Download (a) Gram-positive bacteria

Source of picture: Campbell 8th edition
Objectives:
•
Explain the unique characteristics of Kingdom Monera
(prokaryotic characteristics)
•
Classify Kingdom Monera into Eubacteria and
Archaebacteria (based on cell wall structure,
association of histone to the DNA and structure of
membrane lipids)
•
Describe the diversity of bacteria (based on cell
shapes, gram-stain and position of flagella)
•
State the importance of bacteria (nitrogen fixation,
symbiotic, pathogenic, in research and development)
Source of picture:
http://micro.magnet.fsu.edu
/cells/bacteriacell.html
The generalize structure of a bacterium
Characteristics of Kingdom Monera
(prokaryotic characteristics)

Prokaryotes

Diameters in the range of 0.5-5 μm

Unicellular, but some species can
aggregate in colonies

Lack true nuclei/ nuclear membrane
- DNA not enclosed by nuclear membranelies free in cytoplasm

Lack membrane-bound organelles

Circular chromosome (single circular
naked DNA molecule) located in nucleoid
region

Many species also have plasmids

Have cell wall, made up of
peptidoglycan/murein/muramic acid

Contain 70S ribosome (eukaryotes =80S)
Figure 27.8
Source of picture: Campbell 8th edition
Chromosome
Plasmids (ring of DNA)
1 m
Plasmid: small circular DS DNA molecules carrying accessory genes eg: genes
for resistance to antibiotics.
Figure 27.3a
(a) Gram-positive bacteria: peptidoglycan traps crystal violet.
Cell
wall
Peptidoglycan
layer
Plasma
membrane
Source of picture: Campbell 8th edition
CLASSIFICATION OF KINGDOM
MONERA
The prokaryotes can be classified into two distinct
groups:
a) Eubacteria. (e.g.: E.coli, Cyanobacteria,etc)
b) Archaebacteria. (e.g.:Sulfolobus)
MONERA
EUBACTERIA
- True bacteria
(eg: E.coli )
- Cyanobacteria
environment),
(blue green algae)
lovers”)
ARCHAEBACTERIA
(eg: Sulfolobus)
- Bacteria that live in
extreme environment:(eg:Methanogens ( live in
moderate
Thermophiles (“heat
Halophiles (“salt lovers”)
1. Eubacteria
Characteristics of Eubacteria = bacteria

Mostly bacteria
- gram-positive and gram negative bacteria,
cyanobacteria (blue green bacteria)

Widely distributed in the environment

Unicellular/ live in colonial arrangement

Unique cell wall containing peptidoglycan
(consist of sugar-polymers linked with short
polypeptides) that encloses the entire
bacteria

Some secrete sticky layer of polysaccharide
or protein, forming a capsule outside the cell
wall- acts as additional protective layer,
increase resistance to host and adherence to
a substrate

Move by rotate the flagella
Characteristics of Eubacteria = bacteria

Pili- fine tubule extended out
from the cell membrane through
the cell wall
-
Help cells to adhere to surfaces
-
Attach to another bacteria during
conjugation process

Reproduce asexually (binary
fission, some by budding)

Form a unique resting cell
(endospore) when the
environment becomes
unfavourable

Genetic materials can be
transferred between individuals by
parasexually (transformation,
Binary Fission
Figure 27.9
Source of picture: Campbell 8th edition
Endospore
Coat
0.3 m

Many prokaryotes form metabolically inactive endospores,
which can remain viable in harsh conditions for centuries
Figure 27.12
Source of picture: Campbell 8th edition
1 m
Sex pilus
Characteristics of Eubacteria = bacteria
• Great metabolic diversity:
• Most are heterotrophs (obtain organic
compound from other organism).
• Majority are free-living saprotrophs
/ saprobes
• Some are parasites.
• Some are autotrophs (manufacture
their own organic molecules from simple
raw material)
• photoautrotrophs (obtain energy
from light)
• chemoautotroph (obtain energy by
oxidizing inorganic chemicals)
Characteristics of Archaebacteria

