MMB04 Bacterial Growth And Control Of Microbial Growth Flashcards
Where are microorganisms usually found on the body
On the skin and on mucous surfaces.
They should not be found on or in external organs, blood, lymph and nervous system
Are microorganisms usually pathogenic or benign
Most, but not all pathogens are benign
When are mammals exposed to microorganisms
Since mamas develop in a sterile environment, they are only exposed to microorganisms after birth from skin contact, feeding and being exposed to the environment
What is colonisation
When microorganisms begin to grow after gaining access to host tissues
Why are microorganisms important in gut health
They synthesise important vitamins like B12 and K. Some studies link a healthy gut micro biome to weight loss and mental health
How do microorganisms cause infections in mucus membranes
They may associate loosely to the mucus membrane
They may adhere strongly to the mucous and epithelial cells
They may invade deeper into the epithelial cells
What does infection mean
When a microorganisms is established and growing inside a host. This may not always be damaging to the host
What does disease mean
The damage caused to the host by the microorganisms
What is pathogenicity
The ability of a pathogen to inflict damage onto a host
What causes variation in pathogenicity
The identity of the pathogen
The susceptibility of the host
What is an opportunistic pathogen
A pathogen that only causes disease in the absence of the hosts normal resistance
What is virulence
The quantitive measure for a pathogenicity. It is the relative ability for the pathogen to cause disease
What are exotoxins
Toxic proteins released by the pathogen as it grows. They travel from the site of infection to distant areas
What are the three types of exotoxins
Cytolitic toxins
AB toxins
Superantigen toxins
What are cytolytic exotoxins
They degrade cytoplasmic membrane integrity possibly causing lysis
What are AB exotoxins
Made up of a B subunit and an A subunit. The B subunit binds to the cell membrane receptor which allows A to pass through the membrane and cause damage
What are superantigen exotoxins
They stimulate large numbers of immune cells resulting in swelling and inflammation
What are enterotoxins
Special exotoxins that that affect the small intestine
What are endotoxins
Lipoploysacharaides produced by most gram negative bacteria. They are not secreted and are only released when the cells lyse
What is LD50
The median lethal dose that can kill 50% of hosts infected
What is pasteurisation
A process of heat sterilisation invented by Louis Pasteur.
Kills many organisms, but not all so is not a method of sterilisation.
Heat sterilisation will not kill endopsores
What is autoclaving
Steam heating at 121 degrees C for 15mins at high pressure.
Kills all bacteria including endospores
Sterilises equipment
How does UV light kill bacteria
Leads to DNA modifications and breaks causing cell death
Used do disinfect surfaces, air and water
How does ionising radiation kill microorganisms
Generates electrons, hydroxyl radicals, hydride radicals which disrupt DNA, proteins and lipids
Used to sterilise equipment and food
How do membrane filters work
Made of polymers that create pores too small for bacteria and spores to pass through
Usually used to sterilise liquid in labs
