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