This document discusses the classification and structure of bacteria. It covers topics such as classification based on staining, shape, growth requirements, flagella, and motility. It also describes the key components of the bacterial cell structure, including the cell wall, cell membrane, cytoplasm, nucleoid, capsule, and flagella. Gram-positive and Gram-negative cell walls are compared, highlighting differences in thickness, composition and structure.

1. CLASSIFICATION OF BACTERIA
& IT’S STRUCTURE
PRESENTED BY
MISS TASMIA ZEB

2. Topics
Classification of bacteria
Baterial cell structure
Difference between prokaryotes and
eukaryotes,fungus,bacteria,virus
Obligate intracellular organisms.

3. Classification
• On the basis of Staining :
1. Gram staining :
a) Gram positive
b) Gram negetive.
2. Acid-fast staining.
3. Albert’s staining.

5. Example of Gram positive :
Gram positive
Cocci Bacilli
Streptococcas Staphylococcus Bacillus
Clostridium
Corynebacterium
Listeria
Actinomycescoagulase +
S. aureus
coagulase -
S. epidermitis,
S.saprophyticus
Peptostreptococci
P. magnus
Alpha hemolytic
S. pneumoniae
Viridens streptococci
Beta hemolytic
-group A : S.pyogens
-group B : S. agalactiae
-group D : E. faecalis,
S. bovis.

6. Example of Gram negetive :
Gram negetive
Cocci Bacilli
Neisseria meningitidis
Neisseria gonorrhoeae
Enteric Non-enteric Respiratory Animal source
Escherichia, Klebsiella, Haemophilus, Brucella
Salmonella, Proteus, Bordetella, Francisella
Shigella, Pseudomonas, Legionella Pasturella
Vibrio, Bacteroides Yersinia
Campylobactor

7. Example of Acid-fast bacilli :
Mycobacterium tuberculosis
Mycobacterium leprae
Nocardia
Actinomytes
Example of Albert’s stain :
Corynebacterium diptheriae.

8. • On the basis of Shape :
1. Cocci : oval or spherical; may be arranged in
pairs(pneumococci, meningococci, gonococci),
tetrads (micrococci), chains (Streptococci), clusters
(Staphylococci).
2. Bacilli : rod shaped; may show arrangements like –
a)coccobacilli, in which length and width are
approx. same (e.g-Brucella),
b) streptobacilli, which are arranged in chains
(e.g-Streptobacillus),
c)comma shaped (e.g-Vibrio),
d)spirella (Spirillum).

9. 3. Spirochetes : slender,flexious,spiral (Treponema).
4. Actinomytes : branching filamentous.

11. • On the basis of Growth and nutrition :
A. Oxygen requirements :
1. Aerobic :
a) Obligate aerobe : P. aeruginous.
b) Facultative aerobe : E.coli.
c) Microaerophilic : Campylobactor jejuni.
2. Anaerobic :
a) Obligate anaerobe : Clostridium tetani ,
Bacteroids.
b) Aerotolerant anaerobe : indifferent to O2.

12. B. Carbon dioxide requirement :
1. Capnophilic bacteria : Which require higher amount
of CO2 for their growth (5-10% CO2 and 15% O2).
Ex – H. influenzae, Brucella abortius.
C. Temperature :
1. Psychrophiles : microbes that grow within 0-20°C.
2. Mesophiles : microbes that grow within 25-40°C.
3. Thermophiles : microbes that grow within 55-80°C.
Ex- B. stearothermophilus.

13. D. pH :
1. Acidophile : which grow at acidic pH (below4.0).
Ex- Lactobacilli.
2. Alkaliphile : which grow at alkaline pH (8.2-8.9).
Ex.- V. cholerae.
3. Neutrophile : which grow at neutral pH (7.2-7.6).
Most pathogenic bacterias are neutrophiles.
E. Light :
1. Phototrophs : bacteria deriving energy from
sunlight.
2. Chemotrophs : bacteria deriving energy from
chemical sources.

