This document provides information on the classification and structure of bacteria. It discusses the different shapes bacteria can take including cocci, bacilli, vibrios, spirilla, and spirochetes. It describes bacterial cell structures like flagella, pili, capsules, cell walls, and cytoplasmic membranes. It compares the cell wall structures of gram-positive and gram-negative bacteria and explains their components. It also summarizes bacterial cytoplasm, ribosomes, mesosomes, nuclei, and spores.

1. Drx. Pankaj Dwivedi
Faculty OPP College
BACTERIOLOGY
The study of bacteria
www.oppcollege.com

2. INTRODUCTION
 Bacteria defined as microscopic single celled organism that
can penetrate into healthy tissues & start multiplying into
vast numbers.
 These are unicellular, free living small microorganism
which arevisible under the light microscope.
 Those are belongs to kingdom prokaryotae(Monera).
 Theyoccur in water, soil, air & all natural environments.

3.  The size & shape vary
between the dimensions of 0.75 to 4.0 µm.
 The cocci diameter near about 1 µm & bacilli
are 1 to 8 µm.
 They are found in spherical shape i.e
coccoid forms or as cylindrical form i.e rod
shaped forms.

4. SHAPE OF BACTERIA
 On basisof shape, bacteriaareclassified as follows…
1. Cocci
2. Bacilli
3. Vibrios
4. Spirilla
5. Spirochetes
6. Actinomycetes
7. Mycoplasams

5. COCCI
 Cocci are small, spherical oroval in shape
 In greek ‘kokkos’ meansberry
 E.g. Micrococcus

6. BACILLI
 THEY ARE ROD INSHAPES.
 IT IS DERIVED FROM GREEK WORD ‘BACILLUM’ MEANING
STICK.
 SOME OF THE BACILLI THE LENGTH OF THE CELL MAY BE
EQUAL TO WIDTH THOSEARE CALLED COCCOBACILLI
 E.G. BRACELLA

7. VIBRIOS
 Vibriosarecomma in shaped, curved rods
 E.g. Vibrio comma

8. SPIRILLA
 Thoseare longerrigid rodswith several curvesorcoils.
 Those are helical in shape & rapidbodies.
 E.g. Spirillum ruprem.

9. SPIROCHETES
 Theyare slender & flexuous spiral forms.

10. ACETINOMYCETES
 These are branching filamentousbacteria.
 The characteristics shape due to the presence of rigid
cell wall.
 E.g. Streptomyces species.

11. MYCOPLASMA
 THOSE ARE CELL WALL DEFICIENTBACTERIA
 SO THAT, THEY DO NOT HAVE STABLE MORPHOLOGY.
 THEY OCCUR AS ROUND OR OVAL BODIES
WITH INTERLACING FILLAMENTS.

12. ARRANGEMENT OF BACTERIA
Coccoid cells to exhibit growth in aggregates. Accordingly that
assembly theyagain exist in following five manners:
 As pairs ordiplococci.
 As groupof foursystematically arranged in acubeor sarcinae.
 As unorganized array likea bunch of grapesor staphylococci.
 As chain likea string of beads or streptococci.
 In that cocci divided into two planes & remain in group of four
that is tetrads.

14.  Arrangement of groupings formed by bacilli species
are limited & thosesplitacross theirshortaxis.
 They may appear as pair those called Diplobacillie.g.
klebisella pneumoniae

15.  Some bacilli species are found in chain like structure
those called streptobacilli e.g Bacillussubtilis.

16.  Some bacilli species are found in chain like structure
but have much large area of contact between the
adjacent cells those are called trichomes e.g.
Saprospira species

17. STRUCTURE OF
BACTERIAL CELL

18. FLAGELLA
 Flagella are long, slender, thin-hair likestructure.
 Flagella attached withcytoplasm.
 They play important role in bacteria for motility.
 They have 0.01 to 0.02 µm indiameter.
 They have 3 to 20 µm inlength.
 Flagella found in both Gram-positive & negativebacteria.
 Few coccal forms, most bacilli & almost all of the spirilla &
vibrios are motile byflagella.
 They can be seen by compound microscope with special
staining technique & can be seen easily under electron
microscope & dark filled microscope.

