Intro to Bacteriology Flashcards
What are the components of the cell wall (out to in).. What is special about gram-neg bacteria
- Outer membrane (gram-neg only)
- Peptidoglycan
- Periplasm (gram-neg only)
- Plasma membrane
What are some functions of the cell wall?
- Protection against osmotic damage
- Helps in cell division
- Holds shape of bacterial cell
- Hold target site for antibiotics, lysozymes, bacteriophages
Why are drugs that target the cell wall synthesis useful?
Cell wall is essential for bacteria’s integrity
What is the peptidoglycan layer composed of? (3)
- alternating strands of N-acetylglucosamine + N-acetylmuramic acid
- a set of tetrapeptide side chains attached to the muramic acid
- a set of identical peptide cross bridges
What consists of the gram positive cell wall? (2)
- lipoteichoic acid
- wall techoic acid
(major surface antigens)
Which type of bacteria has higher antibiotic resistance (gram neg/positive)? Why?
Gram negative
- has an outer membrane (only in gram-neg)
- large antibiotic molecules penetrate the outer membrane slowly
What does the outer membrane of gram-neg contain? (2)
Lipopolysaccharide
- LPS will still cause immunoresponse even after bacteria is dead –> must filter out LPS
Porins
- permit passive diffusion flow of low weight, hydrophilic compounds
What is bacteria with defective cell wall called in gram neg/pos
Gram-neg: Spheroplasts
Gram-pos: Protoplasts
What is the gram staining procedure?
Explain which bacteria cells get affected and which don’t
- Apply crystal violet dye
- Apply iodine
- binds crystal violet –> forms large complexes –> trapped in cell - Alcohol wash
- gram positive will hold crystal violet due to thick peptidoglycan layer
- gram negative will wash away crystal violet due to thin peptidoglycan layer - Apply Safranin
- will stain gram-NEG only
- gram-pos have no space for stain
Define L-forms
Differentiate between unstable and stable L-forms
L-forms:
- when cell wall is removed but the bacteria can still grow and divide
Unstable: will revert back to having a cell wall when stimulus (penicillin) removed
Stable: Will not revert back to normal form
What are some functions of the cytoplasmic membrane
- Permeability and transport
- Biosynthetic functions
- Electron transport & oxidative phosphorylation
- Chemotactic systems
What are the 2 distinct areas in the cytoplasm called? What is it composed onf?
- Amorphous matrix:
- contains ribosomes, nutrient granules, plasmids - Inner nucleoid region
- composed of DNA
What do nucleoids in the cytoplasm used for?
Used for prokaryotes to package DNA
Which part of the cytoplasm add bacteria properties such as toxigenicity and drug resistance
Plasmid
- replicate independently
What are functions of Glycocalyx (capsule/slime layer) (3)
- ADHERENCE of bacteria to human tissues (needed for causing infection)
- Enhances bacterial virulence
- Helps form biofilm
What do the different arrangements of flagella mean?
Peritrichous
Monotrichous
Lophotrichous
Amphitrichous
Peritrichous: numerous flagella all over bacteria
Monotrichous: single polar flagella
Lophotrichous: collection of flagella at one end
Amphitrichous: flagella at both poles of the cell
Explain role of pili and fimbriae? Which bacteria is it mainly found in?
Fimbriae (short appendages)
- adherence
- biofilm formation
Pili
- Adherence
- twitching and gliding motility
- Conjugation “sex” pili (transfer of DNA from one cell to another)
Mainly in gram-NEGATIVE bacteria
Endospores (resistant/non resistant) to what? why? Which bacteria is it found in?
ONLY in gram-POSITIVE
Endospores are highly resistant to boiling, heating, disinfectants
- due to low water content, low metabolic activity, high conc. of calcium
Explain the process of germination in endospores? What are the 3 stages?
Endopsore transformation into a vegetative (parent) cell under suitable conditions
3 stages: activation, initiation, and outgrowth
When are pilli formed?
Formed in advance of an unfavourable environment.
- Endospore is very resistant: the parent bacteria could die in bad environment, but endospore will survive
- After good environment is restored, endospore can come out of dormancy and form new parent cell
Differentiate between autotrophs and heterotrophs
Autotrophs:
- synthesize their own essential metabolites from CO2 and Nitrogen
- Ex. Cyanobacteria
Heterotroph
- requires preformed organic compounds
- Cannot synthesize their own metabolites
What are the oxygen requirements for the following terms? Give example of each
Obligate aerobes
Obligate anaerobes
Facultative anaerobes
Aerotolerant anaerobes
Microaerophiles
Obligate aerobes
- aerobic respiration
eg. Pseudomonas aeruginosa (gram-neg)
Bacillus (gram-positive)
Obligate anaerobes
- growth inhibited by oxygen (can’t use it)
eg. Clostridium
Facultative anaerobes
- Able to live with/without oxygen
eg. E coli (gram-neg)
Staphylococci (gram-pos)
Aerotolerant anaerobes
- do not use oxygen, have enzymes that detoxify oxygen’s poisonous forms
eg. Streptocossus mutans
Microaerophiles
- require oxygen @2-10%, limited ability to detoxify hydrogen peroxide/superoxide
eg. Helicobacter pylori
What do low temperatures effect on bacterial membrane?
Becomes rigid and fragile
What are the preferred pH for the following:
Neutrophils
Acidophiles
Alkaliphiles
Neutrophils: pH 6-8
Acidophiles: pH <4
Alkaliphiles: up to pH 11.5
