chapter 20: viruses and prokaryotes section 20-3: diseases caused by bacteria and viruses
TRANSCRIPT
Chapter 20:Viruses and Prokaryotes
Section 20-3: Diseases Caused by Bacteria and Viruses
Bacterial Diseases Pathogens are microorganisms that cause
disease All known prokaryotic pathogens are bacteria Louis Pasteur helped establish the germ theory
of disease by showing bacteria responsible for many human and animal diseases
Bacterial diseases produced in 2 general ways: Destroy living tissue of infected organism, directly or
causing tissue damage by triggering immune system (bacteria that cause tuberculosis)
Release toxins that interfere with normal activity (bacteria that cause diphtheria, botulism)
Common Human Bacterial Diseases
Controlling Bacteria Physical removal – washing hands or other
surfaces under running water does not kill bacteria, but it can dislodge them (also viruses)
Disinfectants – chemical solutions that kill bacteria
Food storage – low temperatures slow bacterial growth, keep foods fresher than room temperature
Food processing – cooking kills bacteria Heat sterilization – instruments are heated to
above 100° C to kill bacteria
Preventing Bacterial Diseases Vaccines are preparations of weakened or
killed pathogens or inactivated toxins
When injected, vaccines prompt body to produce immunity to a specific disease
Treating Bacterial Diseases Antibiotics such as penicillin and tetracylcine
block the growth and reproduction of bacteria by disrupting proteins or cellular processes specific to bacterial cells without harming host
Ineffective against viral infections
Viral Diseases Produce disease by disrupting homeostasis Animal and plant diseases
Disease Mechanisms Some attack and destroy specific cells,
causing disease symptoms – poliovirus
Some viruses cause infected cells to change their growth and development patterns, sometimes leading to cancer
Preventing Viral Diseases Vaccines
1769- Smallpox vaccine, using cowpox virus 1880s- Anthrax and rabies 1923- tuberculosis 1950s- 2 polio vaccines, one used killed viruses and one
using weakened viruses 1981- hepatitis B vaccine using recombinant DNA 2006- vaccine against human papillomavirus (HPV)
Cold and flu viruses often spread by hand-to-mouth contact – wash hands, avoid contact with sick people, do not cough or sneeze on hands
Treating Viral Diseases Few antiviral drugs
Attack specific viral enzymes host cells do not have
Emerging Diseases Pathogens reproduce quickly, evolve easily An unknown disease that appears in a
population for the first time or a well-known disease that suddenly becomes harder to control is called an emerging disease
Emerging Diseases Changes in lifestyle and commerce have
made this a bigger issue
Tend to appear suddenly, resist control methods
Need better understanding of molecular structure and genetics
“Superbugs” Evolution has created many bacteria that are
resistant to antibiotics In the 1940s, penicillin killed everything Widespread use of antibiotics has allowed for
natural selection to favor resistance, and conjugation can transfer drug-resistant genes
MRSA
New Viruses Reproduce so quickly, so simple genetically
they can jump species (SIV to HIV)
Flu virus is always changing – new vaccines and variations (bird flu)
Prions 1972- Stanley Prusiner investigated cause of
scrapie, an infectious disease in sheep Experiments showed clumps of protein
particles in the brains of infected sheep. Prusiner called particles prions, short for
“protein infectious particles” Misfolded proteins in the brain cause a chain
reaction of misfolding in other normal proteins, clogging the brain tissue and causing disease
Mad cow disease