14. F. Osmotic pressure :
1. Halophiles : which can survive at high salt
concentration.
2. Osmophiles : which can survive at high sugar
concentration.
G. Carbon source :
1. Autotrophs : which reduce inorganic carbon into
organic compounds, such as through photosynthesis
2. Heterotrophs : bacteria that grow by using the carbon
that has been reduced by the autotrophs.

15. H. Method of obtaining nutrition :
1. Heterotropic bacteria- Obtain their food from other
living organisms, as they cannot synthesize it on their
own.
2. Symbiotic Bacteria - Obtain nutrition from host
organism by offering something in return. Establish a
mutual give-and-take relationship with host.
3. Pathogenic Bacteria - Obtain food from host but are
harmful to the host, generally causing diseases.
4. Saprophytic Bacteria - Obtain Nutrition from dead
and decaying matter.

16. • On the basis of presence of Flagella :
A. With flagella :
1. Monotrichous (single polar flagellum) : Vibrio
cholerae.
2. Lophotrichous (multiple polar flagella) : Spirilla.
3. Peritrichous (flagella distributed over the entire cell)
: Salmonella, E. coli etc.
4. Amphitrichous (single flagellum at both ends) :
Spirillum minus.
B. Without flagella :
These are called Atrichous bacteria.

17. • On the basis of Motility :
1. Motile :
- Salmonella
- Vibrio cholerae
- Pseudomonas etc.
2. Non motile :
- Staphylococcas,
- Shigella.

19. Cell Structure
Essential components Nonessential components
1. Cell wall :
- Peptidoglycan
-Outer membrane (in Gram –ve
bacteria)
-Surface fibers (in Gram +ve
bacteria).
1. Capsule.
2. Cytoplasmic membrane 2. Glycocalyx
3. Ribosome 3. Pilus/Fimbria
4. Nucleoid 4. Flagellum
5. Mesosome 5. Plasmid
6. Periplasmic space (Gram –ve bacteria) 6. Granules
7. Spore

21. • Cell wall :
- fairly rigid and chemically complexed
outermost component, common to all bacteria
except Mycoplasma species.
- multilayerd,located external to the
cytoplasmic membrane.
- composed of : 1. Peptidoglycan
2. Outer membrane
3. Surface fibers.

22. Illustration of cell wall of Gram +ve and Gram –ve
Bacteria

23.  Gram +ve Cell Wall :
- thick (15-80 nm)
- consists of : 1. peptidoglycan.
2. teichoic acid.
3. teichuronic acid.

24. 1. Peptidoglycan :
- synonym : murein and mucopeptide.
- thick; 40 sheets which comprises 50% of cell
wall.
- complexed polymer consisting
a) a backbone, composed of alternating two
sugar derivatives N-acetyleglucosamine and N-
acetylemuramic acid connected by β-1→4 linkage.
b) a tetrapeptide side chain, consisting of
D- and L- amino acid with L-lysine.
c) a pentaglycine bridge, which connects
the tetrapeptide side chains.

26. Importance :
1. provides rigid support for the cell
maintain its characteristic shape and allows it to
withstand media of low osmotic pressure.
2. good target for antimicrobial which
inhibit transpeptidase thus inhibit synthesis
peptidoglycan.
3. lysozyme, a natural resistance of host,
cleaves disaccharide backbone by breaking
glycosyle bond (β-1→4 linkage).

27. 2. Teichoic acid :
- polymer of polyribitol phosphate or
polyglycerol phosphate which are connected by
phosphodiester linkage.
- two types : a) wall teichoic acid (WTA)
b) membrane teichoic acid or
lipoteichoic acid (LTA).
- most teichoic acids contain large amount of D-
alanine .

28. Importance :
1.togather with peptidoglycan it provides elasticity,
porosity, tensile strength, electrostatic properties of
the envelop.
2. used as antigen for serological classification.
3. binds Mg and supply this ion to the cell.
4. induce inflammation and septic shock.
5. mediate the attachment of staph. to mucosal cell.

