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Bacterial Anatomy. Rashmi.S. Anatomy of a Bacterial Cell. Description. Bacteria are Prokaryotic, unicellular that do not contain chlorophyll. Size of bacteria may range from 0.2-1.5 micrometer in diameter and 3-5 micrometer in length. DIFFERENCES BETWEEN PROKARYOTES AND EUKARYOTES.

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Description
Description

  • Bacteria are Prokaryotic, unicellular that do not contain chlorophyll.

  • Size of bacteria may range from 0.2-1.5 micrometer in diameter and 3-5 micrometer in length


Differences between prokaryotes and eukaryotes
DIFFERENCES BETWEEN PROKARYOTES AND EUKARYOTES

Character Prokaryotes Eukaryotes

Nucleus:

Nuclear Membrane Absent Present

Nucleolus Absent Present

Mitotic Division Absent Present

Cytoplasm

Cytoplasmic Streaming Absent Present

Pinocytosis Absent Present

Lysosomes Absent Present

Golgi Apparatus Absent Present

Endoplasmic Reticulum Absent Present

Chemical Composition

Sterols Absent Present

Muramic Acid Present Absent

Teichoic Acid Present Absent


Classification of bacteria based on their shape
Classification of Bacteria based on their Shape

  • Cocci

  • Bacilli

  • Vibrio

  • Spirilla

  • Spirochetes

  • Actinomycetes

  • Mycoplasma


Cellular arrangement
Cellular Arrangement

In Cocci,

  • Diplococci: Cocci arranged in pairs

  • Streptococci: Arranged in chains

  • Staphylococci: Arranged in grape like clusters


In Bacilli,

  • Coccobacilli: Oval shaped

  • Palisades : Parallel, attached at any one end of the cell

  • Streptobacilli: In chains


Vibrio

Spirilla


Mycoplasma

Actinomycetes


Structure of a bacterial cell bacterial anatomy
Structure of a Bacterial Cell(Bacterial Anatomy)

  • Examination of a bacterial cell reveals components of structures

  • Some external to cell wall

  • Others internal to cell wall



Demonstration of the cell wall
Demonstration of the cell wall

  • Plasmolysis

  • Microdissection

  • Specific Antibodies

  • Differential Staining

  • Electron Microscope


Structure of the cell wall
Structure of the cell wall

  • Bacterial cell wall provides structural integrity to the cell.

  • The bacterial cell wall differs from that of all other organisms by the presence of Peptidoglycan

  • Peptidoglycan (Mucopeptide) is composed of alternating chains of ..

  • N -Acetyl Glucoseamine and N-Acetyl Muramic acid, which is cross linked by Peptide chains



  • Peptidoglycan is responsible for the rigidity of the bacterial cell wall and for the determination of cell shape

  • Based on the composition of cell wall & Staining bacteria are classified into “Gram positive” and “Gram Negative’



Gram positive cell wall
Gram Positive Cell wall

  • The Gram positive cell wall is characterized by the presence of a very thick Peptidoglycan layer

  • 20-80 nm thick

  • Cell wall contains90% Peptidoglycan and 10%Teichoic acid




Gram negative cell wall
Gram Negative Cell Wall

  • Gram negative cell wall contains a thin Peptidoglycan layer adjacent to the Cytoplasmic membrane,

  • In addition to the Peptidoglycan layer, the Gram negative cell wall also contains an additional outer membrane composed by Phospholipids and Lipopolysaccharide which face into the external environment.


The LPS present on the Gm negative cell wall consists of 3 regions:

  • Polysaccharide determining O antigen

  • Core Polysaccharide

  • Glycolipid portion /Lipid A



Cytoplasmic membrane
Cytoplasmic Membrane activities………

  • It is a thin layer lining the inner surface of the cell wall.

  • Semipermiable membrane controlling the flow of metabolites

  • Chemically ,consists of Lipoprotein and carbohydrates. Sterols are absent


Cytoplasm
Cytoplasm activities………

  • Colloidal system of variety of organic and inorganic solutes in Viscous watery solution

  • No ER,& Mitochondria

  • Contains Mesosomes Inclusions and Vacuoles


Mesosomes
Mesosomes activities………

  • Vesicular, convoluted invaginations of the plasma membrane

  • Prominent in GM+ bacteria

  • Principal sites of Respiratory enzymes

  • Analogous to mitochondria in Eukaryotes


Nucleus
Nucleus activities………

  • Bacterial nuclei “have no nuclear membrane “or the nucleolus.

  • Genome consists of a single double stranded DNA.

  • Might be a Circular form or may be open under certain condition to form a long chain.


Plasmids
Plasmids activities………

  • Extra chromosomal DNA

  • Circular capable of autonomous replication.

