Bacteria cells consist of typical bacterial cells, capsules/slimes, flagella/fimbriae, and cell envelopes. Bacterial cells are simpler than animal cells as they lack organelles like nuclei and mitochondria. The cell wall protects the cell and determines shape and Gram staining. Capsules and slimes provide some advantages but are not required for growth. Flagella and fimbriae provide motility and attachment. The cell envelope differs between Gram-positive and Gram-negative bacteria. Gram-positive bacteria have a thick peptidoglycan layer while Gram-negative have an inner peptidoglycan layer and outer membrane. The cytoplasm contains DNA, proteins, water, and reserve materials like

1. BACTERIA
By:Asst. Prof Chaitali Kalamkar
Arihant COP. Ahmadnagar

2. Study Ultra-Structure of Bacteria

3. Bacterial cell consist of:
(i) Typical bacterial cell
(ii) Capsules and slimes
(iii) Flagella and fimbria
(iv) Cell envelope
(v) Gram-positive and gram-negative bacteria
(vi) Significance of teichoic acids
(vii) The cell membrane
(viii) Bacterial cytoplasm
(ix) Ribosomes, and
(x) Cellular reserve materials

4. (i)Typically bacterial cell
• Bacteria being prokaryotic in nature are much
simpler in comparison to the ‘animal cells’.
• They have three distinct characteristic features,
namely :
(a)an extensive endoplasmic reticulum* ;
(b) essentially lack a membrane-bound nucleus
;. (c)mitochondria.
• Infact, the bacterial cell wall has two major roles
to play :
(a) To protect the cell against osmotic rupture
particularly in diluted media, and also against
Certain possible mechanical damage(s), and
(b) To assign bacterial shapes, their subsequent
major division into Gram positive and Gram
negative microorganisms and their antigenic
attributes

5. (ii)Capsules and Slimes
• In the event this specific layer may be visualized by the
aid of light microscopy employing highly sophisticated
and specialized staining techniques, it is known as a
capsule;
• In case, the layer happens to be too thin to be observed
by light microscopy, it is called as a microcapsule.
• If the layer does exist in an absolute abundance such
that quitee many cells are found to be embedded in a
common matrix, the substance is termed as a slime.
• In other words, the terminology capsule usually refers to
the layer both intimately and tightl attachedd to the cell
wall ;whereas, the slime coating (layer) is contrarily the
loose structure which often gets diffused right into the
corresponding available growth medium as depicted .

6. The salient features of capsule and slime are enumerated as under :
(1) These structures are not quite necessary and important for the normal growth and usual
survival of the bacterial cells but their very presence grants some apparent advantages to the
bacterial cells that contain these structures.
(2) A plethora of bacteria are incapable of producing either a capsule or a slime ; and those
which can do so would certainly lose the ability to synthesize legitimately these two components devoid of any
adverse effects.
(3) The prime interest in these amorphous organic exopolymers i.e., capsules and slimes, was to
assess precisely their actual role in the pathogenicity by virtue of the fact that majority of
these pathogenic microorganisms do produce either a capsule or a slime.
• Functions of Capsule:
(a) protection against temporary drying by strategically bound to water molecules.
(b) They may cause absolute blockade of attachment to bacteriophages.
(c) They may be antiphagocytic* in nature.
(d) They may invariably promote attachment of bacteria to surfaces

7. (iii)Flagella and Fimbriae
• Flagellum refers to a thread like structure that provides
motility for certain bacteria and protozoa
• It has been observed that the presence of flagella
strategically located on certain bacteria
• Classification of bacterial variants.
• Filaments : The ‘flagella’ are nothing but surface
appendages invariably found in motile bacteria, and
appear generally as filaments having diameter ranging
between 12–20 nm and length between 6–8 μm.
• Location of Flagella : The exact location of the flagella
in various bacteria varies widely and specificallyy ; and
could be either polar monotrichous or polar or bipolar or
polar peritrichous and the number of flagella per cell
also changes with the various bacterial species.
• Flagellar Apparatus : Basically the flagellar apparatus
consists of three distinct parts, namely :
(a) filament ; (b) hook ; and (c) basal granule

8. Fimbriae [or Pili*]
• Fimbriae or Pili are hollow, non-helical, filamentous hair-
like structures that are apparentl thinnerr, shorter, and more
numerous than flagella.
• Thee terminology ‘fimbriae’ exclusively reserve for all
hair-like structures ;
• whereas, other structures that are directly and intimately
involved in the actual transfer of genetic material solely are
termed as ‘pili’
• Howeverr, these structures do appear on the surface of the
only Gram negative bacteria and are virtually distinct from
the flagella
• The bacterial flagella that may be visualized conveniently
with the help of a light microscope after only suitable
staining ; and the bacterial pili can be seen vividly only with
the aid of an electron microscope.

