5.5 - Bacterial Cells Flashcards
Shape of a bacillus
A rod
Shape of a coccus
A ball
Shape of a vibrio
A small curved rod
Shape of a spirochete
A long curved rod
Shape of a coccobacillus
A “choder,” aka a plump rod
What does strepto mean?
Straight chain
What does staphylo mean?
Cluster
What does diplo mean?
Two
What are the minimum requirements for a bacterial cell?
1) Nucleoid
2) Ribosome
3) Cytoplasm
4) Cytoplasmic Membrane
What are distinguishing features of a Gram Positive envelope?
Techoic acids
Thick layer of peptidoglycan
Plasma Membrane
What are distinguishing features of a Gram Negative envelope?
Outer Membrane containing LPS and porins
Thin layer of peptidoglycan
Periplasmic space
Plasma Membrane
Features and function of teichoic acids
Glycerol phosphate polymers
Ribitol phosphate polymers
Create stability and a negative charge
What are lipoteichoic acids?
Teichoic acids that stretch from the cell wall to the plasma membrane
Features and function of peptidoglycan
Also called “cell wall” or “murein”
Made up of a NAM-NAG disaccharide
Crosslinked with Amino Acids
Creates stability and shape
Features and function of the Outer Membrane
Only found on Gram Negative envelopes
Super hydrophilic permeability barrier
Major factor in resistance
Features of LPS (lipopolysaccharides)
Found in the outer membrane
Made up of O-Antigen and Lipid A
Features and function of Lipid A
Heat stable
Low concentrations are good for the immune system
High concentrations activate complement system
High concentrations are toxic and induce endotoxic shock
What is Gram Negative shock?
Also called endotoxic shock or septic shock, it is the result of abnormally high concentrations of Lipid A in the body
What are porins?
Pores found on the Outer Membrane that allow hydrophilic molecules into the bacterial cell
What are three of the “special” types of bacteria?
Mycoplasma
Chlamydia
Mycobacterium
What are the features of Mycoplasma?
"Pleomorphic" (No cell wall) Contains sterols in cell membrane Found in the GU tract Resistant to penicillin and cephalosporins One of the smallest prokaryotes
What are the features of Chlamydia?
Very thin cell wall, so thin most people say it isn't present Susceptible to penicillin Gram negative under stain Obligate intracellular bacteria Cannot synthesize ATP
What are the features of Mycobacterium?
Acid-fast
Contains an outer layer of mycolic acids that are hydrophobic
Resistant to drying and disinfectants
Mycolic acids act as MAMPs for the immune system
What are mycolic acids?
Fatty acids found on the outside of Mycobacterium that act as MAMPs for the immune system. These fatty acids are extremely hydrophobic, contributing to a waxy layer around the cell that does not allow many things in
Outline the steps of the Gram Staining method
Fixation -> Crystal Violet -> Iodine -> Decolorization -> Counterstain with Safranin
What colors are associated with each step of the gram staining method?
Fixation (Both Clear) Crystal Violet (Both purple) Iodine (Both purple) Decolorization (Gr+ purple, Gr clear) Couterstain with Safranin (Gr+ purple, Gr- pink)
Outline the steps of the Ziehl-Neelsen acid-fast staining method
Carbol Fuchsin -> Acid Alcohol Decolorizer -> Counterstain Malachite Green or Methylene Blue
What colors are associated with each step of the acid-fast staining method?
Carbol Fuchsin (Both pink)
Acid Alcohol Decolorizer (AF pink, Non acid-fast clear)
Counterstain Malachite Green or Methylene Blue (AF pink, Non acid fast blue)
What are the four “accessories” of bacteria?
Capsules
Endospores
Flagella
Fimbriae (Pili)
What are the properties of a capsule?
Consists of polysaccharides
Protects bacteria from dessication and environment
Antiphagocytic
What is an example of a bacterium with a very large capsule?
Streptococcus pneumoniae
Outline the steps needed to stain a capsule
Negatively charged bacteria -> Acidic dyes repel negative ions -> Background stain is used -> Stain cells w/ simple stain
What are the properties of endospores?
Found on some Gram Positive rods Dormant Extremely resistant Contains Calcium Diplicotinate in its core Location is species dependent
What are some examples of bacteria that form endospores?
Bacillus spp.
Clostridium spp.
What is the function of Calcium Diplicotinate?
It stabilizes DNA
Outline the steps needed to stain an endospore
Fixed smear flooded w/ Malachite green -> Heated for 5 minutes -> Washed -> Counterstained w/ safranin
What are the properties of flagella?
Made up of protein
Amino Acid sequence in each one varies
Moves using chemotaxis
What is endoflagella?
Axial filaments within an envelope that aid in movement
They are found in spirochetes
How are flagella able to be seen under a viewing medium?
They are thickened using multiple coats of mordant that contain tannic acid or potassium alum
What are the properties of Fimbriae?
Also called Pili
Attach to cells via adhesins
Contain the protein pilin as a subunit
What is the function of sex pili?
Sex pili are used to exchange genetic information from cell to cell. These are longer than normal pili.
