General Intro to Microbio/Microorganism, Struc & Func - M’s

• What are the 4 main classes of microorganisms?

  TSEs (transmissible spongiform encephalopathies)

  Viruses

  Bacteria

  Eukaryotic microbes: fungi & protozoa
• What are TSEs?

  'Infective' proteins that cause sponge-like lesions in the brain by abnormally folding proteins.

  
  

  Examples of this include Kuru, Scrapie, Creutzfeld-Jacob, etc.
• How can TSEs cause infections?

  TSE's are present in everyone. There are normally folded ones and abnormally folded ones which can form amylcid plaques causing destruction of cells.

  
  

  Abnormally folded proteins can cause conformational changes to normally folded proteins.

  
• How do bacteria, eukaryotes and viruses compare in size?

  Viruses tend to be the smallest, then bacteria are larger but eukaryotes are the largest
• How can you differentiate the different types of microbes?

  + = yes

  - = No

  
• What do viruses infect?

  Bacterial cells, plant cells & animal cells
• How can viruses be made visible and what does this suggest about their size?

  By an electron microscope, suggesting their size is from 10-200nm
• What is the basic viral structure?

  -Nucleic acid packaged in protein and the protein coat is either icosahedral (complex geometric shapes) or helical

  
  

  -Genome can either be DNA or RNA, single stranded or double stranded

  
  

  -Either naked or enveloped

  
• Describe the process of viral replication.

  -Contact/attachment with host cell

  -Entry to interior of cell

  -Releases genome into cell (usually into cytoplasm but can also be into nucleus)

  -Replicates the genome either in form of DNA or RNA using host cell's machinery

  -Assembly of new proteins that will form the new nucleocapsids

  -Will either bud off from the surface of the cell or produce such large numbers that the cell lyses

  
• What is reverse transcription integration?

  Viral genome is RNA and is then converted from RNA to DNA, reversing the transcription process & having done that, these viral genomes can then integrate into the host genome so they become part of it: provirus
• Describe bacterial structure.

  Some proteins can be integrated in the membrane

  Some bacterial cells have cell walls

  
• How do bacteria replicate?

  Binary fission
• What is the specific nomenclature used for naming bacteria?

  Genus & species name always in italics

  Genus name always has a capital letter

  Species name always has lower case letter

  Plural of the genus is lowercase, no italics
• By what criteria can you define bacteria?

  Shape & size

  Arrangement of growing bacteria

  Gram stain

  Culture requirements

  Biochemical reactions

  Antigenic structure

  Nucleic acid technologies
• What are the different shapes of bacteria and give examples?

  Rod-like structures: bacillie.g.E. coliRound spherical shape: coccie.g.S. aureusSpiral shape: spirochaetese.g.B. burgdorferiCurved, comma-type structures: curvede.g.V. cholerae

  
• What are the 2 common arrangements of cocci?

  Streptococci: individual cocci assemble in long chains

  
  

  Staphylococci: individual cocci arrange in groups and bunches

  
• How do you differentiate using Gram staining?

  One will stain purple (Gram +ve), one will stain red (Gram -ve)

  
  

  LPS= lipopolysaccharide, highly immunogenic

  
• How can you differentiate different bacteria by using colony characteristics?


  1. Haemolysis (are they haemolytic, what form of haemolysis do they trigger?)

  2. Surface texture (are they rough, are they smooth, do they look gelatinous, ruffled, solid?)

  3. Colony morphology & size (is it a single defined round colony, is it small, large?)

  4. Indicator dyes (do they produce indicator dyes when fed particular substrates?)

  5. Different nutrients (do they grow better on particular nutrients, or worse?)
• What is alpha haemolysis?

  Incomplete/partial:

  Agar immediately surrounding/beneath the colony appears darker, brown/greenish

  Result of oxidation of the haemoglobin and the destabilisation of the erythrocytes

  
• What is beta haemolysis?

  Complete:

  Area surrounding/beneath the colonies is light yellow/colourless as a result of the complete lysis of the erythrocytes

  Results from the action of pore-forming toxins

  
• What is gamma haemolysis?

  No haemolysis
• What 2 different things can you look at when looking at the biochemistry of an organism?

  Sugar fermentation profiles(if it ferments sugar, does it produce a gas, an acid, a base, does it cause particular changes in substrates?)

  Enzyme profiles(does it have a coagulase profile, an ability to digest a particular compound & release further substrates?)
• How can you define bacteria based on their antigenic structure?

  Base it on their specificity of their antibody-protein interactions.

  the proteins on bacteria surface are unique to that bacterium

  
  

  You can do this by agglutination
• How can you use agglutination to identify a bacteria type?

  Take the individual bacteria with their surface proteins, mix with RBCs (or other markings) which are coated in antibodies which recognise that particular protein.

  
  

  Mix the 2 together, the different bacteria will come into a large immune complex, mixing in with the different RBCs with multiple antibodies on them so you get a big cluster

  This means you'll see the RBCs going from being distributed evenly to large clumping

  
• What is typing an organism?

  Defining it based on a particular type
• What are the different ways of typing an organism?

  Serotyping using antisera

  Phage typing using phage (bacterial viruses) that recognise surface proteins

  Genetic typing using sequence properties of DNA
• How can you carry out genetic typing?

  Plasmid profiles

  Sequence analysis using RFLP

  Probes

  PCR
• How would you carry out a plasmid profile?

  Take 2 particular strains of bacteria, 1 of which has one plasmid (medium sized) and the other of which has a large plasmid & small plasmid

  Extract DNA from these & do gel electrophoresis on it which will give you different bands
• What is the difference between prokaryotic & eukaryotic cells?

  Fungi & protozoa are eukaryotic microbes

  
• What are the 2 different forms fungi can grow as?

  Yeasts:Grow as single cells but can be dimorphic (grow as single cells & as hyphae) e.g.Candida sppMoulds:Grow as hyphae (filamentous) only e.g.Aspergillus spp
• Describe the cell wall structure for a fungus.

  In cell membrane, fungus have ergosterol instead of cholesterol.

  -Chitin layer

  -Glucan layer (provide rigidity)

  -Mannoprotein at the top of cell wall which have high degree of carbohydrates.

  
• What are Koch's postulates?

  The bacteria must be present in every case of the disease

  The bacteria must be isolated from the host with the disease & grown in pure culture

  The specific disease must be reproduced when a pure culture of the bacteria is inoculated into a healthy susceptible host
• What are pathogenic bacteria?

  Bacteria that cause disease
• What are commensals/normal flora?

  Harmless, "good bacteria"

  Helps us by competitive exclusion(outcompeting pathogenic microbes), synthesis of nutrients etc.
• What are opportunistic bacteria?

  Pathobionts: normal commensal bacteria that can cause disease when found in the wrong place
• Describe a host parasite relationship.