9. (iv) Cell Envelope
The cell envelope of th Gram-positive bacteria* is much
more simpler with regard to the structure in comparison to
that of the Gram-negative bacteria.
• For Gram-positive Bacteria : In this instance the cell
envelope contains chiefly the peptidoglyca and the
teichoic acids.
• Interestingly, the peptidoglycan represents a substituted
carbohydrate polymer found exclusively In the
prokaryotic microorganisms.
• It essentially comprises of two major chemical entities
namely :
(a) Two acetylated aminosugars e.g., n-acetyl
glucosamine ; and n-acetylmuramic acid ; and
. (b) Amino acids e.g., D-glutamic acid ; D- and L-
alanine ;

10. (v)Gram-Positive and Gram-Negative
Bacteria
• For Gram-negative bacteria. There are two distinct layers that
have been duly recognized in the cell envelopes of Gram-negative
bacteria, namely :
• (a) An uniform inner layer approximately 2–3 mm wide, and
• (b) A thicker outer layer nearly 8–10 nm wide.
• Importantly, the peptidoglycan is prominently confined to the inner
layer ; whereas, the outer layer (membrane) essentially comprises of
proteins, lipoproteins, and lipopolysaccharides.

12. Difference between gram +ve and gram –ve bacteria

13. (vi)Significance of Teichoic Acids
• The teichoic acid is a polymer invariably found in the wall of certain
bacteria. It has been reported that the walls of two Gram-positive
organisms belonging to the genus of micrococci
• The teichoic* acids may be duly grouped chiefly into two categories,
namely :
(a) wall teichoic acids,
(b) membrane teichoic acids.

14. (vii)The Cell Membrane
• The cell membrane refers to the very fine, soft, and pliable
layer of tissue that essentially forms the outer boundary of a cell
;and it is made of phospholipids, protein, and cholesterol, with
carbohydrates on the outer surface e.g.,Plasma membrane,
• The cell membrane is the bounding layer of the cytoplasmic
contents,
• It represents the principal osmotic and permeability barrier. It is
a lipoprotein (having a ratio of protein and lipid, 70 : 30),
• It examined via an electron microscope shows Up with a distinct
three-layer unit with a prominent unit membrane structure.
• The other three vital regions in the cell membrane are, namely :
. (a) Polar head regions — of the phospholipids are
strategically positioned at the two oute surfaces
(b) Centre of membrane — contain the extended hydrophobic fatty
acid chains, and
(c) Middle protein layer — is duly intercalated into the
phospholipid bilayer.

15. • Mesosomes. It has been observed that in
certain instances of microorganisms,
more specifically and precisely in the
Gram-positive bacteria, solely depending
upon the prevailing growth factor as
well as parameters the cell membrane
vividly seems to be ‘infolded’ at more
than one point. Such infoldings* are
known as mesosomes as depicted in Fig
• The mesosomes are also found in the
following two types of microorganisms,
such as :
i) Sporulating bacteria
ii) Photosynthetic bacteria

16. (viii)Bacterial Cytoplasm
• cytoplasmic contents of it
essentially include not only the
nucleus but also ribosomes,
proteins, water-soluble
components, and reserve material.
• It has also been observed that
plethora of bacteria do contain
extrachromosomal DNA i.e., DNA
that are not connected to the
chromosomes.

17. (ix) Ribosome
• Ribosome refers to a cell organelle made up of ribosomal RNA
and protein
• Ribosome may exist singly, in clusters called polyribosomes, or
on the surface of rough endoplasmic reticulum.
• In protein synthesis, they are the most favoured site of
messenger RNA attachment and amino acid assembly in the
sequence ordered b the genetic code carried by mRNA.
• In other words, the specific cytoplasmic area which is
strategically located in the cell material boundd by the
cytoplasmic membrane having granular appearance and
invariably rich in the macromolecular RNA-protein bodies is
termed as ribosome
• Ribosomes represent ribonucleoprotein particles (comprising of
60 RNA ; 40 Protein) having a diameter of 200 Å, and are
usually characterised by their respective sedimentation physical
properties as depicted in Fig

18. • The three most vital and important organic cellular reserve materials present
in the prokaryotes are namely
(a) poly-β-hydroxybutyric acid;
(b) glycogen; and
(c) starch
(X)Cellular Reserve Materials

20. Thank you