19. FLAGELLA SEEN IN BACTERIAL SPECIES IN
DIFFERENT MANNERS..
 Monotrichous : Single polar flagellae.g. Vibrio cholera
 Lophotrichous : two or more flagella at only one end e.g
Pseudonomas fluorescens
 Amphitrichous : single f lagella or more f lagella at both
end e.g Alcaligenes fecales
 Peritrichous : several flagella present all over the surface
e.g. Salmonella typhi

20. PERIPLASMIC FLAGELLA OR
ENDOFLAGELLA OR AXIAL FIBRIS :
 This type f lagella present in some helical bacteria i.e.
(spirochetes)
 That type of bacteria showing their motility only in highly
viscous media.
 In that type of bacteria flagella like structure present within the
cell.
 E.g. Treponema pallidum.
Gliding motility:
In that type of bacteria showing their motility when they are
contact with solid surface. E.g. Cytophaga species

21. PARTS OF FLAGELLA
Three main parts present in flagella thoseare…
 Filament
 Hook
 Basal body

22. STRUCTURE OF FLAGELLA

23. FIMBRIAE
 Fimbriae are similar structure like flagella but not involved in
motility.
 It is shorter than flagella (3µm).
 Fimbriaecan bedistributed over theentiresurface of thecell.
 Fimbriae act primarily as adhesions & allow to microorganism
to attach tosurface.
 They responsible for haemagglutination & cell clumping in
bacteria.

24. PILI
 Pilis are morphologically & chemicallysimilarto fimbriae.
 But they are present in small in numbers compatibly
fimbriae.
 Pilis joins to the bacterial cell for transfer of DNA
(bacterial conjugation) from onecell toanothercell.
 So pili alsocalled as sex pili or fertilitypili (F-pili).

25. CAPSULES & SLIME LAYER
 Many bacteria secrets EPS (extracelluar polysaccharides) that
areassociated with theexteriorof the bacterial cell.
so, they The EPS contains 2% carbohydrate & 98% water
producegummyexteriorto thecell.
 Morphologically two extreme formsexist…
i. Capsules
ii. Slime
 Capsules: which forms rigid, tightly & closely associated with
cell
 Slimes: which are looselyassociated with cell.

26. FUNCTION OF CAPSULE & SLIME
 They protect fromdesiccation.
 They provide a protection barrier against the penetration
of biocides.
 They protect against engulfment by phagocytes &
protozoa.
 They may promote the stability of bacterial suspension by
preventing the cells from aggregation &settling.
 They may promoteattachmentsof bacteria tosurface.

27. CELL WALL
cytoplasmic
 Cell wall gives definite shape to the bacteria.
 Cell wall situated between the capsule &
membrane.
acid (DAP),
 It is about 20- 30 nm inthickness.
 In the cell wall contains diaminopimelic
murmaic acid & teichoicacid.
 These substance joined together to formed a complex
polymer structure known as peptidoglycan or murein or
mucopeptide.

29.  Theglycan chain act as a backbone to peptidoglycan.
 Those short peptide bridge composed of alternating residues
of N-acetyl muramic acid (NAM) & N-acetyl glucosamine
(NAG).
 Each molecule of NAM attached atetrapeptide.
 Tetrapeptide consisting of the amino acids L-alanine, D-
alanine, D-glutamic acid & lycine or diaminopimelic acid
(DAP).

31.  This glycan tetrapeptide repeat unit is cross -linked to
adjacent glycanchain.
 This adjacentglycan chain occurs through a direct peptide
linkage or a peptideinterbridge.
 The type & number of cross linking amino acids varyfrom
organism toorganism.

32. CELL WALL STRUCTURE OF
GRAM-POSITIVE & GRAM-NEGATIVE
BACTERIA
 On the staining technique bacteria are divided into two
large groups…i. Gram-positive
Gram staining
ii. Gram- negative
 This staining technique are called as
technique.
 In that gram staining technique, the bacterial film
iodine solution & thentreating with crystal violet &
washed with alcoholsolution.

33.  After washing with alcohol solution the gram negative
organism cells appears the colourless while, gram positive
organisms are retain thedye.
 When both gram positive & negative cells are treated with
different colour dye e.g carbol fuchsin (red in colour).
 That time, gram negative cells appears red & gram
positive appearspurple.
 On that it reflects that both have different cell wall
structure.

