Bacterial Ultra Structure
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Transcript of Bacterial Ultra Structure
BACTERIAL CELL
ULTRASTRUCTURES
General Division:
I. External - Capsule - Fimbriae - Flagellum
II. Internal - Cell Wall - Cytoplasmic Membrane - Cytoplasm- Mesosome - Nuclear Body- Ribosome - Plasmid - Inclusion Granule - Endospore
BACTERIAL ULTRASTRUCTURE
A. Bacterial Surface Coating: = are viscous extracellular polymers which surrounds
the bacterial cell
Capsule = well-formed thick viscous jelly-like structure
firmly attached to the cell wall surrounding the cell
= not readily removed. = easily visualized by negative staining using
India ink method
Slime layer
= loose and irregularly arranged network of
fibrils totally detached from the cell
extending outside the cell surfaces
= when present are easily washed off
Chemical Comp.: = water – main component 98-99%= 1-2% of bacterial capsule are
chemically polysaccharide, Except capsule of:
B. anthracis-polypeptide (D-glutamic acid)
S. pyogenes-Hyaluronic acidFunction:
= protection from phagocytosis = correlates with virulence
= act as antigen (used in the identification)
and typing of capsulated bacteria
= allows bacteria to adhere/attach to various
surfaces in its natural environment in order to survive
Detection: 1. Negative staining (India
Ink)2. Special staining (Capsular
method) 3. Serological (Quellung
reaction)
B. Appendages Flagellum & Axial filaments Fimbriae
FLAGELLUM: = long, thick, helical protein filament of uniform
length and diameter
= commonly seen among free-swimming bacteria
= originates in cytoplasmic membrane = composed of 3 parts:
1. Basal body – anchors the flagellum to the
cell wall and plasma membrane
2. Hook – attached to the basal body and
connects to the filament
3. Filament – external to the cell and contains
the flagellar protein
Chemical Comp.: protein monomer - Flagellin
Function - Motility organelle of many pathogenic bacteria
Detection: 1. Darkfield / Phase contrast microscopy
(Wet mount / Unstained smear)
2. Brightfield – using stained specimen
3. Electron Microscopy – stained specimen
4. Serological – use of specific antisera against
flagellar (H) antigen
Types and Arrangement of flagella in relation to the distribution and number:
I. Monotrichous – single polar flagellum at one end
II. Multitrichous – more than one flagella
Types:A) Lophotrichous – tuft of flagella at one
polar end
B) Amphitrichous – single flagellum or tulf of
flagella at both polar end
C) Peritrichous – flagella distributed all over the
body of the bacteria
Axial Filaments = flagella-like sheathed filaments
located in the periplasmic space (between
the inner) and outer membrane of
the cell= move by traveling helical wave on
opposite direction
= motility organelle of spirochete
Fimbriae / Pili / Microfibrils = short, straight, thin hair-like filaments usually
distributed around the body of bacteria.= originates in the cytoplasmic membrane = found virtually among all gram (-) bacteria but
not in gram (+) bacteria
2 types according to function:
1. Common/ordinary – for attachment or adherence
to mucosal surfaces of host cell during colonization and infection.
2. Sex pili – responsible for attachment of donor and
recipient cell during bacterial conjugation whereby genetic material (DNA) from one
cell is transferred to another (reproduction).
Chem. Comp. - Protein (Pilin)
Detection: Electron Microscopy
Cell wall (Peptidoglycan, Murien, Mucopeptide / Glycopeptide)
= complex, rigid, multilayered structure that protects the
protoplast and the underlying fragile plasma membrane
= found in all pathogenic free-living bacteria except Mycoplasma (cell-walless bacteria)
Chemical Comp.:1. Protein (Mesodiaminopimelic acid,Isomers of D-glutamic)
acid and D-alanine
2. Polysaccharide (N-acetylmuramic acid and N-
acetylglucosamine)= responsible for rigidity of cell wall
3. Lipids
Function :1. Responsible for the characteristic shape of bacterium2. Provides strong structural support necessary to keep
bacterial cell from rupturing due to changes in
the environmental osmotic pressure 3. Contain somatic O antigen that can serologically
identify particular bacteria 4. Site of action of some antibiotics 5. Determines differences in gram staining reaction
Detection :1. Microscopy of smear prepared from special
staining method.2. Electron microscopy. 3. By chemical methods using lysozyme.