29. 3. Teichoronic acid :
- consists of repeat units of sugar acids (such as
N-acetylemannuronic acid or D-glucosuronic acid).
- they are synthesized when phosphate is
limiting.
4.Polysaccharides :
-also contains neutral sugars; such as, mannose,
arabinose, rhamnose, glucosamine and acidic sugars;
such as glucoronic and mannuronic acid.

30.  Gram –ve cell wall :
- more complexed than Gram +ve bacteria.
- consists of : 1. peptidoglycan
2. lipopolysaccharides
3. outer membrane
4. lipoprotein layer.

31. 1. Peptidoglycan :
- thin (2-8 nm); 1-2 sheets which comprises 5-
10% of the cell wall.
- complexed polymer consisting
a) a backbone, composed of alternating two
sugar derivatives N-acetyleglucosamine and N-
acetylemuramic acid connected by β-1→4 linkage.
b) a tetrapeptide side chain, consisting of D-
and L- amino acid with mesodiaminopimelic acid.
c) pentaglycine bridge is absent.

33. 2. Lipopolysaccharide :
- is synthesized on the cytoplasmic membrane
and transported to its final exterior position.
- consists of three main component :
a) LipidA
b) core oligosaccharide
c) O polysaccharide or O antigen

35. a) Lipid A:
- consists of phosphorylated glucosamine
disaccharide to which a number of long chain fatty
acids are attached.
- also consists of hydroxymyristic acid, a unique
fatty acid.
b) Core oligosaccharide :
- includes two characteristic sugars :
a) ketodeoxyoctulonate acid
b) heptose
- both joined togather by lipidA.

36. c) O antigen :
- an outer polysaccharide consisting of up to 25
repeating units of 3-5 sugars.
Importance :
1.LPS is the endotoxin which causes fever, shock,
DIC by activating macrophage, complement and
coagulation system.
2. LOS is an important virulent factor.
3.O antigen is used to identify certain organism in
the clinical lab.

37. 1. Outer membrane :
- bilayered structure; outer membrane contains
LPS and inner one resembles cell membrane.
- porins : make special channels of outer
membrane.
- outer membrane protiens : includes Omp C,D,F
and PhoE and LamB, Tsx, Omp A.
- minor protiens:
enzymes,phospholipases,protease.

38. Importance :
1.large antibiotics penetrate it slowly which makes
high antibiotic resistance of gram-ve bacteria.
2.permit passive diffusion of hydrophilic
compounds, such as, sugar, amino acid and certain
ions. Some special molecules are also transported,
such as vitamin B12.
3. exclude hydrophobic molecules, such as bile salt.
4. serve to protect the cell.

39. 4. Lipoprotein layer :
- contains : a) 57 amino acids, representing 15
amino acid sequence.
b) diglyceride thioether linked to a
terminal cysteine.
Impotance :
stabilize the outer membrane and anchor it to the
peptidoglycan layer.

40. 5. Periplasmic space :
- space between the inner and outer membrane.
- contains peptidoglycan layer and 20-40% of cell
volume.
Importance :
1. has binding protein for specific substance.
2. has hydrolytic enzymes that break down
nontransportable substance to transportable one.
3. has detoxifying enzymes that inactivate certain
antibiotic.

41.  The acid fast cell wall :
- contains large amount of waxes,named Mycolic
acid.
- composed of peptidoglycan and asymmetric
lipid bilayer.
- inner lipid bilayer contains mycolic acid linked
to arabinoglycan and outer layer contains extractable
lipids.
Importance :
protect the acid fast bacilli from harsh chemicals
and detergents.

42.  Cell wall deficient bacteria :
1. Protoplast : produced from gram +ve bacteria
on treatment with lysozyme,in hypertonic media.
2. Spheroplast : derived from gram-ve bacteria
treated with lysozyme in presence of EDTA.
3. L-form : produced more easily with penicillin
than with lysozyme. They are able to grow and
devide.
4. Mycoplasma : wall lacking bacteria measuring
50-300nm.

