Lecture 4 Intro To Microbiology

Question 0

Define the following terms:
Genus
Species
Strain
Serotype

Answer 0

Genus: implies the existence of a group of organisms
Species: groups within genera. Species possess discrete but related characteristics.
Strain: subdivision of species describing specific properties.
Serotype: defined by antigenic properties

Question 1

Describe the 3-domain classification of organisms.

Answer 1

Studies in ribosomal RNA lead to the proposition that all organisms should be grouped into 1 of 3 domains:
ARCHAEA: archaebacteria (most primitive organisms)
BACTERIA: Eubacteria (true bacteria)
EUKARYA: contains the kingdoms Protista, fungi, plants and animals

Question 2

Describe PROKARYOTIC cells.

Answer 2

Simple, unicellular structure usually bound by a cell wall.
No nuclear membrane or discrete organelles.
Generally reproduce through binary fission.
Most have outer cell wall which provides the cell with shape and protection.
Nucleoid is region where DNA is concentrated.
May have plasmids
Inclusion bodies: nutrient reserves
May possess flagella for motility
Pili used for sexual conjugation
fibmbriae used in attachment to host cell
May have extra cellular layer: slime layer, glycocalyx or capsule.

Question 3

Describe EUKARYOTIC cells.

Answer 3

May be unicellular (yeasts, Protozoa, some algae), or multicellular (some algae, fungi, higher plants and animals).
Larger and more structurally complex than prokaryotic cells.
Have defined nucleus and organelles.
May reproduce sexually (formation of gametes by meiosis and subsequent fusion of gametes), or asexually (mitosis: Protozoa, some algae and fungi, growth in higher organisms).
Nucleolus: site of rRNA synthesis in nucleus
Centrioles: cytoplasmic structures involved in excel division
ER, ribosomes (structure differs to prokaryotic ribosomes), Golgi,

Question 4

Describe bacteria.

Answer 4

Prokaryotic cells which absorb nutrients and materials from the environment.
Highly adaptable, and capable of rapid reproduction (E. Coli has doubling time of 20 mins).
Many thousands of species, yet only relatively few cause disease in man.
Vast majority of bacteria are extra cellular parasites.
Three most common shapes are spherical, rod shaped and spiral.

Question 5

Describe viruses.

Answer 5

Acellular, obligate Intracellular parasites.
Important cause of disease in plants and animals.
Some can infect bacteria (bacteriophages).
Range in size and shape.
Can contain DNA or RNA.

Question 6

Describe Protozoa.

Answer 6

Unicellular prokaryotes.
Mainly aquatic organisms
Have visible organelles
Relatively few cause human disease.
May have cilia or flagella for movement
Have oral groove and anal pore

Question 7

Describe algae.

Answer 7

Mostly aquatic.
So not cause infectious disease in man, however algal blooms generate various toxins which become concentrated in fish and shellfish.
There is no treatment available for poisoning from contaminated seafood.

Question 8

Describe fungi.

Answer 8

Unicellular and multicellular fungi.
Possess cell wall.
Very few are pathogenic in man (yeasts and filamentous fungi).
Most mycoses are cutaneous.
Systemic mycoses are life threatening.

Question 9

Describe endoparasites.

Answer 9

Includes helminth worms (flatworms and roundworms).
Have microscopic stages in their life cycle and are usually classed as microbial diseases.
Most common in developing countries (poor hygiene and sanitation).

Question 10

Describe ectoparasites.

Answer 10

Includes fleas, ticks and lice.
Form a parasitic relationship on the outside surface of the human body.
Many act as vectors for micro organisms.

Question 11

Describe prions.

Answer 11

Appear to consist of only protein.
Prion protein innitiates a conformational change in the brain protein to cause disease.
Causes unusual neuro degenerative disorders called transmissible spongiform ecephalopathies.