describes the anatomical structures of a prokaryotic bacterial cell

1. Anuswedha Ananthan
Assistant Professor
Microbiology, JBAS College for Women,chennai

2.  Refers to the anatomical structures of a
prokaryotic bacterial cell.
 Divided into
 a)structures external to the cell wall-
capsule, slime, S layer, pili/fimbriae, flagella
 b) cell wall
 c) structures internal to the cell wall- cell
membrane, cytoplasm, ribosomes,
mesosomes, intracytoplasmic inclusion
bodies and nucleoid

4.  Capsules – viscous material secreted by certain
bacteria gets deposited outside the cell wall-
well-organised, sharply defined.
 Capsules- 1. microcapsules(less than 20nm-EM,
macrocapsules(>20 nm- LM)
 Stained by negative/positive staining techniques
 Usually made of polysaccharides but can be
made of other components also.
 Functions
 1. virulence factor- inhibits phagocytosis
 2. contains water- prevents dessication
 3. exclude bacterial viruses and other toxic
detergents

5. • SLIME LAYER
• Loose undemarcated secretion
• Gliding bacteria produce slime- aids in their motility.
• GLYCOCALYX
• Network of polysaccharides extending from the bacterial surface,
above the capsule and slime layer.
• Aids in attachment to solid surfaces
• S LAYER
• Regularly structured layer in some G+ve and G-ve bacteria
• Made of protein and glycoprotein
• FUNCTIONS
• Protects cell against pH, ion fluctuations, osmotic pressure,
enzymes, predacious viruses- bdellovibrio
• Provides rigidity and shape to the cell
• Promote adhesion to surfaces
• Protects against complement and phagocytosis

7.  Many G-ve bacteria carry short, thin, hair-like
appendages- found in motile /non-motile
cells
 Shorter and thicker than flagella, originate
from cell membrane- are antigenic
 Made of protein subunits- pilin
 Can be seen only by EM
 Functions- attachment
 PILI-Sex pili-coded by F plasmids – aids in
the formation of conjugation tube during
gene transfer

8. PILI

9.  One or more, long, thin, threadlike locomotor
appendages, extending from the cell membrane
 Stained by special techniques to increase their
thickness(mordanting) or EM
 Structure
 1. Filament-extendes from the cell surface to the tip-
connected to the basal body by hook- made of
protein subunits(flagellin)
 2. Hook- short, curved segment; flexibility(different
protein subunits)
 3. Basal body- embedded in the cell
 G-Ve bacteria- L,P and M rings(S ring)
 G+ve bacteria- outer (peptidoglycan), inner(plasma
membrane)

10. lophotrichous
Monotrichous
amphitrichous
Peritrichous

11.  Functions
 Shape and structure to the bacterial cell
 Protects them from osmotic pressure
 Is antigenic
 Protects cell from toxic substances
 Site of action of several antibiotics
 Basis for gram’s staining
 Based on Grams staining
 1. Gram positive cell
 2. Gram negative cell

13.  More stronger because of the thick
peptidoglycan layer
 Thin periplasmic space
 Contains large amounts of teichoic acid-
polymers of glycerol and ribitol Phosphate
 Important in maintaining the structure of the
cell wall

14.  Outer membrane
 1. LPS- consists of 3 parts
 a) lipid A- glycolipid portion- responsible for
endotoxic activity
 b) core polysaccharide – is joined to lipid A
 C) Polysaccharide O antigen side chain
 d) porins- transmembrane pores- serve as
diffusion channels
 Wide periplasmic space
 Thin peptidoglycan

16.  Thin , semipermeable membrane, made of
lipoproteins- phospholipid bilayer with integral
proteins and peripheral proteins
 Functions
 1. retains the cytoplasm
 2. Allows ions and molecules to move in and out
of the cell
 3. Respiratory, photosynthesis, synthesis of
lipids, cell wall components synthesis and
chromosome segregation.
 4. Contains receptor molecules that detect and
respond to chemicals in the environment.

18.  Gel- like substance called as cytosol.
 Cytosol is a water like solution & contains
ions, small molecules and macromolecules.
 Cytoskeleton- the cytoplasmic network of
fibers which gives structural rigidity and
shape to the cell is a part of cytoplasm.

19.  Prokaryotic chromosome
is found arranged in an
irregular area in the centre
of the cell-
nucleoid(nuclear body,
chromatin body)
 Single, haploid,
circular/supercoiled ds
DNA
 Not associated with
proteins- no nucleolus
 Extrachromosomal
plasmids- not necessary
for life cycle but confers
important pathogenic
properties

20.  Ribosomes- sites of protein synthesis
 Found in the cytoplasmic matrix
 Found integrated with linear mRNA to form
polysomes
 Smaller and is 70S
 MESOSOMES
 Vesicular, convoluted structures formed as
invaginations of the plasma membrane and
cytoplasm- principle site of respiratory
enzymes
 Associated with the nuclear body and sites of
formation of cross wall septa- aids in nuclear
and cytoplasmic division during binary fission

21. MESOSOMES
&
NUCLEOID

22.  Storage granules- containing organic and
inorganic material
 Can be seen under light microscope and
specific for a particular bacteria
 Volutin granules- polymetaphosphate
 Glycogen granules- stained with iodine
 Lipid granules- stained with Sudan black B
 Gas vacuoles- found in Cyanobacteria, purple
and green phototrophic bacteria- provides
buoyancy to float at the desired level in
aquatic bodies

23. Cytoplasmic
inclusion
bodies