Upload
dinhkhue
View
223
Download
0
Embed Size (px)
Citation preview
What is a bacterium?
Prokaryote
Unicellular
Has a cell wall, DNA, and ribosomes
Found in variety of places
Classification
Two kingdoms of Bacteria:
Archaebacteria (ancient bacteria)
Harsh environments
Primitive
Eubacteria (true bacteria)
Found anywhere
Cause diseases
ArchaebacteriaAbsence of
peptidoglycan
(component of
bacterial cell wall)
Live in extreme
environments:
swamps, salt lakes,
hot springs, volcanic
vents, hydrothermal
vents
Examples of ArchaebacteriaMethanogens: found in swamps, intestines of
animals
Extreme halophiles: salt-loving; live in Great Salt
Lake and Dead Sea; use salt to make ATP
Thermoacidophiles: extremely acidic environments
with high temperatures such as a hot spring; survive
in 110 °C (230 °F) and a pH of 2; live near volcanic
or hydrothermal vents
Eubacteria
Presence of peptidoglycan in cell
walls
Live everywhere on earth except
extreme environments
EubacteriaShapes
Cocci – spheres
Bacilli – rod
Spirilla – spiral
Occur in chains: strep
Occur in clusters: staph
Examples: Streptococcus, Staphylobacillus
Spirochaeta: spiral
Bacteria and archaea have similar structures.
flagellum
pili
plasmid
cell wall
chromosome
plasma
membrance
plasmid DNA
flagellum
pili
Cell wall
Circular
DNA
Prokaryotes provide nutrients to
humans and other animals.
Prokaryotes live in digestive systems of
animals.
make vitamins
break down food
Prokaryotes play important roles
in ecosystems. Prokaryotes have many functions in
ecosystems.
recycle carbon, nitrogen,
hydrogen, sulfur
fix nitrogen for plants
Some bacteria cause disease.
Bacteria cause disease by invading
tissues or making toxins.
A toxin is a poison released by an
organism.
Antibiotics are used to fight
bacterial disease. Antibiotics may stop bacterial cell wall
formation.
Prevention is best method to fight bacterial
disease.
Genetic Recombination
Transformation – takes in DNA from the environment
Conjugation – transferring of DNA between bacteria
Reproduction
Asexual reproduction
Makes more of the
same
Looks like the parent
Bacteria use binary
fission
Bacteria have various strategies
for survival. Prokaryotes
exchange
genes during
conjugation.
conjugation bridge
TEM; magnification 6000x
StructureEndospores
Resistant structure with a thick outer
covering in order to survive harsh
conditions
Environment & Temperature The temperature where bacteria may be
found depends on the species.
Prokaryotes can be grouped by their need
for oxygen.
obligate anaerobes are poisoned by oxygen
obligate aerobes need oxygen
facultative aerobes can live with or without
oxygen
Nutrition
Heterotrophic or autotrophic
Feed on dead and decaying material:
decomposers
Use sunlight: photoautotrophs
Cyanobacteria
Use chemicals as source of carbon:
chemoautotrophs
Found at ocean depths
Bacteria can evolve resistance to
antibiotics. Bacteria are gaining resistance to antibiotics.
A bacterium carries genes for antibiotic
resistance on a plasmid.
A copy of the plasmid is transferred
through conjugation.
Resistance is quickly spread through
many bacteria.