1. Bacteria, Viruses, & Humans

2. 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

3. 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

4. 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)

5. 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

6. 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

7. 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