Transcript Bacterial Morphology Arrangement

Bacterial Morphology Arrangement
1. Bacilli
a.Streptobacilli
b. Bacilli
2. Cocci
a. Cocci
b. Doplococci
c. Streptococci
d. Staphylococci
e. Sarcina ( 3D )
f. Gaffkya( 2D )
Common Shapes & Arrangement
Bacterial morphologies (1)
Bacterial morphologies (2)
Bacterial morphologies (3)
Bacterial Morphology Arrangement
3 Spirl
a. Vibrio
b. Spirillum
c. Spirochete
Bacterial morphologies (4)
Bacterial Cell Structures &
Functions
Size relationships among
prokaryotes
Bacterial Cell Structure
 Appendages
- fdlagella, pili or fimbriae
 Surface
layers - capsule, cell wall, cell
membrane
 Cytoplasm
- nuclear material, ribosome,
mesosome, inclusions etc.
 Special
structure - endospore
Bacterial Cell Structure
Appendages
1. flagella
Some rods and spiral form have this.
a). function: motility
b). origin : cell membrane flagella attach to the cell
by hook and basal body which consists of set(s) of rings
and rods
Gram - : 2 sets of ring and rods, L, P, S, M rings
and rods
e.g. E. coli
Gram + : S, M rings and rods
e.g. B. megaterium
Organ of bacterial locomotion
Structure of the flagellum
Flagella movement(1)
Flagella movement(2)
Flagella movement(3)
b).Origin (continued)
–
The structure of the bacterial flagella allows it to spin
like a propeller and thereby propel the bacterial cell;
clockwise or counter clockwise ( Eucaryotic , wave
like motion.
–
Bacterial flagella provides the bacterium with
mechanism for swimming toward or away from
chemical stimuli, a behavior is knows as
CHEMOTAXIX, chemosenors in the cell envelope
can detect certain chemicals and signal the flagella to
respond.
c). position
monotrichous
lophotrichous
peritrichous
d). structure
protein in nature: subunit flagellin
2. Pili or Fimbriae
Shorter than flagella and straighter , smaller.
Only on some gram- bacteria.
a). function: adhere. One of the invasive
mechanism on bacteria. Some pathogens
cause diseases due to this. If mutant
(fimbriae) not virulent. Prevent
phagocytosis.
pili - sex factor. If they make pili, they are + or
donors of F factor.
It is necessary for bacterial conjugation
resulting in the transfer of DNA from one cell to
another.
It have been implicated in the ability of
bacteria to recognize specific receptor sites on
the host cell membrane. In addition, number of
bacteria virus infect only those bacteria have F
pilus.
b). Origin: Cell membrane
c). Position: common pili , numerous over the
cell, usually called fimbriae sex pile, 1-4/cell
d). Structure: composed of proteins which can
be dissociated into smaller unit
Pilin . It belongs to a class of protein Lectin
which bond to cell surface polysaccharide.
II. CELL SURFACE LAYER
1. Capsule or slime layer
Many bacteria are able to secrete material
that adheres to the bacterial cell but is
actually external to the cell.
It consists of polypeptide and
polysaccharide on bacilli. Most of them
have only polysaccharide. It is a protective
layer that resists host phagocytosis.
Medically important.
2. Bacterial Cell Wall
General structure: mucopolysaccharide
i.e. peptidoglycan. It is made by Nacetylglucosamine and N-acetylmuramic acid.
tetrapeptide ( L-alanine- isoglutamine-lysinealanine) is attached. The entire cell wall
structure is cross linked by covalent bonds.
This provide the rigidity necessary to maintain
the integrity of the cell.
N-acetylmuramic acid is unique to
prokaryotic cell.
Cell walls of bacteria(2)
Cell walls of bacteria(3)
Cell walls of bacteria(4)
Cell walls of bacteria(1)
Structure of peptidoglycan(1)
Structure of peptidoglycan(2)
(a).
Gram positive bacterial cell wall
Thick peptidoglycan layer
pentaglycin cross linkage.
