Morphology & physiology of bacteria dr. someshwaran Microbiology MBBS UG PG MD COllege Class Theory Lecture PPT PDF students Microbe

1. MORPHOLOGY &
PHYSIOLOGY OF
BACTERIA
Dr. R. Someshwaran, MD., Assistant professor,
Department of Microbiology, KFMS&R

2. Objectives of today’s class
To define the term prokaryote &eukaryote
To understand different shapes of bacteria
To describe bacterial anatomy in detail
To explain about bacterial growth curve
To know the factors affecting bacterial growth
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3. Introduction
• Living organisms classified under3 kingdoms:
1.Plant kingdom
2.Animal kingdom
3.Protista
• Under Protista- Microorganismsareclassified as
i.PROKARYOTES (Bacteria& Blue-green algae)
ii.EUKARYOTES (Fungi, Protozoa, slimemolds& other algae)
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4. Prokaryotes
• Bacteria are single celled microorganism containing a single
circularchromosome
• Bacteria lack Nuclearmembrane, nucleolus, deoxyribo-
nucleoprotein.
• Mitotic division is absent in bacteria
• Cytoplasmic streaming, pinocytosis, Mitochondria, Lysosomes,
Golgi apparatus, Endoplasmic reticulum are absent in the
bacterial cytoplasm.
• Chemical composition (Sterols-, Muramic acid+)
• Bacteria do not contain chlorophyll; Bacteria do not show true
branching. Exception: Actinomycetales (Higherbacteria)
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5. Prokaryotic Cells
• Much smaller(microns) and more simple than eukaryotes
• prokaryotes are molecules surrounded by a membrane and cell
wall.
• they lack a true nucleus and don’t have membrane bound
organelles like mitochondria, etc.
• large surface-to-volume ratio : nutrients can easily and rapidly
reach any part of the cells interior

6. Schematic of typical animal (eukaryotic) cell, showing subcellular components.
Organelles: (1) nucleolus (2) nucleus (3) ribosome (4) vesicle
(5) rough endoplasmic reticulum (ER) (6) Golgi apparatus (7) Cytoskeleton
(8) smooth ER (9) mitochondria (10) vacuole (11) cytoplasm (12)
lysosome (13) centrioles

7. Differences between prokaryotic & eukaryotic cells
Character Prokaryotes Eukaryotes
Nucleus Nuclear
membrane
Absent Present
Nucleolus Absent Present
Chromosome One circular One ormore paired and
linear
Cell division Binary fission Mitosis
Cytoplasmic
membrane
Structure and
Composition
fluid phospholipid bilayer,
lacks sterols
fluid phospholipid bilayer
containing sterols
Function Incapable of endocytosis
(phagocytosis and
pinocytosis) and exocytosis
Capable of endocytosis
and exocytosis

8. Differences between prokaryotic & eukaryotic cells
Character Prokaryotes Eukaryotes
Cytoplasm Mitochondria Absent Present
Lysosomes Absent Present
Golgi apparatus Absent Present
Endoplasmic
reticulum
Absent Present
Vacuoles Absent Present
Ribosomes 70 S 80 S

9. Differences between prokaryotic & eukaryotic cells
Character Prokaryotes Eukaryotes
Cell Wall Present Animals &Protozoans –
Absent
Plants, Fungi &Algae -
Present
Composition Peptidoglycan –
complex carbohydrate
Cellulose orchitin
Locomotor
organelles
Flagella Flagella/Cilia

10. Size of bacteria
• Unit of measurement used in bacteriology is micron or
micrometre (µm)
• One micron is equal to one thousandth of millimetre
• One nanometre (nm) ormillimicron (mµ) is equal to
one thousandth of a micron orone millionth of a
millimetre
• One Angstrom unit (Å) is equal to one tenth of a
nanometre
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11. Limit of resolution
• Limit of resolution with the unaided human eye is 200
microns (0.2mm)
• Bacteria are even much smallerand can be visualized
only undermagnification.
• Bacteria of medical importance generally measure 0.2-
1.5µm in diameterand about 3-5µm in length
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12. Microscopy
• Leeuwenhoek – hand ground lenses – First observed bacteria
• Parts of a microscope: Eye piece (5x/10x), Arm, Base,
Mechanical stage, Light source, Condenser, Diaphragm,
Objectives (Scanner, LP, HP, OI), Cylindrical tube length,
Stage adjustor(Horizontal, vertical), Fine adjustment and
coarse adjustment knob.
• Magnification power
• Resolution power
• Total magnification: Objective x Eyepiece
• Refractive index of lens (glass), air, water&oil
• Focal length of lens of human eye (Range:16-25cm)01/31/18 12

