode of Reproduction

Shape Rod-shape: Bacilli Spherical shape: Cocci Spiral and corkscrew: Spirilla

Movement Not all prokaryotes can move Ones that move –Propelled by flagella (whiplike structures for movement) –Lash, snake or spiral –Glide along layer of slime Escherichia coli

Start taking notes here: Metabolic Diversity: Heterotrophs vs. Autotrophs Most are heterotrophic! If autotrophic: –Some are photoautotrophs (similar to plants) –Some are chemoautotrophs (make organic molecules from CO 2 If heterotrophic: –Most are chemoheterotrophs (Take in organic molecules for energy and carbon supply) –Humans are chemoheterotrophs, too! –Some are photoheterorophs (photosynthetic but need organic compounds for carbon source)

Oxygen Needs Facultative anaerobes –Can survive with or without oxygen Obligate anaerobes –Must live in the absence of oxygen Obligate aerobes –Require constant supply of oxygen to live

Growth and Reproduction Conjugation –Asexual Reproduction –Hollow bridge forms between two cells and genes move from one cell to the other; increases genetic diversity –IS a sexual process (NOT REPRODUCTION – does not produce gametes)

Binary Fission Asexual Reproduction –Grows to where it doubles in size then replicates DNA and divides in half –New bacteria gentically identical

The Role of Microorganisms in Maintaining Equilibrium in the Environment

Importance of bacteria Bacteria are vital to maintaining the living world! Not all are pathogenic!!!

Helpful Bacteria Decomposers break down dead organic material Biotechnology - inserting helpful genes into a plasmid Bioremediation - bacteria eat up oil spills Food production Nitrogen fixation – convert atmospheric nitrogen into a usable form the plant can take in from the soil Aid in digestion

Importance of bacteria Some are producers that capture energy by photosynthesis.

Importance of bacteria Others are decomposers breaking down nutrients in dead matter. Bacteria breakdown dead and decaying organisms. Help to recycle nutrients – which helps to maintain equilibrium in the environment. Bacteria also help perform critical steps in sewage treatment.

Importance of bacteria Bacteria convert nitrogen gas into a form plants can use, this is called nitrogen fixation. Nitrogen fixation allows nitrogen atoms to continually cycle through the biosphere.

Nitrogen fixing bacteria in the nodules of roots

Importance of bacteria Bacteria are also used to make some foods such as: -pickles! -ice cream! -yogurt!

Bacteria’s Importance Producers Nitrogen Fixation Human Uses –Food and beverage production –Industry –Drug and chemical production –Live in our intestines; provide vitamins –Biotechnology –Clean up oil spills Decomposers –Recycle nutrients in ecosystem –Sewage treatment

Pathogenic Bacteria Two ways bacteria causes diseases: 1.Break down organism’s cells for food 2.Release toxins that affect the organism’s body

Examples of Bacterial Diseases Streptococcus –Symptoms – fever, sore throat, swollen glands Diphtheria –Symptoms – sore throat, low grade fever **Both cause disease by releasing TOXINS!!

Circulatory System Bacteria can infect the heart valves and the lining of the ventricles. The circulatory system brings oxygen and nutrients to all body cells. Left ventricle

Beneficial Bacteria in the Digestive System Bacteria like E. coli make digestive enzymes and vitamin K in the large intestine.

Nervous System Brain Spinal cord Spinal& peripheral nerves The nervous system responds to changes in the external and internal environment. It is “the communicator”.

Nervous System Infections Both bacteria and viruses can infect the brain causing such diseases as meningitis and encephalitis. Nerve cells or Neurons

Controlling Bacteria Food storage and processing Disinfectants –Chemical solutions that kill bacteria Sterilization –Method to control growth of bacteria by heat Vaccines – Prevention! –Weakened or killed pathogens –Sometimes prompts body to produce immunity Antibiotics – Treatment! –Block growth of bacteria

Comparing VIRUSES and BACTERIA 1.Which is a virus? 2.Which is a bacteria? 3.Which is living? 4.Which is non-living? A. B.