Intro To Microbiology + Bacterial Structures

Question 1

What are the major groups of microbes? + What is used to treat them?

Answer 1

• Bacteria = antibiotics
• Viruses and prions = antiviral drugs
• Fungi (yeasts & moulds) = anti fungal drugs
• Parasites (protozoa & helminths) = Antiprotozoal/helminths drugs

Question 2

Arrange the microbes in size order largest to smallest

Answer 2

(largest)moulds>protozoa>yeasts>bacteria>viruses>prions (smallest)

Question 3

What are the two sub divisions of microorganisms?

Answer 3

*cellular - mono + pluri
*acellular

Question 4

What are examples of cellular microorganisms (prokaryote + eukaryotic)

Answer 4

monocellular - bacteria
pericellular - moulds
prokaryotic - bacteria
eukaryotic - protozoa, yeasts + moulds

Question 5

What are examples of acellular microorganisms?

Answer 5

*viruses (made of protein + nucleic acid)
*prions (made of protein)

Question 6

What does the bacteria entail?

Answer 6

*prokaryotes
*mostly unicellular/monocellular

Question 7

What does fungi entail? (mycology)

Answer 7

*eukaryotes
*yeasts - unicellular
*moulds - pluricellular

Question 8

What does parasites entail?

Answer 8

*eukaryotes
*protozoa - unicellular
*helminths - pluricellular

Question 9

What does a virus/ its structure entail?

Answer 9

• Acellular (Not constituted by cells)
• Small infectious particles consist of nucleic acid
  surrounded by a protective coat of protein(s)
• May contain an addition lipid coat (envelope)
• They do not divide
• They need to infect a cell to replicate (produce viral
  progenies) – requiring cellular machinery

Question 10

What are prions?+ what they entail

Answer 10

simpler infectious particles made up of only misfolded proteins (no nucleic acids)

Question 11

What processes do microbes carry out that are essential for life on earth?

Answer 11

*waste decomposition
*food production (cheese, bread,beer)
*drugs/ enzyme synthesis (penicillin, insulin)
*molecule generation (vitamins)
*oxygen generation (photosynthesis)
*nitrogen fixation (N2 → NH3)

Question 12

What are the different types of bacterial shapes + examples of bacteria (not essential for exam)

Answer 12

*round (coccus)
*rod (bacillus)
*curve rod (vibrio)
*oval (coccobacillus)
*rigid spiral (spirillum)
*spirochete
*pairs (diplococci + diplobacilli)
*clusters (staphylococci)
*chains (streptococci + streptobacilli)
*tetrads

Question 13

What is the function and structure of the plasma membrane in bacteria?

Answer 13

Differences:
 Lacks sterols (e.g. cholesterol of human cells)
 Contains hopanoids, providing stability
* Confers selective permeability → Controls movements of molecules across the cells
* Membrane proteins have specialised functions (enzymatic, signalling, etc)
* Contains infoldings (mesosomes)→ sites for DNA
replication and cellular respiration in prokaryotes

Question 14

What is the function, importance + composition of bacterial cell walls?

Answer 14

• Maintain bacterial cell integrity and shape
• Prevents the cell from bursting when water flows into the cell by osmosis
• Can contribute to pathogenicity (ability to cause disease)
• Only a few bacteria do not posses cell walls (e.g. mycoplasma – atypical bacteria)
• Target of many antibiotics (anti-bacterial drugs)
• Structural difference between these two groups
  (Gram+ and Gram-)

Question 15

Peptidoglycan structure + formation

Answer 15

*rigid, made up of linear chains:
-Nacetylglucosamine (NAG)
-Nacetylmuramic acid (NAM) attached to 5 amino acids
arrangement = NAG TO NAM with peptide cross link bridges between tetrapeptides of peptidoglycan strands

Question 16

What are bacterial transpeptidases responsible for?

Answer 16

Bacterial transpeptidases are responsible for cross-bridge links (direct covalent bonds
or indirect via a short peptide bridge) of NAM peptides of different peptidoglycan chains

-will be targeted by antibiotics

Question 17

What is the structure of Gram +ve cell wall?

Answer 17

a thick structure (multilayered) of peptidoglycan (20-35nm) providing strong structural support.
*NO outermsmbrane

Question 18

What is the structure of the Gram -ve bacteria?

Answer 18

*cell wall is thinner than +ve (2-7nm)
*more complex
*more susceptible to mechanical breakage
*outermembrane

Question 19

What are the differences between +ve and -ve cell wall?

Answer 19

GRAM +VE = (staphylococcus + strep)
* Thick peptidoglycan
* Teichoic acids
* Thin periplasmic space
GRAM -VE = (e.coli, helicobacter, pseudomonas)
* Thin peptidoglycan
* Outer membrane (containing
LPS, lipoproteins, porins)
* Larger periplasmic space

Question 20

What is the staining process and results for gram +ve and -ve?

Answer 20

*primary stain w crystal violet
*iodine treatment
*decolourisation
*counter stain with safranin
results = gram+ve is purple/violet
gram -ve is pink/ red

Question 21

What is the structure of the glycocalyx + functions?

Answer 21

 Capsule: if thick, well organised and firmly attached to the cell
 Slime layer: if thin, unorganised and loosely associated
functions:
* Confer pathogenicity (only capsule)
* Prevent phagocytosis by phagocytes
* Avoid desiccation by preventing water loss
* Aid in attachment to surfaces

Question 22

What are the components of the flagella?

Answer 22

filament: outermost region made of proteins
hook:connecting component
basal body: anchors flagellum to cell wall + cell membrane

Question 23

What is the function of the flagellum?

Answer 23

Propel bacteria toward or away from nutrients
* Sensory structure detecting nutrients/chemicals by
chemoreceptors → CHEMIOTAXIS, or light
(PHOTOTAXIS)

Question 24

What are the fimbriae? overview

Answer 24

• Thin hairlike appendages
• allow for attachment to other cells or surfaces
• Some types are involved in a twitching motility

Question 25

What are the sex pili? + overview

Answer 25

• Hair-like tubular structure
• Are involved in plasmid DNA transfer from one
  cell possessing sex pili (DONOR) to another one
  possessing specific receptors (RECIPIENT)
• Sex pili attachment forms a conjugation channel →
  source of drug resistance to antibiotics