Lecture 2. The Bacterial World Flashcards
What can microbes like other animals do ?
- Defend against predators
- Avoid parasites
- Adapt to harsh environments
- Find food
- Reproduce
What types of microbes are the most abundant ?
Unicellular organisms
What are some disadvantages to being multicellular ?
- Increased disease transmission
- Competition for resources
- Social exploitation
What states can microbes constantly flux between ?
Unicellular and multicellular states
Where are bacteria found ?
- Plants
- Animals
- Soil
- Water
- Artic ice
- Air
- Volcanic vents
What is the function of the pilus ?
Stick to mucosal cells
What is the function of the capsule ?
Causative agent of infection
What are the three features of a bacterial cell ?
- No mitochondria
- Ribosomes free in the cytoplasm or bound to the inner face of the cytoplasmic reticulum
- Single chromosome
What do bacterial cells lack that other cells may have ?
- Endoplasmic reticulum
- Nuclear membrane
- Mitochondria
What is the ribosome that bacterial cells have ?
70s
What is the 70s ribosome composed of ?
30S and 50S subunits
What is another name for multiple extracellular layers ?
Bacterial cell envelope
What is the function of the bacterial cell envelope ?
Help bacteria survive in inhospitable environments
What is the bacterial cell envelope made up of ?
The cell wall and associated membranes
What do gram positive cells have ?
- A thick cell wall
2. Plasma membrane
What do gram negative cells have ?
- Outer membrane
- Thin cell wall
- Periplasmic space
- Plasma membrane
What is the cell wall essential for ?
- Essential for structural integrity
2. Provides cell shape
What is the cell wall primarily composed of ?
Peptidoglycan
What is another name for peptidoglycan ?
Murein
What is peptidoglycan unique to ?
Bacteria
What does peptidoglycan provide to cells ?
Mechanical cells
What are some features of peptidoglycan ?
- Not a hard shell
- Flexible
- Elastic.
- Porous
What are glycan chains connected by ?
Peptide crosslinks
Why is the biosynthesis of peptidoglycan the target of anti-microbials ?
Disrupts cell walls which are essential structures
What is a glycan chain composed of ?
Individual sugars linked by B-1,4 glycosidic linkages
What are peptide cross links composed of ?
Amino acids
What is the most basic subunit of glycan chain ?
Peptidoglycan monomer
What are the two types of peptidoglycan monomers in a glycan chain ?
- N-acetyl muramic acid
2. N-acetyl glucosamine
What does N-acetyl muramic acid have in its structure ?
Lactic acid
What is the function of the peptide side chain ?
Allows 3D structures to form
What are glycan side chains formed by ?
Cross links between peptide side chains
What do cross links between peptide side chains provide ?
Strength
What is there in the structural details of peptidoglycan from different species ?
Variation
What is an example of the 5 amino acids in a peptide side chain and what position are they in ?
- L-alanine
- D-glutamate
- L-diaminopimelic acid
- D-alanine
- D-alanine
What amino acid are present in most species and what positions are they usually in ?
- L-alanine (1)
- D-glutamate (2)
- D-alanine (5)
What amino acid in the peptide side chain never varies and what position is it in ?
- D-alanine
2. Position 4
What position is the amino acid that varies in ?
Third position
What must the amino acid in third position have ?
A free amino acid group
What happens to the peptide chain when it joins to another one ?
It is turned upside down ie. position 1 is at the bottom
What does the position 3 amino acid bind to ?
Position 4
How does the amino acid in position 3 bind to the amino acid in position 4 ?
Direct cross link
What happens to the peptide side chain after two peptide chains join together by direct cross linkage ?
The 5th amino acid on both peptide side chains disappears
What type of linkage does gram negative bacteria have ?
Direct peptide cross links
What is a peptide cross bridge comprise of ?
A series of amino acids
What is the advantage of peptide cross bridge ?
Can attach things to it
What type of linkages do gram positive bacteria contain ?
Peptide cross bridge
What can disrupt cell walls ?
- Lysozyme
2. Penicillin/B-lactams
What do lysozyme do to disrupt the cell wall ?
Hydrolyses every second glycosidic bond
How does penicillin/ B-lactams do to disrupt the cell wall ?
Prevents linking two side chains together
