detail description of bacterial morphology with figure

1. The classification of microorganism.

2. Morphology of Bacteria
• Bacteria are prokaryotic cells
• The bacteria are single celled organism that
reproduce by simple division, i.e. binary fission.
• Most are free living and contain the genetic
information , energy-producing and biosynthesis
system necessary for the growth and
reproduction
• Size of bacteria- very small in size, unit of
measurement in bacteriology is the micron or
micrometer (µm)

3. Shape of Bacteria
• Cocci: cocci (from kokkos meaning berry) are spherical
or nearly spherical.
• Bacilli: Bacilli (from baculus meaning rod) are relatively
straight, cylindrical cells. In some of the bacilli, the
length of the cells may be equal to width, such bacillary
forms are known as coccobacilli
• Vibrions : Vibrions are curved or comma shaped rods
• Spirillas: spirilla are rigid or helical forms
• Spirochetes : spirochetes (from speria meaning coil and
chaite meaning hair ) are flexuous spiral forms.
• Mycoplasm: Mycoplasma are cell wall deficient
bacteria and hence do not possess a stable
morphology.

5. Arrangement of bacterial cells
• Pathogenic bacterial species appear as sphere
(cocci), rods (bacilli), spirals.
• Bacteria sometimes show characteristic
cellular arrangement or grouping.
• The type of cellular arrangement is
determined by the plane through which
binary fission takes place by the tendency of
the daughter cells to remain attached even
after division.

6. • Cocci arrangment
1. Diplococci: cocci may be arranged in pairs when
cocci divide and remain together. Eg.
Pnemococci, Gonococci
2. Long chains: long chains when cells adhere after
repeatd divisions in one plane. Eg.
Streptococcus, Enterococcus, Lactococcus
3. Grape like clusters: when cocci divide in random
planes. Eg. Staphylococcus
4. Tetrads: square groups of four cells when cocci
divide in two planes. Eg. Micrococcus
5. Cubical packets: cubical packets of eight cells
when cocci divide in three planes. Eg. Sarcina

7. • Bacilli arrangement
Bacilli split only across their short axes, therefore
the patterns formed by them are limited.
1. Chains : Eg. Streptobacilli
2. Others are arranged at various angles to each
others, resembling the letter V presenting a
cuneiform or Chinese letter. Eg. Cornybacterium
diptheriae

9. Structure of Bacteria

10. Cell Wall
• The cell wall is the layer that lies just outside
the plasma membrane.
• It is 10-25 nm thick, strong and relatively rigid,
tough with some elasticity.
• It is openly porous, being freely permeable to
solute molecules smaller than 10KDa in mass
and 1 nm diameter.
• Marks the difference between gram +ve and
gram –ve bacteria

11. Functions of Cell Wall
• To impart shape and rigidity to the cell.
• It supports the weak cytoplasmic membrane against
the high internal osmotic pressure of the protoplasm.
• Maintains the characteristics shape of the bacterium.
• It takes part in cell division.
• Provide specific protein and carbohydrates receptors
for the attachment of some bacterial viruses.
• Also functions in interaction (e.g adhesion) with other
bacteria and with mammalian cells.

12. Chemical Structure of Bacterial Cell Wall
• Chemically the cell wall is composed of mucopeptide
(peptidoglycan or murein) scaffolding formed by N-acetyl
glucosamine and N-acetyl muramic acid molecules
alternating in chains, which are crosslinked by peptide
bonds.
• Peptidoglycan consists of three parts
1. A backbone- composed of alternating N-acetyl
glucosamine and N- acetyl muramic acid.
2. A set of identical tetrapeptide side chains attached to N-
acetyl muramic acid.
3. A set of identical pentapeptide cross-bridges
• In all bacterial species, the backbone is the same,
however, tetrapeptide side chains and pentapeptide
cross-bridges vary from species to species.