34. GRAM-POSITIVE CELL WALL
STRUCTURE
 Gram positive bacterial cell wall consist of a single type of
molecules.
 Cell wall thick near about 20 to 80nm.
 In that present of 60 to 80 %peptidoglycan.
 Gram positive walls frequently contains acidic polysachrides
are called teichoicacids.
 Teichoic acid are either ribitol phosphate or glycerol phosphate
molecules that are connected by phosphodiesterbridge.

35.  In some gram positive bacteria glycerol-teichoic acids are
bound to lipids membrane and termed as lipoteichoic
acid.
 Those lipoteichoic acid create infection by killing
bacteria & showsinflammation.

36. CELL WALL STRUCTURE OF
GRAM-POSITIVE BACTERIA

37. GRAM-NEGATIVE CELL WALL
STRUCTURE
 Gram negative cell wall are multilayered & complex type
structure.
 Gram negativecell wall consist 10 to 20 % peptidoglycan.
 In that second layer found outside the peptidoglycan layer.
 This layer is asymmetrical & contains proteins,
lipoproteins, phospholipids & lipopolysaccharide(LPS).

38.  This outer layer is attached to peptidoglycan & the other end is
fixed in the outermembrane.
 In the inner leaf of the outer layer conatins phospholipids & it’s
outer layer composed with LPS (lipopoysaccharide), a
polysaccharide-lipid molecule.
 In gram negative cell, the LPS is an important molecule
because it determine the antigenicity & it is extremely toxic to
animal cell.
 In the LPS molecules contains threeregions
i. lipid A
ii. Core polysaccharide
iii. O-specific polysaccharide

39. •

40.  In the lipid A components are gives toxic & pathogenic
properties to the gram-negativebacteria.
 Gram negative bacterial outer membrane is relatively
permeable to small molecules but not for enzymes or
large molecules.
 The region between the outer surface of the cytoplasmic
membrane & the inner surface of the outer membrane is
called the periplasm.

41. CELL WALL STRUCTURE OF
GRAM-NEGATIVE
BACTERIA

42. CYTOPLASMIC
MEMBRANE
 Cytoplasmic membrane is thin near about 5 to 10nm.
 Biochemically, the cytoplasmic membrane is fragile,
phospholipid bilayer with proteins distributed
randomly throughout.
 In the phospholipids bilayer most of the proteins are
tenaciously held & are called integralproteins.

43.  The phospholipids molecules are arranged in two parallel
rows, called a phospholipidbilayer.
 Each phospholipid moleculecontainsa polar head & tail.
 Polar head composed of a phosphategroup & glycerol.
rigid than
 The non-polar tailsare interiorof the bilayer.
 Prokaryotic plasma membrane are less
eukaryotic due to lack ofsterols.

44. FUNCTIONS OF CYTOPLASMIC
MEMBRANE
 They including in transportation of nutrients.
 Itprovides mechanical strength to the bacterial cell.
 It helps in DNAreplication.
 It contains the enzymes involved in the biosynthesis of
membrane lipids & various macromolecules of the
bacterial cellwall.

45. STRUCTURE OF CYTOPLASMIC
MEMBRANE

46. CYTOPLASM
 In the bacterial cytoplas is a type of suspension, in that contains
organic, inorganic solute in aviscous water.
 It contains the nucleus, ribosomes, proteins & other water
soluble components & reservematerial.
 The cytoplasm bacteria differ from that of higher eukaryotic
microorganisms in not containing endoplasmic reticulum, golgi
apparatus, mitochondria & lysosomes.
 In most of the bacteria also contains extrchromosomal DNA (i.e
DNA are not connected tochromosome) isalso present.

47. RIBOSOMES
 Ribosomes are most important structure in bacterial
cytoplasm.
the rate of protein
 They involved in proteinsynthesis.
 Ribosomes numbers varies with
synthesis.
 If greater the number of ribosomes then the greater the
protein synthesis.
 They have 200 Ao in diameter.
 They arecharacterised by theirsedimentation properties.

