Bacteria

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BACTERIA
INTRODUCTION:
Living material is organized in unit and microorganism were living form of
microscopical size and usually unicellular in structure originally classification is
unsatisfied.
Prokaryotic & Eukaryotic Cells
Bacteria
 Earth’s oldest life forms
– between 3.5 and 3.8 billion years old
 Most abundant life form – up to 2.5 billion individual bacteria in 1 gram of
fertile soil
 Very adaptable – found in all of Earth’s
ecosystems

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 Bacteria Characteristics
 Unicellular
 Circular DNA
 No organelles
 1/10th
the size of eukaryotic cells
 Flagella-long hair-like structure used for movement
 Reproduce asexually –Binary Fission
 Classification
Bacteria can be classified in many ways. The first classification scheme was
published in 1773 and many more have appered since.
Science of microbiology has developed other kind of classification but medically
important classification is as follows
Based on several major properties
 Morphology
 Biochemical reaction
 staining reaction
 Pathogenicity
 Based on relationship of host and microorganism
 DNA composition

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(1) MORPHOLOGICAL
Bacteria can be classified according to morphological
characteristics like their cell shape, size and structure and their specific
arrangement like motility and flagellar arrangement.
A. According to shape:
1)cocci( spherical or oval)
i.cocci in clustre.
Ex staphylococci
ii) cocci in chain. Ex. Streptococci
iii) cocci in pair. Ex. Diplococcus pneumoniae
iv) cocci in group of four. Ex.Tetrad
2) Bacilli (cylindrical or rod shaped)
i)coccobacilli: length of cell is greater than its breadth but not rod
shaped. Ex. Brucella.
ii) cuneiform or chinese letter arrangement: ex.corny bacteria
iii) vibrio: comma shaped.ex. Vibrio cholerae.
iv) spirilla: rigid piral shaped bacteria
v) spirochetes: longer, thinner, flexible and coil shaped bacteria
3) mycobacteria:
some bacteria have no cell wall and they called as cell wall lacking
bacteria and they doent have proper shape.

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(B) According to flagellar arrangement
Monotrichous: 1 flagella
Lophotrichous: tuft at one end
Amphitrichous: tuft at both ends
Peritrichous: all around bacteria
(2) BASEB ON BIOCHEMICAL REACTION
Aerobic and facultative aerobic bacteria:
(a) cocci:
i)gram positive:
. Catalase positive:
-staphylococcus aureus
-staphylococcus epidermidis
-staphylococccus saprophyticus
. catalase negative:
-staphylococcus pyogenes
-staphylococcus pneumoniae
-viridans group streptococci
Gram negative:
- Neisseria gonorrhoeae

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- Neisseria meningitidies
- moraxella catarrhalis
ii) bacilli:
(a) gram positive:
-Bacillus anthracis
-corne bacterium
-mycobacterium
-Nocardia asteroids
-gardenrella vaginalis
(b) Gram negative:
i)Enterobacteriaceae:
-Escherichia coli -Salmonella
-Klebsiella -Yersinia
-Morganella -shigella
ii)Non Enterobacteriaceae( Fermentive bacilli):
-Aeromonas
-Vibrio
-Pasteurella
iii) Non enterobacteriaceae (non fermentive bacilli)
-Pseudomonas
-Moraxella
-Acienobacter
(3) Coccobacilli:
-Actinobacillus -Bartonella
-Brucella -Haemophilus
-Chlamydia -Helicobacter
-Ricketsiae -legionella
(4) Mycoplasma:
Mycoplasma pneumoniae
Mycoplasma hominis
(5) Treponema
Treponema pallidum
Leptospira
Borilia burgoferi

