Classification

Why do we classify or separate different organism into groups?

Aristotle suggested plant and animal Kingdoms.

Why did this system work in 375 BC?

Why doesn’t it work today?

Modern day taxonomy relies on molecular, structural and evolutionary characteristics.

Examples –

Binomial Nomenclature –Each organism is assigned a two word Latin name. Genus, species

Homo sapiens , Homo sapiens

Bacillus anthracis , Bacillus anthracis

Classifications of Microbes

Prokaryoteo Bacteria

o Archea

Eukaryoteo Planta

o Animalia

o Fungi

o Protista

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Kingdom Animalia

Eukaryotic Multicellular No cell wall Consumer (mouth) Typically motile Examples –

Kingdom Planta

Eukaryotic Typically mulitcellular, some unicellular and colonial Cell wall – made of cellulose Producer No movement Examples –

Kingdom Fungi

Eukaryotic Unicellular or multicellular Cell walls – chitin Non-motile Consumer (no mouth), dead feeder, parasite Examples –

Domain Protista

Eukaryotic Unicellular and colonial Two distinct groups

o Plant – like characteristics Green Algae

Diatoms

Euglena

Dinoflagellates

Brown and red algae

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o Animal – like characteristics Ameboids

Flagellates

Ciliates

Sporozoans (no movement)

Domain Bacteria

Prokaryotic

Cell walls, peptidoglycan

Unicellular, some colonial

Parasite, dead feeder

May be motile

Examples –

Domain Archea –

Prokaryote

Unicellular or colonial

Non-motile

No cell wall

Specialized producer

Examples –

How do we classify plants and animals?

How is bacterial classification different from that of plants and animals?

What characteristics do we use to classify bacteria?

Cell wall composition

Morphology

o Shape

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Coccus

Bacillus

Spiral (vibrio, spirillum)

o Arrangement of cells

Diplo-

Strepto-

Staphylo-

Differential staining

o Gram stain

o Endospore stain

Oxygen requirements

DNA base pair comparison = A/T vs. C/G

Biochemical tests – what kind of media will they grow on?

Eukaryotic cell structure

No cell walls

Membrane bound organelles

o Mitochondria

o Nucleus

o Centriole

o Endoplasmic Reticulum

RER

SER

o Golgi Body

o Vacuole

o Peroxisome

Non membrane bound organelles

o Ribosome

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Prokaryotic Cell Structure

Outside the cell wall

o Glycocalyx

Negative staining technique

Capsule

Slime layer

o Flagella

Gives motility towards food (chemotrophic),

light (phototropyic)

Monotrichous

Lophotrichous

Amphitrichous

Peritrichous

o Fimbrae – provide attachment, G- bacteria

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o Pili – used to share DNA segments, a form of sexual

reproduction

o Cell wall – responsible for cell shape, controls osmotic

movement.

Made up of several materials, depending on

species.

Peptidoglycan typical component

Some bacteria have lipid in their cell wall,

special cell wall staining techniques

Gram staining procedure

Adhere to clean, dry slide.

Air dry

Flame, twice

Crystal violet

Gram’s iodine

Alcohol

Safranin (a counterstain)

Gram positive cells

Gram negative cells

Inside the cell wall

o Plasma membrane

Selectively permeable membrane

Fluid mosaic model

Hydrophobic unit

Hydrophilic unit

Proteins

Glycoproteins

o Cytoplasm

Cytosol + organelles

o DNA – one single, circular DNA

How to “stick the bacteria to the slide”

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o Plasmid – small, circular DNA

Replicates independent of DNA

Small number of genes (<10)

Carries information unnecessary to daily life

o Ribosome

site of protein synthesis

composed of rRNA + proteins

o Inclusions – reserve storage (fat, lipids, etc.)

o Endospore – in bacteria they are formed in response to

environmental stress, lack of nutrients, never

reproductive structures, mostly in G+

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