14. Peptidoglycan in Gram positive bacteria
• Linked by polypeptides
8

15. Difference Between Cell Wall of Gram-
positive and Gram-negative Bcateria

16. Gram-positive Bacterial Cell Wall
• It is about 80 nm thick and is composed mostly of several
layers of peptidoglycan.
• Components of gram positve bacterial cell wall.
1.Peptidoglycan – It constitutes 50-90 percent of the dry
weight of the wall and are thicker and stronger than those
of gram negative bacteria.
2. Teichoic acid – the cell wall of gram positive bacteria
contain teichoic acids, which consists primarily of an
alcohol (such as glycerol or sorbitol) and phosphate. There
are two types of techoic acid.
a. Cell wall techoic acid- covalently linked with
peptidoglycan
b. Membrane techoic acid (lipotechoic acid)- covalently
linked with membrane glycolipid and concentrated in
mesosomes.

18. Gram-negative Cell Wall
• It is different from that of gram- positive cell wall.
• It consists of peptidoglycan, lipoprotein, outer membrane,
and lipopolisaccharide.
1. Peptidoglycan layer
• It is a single unit thick and constitutes 5-10 percent of the
dry weight of the wall of gram negative bacteria.
• It is bonded to lipoproteins covalently in the outer
membrane and plasma membrane and is in the
periplasmic, gel like fluid between the outer membrane
and plasma membrane.
• The periplasmic contains a high concentration of
degradive enzymes and transport proteins.
• The periplasmic space is approximately 20 to 40 percent
of cell volume.

19. 2. Lipoprotein
• Lipoprotein or murein lipoprotein seemingly attach to the
peptidoglycan by their protein portion and to the outer
membrane by their lipid component.
• It helps to stabilize the outer membrane and anchor it to the
peptidoglycan layer.
3. Outer membrane
• External to the peptidoglycan, and attached to it by
lipoproteins is the outer membrane.
• It is bilayered structure.
• Its inner leaflets is composed of phospholipid while
phospholipids of outer leaflet are replaced by
lipopolysaccharides molecules.
• It helps as protective barrier which prevent the entry of salts,
antibiotics and other toxic substances.
• Outer membrane also consists of porins or transmembrane
proteins which helps in transportation of nutrition's to the cell.

20. 4. Lipopolysaccharides (LPS)
• A structural component that is unique to the gram negative
outer membrane is lipopolysaccharide (LPS).
• It is a large complex molecule that contains lipids and
carbohydrates and consists of three components.
a. Lipid A- is the lipid portion of LPS and is embedded in the
top layer of the outer membrane. When gram negative
bacteria die they releases Lipid A which functions as an
endotoxin.
b. The core polysaccharide- is attached to lipid A and
terminal series of repeat unit contains unusual sugars. It
role is to provide stability.
c. O polysaccharides –extend outward from the core
polysaccharides and is composed of sugar molecules. O
polysaccharides function as antigens and are useful for
distinguishing species of gram negative bacteria.

23. Demonstration of Cell Wall
• Plamolysis- when placed in a hypertonic solution
the cytoplasm loses water by osmosis and shrinks
while cell wall retains its original shape and size.
• Microdissection
• Exposure to specific antibody
• Mechanical rupture of the cell
• Differential staining procedures
• Electron Microscopy

24. Damage to the cell wall
• (Gram –ve): Lysozyme digests disaccharide in
peptidoglycan
• (Gram +ve): Penicillin inhibits peptide bridges in
peptidoglycan
• Autolysin : bacteria posses autolysin enzyme,
able to hydrolyse their own cell
• Protoplast is a wall-less gram positive cell
• Spheroplast is a wall-less gram negative cell
- Protoplasts and spheroplasts are susceptible to osmotic lysis
• L forms are wall-less cells that swell into irregular
shapes

26. Cytoplasmic Membrane
• Cytoplasmic membrane is a thin, elastic
semipermeable layer.
• It lies beneath cell wall and separating it from the
cell wall.
• It is 5-10 nm is thick.
• It has lipid bilayer with their hydrophilic polar region
externally aligned and inner layer hydrophobic.
• Presence of two proteins externally i.e external
peripheral protein and inner integral protein.
• It is in fluid mosaic in structure.

