Lecture 2: Microbial Cell Structure and Function Part 1 Flashcards
Where do bacteria live?
Live in terrestrial and aquatic environments
How do bacteria reproduce?
Reproduce asexually via binary fission
- What is the size range for bacteria? 2. What is the “average” size?
- Size ranges from 0.3um (micrometers) to 100um 2. Average size is about 4um (size of E. coli)
- What is this genus?
- Is it a bacteria or a virus?
- What is unique about it/it’s energy source?
- Thiomargarita
- Bacteria
- It’s a chemolythotrope that uses sulfur for energy
- Some bacteria and many fungi form long filaments called?
- A network of these filaments is called?
- Hyphae
- Network of hyphae is called a mycelium
What is this?
****
Staphylococcus
What is this cell shape?
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Bacillus (rods), chains of rods are streptobacillus
What is this cell shape?
********
Streptococcus
What is this cell shape? Rigid or flexible?
*****
Sprillum, rigid
- What is this cell shape? ****
- What disease is this?
- Vibrio (Curved Rod)
- Cohlera
- What is this cell shape?
- Is it rigid or flexible?
- What disease does this cause?
- Spirochete
- Flexible
- Lyme’s Disease
- What cell shape is this?
- What is the genus? ******
- What is unique/challenging about this genus?
- Tetrads
- Genus = Deinococcus ****
- Radiation resistant
What are these cell shapes?
Pleomorphic
Some round, some fork shaped, can change shapes under various conditions
Mycoplasma is an example.
What is cytoplasm?
Substance inside of cell which includes chromosomes, ribosomes and inclusions. Mostly water and highly concentrated
__________ and ____________ occur within the cytoplasm of a bacterial cell?
Transcription
and
Translation
occur here in a bacterial cell
RNA polymerase does what?
Transcribes DNA to mRNA
Ribsomes do what?
These structures translate mRNA into protein
In Bacteria and Archaea, transcription and translation occur simutaneously or at different times?
Occur simutanesouly in bacteria and archea
What is the nucleoid?
Region containing chromosomes
What are some characteristics of nucleoids?
- closed, circular, DS DNA
- typically 1 per cell
- NOT membrane enclosed
- some bacteria have more than 1 chromosome
- some have linear chromosomes
What is a plasmid?
Small, closed ciricular loop of DNA
What are characteristics of plasmids?
- They exist and replicate independently of the chromosome
- May carry genes that confer advantage
- Conjugative plasmids
- R plasmids (R= resistance)
What are 4 purposes of the bacterial plasma membrane?
- Selectively permeable barrier
- Transport systems bring nutrients in
- Main site of energy production via the electron transport chain
- Signal transduction systems–sense and respond to environment
Plasma membranes of eukaryotic cells are stablilized by cholesterols called
Sterols
Bacterial cell membranes don’t have sterols, but have sterol like molecules
What are the serol-like (cholesterol) molecules in some bacterial cell membranes that help with stabilization?
Hopanoids
Despide the lipid bilayer (type of bonds, head and tails, other things inside)
Lipids have flexibile ester bonds
Lipids are amphipathic
Polar ends (OUTSIDE) hydrophilic
Non polar tails are hydrophobic
Various proteins can be found within the membrane
What’s the purpose of the bacterial cell wall and where is it?
Bacterial cell wall lies outside of the plasma membrane. The cell wall for Gram + bacteria is different than the cell wall for gram -
Functions
- Gives the bacterial cell shape
- Protection
- toxic substances
- osmotic lysis
*
How does osmosis affect bacterial cells? What can happen that’s bad?
What helps protect bacterial cells?
Cells are usually surrounded by relatively dilute solutions which means the concentration of a solute is greater inside the cell than out, so water is tempted to move in the cell.
The bacterial cell wall helps prevent osmotic lysis—-which is where osomosis causes the cell to burst due to the influx of water into the cell
What color do gram + cells stain?
What about gram -?
Gram + stain PURPLE :)
Gram - stain pink
Where is peptidoglycan found
Bacterial cell WALL
NOT in the membrane
Describe the structure of peptidoglycan:
- Sugars
- Proteins
- Peptidoglycan is an important component of cell walls in gram + and gram - cells.
- It has two alternating sugar groups that form a polysaccharide (NAG + NAM).
- The NAG and NAM sugars are connected by a B 1,4 glycosidic bond
- Coming off of the NAM are cross-linked peptides of alternating D and L amino acids
What is NAG?
N-acetylglucosamine
1 of the sugars in peptidoglycan
What is NAM?
N-acetylmuramic acid
One of the alternating sugars in peptidoglcan. The cross linked peptides come off of the NAM molecule
What type of bond connects NAG and NAM?
What enzyme breaks down that bond?
Connected by B 1,4 glycosidic bonds.
Lysozyme breaks down B 1,4 glycosidic bonds
Describe the combination of peptides in peptidoglycan:
What are the two ways to combine?
The peptides of peptidoglycan are cross-linked
There are 2 types of cross-linking: direct and indirect
What is the process that provides direct cross-linking of proteins within peptidoglycan?
Transpeptidation is the reaction where proteins in the peptidoglycan are cross linked
This provides strength
What is used for indirect cross linking of the proteins in peptidoglycan?
Indirect cross linking uses peptide interbridges
What is the structural feature found within the peptidoglycan of gram + cell walls?
Teichoic acid is polymers of glycerol or ribitol that provide stability in the peptidoglycan of gram POSITIVE cell walls
Which type of bacteria has an outer membrane?
What are 4 things found in the outer membrane?
Gram - bacterial have outer membranes
Lipids, proteins and LPS (lipopolysacchardies), porins are found in the outer membrane
What are porins?
proteins in the membrane that form channels for small molecules to go through
What type of cell is this?
What are the areas labelled?
Gram negative cell
What type of cell is this?
What are the areas that are crossed out?
What molecule is this?
What type of cell is it found in?
Where is it found in that cell?
What are the 3 components?
LPS: lipopolysaccharide found in the outer membrane of gram - bacteria
Comprised of the:
- O side chain
- Core polysaccharide
- Lipid A
What are 4 purposes of LPS?
- Protection from host defenses
- O antigens vary
- Attachment
- Stability
- Toxin
When LPS acts as a toxin, it is called what?
endotoxin
What are 3 types of layers that can be found outside of the cell wall for gram + and gram - bacteria as well as archaea?
- Capsules
- Slime layers
- S layers
What are capsules made from?
Describe them
Polysaccharides
Organized, not easily removed
What are slime layers made from?
Describe them
Polysaccharides
-Diffuse, unorganized, easily removed
What are S layers made from?
Describe them
Proteins!
Organized. Help with structure and stability
What do layers (S layers, capsules, and slime layers) help with?
- Attachment
- Protection from
- Chemicals
- Harsh environments
- Bacterial viruses (bacteriophages)
- Host immune response
- ie. slime layers made it hard for host cell macrophages to consume them
What bacteria is this?
Neisseria meningitidis