Teichoic acid: ribitol TA &
glycerol TA
Some have peptioglycan
teichoic acid.
All have lipoteichoic acid.
Function of TA:
* Antigenic determinant
* Participate in the supply of Mg to
the cell by binding Mg++
* regulate normal cell division.
For most part, protein is not found as
a constituent of the G+ cell wall except
M protein on group streptococci
Structure of the Gram-positive
Cell Wall
(b) Gram Thin peptidoglycan
Tetrapeptide cross linkage
A second membrane structure: protein and
lipopolysaccharide.
Toxicity : endotoxin on lipid A of lipopolysaccharide.
glucosamine- glucosamine-long
polysaccharide- repeated sequences of a few sugars
(e.g. gal- mann-rham) n=10-20 O antigen
Structure of peptidoglycan(3)
Toxicity : endotoxin on lipid A of
lipopolysaccharide.
glucosamine- glucosamine-long
FA
FA
FA
FA
polysaccharide- repeated sequences of
a few sugars (e.g. gal- mann-rham)
n=10-20 O antigen
Chemistry of LPS
The Gram-negative outer membrane(1)
The Gram-negative outer membrane(2)
2. Cell Membrane
Function:
a. control permeability
b. transport e’s and protons for cellular metabolism
c. contain enzymes to synthesis and transport
cell wall substance and for metabolism
d. secret hydrolytic enzymes
e. regulate cell division.

Fluid mosaic model. phospholipid bilayer and
protein (structure and enzymatic function). Similar
to eukaryotic cell membrane but some differs. e.g.
sterols such as cholesterol in Euk not in Prok.
The cytoplasmic membrane
Functions of
the cytoplasmic membrane(1)
Functions of
the cytoplasmic membrane(2)
Transport proteins
Classes of membrane
transporting systems(1)
Classes of membrane
transporting systems(2)
Classes of membrane
transporting systems(3)
III. Cytoplasm
80% water, nucleic acids, proteins, carbohydrates, lipid
and inorganic ions etc.
1. Bacterial chromosomes
a single large circular double stranded DNA no histone
proteins. The only proteins associated with the
bacterial chromosomes are the ones for DNA
replication, transcription etc.
2. Ribosome
protein synthesis
The bacterial chromosome and
supercoiling
3. Mesosomes
A large invaginations of the plasma membrane,
irregular in shape.
a. increase in membrane surface, which may be
useful as a site for enzyme activity in respiration
and transport.
b. may participate in cell replication by serving as a
place of attachment for the bacterial chromosome.
4. Inclusions
Not separate by a membrane but distinct.
Granules of various kinds:
* glycogen,
*polyhydroxybutyric acid droplets (PHB)
i.e. fat droplets
* inorganic metaphosphate (metachromatic granules) - in
general, starvation of cell for almost any nutrients
leads to the formation of this to serve as an
intracellular phosphate reservoir.
PHB
5. Chromatophores
Only in photosynthetic bacteria and blue green
algae. Prok. no chloroplast, pigment found in
lamellae located beneath the cell membrane.
IV. Special Structure
* Endospores
Spore former: sporobactobacilli and sporosarcinae - no
medical importance. bacillus and clostridium have
medical importance.
* Position: median, sub-terminal and terminal have
small water, high calcium content and dipicolinic acid
(calcium dipicolinate)
extremely resistant to heat, UV, chemicals etc. may be
due to many S containing A.A for disulfide groups.
The process of endospore
formation
•
•
After the active growth period approaching
the stationary growth phase, a structure
called forespore develops within the cells.
It consists of coat, cortex and nuclear
structure.
Endospores
Negatively Stained Bacillus: (A) Vegetative Cell (B) Endospore
Dipicolinic acid
Vegetative/spore-containing
cells(1)
Vegetative/spore-containing
cells(2)
Detailed steps
in endospore formation(1)
Detailed steps
in endospore formation(2)
Detailed steps
in endospore formation(3)