Lecture 3 Flashcards
What are the 2 main genus that form bacterial endospores and what is their shape, gram and where are they found
Bacillus and Clostridium. They are typically gram positive and rod shaped environmental bacteria
What are the steps of endospore formation
Starts off like normal binary fission, asymmetrical septum begins to form and DNA becomes more dense. The larger compartment then engulfs the smaller forming the forespore.
The cortex and coat then form and dehydration begins. Parent cell then degrades and lysis of the cell occurs releasing the endospore
What makes up the first structural area of an endospore and what is its main function
The core, inner membrane and the germ cell wall. This area contains all the normal cell structures just held in a metabolically inactive state
What makes up the second structural area of a endospore and what is its main functions
The cortex and the outer membrane. This area is a layered structure that surrounds the core, it’s made up of peptidoglycans with a lower number of cross linking compared to a normal vegetative cell so as to uphold the endospores high level of dehydration
What is the 3rd structural area of the endospore and what is its function
The coat, it surrounds the cortex, is made up of sometimes thick protein layers that makes the endospore impermeable and resistant to physical factors
What is the 4th and final structural area of the endospore and what is its function
The exosporium, it is the final coat surrounding the whole thing. Made up of a lipid carbohydrate protein coat
What are the physical aspects an endospore has that determines its resistance and what do they defend against
The thick layers of coats and the impermeable inner membrane, they defend against UV and chemicals
What are the chemical factors endospore cores have to determine resistance
Low water content, 15%(from the dehydration step), low pH, high Ca2+ content and dipicolinic acid. Small acid soluble proteins that alter confirmation of dna slightly
What are the chemical factors endospore cortex’s have to determine resistance
Decreased peptidoglycan cross linking index (2.9% compared to the 33% that is in normal vegetative cells) this is to maintain the dehydrated state of the cell therefore contributing to metabolic dormancy and heat resistance
Describe the steps of endospore germination and how long does the process take
Activation- preparation for germination
Germination- endospore swells and reverses dehydration, ruptures and loses all of its resistance, regaining all metabolic function
Outgrowth- Emerges from the coat and develops into a vegetative cell starting the process of binary fission again
All this happens in 15mins compared to the 8 hours it takes to form an endospore
Define the death of microorganisms
Loss of ability to multiply under any given condition
Describe sterilisation
Complete removal or destruction of all microorganisms from inanimate objects. Non-selective and is brought about by the use of physical and chemical control methods
Whats the difference between bactericidal and bacteriostatic
Cidal refers killing while static means to inhibit
What are the physical control methods
Moist heat, dry heat, filtration and radiation
What are the moist heat methods and do they achieve sterilisation
Autoclaving/pressurized steam-yes
boiling water-no
pasteurization-no unless UHT
What are the dry heat physical control methods and do they achieve sterilisation
Incineration-yes
Dry oven-yes
How does moist heat affect proteins
denatures vital molecules for the microbes survival
Describe the types of pasteurisation and what is the quality control
Batch(old version)-63 for 30mins
Flash(todays)71 for 15 seconds
UHT-140 for 1 second
for batch and flash quality control is 5x10^5 cells/ml
How does flaming and incineration kill cells
By oxidising the vital proteins within the cell
How does hot air ovens kill cells and what are the requirements to make that happen
By oxidising vital proteins in the cell. It takes 2 hours at 160c
