ANSWERS

1. What is meant by microbiology?
   Microbiology is defined as the study of microscopic living organisms (microorganisms) and their effect on living cells. Examples of microorganisms include bacteria, viruses and protozoa. The name is derived from the Greek: mikros (small), bios (life) and logos (science).
2. What is immunology?
   Immunology is the study of the body's defence mechanisms against foreign
   material and "non-self" invasion.
3. What is a microorganism?
   An organism which is too small to be seen with the naked eye, and therefore requires microscopic examination.
4. What is another name for a microorganism?
   A microbe.
5. What units are frequently used to measure the size of microorganisms?
   Micrometer (micron) or nanometer (used to measure the size of very tiny viruses).
6. What is the name given to the system of naming microorganisms?
   The binomial system. This consists of 2 names: the generic name and the specific name. The generic name indicates the genus to which the organism belongs, whilst the specific name indicates the species.
7. Briefly describe the following: bacterium and virus.
   • Bacterium = (pl. bacteria), a general name given to a group of single celled microorganisms which thrive on organic matter. Bacteria lack a distinct nucleus and most have a rigid cell wall or capsule which is associated with virulence (a measure of the power of a pathogen to cause disease) and protects the organism against phagocytes.
   • Virus = an infectious agent characterised by its simple organisation and unique method of replication. Viruses were originally distinguished by their smallness and inability to replicate outside of a living host cell. They contain either DNA or RNA and are surrounded by a protein coat (or in some cases, a membranous envelope).
8. List 6 differences between bacteria and viruses.
   • Bacteria are larger than viruses.
   • Bacteria are unicellular, whilst viruses are non-cellular.
   • Bacteria reproduce asexually by binary fission, whilst viruses replicate only within another living cell.
   • Bacteria derive their nutrition by various means, whilst viruses are obligate parasites.
   • Bacteria contain both DNA and RNA, whilst viruses contain either DNA or RNA.
   • Some bacteria are able to produce toxins, but viruses cannot.
9. What is a parasite? Describe the main difference between endo- and ectoparasites.
   Parasites obtain their nutrients from another living organism known as the host. Endoparasites live within the host, whilst ectoparasites live on the surface of the host.
10. What is a saprophyte?
    A free-living group of bacteria which feed from dead or decaying organic matter.
11. What is a pathogen?
    A disease causing microorganism.
12. List the 4 main ways in which a pathogen causes infectious disease.
    • Gaining entry into the host.
    • Establishing itself and replicating within the tissues of the host.
    • Overcoming the body defences of the host.
    • Causing damage to the host in some way.
13. What is meant by symbiosis?
    Symbiosis literally means "living together". It describes any close, permanent association between different organisms be they beneficial or harmful.
14. What is meant by mutualistic?
    Parasitic associations of actual benefit to both host and parasite.
15. What is a commensal?
    A microorganism leading a parasitic existence which neither harms nor benefits the host.
16. What are opportunists?
    Parasites which will cause disease if the natural body defence systems are breached or weakened. Escherichia coli is an example. Opportunists are also known as potential pathogens.
17. In addition to bacteria, viruses and fungi; what other microorganism may be pathogenic?
    Protozoa.
18. Can you give 2 examples of protozoa? What disease might each cause?
    • Coccidia - coccidiosis.
    • Toxoplasma - toxoplasmosis/visceral larval migrans.
19. The rickettsias are a group of obligate intracellular organisms that are smaller than bacteria. What is the name of the rickettsia organism associated with feline infectious anaemia?
    Haemobartonella felis.
20. What is the name of the stain used to detect the presence of haemobartonella felis?
    Giemsa.
21. Can you name the 2 groups of microorganisms which may be either unicellular or multicellular?
    • Algae.
    • Fungi.
22. What are toxins, and which group of microorganisms employ them in order to cause infectious disease?
    Poisonous substances secreted by some microorganisms which disrupt specific physiological processes in the host by damaging cells and tissues.
23. What are the 2 types of toxin recognised?
    • Endotoxins = these are manufactured by living microorganisms and released into the surrounding medium.
    • Exotoxins = these are part of the microorganism and are liberated only once the microorganism dies.
24. What is meant by virulence?
    The degree of pathogenicity possessed by a microorganism.
25. How is the virulence of a microorganism enhanced?
    • The capsule surrounding the cell wall aids in the prevention of phagocytosis.
    • Pili provide better adhesion to the surface of host cell.