COMPARISON OF GRAM POSITIVE AND GRAM NEGATIVE CELL WALL
Gram PositiveGram Positive Gram NegativeGram Negative
Peptidoglycan Peptidoglycan Very thick homogenous single Very thick homogenous single layerlayer extensively crossed-linked. extensively crossed-linked. Constitute 50-90% of the cell Constitute 50-90% of the cell wall wall material. material. (NAM, NAG, D-alanine)(NAM, NAG, D-alanine) Diaminophemilic acidDiaminophemilic acid
More complex layer More complex layer composed composed of thin peptidoglycan with of thin peptidoglycan with few few crossed-linked and an outer crossed-linked and an outer membrane layer. membrane layer. Constitute 5-10% of the cell Constitute 5-10% of the cell wall material.wall material.
Auxiliary Auxiliary compounds compounds
Teichoic acid (Polymer of ribitol Teichoic acid (Polymer of ribitol and) and) glycerol phosphateglycerol phosphateLipoteichoic acidLipoteichoic acidSurface protein Surface protein
No teichoic acid No teichoic acid Outer membrane contains: Outer membrane contains: Phospholipids-located in Phospholipids-located in the the inner membrane inner membrane Lipoprotien – connects OM Lipoprotien – connects OM toto the peptidoglycan the peptidoglycan LipopolysaccharideLipopolysaccharide (LPS/Endotoxin layer) (LPS/Endotoxin layer) – – located in the outerlocated in the outer layer of the OMlayer of the OM - contains the lipid A - contains the lipid A
Penicillin Penicillin sensitivity sensitivity
Sensitive Sensitive ResistantResistant
Response to Response to lysozyme lysozyme
Digest/ DegradeDigest/ Degrade Resistant Resistant
Gram Positive
Gram Negative
Damage to the cell wall may result to:
Protoplast= when a gram positive bacteria is exposed to
lysosyme will degrade the peptidoglycan
layer resulting to complete removal of the cell
wall producing a wall-less spherical body = since all cell wall components is removed,
therefore incapable of regeneration
Spheroplast= when a gram negative bacteria is exposed to
lysozyme it looses the peptidoglycan layer
but retain the outer membrane leaving a
less fragile spherical body which are capable
of regenerating the cell wall.
Protoplast: comprises the naked cytoplasmic membrane and
its content
PERIPLASM = space between the plasma inner membrane
and the outer membrane layer = readily observe among gram negative
bacteria(with difficulty among gram +
bacteria) = consist of a gell-like substances which
help secure nutrients from the
environment
CYTOPLASMIC/PLASMA/CELL MEMBRANE: = thin elastic bilayered semi-permeable
membrane lying underneath the cell wall enclosing
the cytoplasm of the cell.
Chemical Composition - Lipoprotein - (composed of phospholipids and protein
molecules)
Functions: 1. Serve as selective permeability barrier
(transport of nutrient material in & out of cell)
2. Site of electron transport and oxidative phosphorylation of substances
involve in the generation of chemical energy (ATP)
3. Helps in the excretion of metabolic waste product
4. Site for excretion of enzyme involved in OM synthesis, CW synthesis and in the
secretion of extracytoplasmic & extracellular
substances:A. Permease for active uptake of
nutrientB. RespiratoryC. Polymerase that manufacture
substancesof the cell wall
D. Hydrolytic
Detection - Electron microscopy
MESOSOME: = usually seen as an invagination of the
membrane associated cytoplasmic sac seen in Gram
(+) cell = contains lamellar, tubular and vesicular
structure = often associated with division septa Chemical Composition - Lipoprotein
Functions: 1. Site for the synthesis of
cytochrome oxidase and reductase enzyme
2. Provide support for enzymes present in the cell
membrane 3. Responsible for compartmenting
DNA during cell division and sporulation
Detection- Electron microscopy
Cytoplasm = refers to everything that is enclosed by the
cytoplasmic membrane = site for most bacterial metabolism = 80% of cytoplasm is composed of water
NUCLEAR BODY: (Nucleus / Nucleoid)= genetic material of bacteria = contains a single circular molecule of double
stranded DNA network which runs parallel to the
long axis of the cell = found homogenous within the cytoplasm not
enclosed in a nuclear membrane. = constitute 2-3% of the cell weight. = no definite form and seen at all stages of
growth cycle of the bacteria.