13. Types of Microscopes
a. Optical orlight microscope
b. Phase contrast microscope
c. Fluorescent microscope
d. Electron microscope
e. Dark field /Dark Ground microscope: 2 types namely
polarisation &interference microscopes
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14. Staining techniques
• Simple stains providecolour contrast but impart samecolour
to all bacteria. Ex: Methyleneblue, Basic fuchsin.
• Negative staining provideuniformly coloured background
against which theunstained bacteriastand out in contrast. Ex:
Indiaink or Nigrosin.
• Impregnation methods for Cellsand structurestoo thin to be
seen under ordinary microscopethat may berendered visibleif
they arethickened by silver impregnation on thesurface. Used
for demonstration of Spirochetesand Bacterial flagella.
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15. Staining techniques – Contd…
• Differential stains: Stainsimpart different colour to
different bacteriaor itsstructures. Ex: Gram stain & Acid fast
stain.
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16. Shape of Bacteria
• Cocci – spherical/oval shaped majorgroups
• Bacilli – rod shaped
• Vibrios – comma shaped
• Spirilla – rigid spiral forms
• Spirochetes – flexible spiral forms
• Actinomycetes – branching filamentous bacteria
• Mycoplasmas – lack cell wall

17. Arrangement of bacteria: Cocci
Cocci in pair – Diplococcus
Sarcina – groups of eight
Tetrad – groups of four
Cocci in chain - Streptococci
Cocci in cluster - Staphylococci
Coccus

18. Arrangement of bacteria: Bacilli

19. Othershapes of bacteria
Comma shaped
Spirochetes
Spirilla

20. Anatomy of a Bacterial Cell

21. Anatomy of A Bacterial Cell
• Outer layer – two components:
1. Rigid cell wall
2. Cytoplasmic (Cell/ Plasma) membrane– present beneath cell wall
• Cytoplasm – cytoplasmic inclusions, ribosomes,
mesosomesand nucleus
• Additional structures – plasmid, slimelayer, capsule,
flagella, fimbriae(pili), spores

22. Structure &Function of
Cell Components

23. CELLWALL
• Outermost layer, encloses cytoplasm
1. Confers shape and rigidity
2. 10 - 25 nm thick
3. Composed of complex polysaccharides (peptidoglycan/mucopeptide) -
formed by N acetyl glucosamine (NAG) & N acetyl muramic acid
(NAM) alternating in chains, held by peptide chains.

24. • Cell wall –
4. Carries bacterial antigens – important in virulence &immunity
5. Chemical nature of the cell wall helps to divide bacteria into two broad
groups – Gram positive &Gram negative
6. Gram +ve bacteria have simplerchemical nature than Gram –ve
bacteria.
7. Several antibiotics may interfere with cell wall synthesis e.g. Penicillin,
Cephalosporins

25. Gram positive cell wall
The Gram-positive cell wall is composed of a thick, multilayered peptidoglycan sheath outside of the
cytoplasmic membrane. Teichoic acids are linked to and embedded in the peptidoglycan, and
lipoteichoic acids extend into the cytoplasmic membrane

26. Gram negative cell wall
The Gram-negative cell wall is composed of an outer membrane linked to thin, mainly single-layered
peptidoglycan by lipoproteins. The peptidoglycan is located within the periplasmic space that is created
between the outer and inner membranes. The outer membrane includes porins, which allow the passage of
small hydrophilic molecules across the membrane, and lipopolysaccharide molecules that extend into
extracellular space.

27. Cell Wall

28. Differences between Gram positive &Gram
negative
Property of bacteria Gram Positive
Gram Negative
Thickness of wall 20-80 nm 10 nm
Number of layers in wall 1 2
Peptidoglycan content >50% 10-20%
Teichoic acid in wall + -
Lipid & lipoprotein content 0-3% 58%
Protein content 0% 9%
Lipopolysaccharide 0 13%
Sensitive to penicillin Yes Less sensitive
Digested by lysozyme Yes Weakly

29. Cytoplasmic (Plasma) membrane
• Thin layer5-10 nm, separates cell wall from cytoplasm
• Acts as a semipermeable membrane: controls the inflow and outflow
of metabolites
• Composed of lipoproteins with small amounts of carbohydrates

30. OtherCytoplasmic Components
• Ribosomes – protein synthesis
• Mesosomes –
1. Multilaminated structures formed as invaginations of plasma membrane
2. Principal sites of respiratory enzymes
3. Coordinate nuclear&cytoplasmic division during binary fission
4. More prominent in Gram +ve bacteria
• Intracytoplasmic inclusions – reserve of energy &phosphate forcell
metabolism e.g. Metachromatic granules in diphtheria bacilli

