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