intro to microbiology

• what are the general properties of micro-organisms?

  • microscopic dimensions (micrometer)
  • ubiquitous - they’re everywhere
  • independent growth and survival - find their own nutrients, some can survive with minimal amenities
  • exist as single cells/cell clusters or consortia(mixing with other microorganisms)
• what significant developments have been made in microbiology?

  • microscopy - visualise
  • sterilisation - elimination of all viable micro-organisms
  • pure culture methods - grow organism in isolation (in the absence of other microorganisms)
  • vaccines - to prevent infection
  • antiseptics/antibiotics
  • antiseptic good for surface materials e.g contact lenses
• whats the definition of microbiology?

  the study of microorganisms, a large and diverse group of microscopic organisms, too small to be seen by the naked eye
• what are the characterisation methods that are able to characterise bacteria?

  • get a pure culture
  • specific staining techniques - to identify key components
  • electron microscopy (TEM & SEM)
• what is TEM?

  Transmission Electron Microscopy - cutting through the cell and looking at the layers
• what is SEM

  scanning electron microscope - looking the outer layers of the microorganism - the surfaces important cause its the surface that interacts with the surrounding environment 
• what are the two basic cell types?

  prokaryotic and eukaryotic
• what organisms have eukaryotic cells?

  Plants, animals, fungi, and protozoa
• what organisms have prokaryotic cells?

  Bacteria and blue green algae
• the basic cell shape - 0.12-5um :

  the most common shape is rod shaped

  A) rod

  B) cocci

  C) ovoid

  D) spirillum

  E) stalked

  
• morphology - unless something chemical affects the organisms the shape of the bacteria will stay the same - rods will stay rods, cocci will stay cocci
• cell arrangements of prokaryotic cells

  A) diploccocci

  B) tetrads

  C) clusters

  D) chains

  E) clumps

  
• prokaryotic cell ultrastructure

  A) slime

  B) capsule

  C) fimbriae

  D) pili

  E) flagella

  F) ribosomes

  G) plasmid

  H) DNA

  I) cell membrane

  J) cell wall

  K) mesosome

  
• what ultrastructure are found in all bacteria?

  mesosome, cell wall, cell membrane, DNA, plasmid, ribosomes
• whats the function of bacterial cell walls?

  • determines cell shape
  • rigid
  • mechanical strength
  • metabolically inert
  • allows entry and exit of materials
• what is the composition of bacterial cell walls?

  made up of:

  • carbohydrates:
  • N-Acetylmuramic Acid (NAM)
  • N-Acetylglucosamine (NAG)
  • peptide chains
  • together the peptide chains give the macromolecule - peptidoglycan
  • they cross-link to give a rigid cell wall
• what is a Gram stain?

  This test differentiates bacteria:

  There are two distinct groups and is reflected by the cell wall structure

  • gram-positive = purple stain
  • gram-negative= red stain
• bacterial cell surface...

  • we can see the difference of the cell wall structure of the bacteria through a TEM (transmission electron micrograph)-
  • cell membrane same as eukaryotic - this is where bacteria produces its energy
  • has not internal membrane bound structures
• what does the cell surface of gram-positive bacteria look like?

  Thick peptidoglycan layer - it makes up about 70% of the cell wall

  Lipoteichoic acids anchor in the cell membrane and extend into the peptidoglycan layer - helps hold the peptidoglycan together so they don't fly off

  
• what does the cell surface of gram-negative bacteria look like?

  Has an outer membrane - contains lipopolysaccharides

  Thin peptidoglycan - thinner nature makes it more susceptible to certain antibiotics

  Periplasm - gel like substance - contains enzymes, transport proteins etc

  Has porins - they from channels that allow the passage of ions, nutrients and other small molecules

  Lipoproteins - helps hold the peptidoglycan

  
• what do Lipopolysaccharides (LPS) consist of?

  Lipid A, a core polysaccharide and an O antigen
• what are the unique components of LPS?

  Lipid A is an endotoxin (very toxic) and contributes to the pathogenicity of gram-negative bacteria

  in the core:

  • Keto-deoxyoctonic Acid (KDO) - can assay fro this to see iff present or not + only found in bacteria
  • amino sugars

  O-antigen:

  • dideoxy sugars (e.g. abequose) - each gram-negative bacteria will have a unique structure of these sugars
  • helps identify different strains of bacteria
• what are the common physiological features of bacteria?

  • fimbriae
  • flagellae
  • pili
• what are fimbriae?

  Fimbriae are small, finger-like projections on the surface of some bacteria that help them attach to surfaces or other cells.

  • proteinaceous
  • attachment - allows cells to stick
  • variable size
  • unique to bacteria
• what are flagellae?

  • proteinaceous, helical
  • mortilty
  • number + distribution vary
  • those without flagella rely on the turbulence of the surroundings
• what are pili?

  • proteinaceous
  • genetic exchange
  • 1-2 per cell
  • unique to bacteria
• whats the morphology of bacterial exopolysaccharides (EPS)

  • can be a slime
  • or a capsule
• whats the function of Bacterial exopolysaccharides (EPS)?

  • protect the cell e.g from antibiotics
  • avoid desiccation due to high water content - survive a bit longer in dry environments
• examples of Bacterial exopolysaccharides (EPS)

  • dextran
  • alginate
• whats the composition of Bacterial exopolysaccharides (EPS)?

  • 98% water
  • 2% carbohydrate
  • sugars
  • uronic acids - gives it a negative charge
  • mucoid - bacteria that produce slime - the slime makes the bacteria larger so harder to get engulfed
  • non-mucoid - does not produce any slime
• what is fungi?

  • are eukaryotes, >10micrometers
  • there are 2 major groups
  • yeasts
  • moulds (filamentous, mycelial)
  • can survive in terrestrial (plant matter, soil) and aquatic habitats
  • causative agents of infection, contamination, degradation
  • ubiquitous (found everywhere)
• what are fungal cell wall like?

  • they differ to bacteria, but still serves to provide rigidity and structure - also depends on the class of fungi
  • made of: mannoproteins, chitin and glucans
  • membrane is comparable to higher eukaryotes but does not contain cholesterol, it contains ergosterol - that can become a selective target
• describe yeast?

  • they are spherical, oval or cylindrical in shape, 3-30 micrometers in size
  • dimorphic - exists in two different forms
  • asexual reproduction in yeast involves either:
  • Fission - grows and splits into two cells over time
  • Budding - e.g. Candida albicans
• describe mould?

  • consist of branched, thread like filaments called hyphae, often below surfaces
  • form a mycelium (tissue like aggregation)
  • multinucleate (multiple nuclei)
  • can reproduce via asexual (exospore/conidia release) for visa sexual reproduction
• properties of viral particles?

  • they are not living so are referred to as particles - acellular
  • small (20-200nm)
  • requires a host - (bacteriophage if bacterial host)
  • variety of shapes
  • no biological machinery
  • no protein synthesis
  • no ATP generation
  • genetic information carried with ss/ds DNA or RNA
• what does the viral structure comprise of?

  • nucleic acid core - can have genetic material of RNA (double or single) or DNA (double or single)
  • capsid (capsomeres) - made of capsular units
• what are the two geometric forms of viral particles?

  Helical and icosahedral (13 sided)
• some viral particles have an envelope or tails - derived from the host cell structure
• what is the sequence of viral replication?

  1. Attachment (adsorption)
  2. Penetration (injection) - genetic material of viral enters host cell
  3. Synthesis of nucleic acid and protein - using the host cells machinery
  4. Assembly and packing - newly synthesised viral components form complete particles
  5. Release (lysis) - new virions released/some can be released without causing immediate death (budding)