2. Bacteria are of
immense importance
because of their rapid
growth, reproduction,
and mutation rates,
as well as, their ability
to exist under adverse
conditions.
The oldest fossils
known, nearly 3.5
billion years old, are
fossils of bacteria-like
organisms.
3. Bacteria can be autotrophs or hetertrophs.
Those that are classified as autotrophs are
either photosynthetic, obtaining energy
from sunlight or chemosynthetic,
breaking down inorganic substances for
energy .
4. Bacteria classified as
heterotrophs derive
energy from breaking
down complex
organic compounds in
the environment.
This includes
saprobes, bacteria
that feed on
decaying material
and organic
wastes, as well as
those that live as
parasites, absorbing
nutrients from living
organisms.
5. Depending on the
species, bacteria can
be aerobic which
means they require
oxygen to live
or
anaerobic which
means oxygen is
deadly to them.
Green patches are green sulfur
bacteria. The rust patches are
colonies of purple non sulfur
bacteria. The red patches are purple
sulfur bacteria.
7. Methanogens
These Archebacteria
are anaerobes. They
make methane
(natural gas) as a
waste product. They
are found in swamp
sediments, sewage,
and in buried landfills.
In the future, they
could be used to
produce methane as a
byproduct of sewage
treatment or landfill
operation.
8. Halophiles
These are salt-loving Archaebacteria that grow
in places like the Great Salt Lake of Utah or salt
ponds on the edge of San Francisco Bay. Large
numbers of certain halophiles can turn these
waters a dark pink. Pink halophiles contain a
pigment very similar to the rhodopsin in the
human retina. They use this visual pigment for a
type of photosynthesis that does not produce
oxygen. Halophiles are aerobes, however, and
perform aerobic respiration.
9. Extreme halophiles can live in extremely salty environments. Most
are photosynthetic autotrophs. The photosynthesizers in this
category are purple because instead of using chlorophyll to
photosynthesize, they use a similar pigment called
bacteriorhodopsin that uses all light except for purple light,
making the cells appear purple.
10. Thermophiles
These are Archaebacteria from hot springs and
other high temperature environments. Some can
grow above the boiling temperature of water.
They are anaerobes, performing anaerobic
respiration.
Thermophiles are interesting because they contain
genes for heat-stable enzymes that may be of
great value in industry and medicine. An
example is taq polymerase, the gene for which
was isolated from a collection of Thermus
aquaticus in a Yellowstone Park hot spring. Taq
polymerase is used to make large numbers of
copies of DNA sequences in a DNA sample. It is
invaluable to medicine, biotechnology, and
biological research. Annual sales of taq
polymerase are roughly half a billion dollars.
13. Cyanobacteria
This is a group of bacteria
that includes some that are
single cells and some that
are chains of cells. You may
have seen them as "green
slime" in your aquarium or in
a pond.
Cyanobacteria can do
"modern photosynthesis",
which is the kind that makes
oxygen from water. All plants
do this kind of
photosynthesis and inherited
the ability from the
cyanobacteria.
14. Cyanobacteria were the first organisms on Earth to
do modern photosynthesis and they made the first
oxygen in the Earth's atmosphere.
15. Bacteria are often
maligned as the
causes of human and
animal disease.
However, certain
bacteria, the
actinomycetes,
produce antibiotics
such as streptomycin
and nocardicin.
16. Other Bacteria live symbiotically in the
guts of animals or elsewhere in their
bodies.
For example, bacteria in your gut produce
vitamin K which is essential to blood clot
formation.
17. Still other Bacteria
live on the roots of
certain plants,
converting nitrogen
into a usable form.
18. Bacteria put the tang
in yogurt and the sour
in sourdough bread.
Saprobes help to
break down dead
organic matter.
Bacteria make up the
base of the food web
in many
environments.
Streptococcus thermophilus in yogurt
19. Bacteria are prokaryotic and unicellular.
Bacteria have cell walls.
Bacteria have circular DNA called plasmids
Bacteria can be anaerobes or aerobes.
Bacteria are heterotrophs or autotrophs.
Bacteria are awesome!
20. Bacteria can reproduce sexually by conjugation or
asexually by binary fission.
26. Penicillin, an antibiotic, comes from molds of the
genus Penicillium Notice the area of inhibition
around the Penicillium.
27. Penicillin kills bacteria by making holes in their
cell walls. Unfortunately, many bacteria have
developed resistance to this antibiotic.
28. The Gram stain, which divides most
clinically significant bacteria into two main
groups, is the first step in bacterial
identification.
Bacteria stained purple are Gram + - their
cell walls have thick petidoglycan and
teichoic acid.
Bacteria stained pink are Gram – their cell
walls have have thin peptidoglycan and
lipopolysaccharides with no teichoic acid.
29. In Gram-positive bacteria, the purple crystal violet stain is
trapped by the layer of peptidoglycan which forms the outer
layer of the cell. In Gram-negative bacteria, the outer
membrane of lipopolysaccharides prevents the stain from
reaching the peptidoglycan layer. The outer membrane is then
permeabilized by acetone treatment, and the pink safranin
counterstain is trapped by the peptidoglycan layer.
30. The Gram stain has four steps:
1. crystal violet, the primary stain:
followed by
2. iodine, which acts as a mordant by
forming a crystal violet-iodine complex,
then
3. alcohol, which decolorizes, followed by
4. safranin, the counterstain.
31.
32.
33. Is this gram stain positive or negative?
Identify the bacteria.
34. Is this gram stain positive or negative?
Identify the bacteria.
35. Gram staining tests the bacterial cell wall's
ability to retain crystal violet dye during solvent
treatment.
Safranin is added as a mordant to form the
crystal violet/safranin complex in order to render
the dye impossible to remove.
Ethyl-alcohol solvent acts as a decolorizer and
dissolves the lipid layer from gram-negative
cells. This enhances leaching of the primary
stain from the cells into the surrounding solvent.
Ethyl-alcohol will dehydrate the thicker gram-
positive cell walls, closing the pores as the cell
wall shrinks.
For this reason, the diffusion of the crystal
violet-safranin staining is inhibited, so the
bacteria remain stained.
