Classification of Bacteria
Dr Zahid Zia
Sr Demonstrator Pathology
Modern Prokaryotic Classification
Eubacteria
Archeabacteria
Cyanobacteria
Thermophiles
Diversity of Bacteria
Classification of Bacteria
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*Kingdom
Phylum
Class
Order
Family
*Genus ( 1st name)
*Species ( 2nd name identifier)
Remember: King Philip Came
Over For Good Spaghetti
Classification of Bacteria
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Morphology – shape, color,
gram specificity
Metabolism
Molecular techniques –
Forensics, DNA finger
prints, RNA, protein
analysis
1 Gram Negative Spiral Bacteria

Slender and flexible, come in a
lot of different shapes

More rigid than spirochetes

Ex. – Campylobacter jejuni
◦ Symptom – tenesmus: the
sensation of desire to
defecate, which is common
and occurs frequently , with
out the production of
significant amounts of feces
(often small amounts of
mucous or blood are alone
passed).
2 Gram Negative Spirochetes
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pathogenic
very flexible
tightly coiled, helically coiled
Example
◦ syphilis
Treponema pallidum
Gram Negative Spirochetes
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Most of pathogenic
Very flexible
Tightly coiled, helically coiled
Example
◦ Lyme disease
Borrelia burgdorferi
(organism gets lodged in
tissues)
3 Gram Negative Aerobic Rods
◦ Legionella pneumophila
 Lower respiratory tract
infection
 Needs oxygen
Gram Negative Aerobic Rods
Bordetella pertussis –
whooping cough
 Needs oxygen
Gram Negative Aerobic Rods
◦ Pseudomonas aeruginosa
(pigmented)
 Needs moisture
 Common in hospitals
 Opportunistic pathogen –
causes UTI, skin, and lung
infection
4 Gram Negative Facultative Rods
Vibrio
◦ V. cholerae
 Most well known of group
 Very severe dysentery. Can lose
10-15 liters of water/day. Leads
to hypovolemia – low water, hardly
any water in body
◦ V. vulnificus
 Very pathogenic
 Can cause flesh eating disease,
if it gets in a wound
◦ V. parahaemolyticus
 Found in shellfish – oysters
 Halophile – loves salt (will find in oceans, estuaries)
 Self limiting
Gram Negative Facultative Rods
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Enteric
◦ Salmonella
◦ Shigella
◦ E. coli (0157H7)
5 Gram Negative Anaerobic Rods

Fusobacterium
◦ Live in between teeth and
gums
◦ Cause tooth abscesses
and periodontal disease
◦ Teeth have nothing to
anchor – bone is
destroyed

6 Gram Negative Cocci or Coccobaccilli
(plump rods)
Neisseria gonorrhoeae –
Usually a diplococcus in
PMN
Sexually Transmitted
Disease
very antibiotic resistant
Gram Negative Cocci or Coccobaccilli (plump
rods)

Neisseria meningitidis
very infectious and
communicable.
Gram Negative Cocci or Coccobaccilli (plump
rods)
Acinetobacter baumanni iv.
lwoffi
opportunistic, UTI, skin,
and upper respiratory
7 Chlamydia Gram Negative Rods (Transitional)
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Very short little rods
Gram negative
Transitional – doesn’t hold stain
well
Do not have the ability to
synthesize own ATP, therefore and
obligate intracellular parasite of
other animals (humans)
Can go asymptomatic for a long
time
Ex.
◦ C. trachomatis – STD, causes eye
infection
◦ C. psittaci – parrot (associated
with birds)
8 Rickettsia Gram Negative Rod (Transitional)
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Small gram negative rods
Transitional – doesn’t hold
stain well
Can’t synthesize it’s own
NAD, coenzyme A, therefore
an obligate intracellular
parasite
Causative agent of Rocky
Mountain Spotted Fever
Example
◦ R. Prowazekii
9 Mycoplasma Gram Positive (Transitional )
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Gram positive – only because
they take in dye in cell
membrane but it washes away
Transitional – doesn’t hold stain
well.
Have no cell wall
Can not treat with penicillin
Ex.
◦ Mycoplasma pneumoniae – causes
LRTI
◦ Ureaplasma urealyticum – causes UTI
◦ Both imbed themselves in the tissue.
The most cell damage is done by the
immune system destroying the
tissue.
10 Gram Positive Cocci
Staphyloccocus aureus
MRSA
These bacteria can break
down all tissues of body.
Gram Positive Cocci
Streptococcus pyogenes –
no antibiotic resistance
right now
These bacteria can break
down all tissues of body.
11 Gram positive Endospore Forming Rods
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Difficult to get rid of
because of endospores
Example
◦ Clostridium tetani
Gram positive Endospore Forming Rods
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Difficult to get rid of
because of endospores
Example
 C. perfringens – gangrene
Gram positive Endospore Forming Rods
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Difficult to get rid of
because of endospores
Common in hospitals
Example
 C. difficile
antibiotic associated
pseudmembraneous
enterocolitis
Clostridium difficile
Gram positive Endospore Forming Rods
Bacillus
 B. anthracis – anthrax
 zoonosis
Gram positive Endospore Forming Rods
Bacillus
 B. cereus – food poising
Especially in high carb
foods – rice, vermicelli
 B. thuringiensis – natures
insecticide
12 Coryneforms
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Pleomorphic (many shapes)
Example
Corynebacterium diphtheriae
13 Mycobacteria
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Gram positive and Acid Fast
Mycobacterium tuberculosis
Respiratory Pathogen
MDR-TB
In the 1950s we sent people
with TB to the sanitariums
Mycobacteria
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Gram positive and Acid Fast
◦ M. avium intracellular complex
(MAC)
 Really bad bug
 Currently no drugs can cure it
 Especially bad for people with
AIDS
 Can cause atypical TB
Mycobacteria
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Gram positive and Acid Fast
◦ M. leprae
 Causative agent of leprosy
 Not very common
 Only affects areas of body
that are below body
temperature
 Natural reservoir is the
armadillo