29. Function of Cytoplasmic Membrane
• Protective outer covering for the cell.
• Cell membrane anchors the cytoskeleton (a cellular 'skeleton' made of
protein and contained in the cytoplasm) and gives shape to the cell.
• Responsible for attaching the cell to the extracellular matrix (non living
material that is found outside the cells), so that the cells group together
to form tissues.
• Transportation of materials needed for the functioning of the cell
organelles without using cellular energy.
• The protein molecules in the cell membrane receive signals from other
cells or the outside environment and convert the signals to messages,
that are passed to the organelles inside the cell.
• In some cells, the protein molecules in the cell membrane group
together to form enzymes, which carry out metabolic reactions near the
inner surface of the cell membrane.
• The proteins help very small molecules to get transported through cell
membrane, provided, the molecules are traveling from a region with lots
of molecules to a region with less number of molecules.

30. Capsule
• Many bacteria synthesize large amount of extracellular
polymer in their natural environments.
• When the polymer forms a condensed, well defined layer
closely surrounding the cell, it is called the capsule.
• It is thin in nature and can be seen only by electron
microscope.
• If the polymer is easily washed off and does not appear to
be associated with the cell in definite fashion, it is referred
as a slim layer.
• Capsule are composed of polysaccharide or of
polypeptide.
• Organism which produce capsule they are mucoid growth
on solid agar.

31. Capsulated Bacteria
• Streptococcus pneumoniae, Nesseria
meningitidis, Klebsiella spps, Hemophillus
influenza, Yersinia, and Bacillus
• Demonstration of Capsule
1. Gram stain
2. Special capsule staining technique
3. India ink staining
4. Electron microscope
5. Serological method

32. Functions of Capsule
• Virulence factor- capsule often act as a virulence
factor by protecting the bacterium from ingestion
by phagocytosis, and nocapsulated mutant of
these bacteria are non virulent.
• Protection of the cell wall- in protecting the cell
wall attack by various kinds of antibacterial
agents. i.e bacteriophage, lysozyme, lytic
enzymes etc.
• Identification and typing of bacteria- capsular
antigens is specific for bacteria and can be used
for identification and typing of bacteria.

34. Flagella
• Motile bacteria, except spirochets posses one or more
unbranched, long, sinuous filaments called flagella.
• They are the organ of locomotion.
• They are long, hollow, helical filaments, usually several
times the length of the cell..
• They are 3-20 µm long and are of uniform diameter (0.01-
0.013 µm).
• It is originates in the bacterial protoplasm and extruded
through the cell wall.
• Flagella consists of largely or entirely of protein, flagellin.
• Flagella are highly antigen and induce specific antibodies in
high titer.
• Flagellar antibodies are not protective but are useful in
serodiagnosis.

35. Parts and Composition
• Each flagellum consists of three parts;
a. Filament
b. Hook
c. Basal Body
a. Filament
The filament is the longest and most obvious portion
which extends from the cell surface to the tip.
b. Hook
The hook is a short, curved segment which links the
filament to its basal body and functions as universal
joint between the basal body and the filament

36. C. Basal body
• The basal body is embedded in the cell (cytoplasmic
membrane)
• In the gram negative bacteria the basal body has four
rings connected to a central rod ( L, P, S and M).
• The outer L and P rings associated with the
lipopolysaccharides and peptidoglycan layers
respectively.
• S ring is located just above the cytoplasmic
membrane and inner M ring contacts the
cytoplasmic membrane.
• Gram positive bacteria have only two basal body
rings, inner ring connected to the cytoplasmic
mambrane and an outer one probably attached to
peptidoglycan.