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Aerobic bacteria:
(a) cocci:
i)gram positive:
Peptostreptococcus
ii) Gram negative:
Bacteriodes
Mobiluncus
(b)Bacilli:Gram negative
-Closteridium species
-Actinomyces
-Lactobacillus
(3)BASED ON STAINING REACTION
(a)Gram stain:
1) Gram positive: after the gram stain organism which occur violet in colour.
2) Gram negative: Which appear pink or red
(b)Acid fast stain:
1) Acid fast organism: after the ziehl –neelsen stain it will show pink in colour
2) Non acid fast organism: after this stain organism will appear blue in colour
4).BASED ON PATHOGENICITY:
A) pathogens: the organism which is able to spread disease and can cause
disease.
B) Non pathogens: which does not cause and disease; e.x: lactobacilli
C) Commensals: normaly non pathogenic but sometime they show the
disease when immunity impaired

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5) BASED ON RELATIONSHIP OF HOST AND ORGANISM
1) saprophytes: free living microbes on dead animals or decaying things that
can be found in soil and water and play important role in degradation of
organic matter.
2) Parasites: that establish themselves and multiply in hosts.
3) Commensals: microbes that live in complete live with harmony but they
can produce disese when host resistance Is lowerd.E.x: normal flora
organism
Bacterial anatomy
• In the bacteria the outer layer or cell envelop or bacteria consist of two
things
(a) rigid cell wall
(b) underlying cytoplasmic membrane or plasma membrane:
it includes granules, ribosomes, mesosomes and circular DNA.
 Some bacteria in addition to possess aditional structures such as
gelatinous material which cover it is called as capsule and when it is too
thin it is called as microcapsule.
CELL WALL:
 Introduction:
most cell poseses a cell envelop consisting of cell wall and underlying
cytoplasmic membrane.
 Definition:
“the tough, rigid structure which surrounds bacterial cell it is called as
cell wall”
• Thickness: 10-20nm
• Weight: 20-25% of dry weight of bacterial cell wall
Peptido-glycan Polymer (amino acids + sugars)

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Unique to bacteria
Sugars; NAG & NAM
 N-acetylglucosamine
 N-acetymuramic acid
Amino acids cross link NAG & NAM
Made of peptidoglycan – a combination of protein and polysaccharides
Some bacteria called Gram negative bacteria have an additional layer of membrane
that contains lipopolysaccharide
- this extra layer inhibits the uptake of antibiotics – protecting the bacteria
Gram positive Vs gram
negative
Gram positive bacteria have a large peptidoglycan structure. As noted above, this
accounts for the differential staining with Gram stain. Some Gram positive
bacteria are also capable of forming spores under stressful environmental
conditions such as when there is limited availability of carbon and nitrogen.
Spores therefore allow bacteria to survive exposure to extreme conditions and
can lead to re-infection (e.g., pseudomembranous colitis fromClostridium difficle)
Gram negative bacteria have a small peptidoglycan layer but have an additional
membrane, the outer cytoplasmic membrane. This creates an additional

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permeability barrier and results in the need for transport mechanisms across this
membrane.
A major component of the cytoplasmic membrane that is unique to Gram
negatives is endotoxin. This component is essential for bacterial survival.
Endotoxin has three components: the lipid, the highly conserved core
polysaccharide, and the species specific O antigen (also polysaccharide). In
contrast with the secreted exotoxins, endotoxin is cell-associated but MID 1 can
be released during cell division or cell death. The Lipid A moiety of endotoxin is
responsible for sepsis which may be fatal. Sepsis is characterized clinically by
confusion, fever, drop in blood pressure and ultimately multi-organ
failure.Endotoxin (also known as lipopolysaccharide-LPS):
Cell Wall function
Determine shape of bacteria
Strength prevents osmotic rupture
20-40% of bacteria
Help in division of bacteria
Contain receptor site
Some antibiotics effect directly: Penicillin
Cytoplasmic membrane:
Definition:
“thin semipermiable membrane which lies just beneath the cell wall that
is called as cyto plasmic membrane”
 The whole bacterial cytoplasm is bound peripherally by very thin,elastic
and semipermiable cytoplasmic membrane also known as cell membrane.
 It is 5-10nm in width
 Electron microscope shows the presence of three layer constituting a unit
membrane structure.
Chemically the membrane consist of phospholipid with small amount of
protein. Sterol is absent except in mycoplasma.

