Bacteria are unicellular prokaryotes that are found virtually everywhere. They come in a variety of shapes and have diverse metabolic functions. Some bacteria are beneficial and even essential to life, while others can cause disease. Bacteria reproduce through binary fission and genetic exchange allows for rapid evolution and antibiotic resistance. The Gram stain test divides bacteria into groups based on cell wall structure and guides treatment of bacterial infections. Bacteria play important economic roles through food production, biotechnology, and more.

1. Bacteria

4. Bacteria are:
•Unicellular
•Prokaryotic…which means?
Fact: Each square centimeter of your skin
averages about 100,000 bacteria. A
single teaspoon of topsoil contains more
than a billion (1,000,000,000) bacteria.

5. Bacteria Characteristics
 Some bacteria are aerobic, meaning that they
require oxygen in order to survive.
 Other bacteria are anaerobes, meaning that
they do not require oxygen to survive.
 Most bacteria are harmless and offer

6. Bacteria contain:
•a singular, circular piece
of DNA
•tiny circular pieces of
DNA called plasmids
•ribosomes

7. Archaebacteria and Eubacteria

8.  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

9.  Bacteria can be autotrophs or hetertrophs.
 Those that are classified as autotrophs are
either photosynthetic, obtaining energy from
sunlight or chemosynthetic, breaking down

10.  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

11.  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.

12. Archaebacteria

13. 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.
 Therefore they may be used to
produce methane as a

14. 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.

15. • 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

16.  Thermophiles
 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.
 It is invaluable to medicine, biotechnology, and biological research.
Annual sales of taq polymerase are roughly half a billion dollars.

18. Eubacteria

19. Cyanobacteria
 This is a group of bacteria that
includes some are single cells and
some 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.

20. Cyanobacteria were the first organisms on Earth to do
modern photosynthesis and they made the first oxygen
in the Earth's atmosphere.

21.  Bacteria are often
maligned
(ದೆ ೋಷಪೂರಿತವಾಗಿದೆ) as
the causes of human
and animal disease.
 However, certain
bacteria, the
actinomycetes, produce
antibiotics such as
streptomycin and

22.  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.

23. Still other
Bacteria live on
the roots of
certain plants,
converting
nitrogen into a
usable form.

24.  Bacteria put the tang in
yogurt (ಮೊಸರು) and the
sour in sourdough bread.
 Saprobes help to break
down dead organic
matter.
 Bacteria make up the
base of the food web inStreptococcus thermophilus in yogurt

25.  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.

26. Reproduction in bacteria

27. Bacteria
reproduce:
Asexually
(mitosis) using binary
fission.

30. Bacteria reproduce:
Bacteria exchangenplasmid DNA.
This is how bacteria become
antibiotic resistant.
sexually using
conjugation.

31. Bacteria have cell walls made of:
•peptidoglycan
(polysaccharide linked
with chains of amino
acids).
•this may be covered
with an outer
membrane of
lipopolysaccharide
(chain of sugar with a

32. Some bacteria:
• have a gelatinous layer called a
capsule surrounding the cell wall.
•form thick-walled endospores around
chromosomes when they are
exposed to harsh conditions
(drought, high temperatures) -

33. Some bacteria have:
• flagella for
locomotion.
•
•pili (short, thicker
outgrowths that
help cell to
attach to
surfaces)

34.  Bacteria can be moved by air and water
currents, and on any surface such as
clothing, hands, or any object.

35.  Bacteria can reproduce sexually by conjugation or
asexually by binary fission.

38. Endospore
 Bacteria can
survive
unfavorable
conditions by
producing an
endospore.

39. ¨Three bacterial shapes:
1. Rod shaped are called bacillus(i)
2. Sphere shaped are called coccus(i)
3. Spiral shaped are called spirillum(I)

40. Shapes of Bacteria

44. Penicillin, an antibiotic, comes from molds of the genus
Penicillium Notice the area of inhibition around the Penicillium.

45.  Penicillin kills bacteria by making holes
in their cell walls.
 Unfortunately, many bacteria have
developed resistance to this antibiotic.

46.  The Gram stain, which divides most clinically
significant bacteria into two main groups, is
the first step in bacterial identification.
 Important in medicine because provides
information for treatment of bacterial disease
 Stained as gram +ve (purple) & gram –ve
(Pink)

47.  +ve tend to reponse to penicillin and like antibioteics.
 -ve respond to type of antiotics unrelated to penicillin.
 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.

49.  Gram stain is
usually performed
on smera
preparation that
has been heat
fixed.
 One function of
fixation is to secure
(fix) the cells to the

50. 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.

51.  Gram Positive = purple
because of large
amount of petidoglycan
in cell wall
 Polymer consisting of
sugars and aminoacids
that forms a mesh like
layer the plasma
membrane of
eubacteria

52. The Gram stain has four steps:
 1. crystal, the primary stain: followed by
violet
 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.

55. Is this gram stain positive or negative? Identify the bacteria.

56. Is this gram stain positive or negative?
Identify the bacteria.

58.  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.

59. m

61. Economic Importance of Bacteria