Download Chapter 19

Chapter 19
Bacteria and Viruses
Remember homeostasis?
• Maintaining proper internal conditions
• pH, temp., water/salt balance, O2, CO2, etc.
Factors for Disease
• 1. genetics- inheritance
• 2. microorganisms
– pathogen: disease-causing agent
• 3. pollutants/poisons (ex: asbestos, lead)
• 4. organ malfunction
• 5. harmful lifestyles (tobacco, alcohol, lack of nutrition or
exercise)
19-1 Bacteria
• Prokaryotes
• Monera
• Can be beneficial or disease-causing
– Good: intestinal bacteria
– Bad: strep throat, pneumonia
• Everywhere!
Identified by:
• Shape- bacilli (rod), cocci (round), spirilla (spiral)
• Cell walls- Gram +/- (peptidoglycan)
• Movement- flagella, slime
• Metabolic diversity- heterotrophs and
autotrophs (chemo- or photo-)
Bacteria Energy Production
• Respiration or fermentation (with or without O2)
• Obligate aerobes: needs O2 to live
• Obligate anaerobes: cannot live with O2
• Facultative anaerobes: can live with or
without O2
Bacteria Reproduction
• Binary fission: (asexual) DNA is replicated
and the organism splits in half
• Conjugation: (sexual) genetic info is
exchanged across a “bridge”
• Spore formation: haploid cell that can
withstand hard conditions and form a new
organisms when the time is right
Importance of Bacteria
• Decomposers- break things down
• Nitrogen fixation- cycles N thru atmosphere
• Human uses: food, oil spills, medicine,
intestines
Treating Bacteria
• Bacteria have homeostasis too! Change the
conditions to stop growth
– Temp, salt, pH, etc.
• Sterilization (heat), disinfection (chemicals)
• Antibiotics- kill bacteria or stop reproduction
19-2 Viruses
• Categorized by what they infect:
– Plant, animal, bacteriophage
• Capsid- protein coat- signifies which host to infect
(host must have a receptor)
• NOT alive- has genetic material but can’t repro on own
• Ex: flu virus, HIV
Virus Replication
• Lytic: enters host cell, copies itself
continuously and bursts (lyses)
• Lysogenic: combines/replicates viral
DNA with host DNA
– Prophage: viral DNA embedded within
host DNA
Treating Viruses
• Antibiotics WILL NOT work!
• Prevention is key!
• Vaccination: inject a weak form of a virus in
order to get the antibodies (immunity)
The Body’s Defense System
• homeostasis= includes regulating microbes
• Lines of defense:
• 1. physical barriers- block entry (skin)
• 2. inflammation- increased blood flow
• 3. immune system
Immune System
• Recognizes the “bad guys”
• Every bacteria/virus has antigens (proteins)
• Immune system makes antibodies
• Antibodies fight the antigens
• Vaccines- shows antigens ahead of time- allows
body to create antibodies (immunity)
White Blood Cells (WBCs)
• Immune system MVP
• 2 types:
• 1. B cells: make antibodies
– Memory B cells
• 2. T cells:
– Killer T cells: kill infected cells
– Helper T cells*: help all other WBCs
When the immune system goes wrong…
• Allergic reactions- increase in system- produces
histamines
• Autoimmune diseases- system attacks self
• Immunodeficiency- decrease in system- helper T
cells destroyed (ex: AIDS)
• inflammation- older people
Other Pathogens
• Protozoa- unicellular parasites
• Algae/Dinoflagellates- produce toxins
– ex: red tide
• Fungi- athletes foot, ringworm
• Parasitic Worms- tapeworm
Viroids and Prions
• Viroids: single stranded RNA molecules enter
infected cells
• Prions: tiny protein particles enter the brain
and affect the nervous system- no DNA/RNA
– Ex: mad cow disease