Bacterial Structures

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Information about Bacterial Structures
Education

Published on November 4, 2008

Author: ElysiaButler

Source: slideshare.net

Description

NZQA Unit 8024 - Demonstrate knowledge of bacterial structures

Unit 8024 Demonstrate knowledge of Bacterial Structure By Elysia Butler

Cell Wall The cell wall of a gram negative bacteria (E.coli) is generally thinner than the cell wall of a gram positive bacteria ( S.aureus)

The cell wall of a gram negative bacteria (E.coli) is generally thinner than the cell wall of a gram positive bacteria ( S.aureus)

Gram Positive Structure Peptidoglycan Cell Wall Cytoplasm Cytoplasmic Membrane Cell Section Enlargement = Within the peptidoglycan stand are teichoic acids and polysaccharides

Gram Negative Structure Cell Wall Cytoplasm Cytoplasmic Membrane Peptidoglycan Outer Membrane Section Enlargement = Cell The outer membrane contains Porin trimers, O antigens and Lipopolysaccharides. There is also a space between the Cytoplasmic Membrane and the Outer Membrane which is known as the Periplasmic Space

Peptidoglycan The Peptidoglycan layer within a cell wall is made up of amino sugars; NAG = N-acetylglucosamine NAM = N acetylmuramic acid Glycosidic bonds link the alternating sugars together. Attached to each NAM is an amino acid chain.

The Peptidoglycan layer within a cell wall is made up of amino sugars;

NAG = N-acetylglucosamine

NAM = N acetylmuramic acid

Glycosidic bonds link the alternating sugars together.

Attached to each NAM is an amino acid chain.

Peptidoglycan Composition Gram Positive (Specific to S.aureus ) Gram Negative (Specific to E.coli) L-alanine D-glutamine L-lysine D-alanine L-alanine D-glutamine L-lysine D-alanine Glycosidic Bond L-alanine D-glutamine Meso-Diaminopimelic acid D-alanine D-alanine D-glutamine L-alanine Glycosidic Bond Meso-Diaminopimelic acid NAM NAG NAM NAM NAM NAG NAG NAG

Gram Positive (Specific to S.aureus )

Gram Negative (Specific to E.coli)

Lipopolysaccharide A Lipopolysaccharide is a Polysaccharide (complex Carbohydrate) joined to a lipid (fat) by the way of a covalent bond (electron sharing) Only Gram negative bacteria contain Lipopolysaccharides. Because of the Lipopolysaccharides, gram-negative bacteria are generally more toxic, more protected from their hosts defence systems, and more resistant to antibiotics than gram positive bacteria.

A Lipopolysaccharide is a Polysaccharide (complex Carbohydrate) joined to a lipid (fat) by the way of a covalent bond (electron sharing)

Only Gram negative bacteria contain Lipopolysaccharides.

Because of the Lipopolysaccharides, gram-negative bacteria are generally more toxic, more protected from their hosts defence systems, and more resistant to antibiotics than gram positive bacteria.

Gram Stain Steps Cells are heat fixed to a microscope slide and then stained to help determine whether a bacterium is either gram negative or gram positive. Crystal Violet (a purple dye) is applied Iodine (a mordant) to set the dye to the cell is applied Ethanol (a decoloriser) is applied Safranin (a counter stain) is applied

Cells are heat fixed to a microscope slide and then stained to help determine whether a bacterium is either gram negative or gram positive.

Crystal Violet (a purple dye) is applied

Iodine (a mordant) to set the dye to the cell is applied

Ethanol (a decoloriser) is applied

Safranin (a counter stain) is applied

Gram Negative Stain Gram negative bacteria have an outer membrane containing lipids. These lipids are dissolved by the ethanol It is now easier for molecules to enter and exit the cell membrane. This enables the crystal violet and iodine complex to be washed away.

Gram negative bacteria have an outer membrane containing lipids.

These lipids are dissolved by the ethanol

It is now easier for molecules to enter and exit the cell membrane.

This enables the crystal violet and iodine complex to be washed away.

Gram Negative Outcome Gram Negative bacterium will stain pink To the left is a photograph of E.coli taken using a light microscope.

Gram Negative bacterium will stain pink

To the left is a photograph of E.coli taken using a light microscope.

Gram Positive Stain Gram positive do not have a lipid containing outer membrane. Therefore the ethanol can be directly absorbed by the peptidoglycan. The ethanol causes the peptidoglycan to dry out and shrink. This shrinking action traps the crystal violet and iodine complex Above is a theory of how the gram positive stain works

Gram positive do not have a lipid containing outer membrane.

Therefore the ethanol can be directly absorbed by the peptidoglycan.

The ethanol causes the peptidoglycan to dry out and shrink.

This shrinking action traps the crystal violet and iodine complex

Gram Positive Outcome Gram Positive bacterium will stain purple To the right is a photograph of S.aureus taken using a light microscope

Gram Positive bacterium will stain purple

To the right is a photograph of S.aureus taken using a light microscope

Nucleic acid All bacteria contain nucleic acid (joined nucleotides) DNA (deoxyribonucleic acid) is a type of nucleic acid. It is responsible for carrying all the hereditary material DNA is made up of nucleotides A nitrogenous base A pentose sugar A phosphate group

All bacteria contain nucleic acid (joined nucleotides)

DNA (deoxyribonucleic acid) is a type of nucleic acid. It is responsible for carrying all the hereditary material

DNA is made up of nucleotides

A nitrogenous base

A pentose sugar

A phosphate group

Cytoplasmic Membrane Made up of Proteins and Phospholipids Polar ends face out Non-polar ends face in Controls what enters and exits the cell Cytoplasmic Membrane Polar end of Phospholipid Non-Polar end of Phospholipid Protein

Made up of Proteins and Phospholipids

Polar ends face out

Non-polar ends face in

Controls what enters and exits the cell

Endospores Only present in some Gram-positive bacteria Form when environmental conditions are un-favourable For example Lack of nutrients Temperature change

Only present in some Gram-positive bacteria

Form when environmental conditions are un-favourable

For example

Lack of nutrients

Temperature change

Dormancy Predictive - When endospores form before environmental conditions become un-favourable Consequential - When endospores form when conditions begin to become un-favourable

Predictive - When endospores form before environmental conditions become un-favourable

Consequential - When endospores form when conditions begin to become un-favourable

Endospore Resistance Resistant to heat, drying and some toxic chemicals eg some disinfectants Gets rid of water when forming Contains dipicolic acid which is not found in a vegetative cell Is non-metabolic in this form Formed through a process called sporulation

Resistant to heat, drying and some toxic chemicals eg some disinfectants

Gets rid of water when forming

Contains dipicolic acid which is not found in a vegetative cell

Is non-metabolic in this form

Formed through a process called sporulation

Endospore Diagram Cortex is thick peptidoglycan which removes water, may be a factor that leads to heat resistance Spore coat is impermeable leading to chemical resistance Exosporium Spore Coat Cortex Cytoplasmic Membranne Nucleoid Note: Diagram is not drawn to scale

Cortex is thick peptidoglycan which removes water, may be a factor that leads to heat resistance

Spore coat is impermeable leading to chemical resistance

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