Living with Microbes HELPFUL BACTERIA HOW THEY HELP

Living with Microbes

HELPFUL BACTERIA • HOW THEY HELP PLANTS • E. g. Rhizobium bacteria: nitrogen-fixing bacteria • Live inside the roots of peas, beans, lentils, peanuts, etc. • Changes nitrogen from the air (form that the plant cannot use) to a usable form. • Plant can now make proteins and nucleic acids. Usable nitrogen travels up the food chain, and finally, to humans! Without these bacteria, we would not have a source of nitrogen!

• HOW BACTERIA HELP HUMANS • Bacteria help human in countless ways! • Bacteria live in warm, moist places. • Examples: • Bacteria on Skin: feed on dead skin cells. • Bacteria in the DS: help digest food. • Bacteria in Intestine: Lactobacillus helps keep harmful bacteria from invading and growing. Sweat is odorless by nature. Armpits are a perfect warm, moist place for bacteria to thrive. So, what is Body Odor? Bacteria that cover the surface of the skin feed on sweat. The waste material produced by bacteria are acidic compounds. The acidic compounds cause B. O. Deodorant & Antiperspirant contain antimicrobials. Antiperspirants also help control sweat.

BACTERIA CAN CAUSE INFECTIONS THAT HAVE MANY DIFFERENT EFFECTS FIRST, SOME TERMINOLOGY: • Infection: invasion of the body by another living organism or biological agent, which causes disease. • Pathogen: disease-causing agent, which can include microbes and viruses. • Toxin: poisonous substance produced by some pathogens which can cause disease.

EXAMPLES OF HARMFUL BACTERIA • Strep Throat • Caused by the bacteria Streptococcus. • Common signs are white patches with redness in the throat and tonsils. • Diagnosis: doctor swabs the infected area and examines how it grows. • Flesh-eating disease • Caused by Streptococcus pyogenes • Produces toxins that destroy skin, fat, and muscle.

STEPS FOR A PATHOGEN TO CAUSE AN INFECTION 1. Finding a Portal of Entry • Must enter body tissues. • Through an opening in the skin (like a cut or scrape). • Being eaten and entering the digestive tract. • Being inhaled into the respiratory tract. 2. Attaching to the Host • Pathogens must become attached to the cells of the tissue. • A structure on the outside of the microbe or virus “fits” with molecules on the surfaces of the cells. 3. Surviving Host Defensive Mechanisms • Host body has several ways to try to fight off the pathogen.

STEPS FOR A PATHOGEN TO CAUSE AN INFECTION 4. Causing Disease • Pathogens cause damage to the tissue in ways that are specific to each pathogen. Releasing toxins is one way that bacteria can cause damage. 5. Exiting the Host • Pathogens continue to survive by eventually being released from the host. • They can infect another host. • Ways pathogens are released are • Through urine • Through feces • Through sneezing or coughing

BACTERIAL INFECTIONS CAN BE PREVENTED AND TREATED Immune System • • Cells and proteins which attack foreign invaders such as bacteria and viruses. There are two components of the immune system: non-specific defences and specific immunity. Non-specific Defences • • • Physical and Chemical Barriers • Skin oils, sweat, and tears contain anti-microbial properties • Earwax, mucus, cilia, and stomach acid prevent microbes from entering the body • Sneezing, coughing, and vomiting help eject pathogens from the body Resident micro-organisms • Live on the skin and in large intestine – take up room so harmful bacteria can’t grow. Inflammation • If pathogens do penetrate the body’s defences, the area that is infected becomes red, warm, swollen, and painful. This reaction stimulates the immune system to act. Immune cells and proteins • White blood cells (WBC) engulf and destroy pathogens • Different proteins are that destroy pathogens are produced Fever • Higher body temperature can kill some pathogens

BACTERIAL INFECTIONS CAN BE PREVENTED AND TREATED Specific Immunity • Takes time to be activated, but much more powerful • Targets specific pathogens • Antigen: carbohydrates or proteins on bacterial cell walls that trigger a series of immune defences. 1) Antigens stimulate certain WBCs to take up pathogen and present antigens to other WBCs. 2) WBCs that receive antigens trigger other WBCs to destroy the pathogen directly or produce immune proteins called antibodies. 3) Antibodies (immune proteins) bind to antigens on pathogens and kill it. 4) Memory cells – special immune cells – stay in the body for an entire lifetime. If the pathogen invades again, memory cells will divide rapidly, and will be able to fight of pathogen faster.

VACCINES & ANTIBIOTICS Vaccine: • a substance that stimulates immunity against a pathogen without causing illness. • Contain part of a virus or bacteria • Contain antigens – these “teach” the immune system to recognize a pathogen • Memory cells are produced. • When real pathogen infects the body, immune system is ready! Antibiotic: • medications that treat bacterial infections • Overuse can make antibiotics less effective