Classification, identification of bacteria of medical importance Flashcards
What is microbiology?
The study of microscopic organisms
Name the two scientist who came up with the germ theory of disease
Louis pasteur and Heinrich Hermann Robert Koch
Name the three types of microorganisms
- Eukaryotes
- Prokaryotes
- Viruses
Name the most abundant micro organism on earth
Bacteria
Name the two types of bacterial cell structure
Gram positive
Gram Negative
Describe the structure of gram negative bacteria
They have a thin cell wall surrounded by a phospholipid membrane
How do we study bacteria
We need to isolate them in a pure culture
Can all bacteria be cultured
No as we can’t re create the environment for some bacteria to grow
State different initial characteristics we look at when studying bacteria
- Colony morphology
2. Cell morphology
What can we look at when studying bacterial colony morphology
1, Shape
- Haemolysis
- Pigment
Name the 3 categories we can put bacteria in when looking at haemolysis
- Alpha haemolysis
- Beta haemolysis
- Gamma haemolysis
What is alpha haemolysis?
A partial or “green” hemolysis associated with reduction of red cell hemoglobin.
What is beta haemolysis?
complete lysis of red cells in the media around and under the colonies: the area appears lightened (yellow) and transparent
What can we look at when studying bacterial cell morphology
- Shape
- Spores
- Gram stains
How do we carry out gram staining
- Fixation : isolate a colony and place it on a glass slide
- Flood the surface of the glass slide with Crystal violet
- Rinse
- Flood the surface of the glass slide with Iodine
- Gram negative will Decolourise and the gram positive will turn purple
- Counter stain to identify gram negative
Following a Gram staining what colour will gram positive bacteria be?
Purple/ violet
Following a Gram staining what colour will gram negative bacteria be?
Pink
List differential characteristics we can look at when studying bacteria
- Metabolic activities
- Antigens
- Cellular composition
- DNA
How do we describe a bacterias metabolic activities?
- Fermentations
- Gas or gas production
- Enzymes
- utilisation of carbohydrates and proteins
Name some Molecular techniques we can use to look at bacterial DNA
- PCR
- Nucleic acid sequences
- Homology
- Probes
Name different tests we use to classify bacteria
- The Ziehl-Neelsen stain
- Catalase test
- Coagulase test
What is another name for the Ziehl-Neelsen stain ?
The acid fast stain