Chapter 20 Bacteria & Viruses. Germ Theory Discovery that microorganisms are PATHOGENS (disease...

Chapter 20

Bacteria & Viruses

Germ Theory

• Discovery that microorganisms are PATHOGENS (disease causing agents) The germ theory of disease states that some diseases are caused by microorganisms. These small organisms, too small to see without magnification, invade humans, animals, and other living hosts. Their growth and reproduction within their hosts can cause a disease.

I. Bacteria

• Are ________________________-lack a nucleus and have few organelles

• Much smaller than eukaryotes• Eubacteria-larger kingdom than

archaebacteria;usually have protective cell wall and determines shape

Prokaryotes

• __________________________-not such a strong,if any,cell wall,DNA sequences more like eukaryotes;live in HARSH environments like hot springs or volcanic vents

Archaebacteria

Identifying bacteria:

– by shape• 1) rod-shaped are __________________• 2) spiral-shaped

are_______________________• 3) spherical-shaped are cocci(coccus-

singular)

Bacillus or bacilli

Spirillus or spirilla

• by cell walls-use Gram Staining-Gram(+) have thick_______________________walls/gram(-) have thinner walls

• by movement-some do not move and some have flagella

peptidoglycan

B. Metabolic Diversity

• Heterotrophs– _____________________-must take in organic molecules

for energy and supply of Carbon-as do we– _____________-

• Autotrophs– ____________________-– ______________-as those found in volcanic vents

Chemoheterotrophs

photoheterotrophs

photoautotrophs chemoautotrophs

Releasing Energy

– 1) Obligate aerobes-need constant supply of O2– 2) _______________________-do not need O2– 3) Faculatative anerobes-can survive w/or w/o

O2-example-E.coli

Obligate anaerobes

C. Growth and Reproduction

• _________________________grows,replicates DNA

and splits in half

Binary fission

• ________________________-exchange genetic info w/ a “bridge”

conjugation

• Some produce_________________________, which can lie dormant and germinate

spores

D. Importance of Bacteria

• Decomposers

• N-fixers-for plants

• Human uses-food production ;cleaning up oil spills

• Assist digestion

II. Viruses-particles of nucleic acids,protein and sometimes lipids

• Not living-reproduce only by infecting living cells• Usually has a DNA or RNA core w/outer protein coat• Outer protein coat called a ______________-which

enable it to enter a host cell—often destroying host cell

• ________________________-viruses that infect bacteria

capsid

bacteriophage

• ____________________infection-virus enters cell,makes copies ,and causes cell to burst

• _____________________________-virus integrates DNA into DNA of host cell,and viral genetic info replicates along w/host

Lytic

Lysogenic

• _______________________________-contain RNA as genetic info and produce DNA copy of RNA

retroviruses

III. Diseases

• Bacterial– Infect by damaging cells or releasing toxins– Mycobacterium tuberculosis– Streptococcus– Cornyebacterium diptherae– Anthrax– Lyme’s disease– Tetanus– Meningitis– Tooth decay

• prevention – -_______________________preparation of weakened

or killed pathogens– ________________________-compounds that block

the reproduction or growth of bacteria

vaccination

antibiotic

• 2)control-sterilization,heat,disinfectantants,proper food processing and storage

B. Viral

• Common cold• Influenza• Smallpox• Warts• AIDS• Chickenpox• Measles• Hepatitis A,B, or C• West Nile• Polio

– ________________________________single-stranded RNA moleculesw/no capsid-attack plants

– ______________________-virus –like particles of protein-may cause protein clumps that induce new prions---example-Mad Cow Disease

viroids

prions