Structure & Functions of Bacterial Components Flashcards
Label the structure
A. Lipid A: embedded within the membrane and is released after cell death
B. Core oligosaccharide: similar among species and is essential for LPS structure and bacteria viability
C. O antigen: can bind to antibody or antigen (antigenic) and is variable among species or strains
Define Primary Pathogen
can cause disease in a host regardless of host’s resident microbiota or immune system
What are structures found inside the cell wall of the bacteria?
- plasma membrane
- nuclear region & plasmids
- ribosomes
- endospores
What is the role of teichoic and mycolic acid and where are they found?
- teichoic acid: repeating subunits of sugar-phosphate molecules that act as important surface antigens
- mycolic acid: produced by Mycobacterium and is a waxy layer surrounding the cell that resists environmental stress and provides a barrier against many antibiotics
What is the function of the bacterial cell wall?
protects against osmotic pressure changes and other environmental stresses
What is the primary structure of the cell wall and how can it be degraded?
- peptidoglycan
- degraded by lysozymes (can be found in human tears / mucous)
Characteristics of the capsule in bacteria
- very sticky (made of polysaccharides and/or polypeptides)
- tightly attached
- highly organised
- major virulence
- antiphagocytic
Characteristics of the slime layer
- very sticky (made of polysaccharides and/or polypeptides)
- loosely attached to cell wall
- involved in dental decay (Streptococcus mutans)
- biofilm
Function of the flagella
- induces movcement of the bacteria via rotary (spinning) of the flagella
: anti-clockwise (run)
: clockwise (random- tumble)
- movement is directional (towards chemoattractant / away from chemorepellent)
4 types of flagella
- monotrichous: 1 flagella
- amphitrichous: 2 flagella (1 on each side)
- lophotrichous: 2+ flagella on the same end
- peritrichous: entire cell surrounded
Label the image
Endotoxins are a characteristic of what type of bacteria and why?
- characteristic of Gram-negative bacteria
- endotoxins are lipopolysaccharides (LPS) and these are found only within the outer cell membrane (which only Gram-negative bacteria have)
What are structures found outside the bacterial cell wall?
- flagella
- fimbriae & pilli
- glycocalyx (capsule & slime layer)
Function of the slime layer in bacteria?
- prevents dessication
What are fimbriae & pilli made of?
- pillin proteins
Explain how penicillin is expected to work against some bacteria?
Penicillin is a beta-lactam drug containing PBPs and a beta-lactam ring. This beta-lactam ring is expected to cleave to sites on the NAG-NAM chain to dissallow pentapeptide chains to link other NAG-NAM chains together. If the drug succeeds in doing this, the peptidoglycan layers will be unable to form
Define Pathogen
microorganism capable of causing disease in a susceptible host
What are endospores and what are their functions?
How are they formed and where are they mostly found?
- endospores are a defense mechanism formed in response to environmental stress and lack of nutrients
- it protects against dessication, heat, toxic chemicals, antibiotics, UV light, etc.
- formed via sporulation
- mostly found in Gram-positive bacteria
4 types of pathogens
- bacteria 2. virus 3. fungi 4. parasite
What are plasmids in bacteria and what are their functions?
- extrachromosomal pieces of DNA
- carry genes for toxins, antibiotic resistance, etc. that are able to be transferred between cells via pilli during conjugation
What is the peptidoglycan layer made up of?
- NAM (N-acetyl muramic acid)
- NAG (N-acetyl glucosamine)
- peptide chain links
How does beta-lactamse work against beta-lactam drugs?
Beta-lactamase enzymes cleave to the beta-lactam ring found within the beta-lactam drug and break the ring open via hydrolysis so that the ring will not be able to stop the peptidoglycan layer from forming
Function of the capsule on bacteria?
- prevents dessication (drying)
Example of Opportunistic Pathogen
Streptococci normally found in the URT, but if in the blood can cause endocarditis
Label the image
Define Secondary Pathogen
normally harmless but can cause disease when introduced to a foreign location or in immunocompromised hosts
Which bacteria has an outer cell membrane and what is the use of this structure?
- Gram-negative
- outer cell membrane has porins for transport and contains lipopolysaccharides which are an endotoxin
How can the Gram-positive cell wall be distinguished?
- thick peptidoglycan layer with only an inner cell membrane
- presence of teichoic and mycolic acid
- the cell wall stains purple with Gram-stain (excl. Myobacterium which does not retain crystal violet but is considered Gram-positive due to the lack of an outer cell membrane)
Which bacteria are fimbriae & pilli found on?
- fimbriae are found on some Gram-positive and Gram-negative bacteria
- pilli are found only on some Gram-negative bacteria
What are the additional components found within Gram-positive bacteria?
- teichoic acid: repeating subunits of sugar-phosphate molecules
- myocolic acid: produced by Mycobacterium and is a waxy lipid around the cell used as protection from environmental stress and against manny antibiotics
What is vancomycin?
Vancomycin is prescribed to patients that have resistance to pencillin. It’s a drug that interferes with the peptidoglycan cell wall synthesis by disrupting the bonds between the NAM and NAG
What are the major targets of antibacterial drugs and why?
- proteins and RNA of ribosomes in prokaryotes, as the the ribosomes are different in comparison to eukaryotes
Which bacteria has a periplasmic space and what is the use of this structure?
- Gram-negetive bacteria
- contains beta-lactamase enzymes which cleave beta-lactam drugs (i.e. penicillin, cephalosporins)
- contain protein translocation systems for transportation of substances out of the cell
Function of fimbriae & pilli
- adherence
- transfer of genetic material
Function of plasma membrane
- electron transport, energy production
- transport of nutrients, waste
- shape, cell division
How can the Gram-negative cell wall be distinguished?
- thin layer of peptidoglycan surrounded by an inner and outer cell membrane
- presence of a periplasmic space
- stains pink/red with a Gram-stain
Label the image
How does the peptidoglycan layer appear within Gram-positive and Gram-negative bacteria?
- Gram-positive: thick peptidoglycan layer
- Gram-negative: thin peptidoglycan layer
What is the glycocalyx composed of?
- capsule
- slime layer
Additional components found within Gram-negative bacteria?
- outer cell membrane: porins & LPS
- periplasmic space: beta-lactam enzymes & protein translocation systems
Chromosomes of bacteria are found where?
nucleioid (as they have no nucleus)
