Intro To Microbiology + Bacterial Structures Flashcards
What are the major groups of microbes? + What is used to treat them?
- Bacteria = antibiotics
- Viruses and prions = antiviral drugs
- Fungi (yeasts & moulds) = anti fungal drugs
- Parasites (protozoa & helminths) = Antiprotozoal/helminths drugs
Arrange the microbes in size order largest to smallest
(largest)moulds>protozoa>yeasts>bacteria>viruses>prions (smallest)
What are the two sub divisions of microorganisms?
*cellular - mono + pluri
*acellular
What are examples of cellular microorganisms (prokaryote + eukaryotic)
monocellular - bacteria
pericellular - moulds
prokaryotic - bacteria
eukaryotic - protozoa, yeasts + moulds
What are examples of acellular microorganisms?
*viruses (made of protein + nucleic acid)
*prions (made of protein)
What does the bacteria entail?
*prokaryotes
*mostly unicellular/monocellular
What does fungi entail? (mycology)
*eukaryotes
*yeasts - unicellular
*moulds - pluricellular
What does parasites entail?
*eukaryotes
*protozoa - unicellular
*helminths - pluricellular
What does a virus/ its structure entail?
- 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
What are prions?+ what they entail
simpler infectious particles made up of only misfolded proteins (no nucleic acids)
What processes do microbes carry out that are essential for life on earth?
*waste decomposition
*food production (cheese, bread,beer)
*drugs/ enzyme synthesis (penicillin, insulin)
*molecule generation (vitamins)
*oxygen generation (photosynthesis)
*nitrogen fixation (N2 → NH3)
What are the different types of bacterial shapes + examples of bacteria (not essential for exam)
*round (coccus)
*rod (bacillus)
*curve rod (vibrio)
*oval (coccobacillus)
*rigid spiral (spirillum)
*spirochete
*pairs (diplococci + diplobacilli)
*clusters (staphylococci)
*chains (streptococci + streptobacilli)
*tetrads
What is the function and structure of the plasma membrane in bacteria?
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
What is the function, importance + composition of bacterial cell walls?
- 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-)
Peptidoglycan structure + formation
*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
What are bacterial transpeptidases responsible for?
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
What is the structure of Gram +ve cell wall?
a thick structure (multilayered) of peptidoglycan (20-35nm) providing strong structural support.
*NO outermsmbrane
What is the structure of the Gram -ve bacteria?
*cell wall is thinner than +ve (2-7nm)
*more complex
*more susceptible to mechanical breakage
*outermembrane
What are the differences between +ve and -ve cell wall?
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
What is the staining process and results for gram +ve and -ve?
*primary stain w crystal violet
*iodine treatment
*decolourisation
*counter stain with safranin
results = gram+ve is purple/violet
gram -ve is pink/ red
What is the structure of the glycocalyx + functions?
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
What are the components of the flagella?
filament: outermost region made of proteins
hook:connecting component
basal body: anchors flagellum to cell wall + cell membrane
What is the function of the flagellum?
Propel bacteria toward or away from nutrients
* Sensory structure detecting nutrients/chemicals by
chemoreceptors → CHEMIOTAXIS, or light
(PHOTOTAXIS)
What are the fimbriae? overview
- Thin hairlike appendages
- allow for attachment to other cells or surfaces
- Some types are involved in a twitching motility
What are the sex pili? + overview
- 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