48.  These bacterial ribosomes are called as 70 Sribosomes.
S= svedberg unit..unit of sedimentation.
 After sedimentation carried in ultra-centrifuge & then placed
in low concentration of magnesium that time 70 S ribosomes
dissociated into 50 S & 30 S particles.
 Each 50 S particles contain…one molecule of 23 S RNA, one
molecule of 5 S RNA & 32 differentproteins.
 And, each 30 S particles contains…one molecule of 16 S RNA &
21 differentproteins.
 During protein synthesis these ribosomes are associated with
the m-RNA & such association arecalled polysomes.

49. MESOSOMES
 In most of the bacteria, particularly in Gram-positive bacteria the
growth condition depending upon the membrane appears to be
infolded at more than one point.
 Such infoldings are called mesosomes.
 Mesosomes presents in twotypes…
In central (septal) mesosomes & peripheral (lateral) mesosomes.

50. STRUCTURE OF
MESOSOMES

51.  Central mesosomes present deep into the cytoplasm & locate
near the middle of thecell.
 These are involved in the DNA segregation & in the formation
of cross walls during celldivision.
 The peripheral mesosomes are not present at central location
& are not associated with nuclearmaterial.
 Mesosomes are also called as chondroids & are visible only
under electron microscope.
 Larger numbers of mesosomes have a higher respiratory
activity e.g. Azotobacter.

52. NUCLEU
S
 Nucleus appears oval or elongated bodies & generally present
one percell.
 The genome consists of a single molecule of double stranded
DNA arrangement in acircle.
 It may open under certain conditions to form a long chain
about 1000 µm in length.
 In bacterial nucleus does not contains nuclear membrane,
nucleous & deoxyribonucleoprotein.
 The bacterial chromosome is haploid & replicated by simple
fission instead of mitosisas in an eukaryoticcell.

53. SPORES
 Many bacterial species produce spores inside the cell & outside
thecell.
 Inside the spores are called endospores & outside the spores
are called exospores. E.g Bacillus anthracis, Bacillus subtilis
etc.
 Spores are extremely resistant to desiccation, staining,
radiation, disinfecting chemicals & heat.
 Each bacterial spore on germination forms a single vegetative
cell.
 They remain viable for long time & help bacteria to survive for
long period under unfavourablecondition.

54.  Endospores are thick-walled, highly refractile bodies that are
produced one percell.
 It occurs in combination with large amount of calcium, which
is present in central partof the spore (core).
 That calcium & DPA complex play important role in the heat
resistant of endospores.
 Endospores consists of a core orenvelopeor protoplast.
 In the core or protoplast consist of DNA & ribosomes, t-RNA &
enzymes.
 The spore envelop consist of the inner membrane, outer
membrane, cortex & sporecoat.
 In some species have the outer layer called exosporium which
bears ridges & fold.

56. SPORULATIO
N
 The process of endospore formation is known as
sporulation it may take 4 to 8 hrs in avegetativecell.
 Firstly..a newly replicated bacterial chromosomes & small
portion of cytoplasm are isolated by an ingrowth of the
plasma membrane called a spore septum.
 The situated septum derived from the cytoplasmic
membrane is then formed by a process of invagination
which divides intoa forespore & sporangium.
 The forespore is subsequently encircled by a dividing
septum as a doublelayered membrane.
 Between the two layers is laid a spore cortex & outer layer is
transformed intosporecoatwhich consistsof several layer.

58. GROWTH & GENETIC
EXCHANGE
 Three majorprocess involved in geneticexchange….
Transformation
Transduction
Conjugation

59. TRANSFORMATI
ON
 The early work of Fred Griffith in 1928 on the transfer of virulence in
the pathogen Streptococcus pneumoniae .
 The stage for the research that first showed that DNA was the genetic
material.
 Griffith found that if he boiled virulent bacteria and injected them
into mice, the mice were not affected and no pneumococci could be
recovered from theanimals.
 When he injected a combination of killed virulent bacteria and a
living nonvirulent strain, the mice died; moreover, he could recover
living virulent bacteria from the deadmice.
 Griffith called this change of nonvirulent bacteria into virulent
pathogens transformation.