Chemical Composition – DNAFunction:
1. Controls the growth and metabolic activity of
the bacteria 2. Responsible for hereditary
characteristics of the cell. Detection- Electron microscopy, Feulgin staining
(+)
PLASMID/EPISOME: = extrachromosomal genetic material capable of
autonomous replication usually located near
the chromatin body.
Chemical Composition – DNA
Function:1. Transfer of genetic material from one cell to another
by conjugation (Transmissible Plasmid)2. Carry genes for activities like:
a) Antibiotic resistance b) Toxin production c) Synthesis of enzyme d) Tolerance to toxic
metals
Detection– Feulgin staining (+), Electron microscopy
RIBOSOME: = histone-like particles composed of ribosomal
RNA (rRNA) and protein molecules found in the cytoplasm of the cell.
= site of action for many antibiotics that inhibit protein
synthesis.= made up of 2 subunits
larger subunit (50S) smaller subunit (30S)
= size 10-15nm with sedimentation coefficient of 70S
= procaryotic ribosome - 70s= eucaryotic ribosome - 80s
Function – Site of protein synthesis
Detection– Feulgin staining (-), Electron microscopy
INCLUSION / CYTOPLASMIC GRANULE: = large granules found anywhere in the
cytoplasm= are accumulation of organic and inorganic
substances which serves as source of energy and
nutrient supply to the organism
Kinds:1. Babes Ernst / Volutin / Metachromatic granules
Chemical Composition – polymerized metaphosphate which can be
used in the synthesis of ATP
Function – reserve energy supply
Demonstration – simple staining / special staining (Albert’s stain)
2. Lipid granules
Chemical Composition – polymer of beta-
hydroxybutyric acidFunction – reserve food supply.
3. Sulfur granules – derived energy by oxidizing
sulfur and sulfur-containing
compounds.
Function – reserve energy supply for sulfur-containing bacteria.
4. Glycogen granule – polymer of glucose.
Function – reserve food supply.
ENDOSPORES:
= highly refractile body formed within vegetative
bacterial cells in response to adverse
environmental
condition and due to deficient nutrient supply
= known as endospore, because it is formed inside
the
bacteria cell
= formation of endospore is genetically controlled
= another life of the cell in a resting phase
= found in the cytoplasm of rod-shaped
sporeforming
bacteria of the genus Bacillus & Clostridium
Classification accdg. to:
A. Location - Central, Subterminal, Terminal
B. Shape - a) Ovoid b) Circular
C. Swollen/not swollen (swollen when the diameter is more
than the of the bacterial cell, not swollen diameter the same as bacterial cell)
Composed of five parts: 1. Core – located at the center which is the
spore cytoplasm/protoplast.
- contains the nucleus and enzyme dipicolinic acid
2. Spore wall – enclosing the core.3. Cortex – laminated structure surrounding the
spore wall
4. Spore coat – multilayered membrane enclosing the
cortex 5. Exosporium – the outermost covering of the
spores which give the spore a
rigid appearance.
Chemical Comp. – Calcium Dipicolinate
Function: serves as another life of the cell (survival) = can undergo spore formation or
sporulation = only one spore is found in a bacterial
cell
Detection: 1. Microscopy of stained smear
A) Negative staining B) Positive staining
2. Phase contrast microscopy