Bacteria Notes
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Transcript Bacteria Notes
The Basics of Bacteria
What are bacteria?
Bacteria are single-celled prokaryotes
DNA is not located in a nucleus
Bacteria appeared on Earth at least 3.5 billion
years ago
Bacterial Shapes
Most bacteria have one
of the following shapes:
Bacilli
Cocci
Spirilla
Bacterial Structures
Most bacteria have the following structures:
Cell wall (contains peptidoglycan, a
compound composed of amino acids and
carbohydrates)
Cell membrane
Cytoplasm
Chromosome (Single-loop of DNA)
Additional Bacterial Structures
Some bacteria may have the following
structures:
Capsule (covering outside of cell wall that protects
bacterial cell)
Pili (hair-like structures used to transfer genetic
material from one bacterium to another)
Endospore (Thick covering around DNA;
developed under harsh conditions)
Plasmid (small, additional loop of DNA)
Flagella (Used for motion)
Nutrition and Growth
Bacteria obtain their energy in one of
two ways:
Heterotrophs (must obtain “food” for
energy)
Autotrophs (obtain energy from
sunlight or minerals)
Nutrition and Growth continued
Oxygen requirements
Obligate anaerobes (can’t survive in
presence of oxygen)
Facultative anaerobes (don’t require
oxygen, but can survive around it)
Obligate aerobes (require oxygen)
Bacterial Reproduction
Bacteria reproduce by binary fission:
One cell divides to form two
identical cells
http://www.yteach.com/index.php/resources/amino_acids_antibiotics_autotroph_protein_cell_wall_chem
oautotrophic_chemosyntesis_chlorophyll_saccharides_carbohydrates_cytoplasm_DNA_energy_enzyme_ev
olution_fermentation_phospholipids_histone_nucleus_DNA_RNA_population_t_page_37.html
Genetic Recombination
If bacteria reproduce “clones” by binary fission,
why aren’t all bacteria identical?
Transformation: cell takes in DNA from
environment and replaces a portion of its own DNA
with this new DNA
Conjugation: A bacterium attaches its pilus to
another cell and transfers a copy of its plasmid to
this cell
Transduction: Virus “infects” a bacterium with a
piece of bacterial DNA it is carrying from a
different bacterial cell
Transformation
transformation and conjugation video
http://highered.mcgrawhill.com/sites/0072556781/student_view0/chapter13/animation_quiz_
1.html
Conjugation
http://www.hhmi.org/biointeractive/animation
s/conjugation/conj_frames.htm
Transduction
http://faculty.ircc.edu/fac
ulty/tfischer/images/speci
alized%20transduction.jpg
http://highered.mcgraw-hill.com/sites/0072556781/student_view0/chapter13/animation_quiz_2.html
Bacterial Defenses
Bacteria have numerous defenses against
the threats in their environment:
Exotoxins: Poisonous proteins secreted
by bacteria
Endotoxins: Toxin in bacterial cell wall;
released when bacteria die
Naturally-Occurring Antibiotics
Antibiotics
Chemicals that interfere with cell
functions; inhibit bacteria growth.
Bacteria are sensitive if they don’t grow
in the presence of the antibiotic.
Bacteria are resistant if they do grow in
the presence of the antibiotic.
Bacteria Growth and Antibiotics
http://www.sumanasinc.com/scienceinfocus/sif_antibiotics.html