37. P ring
L ring
S ring
M ring

38. Arrangements/Types
• Atrichous- without flagella.e.g Staphylococcus
spps.
• Monotrichous- single polar flagellum. E.g Vibrio
cholera
• Amphitrichous- single flagellum at both ends.e.g
Alcaligens faecalis
• Lophotrichous- tufts of flagella at one or both
ends. E.g spirilla
• Peritrichous- flagella surrounding the cell. E.g
salmonella thyphoid

40. Demonstration of flagella
• By using Dark field microscope
• Flagellar staining method
• Electron microscopy
• By using hanging drop method for detection
of motility of microorganism
• By spread of bacterial growth as a film over
agar
• Turbidity spreading through semisolid agar

42. Fimbria or pilli
• Many gram negative bacteria have short, fine,
hair like appendages called fimbria or pilli.
• They are shorter and thinner than flagella.
• They originate from cell membrane but emerge
from the cell wall.
• Single cells have been seen to be covered with as
few as 10 fimbriae to as many as 100.
• It is composed of structural protein called pillin.
• They act as virulence factor by attaching to host
cell.
• Antigenicity of pilli is useful for the serodiagnosis,
preparation of antisera.

44. Function of fimbriae
• A. ordinary (common) pilli- it functions as organ
of adhesion that allow attachment of bacterial
cell to other cell surface.
• B. sex pilli- sex pilli are similar to fimbriae but
they are functionally different. These are longer
and fewer in numbers. They are genetically
determined by sex factors or conjugation
plasmids and are appeared to be involved in the
transfer of DNA during congugation.
• It posses antigen hence can be used for
serodiagnosis.

45. Demonstration of fimbriae
• Electron microscopy
• Haemagglutination- attachment to red blood
cells and forms agglutination

46. Cytoplasm
• The cytoplasm of bacterial cell is viscous
watery solution or gel.
• It contains a variety of organic and inorganic
solutes, and numerous ribosomes and
polysomes.
• The cytoplasm may contain granules or
inclusion such as starch, glycogen, poy-β-
hydroxy/alkanoates, sulphur globules, vesicles
and endospores.

47. Ribosomes
• It is small, electron-dense particles situated in
cytoplasm of bacterial cell.
• The ribosomes are the location for all bacterial
protein synthesis.
• In bacterial cell there are presence of 70S
ribosomes being composed of 30S and 50S
subunit
• Ribosomes are associated with different
ribonucleic acid (mRNA, rRNA, tRNA) for the
synthesis of protein.
• Some drugs like streptomycin, tetracyclin acts on
ribosome and inhibit the synthesis of protein.

49. Mesosomes
• These are convoluted or multilaminated
membranous bodies formed as invaginations of
the plasma membrane.
• Mesosomes develop sometimes in relation to the
nuclear body and often from the sites of cross
wall formation in gram positive bacteria.
• Types of mesosome
A. septal mesosome-they function in the formation
of cross-wall during cell division
B. lateral mesosomes- they are present in a more
random fashion

51. Function of Mesosomes
• Compartmenting of DNA- involved in
mechanism responsible for the
compartmenting of DNA at cell division and
sporulation.
• Sites of the respiratory enzymes- they provide
increased membrane surface and are the
principle sites of the respiration enzyme in
bacteria

52. Intracytoplasmic inclusion bodies
• Depend upon the nutritional availability and
environmental condition cell form inclusion
bodies.
• The bodies are usually for storage and reduce
osmotic pressure by trying up molecules in
particulate form.
• They consists of volutine (polyphosphate), lipid,
glycogen, starch or sulfur
• They are mostly found in diptheria bacillus,
plague bacillus, and mycobacterium tuberculosis.

53. Demonstration of inclusion bodies
• Methylene blue staining- they stain a red violet
color for inclusion bodies and blue staining for
protoplasm
• Albert staining- it stains inclusion bodies with
dark blue stain
• Acid-fast staining- inclusion bodies resist
decoloration by 1% sulfuric acid
• Wet flim- they are more refractile than the
protoplasm
• Electron microscopy- they appear as very
opaque, clear demarcated bodies

54. Bacterial Nucleus
• The genetic material of a bacterial cell is
contained in single, long molecule of double
stranded deoxyribonucleic acid (DNA).
• It appears as closed circular thread about 1 mm
long.
• It occurs tightly coiled like as skein of woollen
thread.
• It consists of haploid chromosomes and replicates
by simple fission (binary fission).
• It does not posses nuclear membrane, nucleolus,
and deoxyribonucleoprotein.