Can survive in extreme
environments (salt pond, hot
springs, acidic medium)
Source of picture: Campbell 8th
edition
- Have unique features
structurally and biochemically

Appear to be more closely
related to eukaryotes than to
bacteria  in term of genes
and several metabolic pathways

Cell wall is composed of
polysaccharides and protein,
lack peptidoglycan

Eg: extreme halophiles (in highly
saline environments), extreme
thermophiles (in very hot
environments), and
Orange and yellow colonies of
thermophilic prokaryotes grow in hot
water of a Nevada geyser
Differences between eubacteria and archaebacteria
Characteristics Eubacteria
(eg: E. coli)
Archaebacteria
(eg: Sulfolobus)
Cell wall
Consist unique layer of
peptidoglycan
Polysaccharides and
protein (do not have
peptidoglycan)
Structure of
membrane lipids
The lipids in the plasma
membrane are composed
of unbranched
hydrocarbon chains
The lipids in the plasma
membrane are
composed of branched
hydrocarbon chains
Association of
histone to the
DNA
DNA is single, circular
molecule – no histone
protein associated with
DNA
DNA associated with
histones
RNA polymerase
Several kinds
1 kind
1. coccus / cocci
(spherical shape)
Cell shapes
2. bacillus / bacilli
(rod shape)
3. spirillum / spirilla
(spiral shape)
4. Vibrio
(comma-shape)
DIVERSITY OF
BACTERIA
Gram-negative
Gram stain
Gram-positive
Position of flagella
The different types of
bacteria classified based
on their shapes:
 Spherical shape
(coccus)
 Rod shape (bacillus)
 Spiral shape (spirilium)
 Comma shape (vibrio)
•
•
•
•
Single cell: coccus &
bacillus
Diplo_ (cells existing in
pairs)
Strepto_ (cells existing in
filaments)
Staphylo_ (cells existing
in clusters)
Source of picture:
http://en.wikipedia.org/wiki/Bacterial_cell_structure
Figure 27.2
1 m
1 m
3 m
Source of picture: Campbell 8th edition
(a) Spherical
(b) Rod-shaped
(c) Spiral
*Gram’s stain differentiates between 2 major cell-wall
types.
Procedure:
 1) Bacteria is stained by using crystal violet solution
and followed by iodine solution.
 2) Crystal violet-iodine complex which is purple in
colour is formed at the cell wall  stains the
peptidoglycan of cell wall
 3) Then alcohol is used to rinse the staining. Staining
again with a red dye.
 4) As a result :
a) Gram positive – cell wall stain purple or blue

GRAM STAIN:
• Gram positive bacteria
• Stains blue or purple
• Simple cell walls with lots of peptidoglycan, no
lipopolysaccharides
• Purple or blue stain is trapped in cell wall
• Less threatening pathogens,
• Eg : Bacillus, Clostridium staphylococcus
and Streptococcus.
•
Gram negative bacteria
• More complex cell walls with less peptidoglycan but
with another outer lipoprotein membrane with
lipopolysaccharides
• Blue dye wash out so they stain red
• More pathogenic than gram positive, eg: typhus,
gonorrhea
• Lipopolysaccharides in outer membrane often toxic
• Eg: Salmonella, Echerichia and Azotobacter
Figure 27.3
(a) Gram-positive bacteria: peptidoglycan traps crystal violet.
Gram-positive
bacteria
(b) Gram-negative bacteria: crystal violet is easily rinsed
away, revealing red dye.
Gram-negative
bacteria
Carbohydrate portion
of lipopolysaccharide
Cell
wall
Peptidoglycan
layer
Cell
wall
Plasma
membrane
10 m
Outer
membrane
Peptidoglycan
layer
Plasma membrane
Source of picture: Campbell 8th edition
Gram-Positive Bacteria
Gram-Negative Bacteria
The cell wall is made up of a thick
layer of peptidoglycan
The cell wall consists of an thin
inner peptidoglycan layer & a thick
outer lipoprotein layer
Advantageous cell wall feature: The
thick peptidoglycan layer is strong &
is not easily broken.
Disadvantagesous cell wall feature:
The peptidoglycan layer is easily
digested by lysozyme
The peptidoglycan layer is protected
from the action of lysozyme by the
outer lipoprotein layer
Penicillin antibiotic prevents
The presence of the thick outer
synthesis of peptidoglycan. So the
lipoprotein layer, penicillin is less
cell wall is brittle & easily destroyed. effective in destroying the bacteria
Eg: Streptococcus, Staphylococcus
Eg: Escherichia coli, Salmonella