31. Nucleus
• No nucleolus
• No nuclearmembrane
• Genome –
• single, circulardouble stranded DNA.
• Haploid
• Divides by binary fission

32. Additional Organelles
1. Plasmid –
• Extranucleargenetic elements consisting of DNA
• Transmitted to daughtercells during binary fission
• May be transferred from one bacterium to another
• Not essential forlife of the cell
• Confercertain properties e.g. drug resistance, toxicity

33. Additional Organelles
2. Capsule &Slime layer–
• Viscous layersecreted around the cell wall.
• Polysaccharide /polypeptide in nature
a) Capsule – sharply defined structure, antigenic in
nature
• Protects bacteria from lytic enzymes
• Inhibits phagocytosis
• Stained by negative staining using India Ink
• Can be demonstrated by Quellung reaction (capsule
swelling reaction)
a) Slime layer– loose undemarcated secretion

34. Additional Organelles
3. Flagella –
Long (3 to 12 µm), filamentous surface appendages
Organs of locomotion
Chemically, composed of proteins called flagellins
The numberand distribution of flagella on the bacterial surface are characteristic fora
given species - hence are useful in identifying and classifying bacteria
Flagella may serve as antigenic determinants (e.g. the Hantigens of Gram-negative
enteric bacteria)
Presence shown by motility e.g. hanging drop preparation

35. Types of flagellararrangement
Polar/ Monotrichous – single flagellum at one
pole
Lophotrichous – tuft of flagella at one pole
Peritrichous – flagella all over
Amphitrichous – flagella at both poles
Amphilophotrichous – tuft of flagella at both ends

36. Flagella
• Long unbranched sinuous filaments present on motile bacteria
• Made of 3 parts
• Filament, hook, and basal body
• Filament is external and hook basal body complex embedded in the cell
envelope
• Hook and basal body are antigenically different

38. • Detachment of flagella does not affect the viability of cell
• 3-20 m long, uniform diameterμ
• Made up of a protein flagellin
• Flagella of different genera - similarchemical composition they
are antigenically different
• Flagellarantibodies help in serodiagnosis

39. Flagellar stains – Leifson stain

40. Electron microscopy

41. Flagella and fimbriae (Pili)

42. Shape & position of bacterial spore
Oval central
Spherical central
Oval sub terminal
Oval sub terminal
Oval terminal
Spherical terminal
Free spore
Non bulging
Bulging

43. Capsule/ slime layer
• Bacteria secrete viscid material
• organised into capsule - pneumococcus
• Loose undemarcated secretion (slime layer) -
leuconostac
• Microcapsules – too thin to be seen underlight
microscope
• Both capsule and slime layermay be present

44. •Slime layer/capsule
• polysaccharide orpolypeptide
• mucoid colonies on culture media
•Slime layer
• little affinity forgram stain
•Capsule
• stained by negative staining
• Capsularmaterial antigenic.
• Serological tests with anti capsularserum
• Quellung reaction – Neufeld in 1902

45. Capsule
•contribute to virulence by inhibiting phagocytosis
• lost by mutation or repeated subcultures

47. Fimbriae / Pili

48. • Fine hairlike appendages
• Shorterand thinnerthan flagella projecting from cell membrane
• Present on both motile and non motile bacteria
• Made up of pilin
• 8 morphological types known
• Classified as common orsex pili
• Conferadhesive property to the cell
• Disappearfollowing subcultures

49. Properties
• Agglutinate red blood cells of guinea pigs, horses and pigs
strongly
• Human and sheep cells weakly
• Detected by hemagglutination
• Antigenically similarand may cause cross reaction in
serological tests

50. Sex pili
• Longerand fewer
• Found on male bacteria
• Attach to female bacteria
forming hollow conjugation
tubes through which genetic
material is transferred

52. Spores
• Highly resistant resting stages
• Endospores – formed inside cell
• Due to deletion of exogenous nutrients /unfavourable environment
• Young spores are seen attached to parent cell
• Appearas unstained area in gram stain
• Special spore stain can be used

53. Gram stain – Never comment
on spore

54. Spore cycle

55. Section of spore

56. Types of spore formation
• Spores may bulging or non
bulging

57. Clostridium tetani –
terminal spore
Bacillus anthracis –
central spore

58. Spore stain
Wirtz –Concklin method

59. Pleomorphism & involution forms
• Variation in shape and size of bacteria – pleomorphism
• Aberrant forms in ageing cultures – involution forms
• Due to defective cell wall synthesis

60. L forms
• Swollen cells and aberrant morphological forms observed by
Kleinberger Nobel at Lister institute, London
• Develop spontaneously or in the presence of agents that interfere
with cell wall synthesis
• May be stable or unstable
• Resemble mycobacteria