43. • Cytoplasmic membrane :
- thin (5-10nm) semipermiable membrane.
- composed of a phospholipid bilayer and 200
different kinds of protein.

44. Importance :
1.acts as osmotic barrier and regulate the
tranportation of metabolites to and from protoplasm.
2. electron transport and oxidative phosphorylation.
3.excretion of hydrolytic exoenzyme and
pathogenicity protein.
4. Biosynthetic function.
5. Chemotactic systems.

45. • Cytoplasm :
- matrix is largely formed with 70% water.
- lack endoplasmic reticulam, mitocondria.
- consists : 1. Ribosome
2. mesosome
3. Intracytoplasmic inclusion bodies.

46. 1. Ribosome :
- look like small featureless particle.
- two subunits of 30S and 50S, giving a net 70S.
Importance :
1. serve as a site for protein synthesis .
2.site of action of antibiotic such as
aminoglycosides, macrolids and tetracycline.

47. 1. Mesosome :
- vesicular and multilaminated structure formed
as invagination of plasma membrane into the
cytoplasm.
- two types : 1. septal
2. lateral.
Importance :
1.septal mesosome coordinate nuclear and
cytoplasmic divisions during binary fission.
2. principal sites of respiratory enzymes in bacteria.

48. 3. Intracytoplasmic inclusion bodies :
- two types :
i) organic : contains glycogen or
polyhydroxybutyrate.
ii) inorganic : polyphosphate granules or
sulfer granules.
Importance:
1. used for storage; they are the source of carbon,
inorganic substance and energy.
2. some func to reduce osmotic pressure.

49. • Nucleoid :
- absence of nuclear membrane and mitotic
apparatus.
- consists of a single circular molecule of loosely
organised DNA (.58-10million base pairs).
- exception : V.cholerae and Brucellamelitensis
have two dissimilar chromosome.
- bacterial DNA has no introns.

50. • Capsule :
- a condensed,well defined layer closely
surrounds the cell, which excludes particle like india
ink.
-composed of polysaccharide, collectively
reffered as exopolysaccharide, which are sometimes
homopolysaccharide or negetively charged (except in
Bacillus anthracis, in which capsule comprises of
polypeptide, such as D-glutamic acid.)

51. Importance :
1.It is a determinant of virulence of many bacteria
for its antiphagocytic property.
2.Specific identification of an organism can be
made by ‘Quellung reaction’.
3.Used as vaccines due to their capability of
eliciting protective antibodies.
4.May play a role in the adherence of bacteria to
human tissue.

52. • Glycocalyx :
- is defined as polysaccharide-containing
material lying outside the cell.
-if it is loosely associated with the cell and does
not exclude particles, it is refered to as Slime layer.
Importance :
1. helps in adherence with foreign body to host cell.
2.facilitates Streptococcas mutens to adhere tightly
with tooth enamel and the acid excreted by this
bacteria causes dental carries.

53. • Flagella :
- thread like appendages intricately embedded in cell
envelop.
- 3-20μm in length and .01-.03μm in diameter.
- consists of :
a) filament, made up of protein flagellin.
b) hook, acts as propeller.
c)basal body, a set of rings;
one pair in gram +ve
and two pairs in
gram –ve bacteria.

54. Function :
1.primarily responsible for motility of bacteriam by
chemotaxis.
2.may play a role in bacterial survival
pathogenesis.
3.highly antigenic, possess H antigens, which are
different in different bacterias. Important in
serological diagnosis.

55. • Pili/Fimbria :
- hair-like filaments that extend from cell surface
and exclusively present in gram –ve bacteria.
- composed of structural protein subunit pilin
arranged in helical structure..
- .5μm long, 10nm thick.
- antigenic in nature.
Importance :
1. adherence of symbiotic and pathogenic bacteria to
host cells.

56. 2.Transfer of bacterial DNA takes place through
sex pili during the process of conjugation.
3.Antigenic variation of pili of Neisseria
gonorrhoeae makes it to survive even after the
presence of antibody against the original type of pili.
4. Inhibit phagocytic ability of leukocyte.
5. Helps in identification by haemagglitination.

