Classification of bacteriaClassification of bacteria

DR.THAMINA SAYYEDDR.THAMINA SAYYED

REGISTRARREGISTRAR

MICROBIOLOGYMICROBIOLOGY

KKUHKKUH

Bacterial cellsBacterial cells

Classification SystemClassification System 3 Domains 1978 Carl Woese3 Domains 1978 Carl Woese

1. Bacteria 1. Bacteria • Unicellular prokaryotes with cell wall containing Unicellular prokaryotes with cell wall containing

peptidoglycanpeptidoglycan 2. Archaea2. Archaea

• Unicellular prokaryotes with no peptodoglycan Unicellular prokaryotes with no peptodoglycan in cell wallin cell wall

3.3. EukaryaEukarya• ProtistaProtista• FungiFungi• PlantaePlantae• AnimaliaAnimalia

Comparing Prokaryotic and Eukaryotic CellsComparing Prokaryotic and Eukaryotic Cells

Taxonomic Classification CategoriesTaxonomic Classification Categories

arranged in hierarchical orderarranged in hierarchical order species is basic unitspecies is basic unit

DomainDomainKingdomKingdom

Phylum or DivisionPhylum or DivisionClassClassOrderOrderFamilyFamilyGenusGenus

SpeciesSpecies

Prokaryote ClassificationProkaryote Classification

Technologies used to characterizeTechnologies used to characterize

and ID prokaryotesand ID prokaryotes microscopic examinationmicroscopic examination culture characteristicsculture characteristics biochemical testingbiochemical testing nucleic acid analysisnucleic acid analysis combination of the above is most accuratecombination of the above is most accurate

Phenotypic & Genotypic classificationPhenotypic & Genotypic classification

Phenotypic Characteristics for Identifying Phenotypic Characteristics for Identifying ProkaryotesProkaryotes

often does not require sophisticated often does not require sophisticated equipmentequipment

can easily be done anywherecan easily be done anywhere

Microscopic Phenotypic ExamMicroscopic Phenotypic Exam size and shape and arrangementsize and shape and arrangement

enough information for diagnosis of certain infectionsenough information for diagnosis of certain infections

Gram stainGram stain distinguishes between distinguishes between

Gram + and Gram – Gram + and Gram – bacteriabacteria

narrows the possibilities narrows the possibilities quicklyquickly

Microscopic Phenotypic ExamMicroscopic Phenotypic Exam

special stainspecial stain allows for the distinction of allows for the distinction of

microorganisms with unique microorganisms with unique characteristicscharacteristics• capsulecapsule• acid fast staining detects acid fast staining detects

the waxy presence of the waxy presence of Mycobacterium Mycobacterium tuberculosistuberculosis

Capsule staining

Acid fast staining of M. tuberculosis

CELL WALLCELL WALL

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Gram positive cell wallGram positive cell wall Consists of Consists of

a thick, homogenous a thick, homogenous sheath of peptidoglycan sheath of peptidoglycan 20-80 nm 20-80 nm thickthick

tightly bound acidic tightly bound acidic polysaccharides, polysaccharides, including including teichoic acid teichoic acid and lipoteichoic acidand lipoteichoic acid

cell membranecell membrane

Retain crystal violet and Retain crystal violet and stain purplestain purple

Gram negative cell wallGram negative cell wall Consists ofConsists of

an outer membrane an outer membrane containing containing lipopolysaccharide (LPS)lipopolysaccharide (LPS)

thin thin shell of shell of peptidoglycanpeptidoglycan

periplasmic spaceperiplasmic space inner membraneinner membrane

Lose crystal violet and Lose crystal violet and stain pink from safranin stain pink from safranin counterstaincounterstain

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Gram PositiveGram Positive Gram Negative

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Crystal violet

Gram's iodine

Decolorise with acetone

Counterstain withe.g. methyl red

Gram-positives appear purple

Gram-negatives appear pink

The Gram Stain

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Gram-positive rods

Gram-negative rods

Gram-positive cocci

Gram-negative cocci

Metabolic Phenotypic ExamMetabolic Phenotypic Exam cultural approachescultural approaches

required for positive diagnosis of infectionrequired for positive diagnosis of infection isolation and ID of pathogenisolation and ID of pathogen accuracy, reliability, and speedaccuracy, reliability, and speed

methods used includemethods used include culture characteristicsculture characteristics biochemical reactions processbiochemical reactions process

Serological Testing Serological Testing Phenotypic ExamPhenotypic Exam

serological testing serological testing uses ELISA testinguses ELISA testing fast and easy to usefast and easy to use

Classification of bacteriaClassification of bacteria

Classification of medically significant bacteriaClassification of medically significant bacteria

I.Thick rigid walled cellsI.Thick rigid walled cells

A. Free living extracellularA. Free living extracellular

1.Gram positive1.Gram positive

a.Cocci a.Cocci Staphylococcus - abcessStaphylococcus - abcess

Streptococcus - puemonia,Streptococcus - puemonia,

Pharyngitis cellulitisPharyngitis cellulitis

b.Spore forming rods b.Spore forming rods

Aerobic Bacillus - AnthraxAerobic Bacillus - Anthrax

Anaerobic Clostridium - tetanus,gas gangreneAnaerobic Clostridium - tetanus,gas gangrene

botulism botulism

c.Non spore forming rods (c.Non spore forming rods (GRAM POSTIVE GRAM POSTIVE CONTD)CONTD)

1-Non filamentous1-Non filamentous Cornybacterium – Diphtheria Cornybacterium – Diphtheria

Listeria - meningitisListeria - meningitis

2.Filamentous 2.Filamentous Actinomycetes – ActinomycosisActinomycetes – Actinomycosis