60. TRANSDUCTION
 Defined as: a phenomenon causes genetic recombination in bacteria
wherein DNA is carried from one specific bacterium to another by a
bacteriophage.
 There are group of viruses are called bacteriophage. Bacteriophage
have bacterial cells as theirhosts.
 These bacteriophage inject viral DNA into the bacterial cell & after
that viral DNA is then replicated & transcribed at the expense of the
host & assembled into new viralparticles.
 This is known as temperatephage.

61.  Then, viral DNA forms part of the bacterial chromosome
& will becopied toall daughtercells.
 As well as temperate phage will be active once again at a
low frequency & phasing between temperate & lytic forms
ensures the long-term survival of thevirus.

62. CONJUGATION
 In that transcribed to produce singular viral elements, which cannot
assemble or lyse the host cell. Such DNA strand are known as
plasmids.
 Plasmids are circular & can either be integrated into the
chromosome, in which case they are replicated along
main
with
chromosome & passed to daughter cells or they are separate from it &
can replicateindependently.
 The simplest formof plasmid is F-factor (fertility factor).
 This can be transcribed at the cell membrane to generate F-pilus
within thecell envelop & cells containing an F-factoraredesigned F+

63.  The F-pilus is a hollow appendage that is capable of
transferring DNA from one cell toanother.
 In its simplest form an unassociated F-factor will simply
transfer a copy to a recipient cell & such a transfer process
is known ascojugation.

64. NUTRITIONAL
REQUIREMENTS
Bacteria required the nutrition's, pH, oxygen & temperature
for growth & multiplicationprocess.
 So, for cultivation of microorganism required elements
such as sodium, potassium, magnesium &iron.
 As well as in media required contains of source of carbon,
nitrogen, hydrogen, oxygen & phosphorus.
 Bacteria can be classified depending upon nutritional
requirements…such as carbon, energy, electronetc.

65. Energy obtained from sunlight are called phototrophs bacteria
e.g. Rhodospirillum rubrum.
Energy obtained from chemical reaction those called
chemotrophs bacteria e.g. Escherichia coli or E-coli.
 Source of electrons:
All bacteria required electrons formetabolism.
Lithotrops : In that type of bacteria species use the inorganic
compounds as electron donor e.g pseudomonaspseudoflava.
Organotrophs : In that type of bacteria species use the organic
compounds as electron donor e.g Escherichia coli orE-coli.

66. Photolithotrophs : some
inorganic compound (H2S) as source
phototropic bacteria use
of electron.
e.g. Chromatium okenii.
organic compound such as fatty acids & alcohols
Photoorganotrophs: some phototropic bacteria use
as
electrondonors e.g Rhodospirillum rubrum.
Chemolithotrophs: some chemotrophic bacteria use
inorganic compound as source of electron.
e.g. Nitrosomonas europaea.
Chemoorganotrophs: some chemotrophic bacteria use
organic compound such as sugar &amino acids as electron
donors e.g Escherichia coli or E-coli.

67.  Source of carbon: microorganism required carbon for
synthesizing cell components.
Autotrophs: some species use CO2 as the major source of
carbon these microorganisms are called autotrophs.
e.g. Chromatium okenii.
Heterotrops: some species use organic compounds as a
source of carbon such species are called heterotrophs.
e.g. Escherichia coli or E-coli.

68.  Nitrogen:
Nitrogen is the majorcomponent of protein & nucleicacids, so
that bacteria can use nitrogen from the atmosphere or from
inorganic compounds such as nitrites,nitrate.
 Sulphur:
Sulphur is needed forsynthesisof aminoacids.
 Phosphorus:
Phosphorus usually supplied in the form of phosphate is an
essential component of nucleotides, nucleic acidetc.

69.  Water:
It is the major essential nutrient as it account for about 80
to 90% of the total weight ofcell.
 Mineral salts:
Bacteria require salts, particularly the anions such as
phosphate & sulphate & the cations as sodium,
potassium, magnesium, iron & calcium. These are present
in the natural environment or may be added in cultural
media.