  • Transferred from one bacterium to another .


Importance
Importance activities………

  • Their presence confers certain special characters……

  • Toxigenicity

  • Antibiotic Resistance

  • Ability to use certain unusual components as nutrients


Structures external to bacteria
Structures external to Bacteria activities………

  • Capsule

  • Flagella

  • Pili(Fimbriae)


Capsule
Capsule activities………

  • Viscid material secreted by bacteria around the cell surface

  • Capsule is a sharply defined, organized structure (Eg: Pneumococcus)

  • Loose undemarkated structure as in Lueconostoc is a Slime layer.



Capsular Staining activities………



Quellung reaction
Quellung Reaction activities………

  • Described by Neufeld(1902).

  • Serological method of demonstrating the capsule.

  • Suspension of capsulated bacterium is mixed with its specific anticapsular serum & examined under the microscope ,capsule appears prominent & swollen.

  • Used to type Pneumococci.


Functions of capsules
Functions of Capsules activities………

  • Antiphagocytic,thus contribute “Virulence”.

  • Protects against “Lysozyme”

  • Promote attachment of bacteria to surface(Eg: Streptococcusmutans).

  • Permits bacteria to adhere to Medical Implants & Catheters.


  • Toxicity to host cell – Eg: activities………Bacteroidesfragilis.

  • Provide protection against temporary drying.

  • Block the attachment ofBacteriophages.


Applications: activities………

  • Used in serological typing

  • Detection of capsule in Blood, CSF provides a rapid method of diagnosis

  • Used in preparation of vaccines

    Eg: H.influenzae


Flagella
Flagella activities………

  • Unbranched, long ,filaments ,made up of protein “Flagellin”

  • Organs of locomotion

  • Found in all motile bacteria except Spirochetes



Structure
Structure activities………

  • 3-20 Micrometer.

  • Each flagellum consists of 3 parts

    1.Filament

    2.Hook

    3.Basal body


Flagellar Arrangement activities………


Kinds of Motility activities………:

  • Darting motility : V.cholerae

  • Tumbling motility: L.monocyctogenes

  • Cork &screw motility: T.pallidum

  • Stately motile : Clostridium spp.

  • Serpentine motility: Salmonella (Except S.gallonarum pullorum)


Detection of motility : activities………

  • Direct observation by hanging drop

  • Dark field microscopy

  • Motility media


  • Flagellar staining activities………

  • Electron microscopy

  • Immunological detection of “H” antigen


Fimbriae
Fimbriae activities………

  • Hair like surface appendages

  • 0.5-10 nm thick

  • Shorter thinner than flagella

  • Formed of protein subunits – Pilin


Functions
Functions activities………

  • Organs of adhesion

  • Forms “Pellicles”

  • Hemagglutination –Clumping of RBC’s (Escherichia,Klebsiella)

  • Special type of Fimbriae called Sex pili,help in attachment to other bacteria


Endospores
Endospores activities………

  • Highly resistant stages of bacteria

  • Spores germinate to form a single Vegitative cell.

  • It is formed inside the cell .

    Eg: Bacillus, Clostridium


Endospore activities………


  • Core contains the Nuclear body activities………

  • Surrounded by a Spore Wall.

  • Outside this is a thick Spore cortex

  • This is covered in turn by a tough Spore coat.

  • Exosporium is additional outer covering, which exhibits ridges and grooves


Factor responsible for the resistance of spores activities………

  • Presence of calcium dipicolinic acid


Endospore inside bacteria activities………


Position of Spores activities………

A = oval, terminal;

B = rectangular, terminal;

C = rectangular, sub terminal,

D = rectangular, central;

E = circular, terminal;

F = circular, central;

G = terminal, club-shaped.


Pleomorphism and involution forms
Pleomorphism and Involution forms activities………

  • Process of exhibiting variation in the shape and size of individual cells – Pleomorphism

    Eg: H.influenzae

  • Certain bacteria exhibit swollen and aberrant forms in ageing cultures – Involution forms

  • This may be due to defective cell wall synthesis or due to Autolytic Enzymes

    Eg: Yersinia, Gonococcus


Protoplasts spheroplasts and l forms
Protoplasts,Spheroplasts and L-Forms activities………

  • Removal of bacterial cell wall by hydrolysis with Lysozyme or antibiotics like Penicillin, liberates ..

  • “Protoplasts” from Gram positive cells

  • “Spheroplasts” from Gram negative cell

    (retain the outer membrane and PG.)


When Protoplasts and Spheroplasts are able to grow and divide they are called the L-Forms.

First observed by Kleineberger-Nobel

Named it as L forms after Lister Institute London.

Eg: Streptobacillus moniliformis


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