Nocardia - NocardiosisNocardia - Nocardiosis

2.Gram negative2.Gram negative A.Cocci A.Cocci Neisseria -Gonorrhoea,Neisseria -Gonorrhoea, meningitismeningitis B.Rods B.Rods 1.Facultative1.Facultative a. Straighta. Straight 1.Respiratory org. 1.Respiratory org. Haemophillus- meningitisHaemophillus- meningitis Bordatella-Whooping Bordatella-Whooping

coughcough Legionella- PneumoniaLegionella- Pneumonia

2.2.Zoonotic Zoonotic Brucella – Brucallosis Brucella – Brucallosis FrancisellaFrancisella – –TularemiaTularemia Pasteurella –CellulitisPasteurella –Cellulitis Yersinia - PlagueYersinia - Plague

3.enteric & related 3.enteric & related ((GRAM NEGATIVE CONTDGRAM NEGATIVE CONTD))

E.coli - UTI,DiarrhoeaE.coli - UTI,Diarrhoea

Enterobacter – UTIEnterobacter – UTI

Serratia – PneumoniaSerratia – Pneumonia

Klebsiella – Pneumonia.UTIKlebsiella – Pneumonia.UTI

Salmonella – enterocolitis,typhoid feverSalmonella – enterocolitis,typhoid fever

Shigella – EnterocolitisShigella – Enterocolitis

Proteus – UTIProteus – UTI

b. Curvedb. Curved

Campylobacter – EntericolitisCampylobacter – Entericolitis

helicobacter – Gastritis,Peptic ulcerhelicobacter – Gastritis,Peptic ulcer

Vibrio - CholeraVibrio - Cholera

(Gram negative) (Gram negative) C.Aerobic C.Aerobic Pseudomonas – pneumonia,UTIPseudomonas – pneumonia,UTI D. Anaerobic D. Anaerobic Bacteroids – peritonitisBacteroids – peritonitis

3.ACID FAST 3.ACID FAST MYCOBACTERIUM -MYCOBACTERIUM - Tuberculosis & Leprosy Tuberculosis & Leprosy

B . Non free living obligate intracellular B . Non free living obligate intracellular parasitesparasites

1.Rickettsia1.Rickettsia – Rocky mountain spotted fever – Rocky mountain spotted fever

Typhus, Q feverTyphus, Q fever

2.Chlamydia 2.Chlamydia urethritis, trachoma. Psittacosisurethritis, trachoma. Psittacosis

Flexible thin walledFlexible thin walled Spirochaetes -Spirochaetes - Treponema – Syphilis Treponema – Syphilis

Borrelia – Lyme diseaseBorrelia – Lyme disease

Leptospira - leptospirosisLeptospira - leptospirosis

Wall- less cellsWall- less cells Mycoplasma - Mycoplasma - pneumoniapneumonia

Subtyping & Its applicationsSubtyping & Its applications To distinguishinguish between strains of different To distinguishinguish between strains of different

speciesspecies BiotypingBiotyping SerotypingSerotyping Antimicrobial susceptibility systemAntimicrobial susceptibility system Bacteriophage typingBacteriophage typing Bacteriocin typingBacteriocin typing

Genotypic Characteristics for Identifying Genotypic Characteristics for Identifying ProkaryotesProkaryotes

the use of genotypic testing has increased with the use of genotypic testing has increased with the availability of technologythe availability of technology

genotypic testing is particularly useful in the genotypic testing is particularly useful in the case of organisms that are difficult to identifycase of organisms that are difficult to identify

several techniques includeseveral techniques include gene probesgene probes PCRPCR sequencing rRNAsequencing rRNA

gene probesgene probes single stranded DNA that has been labeled single stranded DNA that has been labeled

with a identifiable tag, such as a fluorescent with a identifiable tag, such as a fluorescent dyedye

are complementary to target nucleotide are complementary to target nucleotide sequencessequences

• unique in DNA of pathogenunique in DNA of pathogen

PCR: polymerase chain reactionPCR: polymerase chain reaction used to detect small amounts of DNA present in a used to detect small amounts of DNA present in a

sample (blood, food, soil)sample (blood, food, soil) the PCR chain reaction is used to amplify the the PCR chain reaction is used to amplify the

amount of DNA presentamount of DNA present

Genotypic Characteristics used inGenotypic Characteristics used in Classifying Prokaryotes( non culture methods) Classifying Prokaryotes( non culture methods)

sequencing ribosomal RNAsequencing ribosomal RNA of particular use for identifying prokaryotes of particular use for identifying prokaryotes

impossible to grow in a cultureimpossible to grow in a culture focus is place on the 16S molecules of the RNA focus is place on the 16S molecules of the RNA

because of it’s sizebecause of it’s size• approximately 1500 nucleotidesapproximately 1500 nucleotides

once the 16S molecule is sequenced, it can then be once the 16S molecule is sequenced, it can then be compared to the sequences of known organismscompared to the sequences of known organisms

Genotypic Characteristics used inGenotypic Characteristics used in Classifying Prokaryotes Classifying Prokaryotes

comparison of nucleotide sequencescomparison of nucleotide sequences differences in DNA sequence can assist in differences in DNA sequence can assist in

determination of divergence of evolutionary path determination of divergence of evolutionary path for organismsfor organisms

DNA hybridizationDNA hybridization single strands of DNA annealsingle strands of DNA anneal

16S ribonucleic acid16S ribonucleic acid comparing sequence of ribosomal RNAcomparing sequence of ribosomal RNA

relatedness to other organisms can be determined relatedness to other organisms can be determined using using numerical taxonomynumerical taxonomy determined by the percentage of characteristics determined by the percentage of characteristics

two organisms have in commontwo organisms have in common