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Chapter 18 Bacteria and Viruses
516 - 531
18.1 Bacteria
p. 516 - 524
Main idea
! Bacteria are prokaryotic cells
Prokaryotic – no nucleus Eukaryotic – DNA contained in a nucleus
What are bacteria?
! Microscopic organisms that are prokaryotes
What are the prokaryotic domains?
! Domain Bacteria (eubacteria) ! Domain Archaea (archaebacteria)
What do eubacteria have that archaebacteria do not?
! Peptidoglycan in their cell walls
Archaebacteria Diversity:
! Halophiles – live in very salty environments
! Methanogens – cannot live in presence of oxygen
Prokaryote structure
What is the nucleoid?
! Where the genetic material of a prokaryote is located
What is a capsule?
! A layer of polysaccharide around a cell wall Helps cell from drying out Protects cell
What is the pili?
! Hair-like structures that are made of protein Help bacterial cells attach to surfaces
What are the three different shapes of bacterial cells?
! Cocci – spherical or round ! Bacillus – rod-shaped ! Spirilli – spiral shaped
What do flagella do?
! Help prokaryotes move toward light, oxygen, or chemicals they need to survive
What is binary fission?
! The division of a cell into two genetically identical cells
What is conjugation?
! When two prokaryotes attach to each other and exchange genetic material
How do photosynthetic bacteria obtain nutrients?
! They carry out photosynthesis similar to plants
How do chemoautotrophs obtain nutrients?
! They break down inorganic compounds such as ammonia and hydrogen sulfide
What are aerobes?
! Require oxygen to grow
What are anaerobic bacteria?
! They do not use oxygen for growth
What are three important uses of bacteria?
1. Nutrient cycling and nitrogen fixation 2. Normal flora 3. Foods and medicines
Nutrient cycling
! Bacteria are decomposers
Normal Flora
! Bacteria that live in or on you Most are HARMLESS Type of E. coli that live in your intestines
that help break down food
What foods and medicines are made from bacteria?
! Cheese ! Yogurt ! Buttermilk ! Pickles ! vitamins
Name 3 diseases caused by bacteria:
! Strep throat ! Pneumonia ! Types of food poisoning ! Bacterial meningitis ! Lyme disease
18.2 Viruses
p. 525 - 531
Main idea
! Viruses are smaller and less complex than bacteria – they invade cells and can alter functions
What is a virus?
! A nonliving strand of genetic material within a protein coat
What is a capsid?
! The outer layer of a virus, made of protein
How do viruses replicate?
! they must enter a host cell
What is the lytic cycle?
! The host cell makes many copies of the viral RNA or DNA
What is the lysogenic cycle?
! The viral DNA enters the nucleus of the host cell and becomes a part of the host cells DNA