Download classification of bacteria

Classification of bacteria
DR.THAMINA SAYYED
REGISTRAR
MICROBIOLOGY
KKUH
Bacterial cells
Classification System
3

Domains
1978 Carl Woese
1. Bacteria
• Unicellular prokaryotes with cell wall containing
peptidoglycan

2. Archaea
• Unicellular prokaryotes with no peptodoglycan
in cell wall

3. Eukarya
•
•
•
•
Protista
Fungi
Plantae
Animalia
Comparing Prokaryotic and Eukaryotic Cells
Taxonomic Classification Categories


arranged in hierarchical order
species is basic unit
Domain
Kingdom
Phylum or Division
Class
Order
Family
Genus
Species
Prokaryote Classification

Technologies used to characterize
and ID prokaryotes
 microscopic examination
 culture characteristics
 biochemical testing
 nucleic acid analysis
 combination of the above is most accurate
Phenotypic & Genotypic classification
Phenotypic Characteristics for Identifying
Prokaryotes
 often
does not require sophisticated
equipment
 can easily be done anywhere

Microscopic Phenotypic Exam
size and shape and arrangement

enough information for diagnosis of certain infections

Gram stain
 distinguishes between
Gram + and Gram –
bacteria
 narrows the possibilities
quickly
Microscopic Phenotypic Exam
 special

stain
allows for the distinction of
microorganisms with unique
characteristics
• capsule
• acid fast staining detects
the waxy presence of
Mycobacterium
tuberculosis
Capsule staining
Acid fast staining of
M. tuberculosis
CELL WALL
Gram positive cell wall
 Consists of




a thick, homogenous
sheath of peptidoglycan
20-80 nm thick
tightly bound acidic
polysaccharides,
including teichoic acid
and lipoteichoic acid
cell membrane
Retain crystal violet and
stain purple
Gram negative cell wall
 Consists of





an outer membrane
containing
lipopolysaccharide (LPS)
thin shell of
peptidoglycan
periplasmic space
inner membrane
Lose crystal violet and
stain pink from safranin
counterstain
11
Gram Positive
Gram Negative
12
The Gram Stain
Gram's
iodine
Crystal
violet
Decolorise with
acetone
Gram-positives
appear purple
Counterstain with
e.g. methyl red
Gram-negatives
13
appear pink
Gram-positive cocci
Gram-positive rods
Gram-negative cocci
Gram-negative rods
15
Metabolic Phenotypic Exam

cultural approaches
 required for positive diagnosis of infection
 isolation and ID of pathogen
 accuracy, reliability, and speed

methods used include
 culture characteristics
 biochemical reactions process
Serological Testing
Phenotypic Exam
 serological
testing
uses ELISA testing

fast and easy to use
Classification of bacteria
Classification of medically significant bacteria

I.Thick rigid walled cells
A. Free living extracellular
1.Gram positive
a.Cocci
Staphylococcus - abcess
Streptococcus - puemonia,
Pharyngitis cellulitis
b.Spore forming rods
Aerobic
Bacillus - Anthrax
Anaerobic
Clostridium - tetanus,gas gangrene
botulism
c.Non spore forming rods
(GRAM POSTIVE CONTD)
1-Non filamentous Cornybacterium – Diphtheria
Listeria - meningitis
2.Filamentous
Actinomycetes – Actinomycosis
Nocardia - Nocardiosis

2.Gram negative
A.Cocci
Neisseria -Gonorrhoea,
meningitis
B.Rods
1.Facultative
a. Straight
1.Respiratory org. Haemophillus- meningitis
Bordatella-Whooping cough
Legionella- Pneumonia
2.Zoonotic
Brucella – Brucallosis
Francisella –Tularemia
Pasteurella –Cellulitis
Yersinia - Plague

3.enteric & related
(GRAM NEGATIVE CONTD)
E.coli - UTI,Diarrhoea
Enterobacter – UTI
Serratia – Pneumonia
Klebsiella – Pneumonia.UTI
Salmonella – enterocolitis,typhoid fever
Shigella – Enterocolitis
Proteus – UTI
b. Curved
Campylobacter – Entericolitis
helicobacter – Gastritis,Peptic ulcer
Vibrio - Cholera


C.Aerobic
D. Anaerobic
(Gram negative)
Pseudomonas – pneumonia,UTI
Bacteroids – peritonitis
3.ACID FAST
MYCOBACTERIUM - Tuberculosis & Leprosy

B . Non free living obligate intracellular
parasites
1.Rickettsia – Rocky mountain spotted fever
Typhus, Q fever
2.Chlamydia urethritis, trachoma. Psittacosis
Flexible thin walled
Spirochaetes -
Treponema – Syphilis
Borrelia – Lyme disease
Leptospira - leptospirosis
Wall- less cells
Mycoplasma
-
pneumonia
Subtyping & Its applications
 To distinguishinguish between strains of different
species
 Biotyping
 Serotyping
 Antimicrobial susceptibility system
 Bacteriophage typing
 Bacteriocin typing
Genotypic Characteristics for Identifying
Prokaryotes

the use of genotypic testing has increased with
the availability of technology

genotypic testing is particularly useful in the
case of organisms that are difficult to identify

several techniques include
 gene probes
 PCR
 sequencing rRNA

gene probes


single stranded DNA that has been labeled
with a identifiable tag, such as a fluorescent
dye
are complementary to target nucleotide
sequences
• unique in DNA of pathogen
Genotypic Characteristics used in
Classifying Prokaryotes( non culture methods)


PCR: polymerase chain reaction
 used to detect small amounts of DNA present in a
sample (blood, food, soil)
 the PCR chain reaction is used to amplify the
amount of DNA present
sequencing ribosomal RNA
 of particular use for identifying prokaryotes
impossible to grow in a culture
 focus is place on the 16S molecules of the RNA
because of it’s size
• approximately 1500 nucleotides
 once the 16S molecule is sequenced, it can then be
compared to the sequences of known organisms
Genotypic Characteristics used in
Classifying Prokaryotes




comparison of nucleotide sequences
 differences in DNA sequence can assist in
determination of divergence of evolutionary path
for organisms
DNA hybridization
 single strands of DNA anneal
16S ribonucleic acid
 comparing sequence of ribosomal RNA
relatedness to other organisms can be determined
using numerical taxonomy
 determined by the percentage of characteristics
two organisms have in common