Bacteria, Viruses, & Humans

Roles of Bacteria & Viruses Bacteria play important roles in the environment & in industry Produce oxygen, make nitrogen available to other organisms, & decompose dead organisms Live in humans’ large intestines & produce vitamin K Help make foods (pickles, soy sauce, etc.), produce chemicals, mine minerals (copper & uranium), clean oil spills, & used in sewage plants Both bacterial & viruses are important to genetic research Provide information about DNA replication, transcription, & translation Viruses used in gene therapy to deliver genetic material to target cells

Koch’s Postulates Developed by German physician, Robert Koch, to help determine what causes diseases 4 steps: Find & isolate the pathogen in an animal with the disease Grow the pathogen in a laboratory Infect a healthy animal with the disease Isolate the pathogen from the second animal, & prove it to be the same as the pathogen in the first animal

Bacterial Diseases Bacteria cause diseases by producing toxins or by destroying body tissues Botulism, caused by Clostridium botulinum, destroys the tips of nerve cells Can cause double vision & paralysis; used in cosmetology (Botox) Tuberculosis & strep throat caused when bacteria destroy tissue Can be fatal when in muscle or skin tissue (necrotizing fasciitis)

Antibiotic Resistance Antibiotics are chemicals that stop the growth of or kill microorganisms Resistance is the ability of bacteria to tolerate antibiotics Widespread use of antibiotics allow resistance to spread Normal bacteria stop growing or die when antibiotics are present Resistant bacteria thrive & spread, causing bacterial diseases to be harder to treat

Viral Diseases Are very specific, but can be transmitted in many ways Most symptoms of viral infections come from the body’s response to infection Some can cause cancer Many can be prevented with vaccines Vaccines—weakened forms of the pathogen that prepares the immune system to recognize & destroy the pathogen

Emerging Diseases Can be: Newly recognized (bird flu) Spread to a new host (SARS—spread from cats to humans) Spread to a new area (travel between parts of the world allow diseases to spread easily) Re-emerging when thought to be under control (whooping cough, measles, etc.) Human activity, environmental changes, & frequent use of antibiotics play large roles in spreading diseases