Classification

Classification of Classification of MicrobesMicrobes

What are Microbes?What are Microbes? A microbe is any living thing that spends its A microbe is any living thing that spends its

life at a size visible sometimes only with a life at a size visible sometimes only with a microscope. microscope.

It is too tiny to be seen with the naked eye. It is too tiny to be seen with the naked eye. Microbes are the oldest form of life on Earth. Microbes are the oldest form of life on Earth.

The term microbe is short for microorganism, The term microbe is short for microorganism, which means small organism. which means small organism.

To help people understand the different types To help people understand the different types of microbes, they are grouped or classified in of microbes, they are grouped or classified in various ways. various ways.

Microbes are very diverse and represent all Microbes are very diverse and represent all the great kingdoms of life. the great kingdoms of life.

Prokaryotes Prokaryotes (Bacteria)(Bacteria)

EubacterEubacter "True" bacteria "True" bacteria Human pathogensHuman pathogens Clinical or environmentalClinical or environmental One kingdomOne kingdom

ArchaeaArchaea Environmental organisms Environmental organisms Second kingdom Second kingdom

EukaryotesEukaryotes

Other cell-based life e.g.Other cell-based life e.g. PlantsPlants AnimalsAnimals Fungi Fungi

Prokaryotic vs. Prokaryotic vs. Eukaryotic CellsEukaryotic Cells

Prokaryotic cellsProkaryotic cells No NucleusNo Nucleus No OrganellesNo Organelles Cell Wall of Cell Wall of

peptidoglycanpeptidoglycan Binary FissionBinary Fission 1 circular 1 circular

chromosomechromosome

Eukaryotic CellsEukaryotic Cells NucleusNucleus OrganellesOrganelles If cell wall, If cell wall,

Cellulose or chitinCellulose or chitin MitosisMitosis Linear Linear

chromosomeschromosomes

Here is an outline of the major Here is an outline of the major groups of microorganisms: groups of microorganisms:

VirusesViruses BacteriaBacteria AlgaeAlgae FungiFungi ProtozoaProtozoa

BacteriaBacteria Bacteria consist of only one cell, but they're a very Bacteria consist of only one cell, but they're a very

complex group of living things. complex group of living things. Some bacteria can live in temperatures above the Some bacteria can live in temperatures above the

boiling point and in cold below the freezing point. boiling point and in cold below the freezing point. There are thousands of species of bacteria, but all There are thousands of species of bacteria, but all

of them are basically one of three different shapes. of them are basically one of three different shapes. Some are rod- or stick-shaped; others are shaped Some are rod- or stick-shaped; others are shaped

like little balls. like little balls. Others still are helical or spiral in shape. Others still are helical or spiral in shape. Some bacteria cells exist as individuals while Some bacteria cells exist as individuals while

others cluster together to form pairs, chains, others cluster together to form pairs, chains, squares or other groupings.squares or other groupings.

Classification of Microbes

Taxonomic Hierarchy For eg: Escherichia coli

Domain Bacteria

Kingdom Monera

Phylum Proteobacteria

Class Gammaproteobacteria

Order Enterobacteriales

Family Enterobacteriaceae

Genus Escherichia

Species E. coli

Classification of bacteriaClassification of bacteriaThere are several approaches to bacterial There are several approaches to bacterial

classificationclassification

A. A. Morphological classsificationMorphological classsification..Based on morphology bacteria are divided into Based on morphology bacteria are divided into various groupsvarious groups1. Filamentous or higher bacteria- Actinomycetes1. Filamentous or higher bacteria- Actinomycetes

2. True or lower bacteria2. True or lower bacteria I. Gram positive bacilliI. Gram positive bacilli

Aerobes- corynebacterium, bacillusAerobes- corynebacterium, bacillus Anaerobes-Clostridium, lactobacillusAnaerobes-Clostridium, lactobacillusII. Gram positive cocciII. Gram positive cocciIII. Gram negative cocciIII. Gram negative cocciIV. Gram negative bacilli or rodsIV. Gram negative bacilli or rods

Gram-positive rods

Gram-negative rods

Gram-positive cocci

Gram-negative cocci

V. coccobacilli- BrucellaV. coccobacilli- Brucella

3. Comma chaped- vibrios3. Comma chaped- vibrios

4. Spirochaetes- Borrelia, Treponema4. Spirochaetes- Borrelia, Treponema

5 . Mycoplasmas- Cell wall deficient5 . Mycoplasmas- Cell wall deficient

6 . Ricketsia and chlamydia- Obligate 6 . Ricketsia and chlamydia- Obligate parasitesparasites

B.Nutritional classificationB.Nutritional classificationI. Based on Energy requirementsI. Based on Energy requirementsPhototrophs: Derive energy from sunlightPhototrophs: Derive energy from sunlightChemotrophs: Use ChemicalsChemotrophs: Use Chemicals

II. Based on ability to synthesize II. Based on ability to synthesize essential metabolitesessential metabolitesAutotrophs: Synthesize organic coumpounds Autotrophs: Synthesize organic coumpounds from from carbon dioxide carbon dioxide and nitrogenand nitrogenHeterotrophs: Depend on preformed organic Heterotrophs: Depend on preformed organic

compounds eg compounds eg pathogenspathogens

III. Based on oxygen requirementsIII. Based on oxygen requirementsAerobesAerobesAnaerobesAnaerobes

Gram-positive cocci

AnaerobicGram-positive rods

AnaerobicGram-negative rods

AnaerobicGram-positive cocci

AnaerobicGram-negative cocci

IV. Based on temperatureIV. Based on temperature

Psychrophiles: Below 20°C Psychrophiles: Below 20°C

Mesophiles: 25-40°CMesophiles: 25-40°C

Thermophiles: 55-80°CThermophiles: 55-80°C

C . Biochemical classificationC . Biochemical classification:: LF LF NLF NLF LLFLLFProduction of Indole, H2S, Catalase, Oxidase, Production of Indole, H2S, Catalase, Oxidase,

Urease etcUrease etc

D. Classification based on D. Classification based on staining reactionstaining reaction::I. Based on Grams stainI. Based on Grams stain::

Gram positive bacteriaGram positive bacteria

Gram negative bacteriaGram negative bacteria

II. Based on acid fast stainII. Based on acid fast stain::

Acid fast bacilliAcid fast bacilli

Non acid fast bacilliNon acid fast bacilli

E. Serological/ antigenic E. Serological/ antigenic classificationclassification

Microorganism possess many different Microorganism possess many different kinds of antigens, based on which kinds of antigens, based on which they are classified intothey are classified into

I. Serovars or SerotypeI. Serovars or Serotype

II. Sero groups II. Sero groups

Major Taxonomic Groups of Bacteria per Bergey’s manual

Gracilicutes – gram-negative cell walls, thin-skinned

Firmicutes – gram-positive cell walls, thick skinned

Tenericutes – lack a cell wall & are soft

Mendosicutes – archaea, primitive procaryotes with unusual cell walls & nutritional habits

Assignment:Assignment: Find out what isFind out what is Bergey’s manual

in detail.