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DEMONSTRATION:
 The seperation of membrane from cell wall is achived by readily in gram
negative bacteria when they are suspended in medium of high osmotic
tension.such phenomenom is called as plasmolysis
 Electron microscope
Function:
Transport:
(1) Active transport:
it is site of numerous enzymes (oxidase polymerase, permease)
involved in the active transport of selective nutrients. It is impermiable to
macromolecule nd ionised substances.
(2) Passive transport:
It is act as semipermiable membrane through inward and outward
passage of water and passive trnsport of molecule lipid soluble solutes take
place by diffusion
Concentration:
it is also concentration sugar, amino acids and phosphate so that a 300-
400 fold grandient exists across osmotic barrier.

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Enzymatic function:
it also contain cytochrome oxidase, enzyme of tricarboxylic acid cycle and
polymerising enzyme necessary for synthesis of cell wall
Cytoplasm
“Bacterial cytoplasm is suspension of organic and inorganic solutes in
viscous watery solution”
It is not exhibiting protoplasmic streaming and it lacks endoplasmic
reticulum or mitochondria. It contains ribosomes, mesosomes, inclusion
and vacuoles.
All the organills which cytoplasm contains is as follows:
(1) Ribosomes:
Ribosomes appear as small granules and pack the whole cytoplasm. These
are strung together on strands of mRNA to form polymers.
the code of mRNA is translated in to peptides sequence t this place.
The ribosomal particles become linked up and travels along the mRNA
strand.
Function:
Site for protein synthesis.
Polysomes:
They are the group of ribosomes linked together like beads of chain by
messanger RNA
 Mesosomes:
They are vesicular, convulated or multilaminted structures formed as
invagination of plasma membrane in cytoplasm .
They are more prominent in the gram positive bacteria.
Two types of mesosomes

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(a) septal mesosomes:
It is attached to bacterial chrosome nd involved in dna segregation and in
formation of cross wall during cell division.
(2) Lateral mesosomes:
They are at lateral side
Functions:
 They are site of respiratory enzymes
 Coordinate nuclear and cytoplasmic membrane division during binary
fission
 Responsible for compartmenting DNA at sporulation
Bacterial capsule:
“ It is an outer covering of thick jelly like material that surrounds the
bacterial cell wall”
 Width: 0.2 micrometer
 Contains about 90% water and 2% solid
 The solid constitutes may be complex polysccharide (pneumococcus
klebsiella, enterobacter) or polypeptides (anthrax bacillus) or hyaluronic
acid (streptococcus)
Demonstration:
the capsule is best seen in pathological specimens like pus, blood, sputum,
and exudates
(1) By ordinary stain (gram or acid fast) capsule can not be stained, it apper
as halo arround the stained bacterial body.
(2) In negative staining (india pink preparation), capsule appears as clear halo
around the bacterium as link can not penetrate capsule.

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Immunological method: in that stained with antiserum that swallowed by
capsule so it appear as swollen under microscope so it is called as capsular
awelling reaction. E.g pneumococcus
Capsulated organism: s.pneumoniae,Bacillus anthracis, C.perfringes,
pneumobacillus, H.influenzae
Function:
 Capsule serve as protective covering against antibacterial substances such
as bacteriophase, phagocytes and enzymes
 Enhance bacterial virulance
 Capsular antigen is hapten in nature and specific for bacteria
Flagella
Composed of a flagellin subunit.
Usually sheathed (covered).
Rotates by way of a basal body in the bacterial cell.
Unique to bacteria.

