UNIT 4 BACTERIA, VIRUSES & THE IMMUNE SYSTEM 1

BACTERIA Prokaryotes are the smallest and most common microorganisms Single celled organisms; no nucleus; have ribosomes Divided into 2 kingdoms: A. Archaebacteria B. Eubacteria 2

Archaebacteria Eubacteria Smaller, more “primitive” of 2 kingdoms Live in harsh environments – ice, volcanoes, hot springs DNA very similar to eukaryotes Generally not pathogenic Larger, less “primitive” of 2 kingdoms Organisms have many different lifestyles This kingdom’s DNA is most different from all others Many pathogenic members 3

IDENTIFYING PROKARYOTES Shape: 1. Bacilli: rod-shaped 2. Cocci: spherical 3. Spirilla: spiral and corkscrew Movement: 1. No movement 2. Flagella propel them forward 3. Glide along a slime-layer 4

HOW THEY GET THEIR ENERGY Autotrophs: Use sunlight or chemicals (like methane) to convert CO 2 & H 2 O to sugar and oxygen Heterotrophs: Take in organic molecules for a supply of energy and carbon 5

HOW THEY RELEASE ENERGY Aerobes: must have oxygen to release energy Anaerobes: do not need (and might be killed by) oxygen Some bacteria can live in both environments which allows them to live almost anywhere 6

HOW THEY GROW AND REPRODUCE Growth: Controlled by availability of food and amount of waste production Reproduction: 1. Binary fission-when the cell reaches a certain size it divides (mitosis) 2. Conjugation-when bacteria exchange genes with each other before they divide 3. Budding-new bacteria grows from side of original 7

8 Binary Fission Budding Conjugation

Eubacteria are able to form an endospore when they are not in a favorable condition to reproduce This is a thick internal wall around the DNA and a portion of the cytoplasm The endospore can protect the bacteria indefinitely 9

IMPORTANCE OF BACTERIA Decomposers – break down organic material and recycle materials back into environment Found in soil and water 10

IMPORTANCE OF BACTERIA Nitrogen fixers – certain bacteria take nitrogen gas from the atmosphere and convert it into a form plants can use Critical part of nitrogen cycle 11

IMPORTANCE OF BACTERIA Human Uses: 1. Wastewater treatment 2. Live in a symbiotic relationship with organisms in their digestive tracts 3. Used in production of food 12

VIRUSES Viruses are a core of DNA or RNA (not both) They are surrounded by a protein coat - capsid Can reproduce only by infecting living cells Are submicroscopic – cannot be seen with a light microscope Viruses have a specific host cell Capsid allows virus to bind to the host cell and “trick” the cell into letting the virus in 13

14 Bacteriophage Tobacco Mosaic Influenza - General Avian Flu

TYPES OF VIRAL INFECTIONS Lytic Infection 1. Virus enters cell 2. Makes multiple copies of itself 3. Cell bursts and send thousands of copies into the organism to infect other cells 15

Lysogenic Infection: 1. Virus enters cell 2. It inserts its DNA into the host cell’s DNA 3. Cell and virus reproduce together, sometimes for years 4. Something triggers the virus to become active 5. It becomes lytic 16

Retroviruses – some viruses contain RNA instead of DNA for genetic info Infect cell and produce DNA copies until becoming active and destroying cell Cancer and HIV are examples 17

THE IMMUNE SYSTEM AND DISEASE 18

Section 1 - Infectious Disease Disease – any change, other than injury, that disrupts the normal functions of the body Germ theory of disease – infectious diseases are caused by microorganisms of different types; commonly called germs 19

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Pathogens – disease causing agents; the human body provides just the right environment for growth of these agents 1. Bacteria 2. Viruses 3. Fungi 4. Environmental Toxins 21

Disease Bacteria produce disease by: A. Directly breaking down cells for food B. Releasing toxins that travel through host Preventing bacterial disease: A. Vaccine – injection of weakened/killed pathogen; helps body produce immunity to disease B. Antibiotics – block growth/reproduction of bacteria 22

Controlling Bacteria: A. Heat sterilization B. Disinfectants C. Proper food storage/preparation Viral Diseases: 1. Disrupt organism’s homeostasis 2. Treated with antivirals 3. Best protection is prevention 23

How Diseases are Spread Physical contact - coughing, sneezing or direct contact Some of the most dangerous pathogens are spread through sexual contact Contaminated food and water – undercooked or improperly prepared meat; raw sewage in water supply Infected animals – called vectors 24

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Section 2 – The Immune System Recognizes, attacks, destroys and “remembers” each type of pathogen that enters the body Produces specialized cells to inactivate pathogen – called immunity 2 general categories of defenses against disease – specific and non-specific 26

Nonspecific Defenses Do not discriminate between one threat and another First line of defense: skin, mucus, sweat and tears; skin is the most important of these Second line of defense: 1. Inflammatory Response - millions of white blood cells are made and sent to sight of infection; causes area to become swollen and painful 27

2. Fever – elevated body temperature; slows or stops the growth of pathogens; allows the white blood cells to work better 28

Specific Defenses If a pathogen is able to get past the nonspecific defenses, the immune system reacts with a series of specific defenses that attack a particular disease-causing agent This process is called immune response The substance that triggers this response is called an antigen 29

Two types of lymphocytes (B cells and T cells) recognize specific antigens 1. Humoral immunity – immunity against antigens and pathogens in the body fluids; (B cells) Produced in bone marrow from stem cells 30

2. Cell-mediated immunity – immunity against abnormal cells living inside of living cells; (T cells) Body’s main defense against its own cells when they become cancerous or infected Recognize cells that are defective/foreign and destroy them 31

Killer T-Cell (upper right) attacking a cancer cell 32

Acquired Immunity Active immunity – body is injected with a vaccine to stimulate the production of antibodies; long term protection from pathogen (MMR & tetanus shots) Passive immunity – antigens produced by other animals that are directly injected into the bloodstream; temporary protection from pathogen (rabies, malaria, flu) 33

Section 3 – Immune System Disorders HIV budding from a Helper T cell 34

Allergies Most common overreaction of immune system Antigens that cause allergic reactions are called allergens (dust, mold, pollen, stings) 35

When allergens enter body they attach themselves to mast cells, specialized immune cells that initiate an inflammatory response Mast cells release histamine which increases blood and fluid flow to affected area Antihistamines counteract the affects of histamine 36

Autoimmune Diseases When the immune system makes a mistake and attacks the body’s own healthy cells A. Rheumatoid arthritis – antibodies attack connective tissue around joints B. Multiple sclerosis – antibodies destroy the myelin sheaths of the neurons in the brain and spinal chord 37

AIDS, an Immunodeficiency Disease HIV virus attacks helper T cells (makes individual HIV positive); Cells die and the immune system response starts to break down As virus progresses to AIDS, the body starts to become vulnerable to any type of pathogen that it encounters HIV is a retrovirus, its genetic material is RNA that is copied into the T cell’s DNA 38

HIV is transmitted in one or more of four main ways 1. ANY form of sexual contact with an infected person 2. Shared needles or syringes that have come in contact with the blood of an infected person 3. Contact with blood or blood products from an infected person 4. Infected mother to child 39

Facts About AIDS There is NO cure for AIDS; new drugs make it possible to live longer with the disease. This does not prevent you from dying from AIDS related diseases, it just slows down when it will happen! The only no-risk sexual behavior with respect to HIV and AIDS is abstinence! 40

In one year, more than 5 million people worldwide became infected with HIV, including ~ 800,000 people under 15 In that same year, 3 million people died from complications of AIDS This brought the total number of deaths around the world to more that 20 million people 41

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