57. • Difference between Flagella and Pili :
Characteristics Flagella pili
1. Definition Long, whip like, helical
appendages, made up of
flagellin, that protrude
through the cell membrane.
Short, straight, hair like,
filamentous appendages,
made up of pilin, that
protrude from the surface
of cell.
2. Length, width 3-20μm long .5μm long
3. Thickness 0.01-0.03μm 10nm thick
5. Number Can also be one in number numerous
6.Occurance Polar, lateral or peritrichous Thouthout the surface
7. Found in Both Gram +ve and Gram
–ve bac.
Exclusively on Gram –ve
bac.
10. Required for
conjugation
No Yes
12. Function Motility Attachment, transfer of
DNA.
13. Motion Wave like, undulating. Twitching motility.

58. • Plasmid :
- extrachromosomal, double-standed, circular DNA
molecules.
- capable of replicating independently of the
bacterial chromosome.
- occurs both in gram +ve and gram -ve bacteria.
- types :
a) transmissible
b) non-transmissible.

59. Importance :
they carry genes for –
a) resistance to antibiotic, heavy metal,
ultraviolet light.
b) synthesis of pili.
c) enzymes and toxins- exotoxin, enterotoxin.

60. • Spore :
- highly resistance, metabolically inart structure.
- contains bacterial DNA, a small amount of
cytoplasm, cell membrane, peptidoglycan, very little
water and a thick keratin coat.
- composed of : 1. core.
2. spore wall
3. cortex
4. protein coat (keratin)
- resistance of spore is due to dipicolinic acid, a
calcium chelator.
- spores may be central, subterminal or terminal
and oval or spherical, bulging or non bulging.

62. Difference Between Prokaryotes
& Eukaryotes

64. Structure Prokaryotes Eukaryotes
Nucleus
1. Nuclear membrane Absent Present
2. Nucleolus Absent Present
3. Chromosome One, circular More than one,linear
4.Location Free in cytoplasm, Attached tomesosome. Contained in membrane bound structure
6. Replication Binary fission Mitotic division
6. Extrachromosomal DNA Plasmid Inside the mitochondria
Cytoplasm
1. Cytoplasmic organalle Absent Present
2.Cytoplasmic streaming Absent Present
3. Lysosomes Absent Present
4. Ribosome 70S(50S+30S),free in cytoplasm or boundto
cell membrane
80S(60S+40S),attached to rough ER
Chemical composition
1. Cell wall Present Absent,except for fungi
2. Sterols Absent Present
3. Muramic acid Present Absent
4. Energy production site Electron transport chain located in the cell
membrane.
Within membrane bound mitochondria

65. Characteristics Viruses Bacteria Fungi Protozoa and
Helminths
1. Cell No yes Yes Yes
2. Approximatediameter
(μm)
.02-.2 1-5 3-10 15-25
3. Nucleic acid Either DNA orRNA Both DNA andRNA Both DNA andRNA Both DNA andRNA
4. Type of nucleus None Prokaryotic Eukaryotic Eukaryotic
5. Ribosomes Absent 70S 80S 80S
6. Mitochondria Absent Absent Present Present
7. Nature of outer
surface
Protein capsid and
lipoprotein envelop
Rigid wall
containing
peptidoglycan
Rigid wall
containing chitin
Flexible membrane
8.Motility None Some None Most
9. Method of replication Not binary fission Binary fission Budding or mitosis Mitosis

66. • Obligate Intracellular Organism :
- organisms that can not reproduce outside the
cell.
- includes :
a) viruses
b) bacteria: Chlamydia, Rickettsia,
Coxiella, Mycobacterium leprae.
c) protozoa: Plasmodium spp., Toxoplasma
gondi, leishmania spp., trypanosoma cruzi.
d) fungi: Pneumocystis jirovecii
- people with T-cell deficiencies are particularly
susceptible to intracellular pathogen.

67. THANK YOU