Bacterial Structure and Function Flashcards
- It is formed when large amounts of EXTRACELLULAR POLYMERIC SUBSTANCES forms a condensed, well-defined layer closely surrounding the cell.
- Thicker, gummy consistency
- Prominently sticky (mucoid) character.
Capsule
- The EPS forms a LOOSE MESHWORK of fibrils extending outward from the cell.
- Slimy, gelatinous material.
- produced by the plasma membrane.
Glycocalyx
- The EPS appears to be TOTALLY DETACHED from the cell but in cell may be entrapped.
Slime Layer
A polymers of glucose and fructose that can be synthesized by the several strains of Streptococci
Polysaccharide
- A polysaccharide that may be complexed2 with various proteins.
- Some polypeptides occupies spaces produced by the polysaccharide frameworks.
Polysaccharide complexes
It produces capsules that are mixed polymers of glucose, galactose, and glucuronic acid
Streptococcus pneumonia
- Capsule that may consist of polypeptides of one or two amino acids.
Polypeptides
An organism that produces a capsule consisting of polyglutamic acid
Bacillus anthracis
- Capsules, glycocalyx, and slime layer are synthesized by..
An enzyme located at the surface of a bacterial cell wall
- Protects cell from phagocytosis, UNLESS they are coated with anti-capsular antibiotics.
- Prevents some viruses to attach at the bacterial cell walls (bacteriophage)
- Glycocalyx plays a major role in the adherence of bacteria to the surfaces in their environment.
Function of capsule
- The degree to which some organisms are able to cause disease.
Virulence
- Are not essential in terms of life of the bacteria, but makes survival longer due to its protective activity.
Capsule
- Stains used to visualize the capsules.
- India Ink
- Nigrosin
- Can be source for vaccines
Smooth and Mucoid culture appearance
Capsulated bacteria
Rough
Non-capsulated
To study the morphological shape, size, and arrangement of the bacterial cells that is difficult to stain
Purpose of negative staining
Used to stain cells that are too delicate to be heat fixed.
Negative staining
It is used to prepare sample for the electron microscopy
Negative staining
Used to view viruses, bacteria, flagella, biological membrane structures and protein aggregated which has low scattering power
Negative staining
It’s principle requires an acidic dye
Negative staining
Are acidic stain
- Nigrosin
- India Ink
- Nigrosin 100gm/L, Formalin 5ml/L in water
This means that the stain readily gives up a hydrogen ion (proton) and the chromophore of the dye becomes negatively charged.
Principle of negative staining
- Found beneath the capsule, lying between the cytoplasmic membrane and the capsule
Cell wall
Major structural component of the bacterial cell
Cell wall
Rigid and non-elastic but highly DUCTILE, high TENSILE strength structure
Cell wall
Contains pores 1nm in diameter which allows diffusion of metabolites to the plasma membrane
Cell wall
Also known as murcin and mucopeptide , which is a layer of high tensile strength.
Peptidoglycan
It allows the differentiation of 2 distinct types of bacteria
Peptidoglycan
The 2 distinct differentiation of bacteria
Gram positive and Gram negative
The outer most component of the cell wall of a bacterium, and can be found in both gram positive and gram negative bacteria
Slime layer
- A lattice made up of protein or glycoprotein molecules.
- Believed to protect the cell wall from
1. Wall degrading enzymes
2. Invasion by predatory bacteria
3. Bacteriphages
Slime layer
- A complex polymer consisting of 3 parts
1. Backbone - has alternating sugars
2. Set of identical tetrapeptide
3. Set of identical tetrapeptide cross bridges - A backbone for all bacterial species, however the the tetrapeptide side chain and peptide cross bridges varies from species to species
Peptidoglycan layer
Position 1 : L-alanine
Position 2 : D-glutamate
Position 4 : D-alanine
Position 3 : most variable
The common tetrapeptide chain
An acid that carries in a gram negative bacteria
Diaminopimelic acid
As many as 40 sheets of sheets of peptidoglycan comprising up to 50-90% of the cell wall materials (10-20% of the total dry weight of the cell)
Gram Positive Bacteria
Only 1-2% comprising 5-10% of the wall material
Gram Negative Bacteria
- A water soluble polymer, containing ribitol or glycerol residues joined through PHOSPHODIETHER LINKAGES
- Believed to be covalently linked to sugar
Teichoic acid
Composed of …
- Neutral sugars, mannose, arabinose, and rhamnose.
- Acidic sugar, glucoronic acid and mannuronic acid.
Polysaccharide
