Transcript Chapter 18 Bacteria Notes

KINGDOMS EUBACTERIA &
ARCHAEBACTERIA
• Bacteria are 1- celled organisms that live
everywhere. They are the oldest life forms on
Earth. E. coli is the most studied bacterium. All
bacteria are prokaryotic meaning they have no
true nucleus (they do still have genetic
material). Bacteria do contain cell walls
containing acids & sugars that provide support as
well as a cell membrane inside of this cell
wall. Some antibiotics work by attacking this
structure.
KINGDOM ARCHAEBACTERIA
• Anaerobic & aerobic bacteria adapted to
environments with extreme temps, acidity, or
salt content; differ from eubacteria in
structure of cell wall & cell membrane – RNA
polymerase & ribosomal protein very similar
to eukaryotes (believed to be more closely
related to eukaryotes than eubacteria) –
asexual reproduction only
Examples of Archaebacteria
• Thermophiles
• Acidophiles
• Halophiles
Habitat of Archaebacteria
• Extreme environments – swamps, deep seas,
cow stomachs, sewage treatment, Dead Sea,
volcanoes, geysers
Nutrition Methods of Archaebacteria
• Can be heterotrophic or chemosynthetic.
Cyanobacteria are photosynthetic.
KINGDOM EUBACTERIA
• No membrane-bound
organelles, nutrition by
absorption (some are
photosynthetic or
chemosynthetic),
reproduce by fission or
budding.
Bacteria come in 3 primary shapes
• 1. Cocci - sphere-shaped
•
2. Bacillus - rod-shaped
• 3. Spirilla - corkscrew-shaped
Bacteria may also be classified based on
their shapes in a group
• These include
1. Diplo - found in pairs
• 2. Staphylo - found in
clusters
•
3. Strepto - found in
chains
• The walls of bacteria can be either rigid or
flexible. Some produce a slime layer known as
a capsule. This structure protects the
bacterium from the immune system. Bacteria
may also be classified as Gram positive or
Gram negative based on their colors after a
Gram stain.
• Those that are Gram
positive stain purple
because of a thick
peptidoglycan layer in
the cell wall (treat
these with
pencillin). Those that
are Gram negative
stain pink because the
outer membrane is
removed by the
alcohol rinse & the
peptidoglycan layer
allows the dye to
leave (treat these with
tetracycline).
• Bacteria contain many ribosomes & plasmids
that are small segments of DNA. Some
bacteria may have flagella while others may
have pili that resemble cilia. These allow the
bacteria to attach to food. Some bacteria are
motile while others cannot move. Some
bacteria are heterotrophic while others make
their own food & are therefore considered to
be autotrophic.
• Some bacteria are saprophytic
which means they feed on dead
organisms. Those bacteria that
require oxygen to live are called
obligate aerobes. An example is
Tuberculosis. Those that can
survive without oxygen are
termed obligate anaerobes. An
example is Botulism. Those that
can live with or without oxygen
are termed facultative
anaerobes. An example is E.
coli.
• A colony is a large group
of bacteria living
together. All members
are descendants of a
single bacterium.
• Some bacteria form
endospores when
conditions are
harsh. The bacterium
makes a membrane
around itself when food
or nutrients become
low. The membrane
wraps around one
strand of DNA & some
cytoplasm & becomes
dormant.
Reproduction of bacteria
• Asexually – binary fission, budding (some can
also use transformation, transduction, &
conjugation)
• Most bacteria can
reproduce at a rate of every
20 – 30 minutes. This
occurs through the process
of fission usually, but may
also occur through the
process of conjugation. In
this process a donor
bacterium transfers genetic
material to an acceptor
bacterium through direct
contact .
BACTERIA IN NATURE
• Bacteria help the ecosystem recycle
nutrients. Because they break
down materials, they are known as
decomposers. They play a
significant role in sewage
treatment. Bacteria also are
involved in Nitrogen fixation, a
process where they convert
atmospheric nitrogen into a form
plants can eventually use. Humans
also use bacteria to produce
yogurt, cheese, pickles,
sauerkraut.