55. Demonstration of Nucleus
• Electron microscopy
• Light microscopy

56. Plasmid
• It is circular, extrachromosomal genetic in addition to
chromosomal DNA elements.
• It consists of a circular piece of double-stranded DNA.
• It replicates autonomously (independent replicons).
• They are found mostly in bacteria but also in some
eukaryotic microorganism.
• Types of plasmid
• A. conjugative plasmid- such plasmid that contains the
information for self transfer to another cell by
conjugation
• B. non conjugative plasmid- those plasmid which do not
posses information for self transfer to another cell .

57. Uses of Plasmid
• As vectors in genetic engineering
• To transfer drug resistant gene
• To produce bacteriocin
• To enhance pathogenicity
• To produce enterotoxin
• To clean up of environmental waste

59. Bacterial Spore
• Dormant cell.
• Produced when starved.
• Resistant to adverse conditions, ultraviolet
radiation, high temperatures, extreme freezing
and chemical disinfectants.
• Contain calcium dipicolinate, dipicolinic acid
(DPA).
• Mostly gram positive bacteria (Bacillus and
clostridium).

60. Structure of Bacterial Spore

61. • Core- fully developed spore has core which is the spore
protoplast containing the normal cell structures but is
metabolically inactive.
• Core wall- the innermost layer surrounding the inner spore
membrane. It contains normal peptidoglycan and
becomes the cell wall of the germinating vegetative cell.
• The cortex -is the thickest layer of the spore envelope. It
contains an unusual type of peptidoglycan. Cortex
peptidoglycan is extremely sensitive to lysozyme, and its
autolysis plays a role in spore germination.
• The coat- is composed of a keratin-like protein containing
many intramolecular disulfide bonds. The impermeability
of this layer confers on spores their relative resistance to
antibacterial chemical agents.
• The exosporium- is a lipoprotein membrane containing
some carbohydrate.

62. Sporulation (Spore formation/
Sporogenesis)
1. Spore septum
• In the first observable stage of sporulation, a newly replicated bacterial
chromosome and a small portion of cytoplasm are isolated by an
ingrowth of plasma membrane called spore septum.
2. Forespore
• The spore septum becomes a double layered membrane that surrounds
the chromosome and cytoplasm.
• Structure entirely enclosed within the orginal cell, is called forespore.
3.Spore coat
• The forespore is subsequently completely encircled by dividing septum
as a double layered membrane.
• The two spore membranes now engage in active synthesis of various
layers of the spore.

63. • The inner layers becomes the inner membrane. Between two
layers is laid spore cortex and outer layer is transformed into
spore coat which consists of several layers.
• In some species from outer layer also develops exosporium which
bears ridges and folds.
4. Free endospores
• finally exosporium disintegrates and endospore is freed.

65. Shape and position of spores
• The shape and position of the spore and its size is
relative to the parent cell are species characteristics.
• Spores may be central (equatorial), sub-
terminal(close to one end), or terminal.
• The appearance may be spherical, ovoid, or
elongated and being narrower than the cell or
border and bulging it.
• The diameter of spore may be same or less than the
width of bacteria (Bacillus) or may be wider than the
bacillary body producing a distension or bulge in the
cell (clostridium).

67. Resistance
• Due to presence of calcium dipicolinate and
acid soluble protein stabilization of DNA,
protoplast dehydration, the spore coat, the
greater stability of the cell protein, hence it is
resistance to heat.
• It can resist boiling point and can survive for
decades of times.
• Spores are resistant to Disinfectants used for
disinfection

68. Demonstration
Unstained. Being
recognized by its
greater
refractivity.
Gram’s stain. Appearing as a clear space
within the stained cell protoplasm.
The spore stain

69. Uses of Spores
• Importance in food, industrial and medical
microbiology.
• Sterilization control-
Bacillus stearothermophilus for autoclave
Bacillus subtilis susp.niger for hotair oven