Microorganisms & The Body Defenses Bacteria & Viruses

Microbes: Friend or Foe? The world around you is full of life. Tiny life forms have existed for 3.5 billion years. They are the smallest and most diverse life forms. They are vital to life on earth.

FRIEND: How are Microbes Vital for Life? Decomposers-feed on dead plants and animals. Provide food for other living organisms. Help many animals digest food and help maintain a health digestive system (intestines). Allow plants to grow. Live on our skin preventing harmful microbes access into our bodies.

FOE: some Microbes are Harmful! 95% of all microbes do not harm other living organisms but are helpful. 5% of all microbes cause disease. –called pathogens Pathogens cause communicable disease. –Spread person to person. Some pathogens cause epidemics. –A widespread outbreak

So What are Microbes Anyway? Bacteria –4000 different species. –Made of 1 cell Fungi –100,000 different species –I cell but form clusters of cells, that is why we can see them Protists –200,000 different species –Larger and more complex than bacteria but 1 cell Viruses –Millions of different types –1000X smaller that bacteria

FRIEND: Microbes are Essential for the Health of Our Bodies 100 microbes to 1 human cell 10% of our body weight.

Where Are Microbes Found Head- around each strand of hair Lungs-few live here unless damaged by smoking Armpits-feed off our sweat (smelly!) Hands and under fingernails

FRIEND: Where Are Microbes Found Continued Feet-toes and nails Eyes- antibacterial tears Mouth-tongue and teeth (feel the slime over your teeth) Stomach- only hardy ones survive (H. pylori) Intestines-trillions live here –Some produce vitamins we need –Help digest carb’s we can’t –Produce flatulence…..STINKY!

How do Microbes (Pathogens) Invade Us? Air –Sneezing, coughing, recycled air in an airplane Food and Water –Unwashed or under-cooked food –Fecal matter mixes with food or water supplies Contact –Blood, saliva, open wounds, touch, animal or insect bite –Kissing, sharing drinks and food, sexual contact

Pathogens: Bacteria Harm us in 2 ways: 1.Compete for nutrients and crowds out our normal flora or invades our body cells and kills them. Example: Strep throat 2. Produce toxins that can harm or kill the host (us). Example: Botulism

Pathogens: Viruses Tiny particles-must magnify 250,000X to be visible. Strand of DNA or RNA enclosed in a protein shell. Does not grow, use energy or metabolize

How Do Viruses Get Into Our Body 1.Attaches to proteins on our cell membrane 2.The cell tries to destroy the virus by digesting it in the lysosome. 3.Instead of killing the entire virus it only destroys the protein coat and allows the viral DNA to enter the nucleus. 4.In the nucleus viral DNA forces our DNA to replicate viral DNA instead. 5.The result: a cell bursting with new virus.

Pathogen: Protists Single celled organisms can enter our body and blood stream. Here they may enter RBC’s or other body tissue and destroy them.

Body Defenses Physical and Chemical 1. Skin: dense layers of dead cells filled with a protein keratin. Keratin: Prevents pathogens from penetrating the skin Sweat glands: secretes chemicals that kill pathogens Then how do they enter the skin????

Body Defense: Physical and Chemical Digestive, Reproductive and Respiratory Tracts Lined with mucus that secrete a chemical that kills pathogens (nose, eyes and mouth) Urine flushes out pathogens before they have a chance to invade Sneezing, coughing and vomitingforcefully remove invading pathogens. However, can this also help spread pathogens to others?

What Happens if these defenses do not work and pathogens get into the body?

Immune System White Blood Cells (WBC’s) respond to pathogens and kill them. Produce antibodies that destroy the pathogen. –Coat the toxin and neutralizes it –Coats virus’s and prevents them from binding to the cell membrane –Kills bacteria

Vaccines Vaccines trigger your body to make antibodies BEFORE the actual pathogen enters your body. So when the pathogen does enter your body a army is already made for that specific pathogen. May need to get boosters every year (flu) or many tears (tetanus) because the vaccine has a limit of years it can work.

What is an Anti-serum? Antibodies that are made from other organisms and given when you get bitten by a poisonous animal. Example: –snake,spider or rapid dog.