70. CULTURAL MEDIA
 Cultural or bacteriological media are mainly used for growth,
isolation, purification, maintenance & identification of
many bacterial
microorganisms.
 Nutrient agar is mainly used for growth of
species.
 Common ingredients present in cultural mediaare..
 Water
 Peptone
 Yeastextract
 Meatextract
 Agar

71. IDENTIFICATION PROCEDURE
 Identification of microorganism means in that study
included for determination of morphological structure of
microorganisms.
 In the morphological studies depending upon the no.of
factors such as, stain studied, nature of culture media,
temp. & duration of incubation.
 By using differential staining technique was present on that
we can easily determined the nature of microorganism, the
size of microorganism, shape of microorganism & also
determined their nature of microorganism with using
microscope.

72.  Stain is an organic compounds which contains benzene
ring with chromophore & auxochromegroup.
 Different techniques was used for visualisation,
differentiation & separation of bacteria in terms of
morphology.
 Staining different techniquesare…
1. Simplestaining
2. Negativestaining
3. Gram staining
4. Acid-faststaining
5. Spore staining
6. Capsulestaining
7. Otherstaining

73. SIMPLE STAINING
 By using simple staining technique, we can easily
determine their morphology & arrangement of
bacterial cell.
 In the simple staining technique used the single stain
e.g. crystal violet, methylene blue, carbol fuchsin
safranin etc.
 In that used the basic stain with a positively charged
chromogen.
 When, positively charged chromogen react with
bacteria, having a negative charge on nucleic acid &
certain cell wallcomponents.
 That time, negative charge components strongly binds
with positively chargedchromogen.

74. NEGATIVE STAINING
 In negative staining technique use the acidic stain e.g.
nigrosin oreosin.
 Acidic stain are negative charge so they not penetrate into
thecell but, itdeposit thearound thecell.
 So that, unstained cells are easily observed against the
coloured background.
 Advantage of that staining tech. compare with simple
technique that, it doesn’t required heat fixation & in that
technique determine the natural size & shape of
microorganism can beseen.

75. GRAM STAINING
 Gram staining technique discovered by Dr. Christian
Gram in 1884.
 By that technique use for not just for determination of
morphology but also use for the differentiae in
between Gram-positive & Gram negativecell.
 Gram positivecell retain thevioletstain.
 But gram negative cell decolourised & appears the red
colour in some species e.g E-coli, salmonella typhi,
vibrio cholerae, klebsiella pneumoniae etc.

76. ACID-FAST STAINING
 Acid fast staining technique used for differentiate between
acid-fast & non-acid fast bacteria.
 Mycobacterium species & actinomycetes bacterial species
containig mycolic acid & other waxy material in their cell
wall.
 Such bacterial species do not get stained with ordinary
staining technique. So, ZNCF (Zhiel-Neilson Carbol
Fuchsin) stain is used with steamheating.
 The acid fast bacteria appear pink & non acid bacteria
appears blue.

77. SPORE STAINING
 Spore staining technique used for detection of spore
carrying bacteria & type of spores.
 For spore staining use Dornersmethod.
 In Dorners method, carbol fuchsin is used as primary
satin.
 After heating the slide with stain for 5 to 10 minutes,
wash it & perform negative stainingprocedure.

78. CAPSULE STAINING
 Capsule staining technique used for determination of
capsule outside the cell. For performing, using the
positive staining & negative stainingtechnique.
 By positive staining the crystal violet is applied & also
applied copper sulphate solution (20%) which is
created osmotic difference, which causes diffusion of
stain towards the outersurface.
 After removing stain, the capsular layer as light violet
colouragainstdeepvioletcell.
 In negative staining, stains the cell & capsule are
visible colourless. By negative staining technique it can
easilyvisible.

79. CHARACTERISTICS OF
STAPHYLOCOCCUS
 Staphylococcus means staphyle (bunch of grapes) &
kokkos (grain or berry) wasderived from Greek words.
 Classification:
1. On the basis of pigmentproduction:
i. Staphylococcus aureus: golden yellowcolnies
ii. Staphylococcus albus: whitecolnies
iii. Staphylococcus citreus: lemon yellowcolnies
2. On the basis ofpathogenecity:
i. Pathogenic species :e.g. Staphylococcus aureus
ii. Non-pathogen species: e.g. Staphylococcus epidermidis
3. Baird-parker classified Staphylococcus into subgroup I
toVI

80. •
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