LAB 7 - Isolation of Endospore Forming Bacteria from Soil Flashcards
What is the ability of endospores to withstand heat and other adverse conditions due to
- Outer spore coat made up of dense proteins
- Extremely impermeable inner membrane
- The composition of the spore core
Composition of spore core
Has a low water content and high amounts of calcium-dipicolinic acid complexes, which preserve the structural integrity of core molecules such as DNA.
Genera that can produce endospores
- Bacillus (facultative anaerobes)
- Clostridium (strict anaerobes)
- Clostridiodies (strict anaerobes
Diseases caused by endospore forming bacteria
- Anthrax (Bacillus anthracis)
- Botulism (Clostridium botulinum)
- Gas gangrene (Clostridium perfringens)
- Tetanus (Clostridium tetani)
Endospore forming bacteria isolation
- Endospores can withstand pasteurisation (e.g. 80ºC for 20 mins), which is lethal to vegtative cells
- The use of pasteurisation can destroy all competing vegetative cells in the sample, leaving only endospores, which can then germinate into vegetative cells under the right conditions
2 different media used in experiment
- Peptone Yeast Extract Agar (General-purpose medium used for isolating organisms from environmental sources)
- Blood agar
Stains used in experiment
Gram stain and Schaeffer-Fulton spore stain
Did you detect any major differences between the types of colonies observed on the PYEA plates and the BA plates?
- Yes, PYEA plates are more general, so various types of colonies might appear.
- BA plates are more selective and nutrient-rich, possibly promoting growth of fastidious bacteria, leading to differences.
On the soil plates, did you observe Gram-negative organisms, Gram-positive organisms, or both?
Mainly gram positive endospore forming due to pasteurisation step that would’ve killed non endospore forming and gram negative bacteria