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Bacterial Flagella Structure:
Composed of filament, hook, and basal body
Flagellin protein (filament) is deposited in a helix at the lengthening tip
Base of filament inserts into hook
Basal body anchors filament and hook to cell wall by a rod and a series of
either two or four rings of integral proteins
Filament capable of rotating 360º
Motility - movement
Swarming occurs with some bacteria
 Spread across Petri Dish
 Proteus species most evident
Arrangement basis for classification
 Monotrichous; 1 flagella
 Lophotrichous; tuft at one end
 Amphitrichous; both ends
 Peritrichous; all around bacteria
Observe Picture in Micro Lab.
SPORES:
“ spores are highly resistant dormant stage of bacteria formed in
unfavourble environmental condition such as starvation and dessication”
 As spores are formed within the parent bacterial cell so they are also
called as endospores
 During germination each spore give rise to only one vegetative bacteria
 Exospores found in fungi(conidia) formed extracellularly from end of
parent cells.

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Spore forming bacteria:
A. Gram positive bacilli:
(1) obliterate aerobic- genus bacillus.e.g B.anthracis, B.subtilis
(2) obliterate anaerobic:genus clostridia.e.g C.tetani, C.welchii, C.botulism
B. Other bacteria:
Gram positive coccus (porosarcina) gram negative bacilli (coxiella burnetii)
Spore morphology :
Sporogenesis:
spontaneous sporulation occurs in
condition unfavourable condition such as
starvation, dessication, presence of
disinfectants and in extreme temperature.

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SPOROGENESIS PROCESS:
Shape and position:
The young spore remain attached t parant cell. The precise position and
shape and relative size of spores remain constant within particular
bacteria.
Spore may be central,sub terminal or terminal
Spore formation is initiated by apperance of clear area in portion of
protoplasm near one end of bacterial cell and that protoplasm gradually
become more opaque that form forespore
The cell membrane grow inwards and undergoes infolding forming double
layered membrane structure around the core
The inner most layer of spore wall forms spore membrane in future vegetative
bacterium will develop. The spore wall synthesis a thick covering lyer cortex
and multilayered thin but tough outer layer spore coat
Spore formation is initiated by apperance of clear area in portion of
protoplasm near one end of bacterial cell and that protoplasm gradually
become more opaque that form forespore
The cell membrane grow inwards and undergoes infolding forming double
layered membrane structure around the core
The inner most layer of spore wall forms spore membrane in future vegetative
bacterium will develop. The spore wall synthesis a thick covering lyer cortex
and multilayered thin but tough outer layer spore coat

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A: Oval subterminal
B: Spherical terminal
C: Spherical subterminal
D: Spherical central
E: Oval terminal
F: Oval central
G: Free spore
Resistance:
Bacterial spores are resistant to ordinary boiling, heating, and
disinfectant. They can withstand boiling up to 3 hr, dry heat at 150c for 1
hr however they are destroyed by autoclaving at 121c for 15-20 min.
The highly impervious spore coat, low water content, low metabolic
activity and high concentration of calcium dipicolinate of spore make
resistant to drying and heat.
Germination:
Definition:
“ The process of conversation of spore in to vegetative cell under suitable
environment is known as germination”
There are three stages of germination
1. Activation:
The germintion of bacterial spore do not occur even when placed in
environment that favour process.
Unless first activated by one or onother agent damage the coat of spore
such as heat, abration and compound containing free sulphydryl groups.

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2.Initiation:
The process of initiation is not clear, however the spore will initiate
germination in favourable condition.
Different species of bacteria recognizes different effactors as signalling a
rich medium such as L-alanine for one spesis
3. Out growth:
With the swelling of spore wall and disintegration of cortex a single germ
cell emerge after breaking open the spore coat.
The new vegetative cell consist of spore protoplast with its surrounding
wall.
Formation of vegetative cell.
Demonstation:
 By ordinary stain and modified Z-N stain.
Laboratory:
for making sterilization

Bacteria

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