61. Gram variable bacteria

62. Pleomorphism & Involution forms
• Pleomorphism – great variation in shape &size of individual cells
e.g. Proteus species
• Involution forms – swollen &aberrant forms in ageing cultures,
especially in the presence of high salt concentration e.g. plague
bacillus
• Cause – defective cell wall synthesis

63. Bacterial Taxonomy
• Includes three components:
1. Classification : orderly arrangement
2. Identification of an unknown unit
3. Nomenclature: naming theunits

64. Bacterial Taxonomy: Classification
• Orderly arrangement :
• Kingdom – Division – Class– Order – Family – Tribe– Genus– Species
Phylogenetic classification – representsabranching treelikearrangement. One
characteristic being used for division at each branch or level
Molecular or Genetic classification – based on thedegreeof genetic relatednessof
different organisms
Intraspeciesclassification – based on biochemical properties(biotypes), antigenic
features(serotypes), bacteriophagesusceptibility (phagetypes)

65. Bacterial Taxonomy: Nomenclature
• Two kinds of name are given to bacteria
• Casual /common name – forlocal use, varies from country to country
e.g. “typhoid bacillus”
• Scientific /International Name – same all overworld, consists of two
words (in Italics) e.g. Salmonellatyphi,
Staphylococcus aureus

66. What is Physiology?
• Study of the mechanical, physical and biochemical functions
of living organisms.

67. Oxygen requirements
• Aerobic respiration is the release of energy from glucose or
anotherorganic substrate in the presence of Oxygen.
• Obligateaerobes-Pseudomonas
• Microaerophilic –Streptococcus

68. • Anaerobic respirationis oxidationof molecules intheabsenceof
oxygentoproduceenergy
• Obligateanaerobes - clostridia
• Facultativeanaerobes - vibrio
• Aerotolerantanaerobes - lactobacilli
• Fermentation
• conversionof carbohydrates intoalcohols oracids underanaerobic
conditions.
• Eg: lactobacillus

69. Carbondioxide – factor affecting growth
• Small amount of CO2 is produced by most bacteria and used
endogenously formetabolism
• Capnophiles – bacteria which require a higherCO2 tension (5 –
10%) to grow.
• eg: Brucellae, meningococcus , gonococcus

70. Bacterial vitamins
• Growth factors to be provided exogenously forgrowth.
• Essential
• Accessary
• H.influenzae requires accessary factors X (haemin) and V
(NAD) present in blood to grow.

71. Effect of light
• Bacteria usually grow well in the dark.
• Phototrophs – need light to grow
• Pigmented bacteria like cyanobacteria

72. Reaction
AUTOTROPHS HETEROTROPHS
PHOTO CHEMO PHOTO CHEMO
ENERGY
FIXING
Light
energy
Inorganic
compnds
Light
energy
Organic
compnds
CARBON
FIXING
CO2 CO2 Organic
compnds
Organic
compnds
Cyanobacteria
Green sulphur &
Purple sulphur
bacteria
Nitrosomonas
Nitrobacter
Non Purple sulphur
Non green sulphur
bacteria
Most bacteria
All fungi
protozoa

73. Bacterial growth curve
( batch culture)

74. • Lag phase - adaptation
- build necessary enzyme &metabolic intermediates
• Log/exponential phase – division by binary
fission
numberof cells
• Stationary phase – cell division stop due to depletion of nutrients &
accumulation of toxic products
• Phase of decline – population decrease due to cell death

75. MITOSIS

76. E.coli M.leprae
20 minutes 20 days
• At extremes we eitherhave a mass progeny (4000 tones) in
24 hours in a continuous culture (or) no replication at all.
• In laboratories it is always a batch culture where the nutrients
are limited and toxic products accumulate.
• GENERATION TIME

77. Bacterial count
• Total count – total numberof bacteria in the sample
• Direct counting
• Coultercounter
• Viable count – measures the numberof living organisms
• Dilution methods
• Plating methods

78. Other factors affecting bacteria
• Temperature
• PH
• Mechanical stress
• Osmosis

79. Effect of T0
on
bacteria

80. Effect of PH
on Bacteria

82. Osmotic effect and mechanical stress
• Tolerant to osmotic variations esp Gram positive bacteria
• Sudden transfer from concentrated solution to distilled water –
plasmoptysis
• Mechanical stress like grinding, vigorous shaking with glass beads or
exposure ultrasonic vibration – rupture of cell

83. Summary
• Prokaryote
• GPVs GN Difference
• Pleomorphic bacteria
• Lforms
• Cell appendages
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84. Thank you
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