Gram-positive and gram-negative bacteria

The positions of the flagella give the bacteria
different names as follows:
- Atrichous – absence of flagella.
- Monotrichous – a single flagellum present at one
end.
- Amphitrichous – a flagellum occurs at each of the
two ends.
- Cephalotrichous – a group of flagella found only
at one end.
- Lophotrichous – a group of flagella occurs at
each of the two ends.
- Petritrichous – a number of flagella distributed all
over the surface.
Position of flagella
Monotrichous
Cephalotrichous
Amphitrichous
Petritrichous
Source of picture: http://evillusion.wordpress.com/dr-millers-paper-onirreducible-complexity-and-my-comments/
TYPES OF CYNOBACTERIA




E.g. Nostoc, Anabaena
Can recycle nitrogen from
atmosphere
Importance to increase
nitrate and maintain
enrichment oil
Importance component
‘algae bloom’.
CHARACTERISTIC CYNOBACTERIA





Cell shape : round
Cells look like filament and no branch
Habitat : pond water
Heterocyst – Heterocysts are
enlarged cells with thick cell walls.
They lack of chlorophyll and give colourless
appearance. They are the site of nitrogen fixation.
Akinete – A nonmotile reproduction cell. It is an
enlarged resting cell with thick wall and large
amount of food reserves an DNA. After cell division
has occurred within the akinete the cell wall
ruptures, releasing a filament of cells
Akinetes
ANOTHER CHARACTERISTIC





Only have chlorophyll a for
photosynthesis
Surrounded by mucilage (mucus)
Have red / blue pigment
Food storage : starch or glycogen
No flagellum
The importance of bacteria
1.
Pathogenic Bacteria (Bacterial parasites that cause diseases called
pathogens – tuberculosis, cholera, tetanus, syphilis)
2. Beneficial Bacteria:
Bacteria are essential to the nitrogen cycle  recycling the
chemical elements in ecosystem
- Rhizobium: nitrogen-fixing bacteria that convert
gaseous nitrogen (N2) to ammonia (NH3)
- Bacteria involved in nitrification:
i. Nitrosomonas & Nitrococcus:
convert ammonia (NH3) to nitrite (NO2-).
ii. Nitrobacter: oxidizes nitrite (NO2-) to nitrate (NO3-)

Decomposers:

Control the breakdown of plants and animals

Recycling carbon and phosphorus into the atmosphere

Symbiotic relationships:
 E. coli live symbiotically in the human intestine of
human – aid in digestion of food materials that human
intestine cannot break
 Breaking cellulose in herbivores

Food production:
 Eg: cheeses, yogurt (fermentation) and vinegar
production

Manufacturing processes:
 Making soap powders

Medical research:
 For making antibiotics, amino acids & enzymes.
Sewage treatment
- the main cleansing agents in septic tanks
 Soil enrichment
- Bacteria & Leguminous crops used in
agriculture
 Preservation
- For food & alcoholic beverages
 Clean up environmental
- Oil spills (bacteria can digest petroleum)
- Specific enzymes extracted from bacteria –
household detergents
