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