Bacterial Cultivation, Preservation and Innactivation Flashcards
What is the process of bacterial reproduction?
Binary fission
What are the 4 growth cases of a bacteria?
Lag, exponential, stationary, decline
What occurs during the lag phase?
Metabolism to acquire essential constituents ready to divide
What happens during exponential phase?
binary fission causes exponential increase
What happens during the stationary phase?
Essential nutrients depleted and toxic metabolism products accumulate in media
What occurs during the decline phase?
Old cells die rapidly, followed by young
How can bacteria be quantified?
Microscopic counting, colony counting, opacity/ turbidity
What is a heterotroph?
bacteria that feed on pre-formed living organisms
What is an autotroph?
bacteria that use carbon dioxide
What needs to be considered for bacterial nutrition?
Large quantities of C and N, Peptones (protein) in culture media, phosphates for nucleic acid, sulphur for amino acids, Ca2+, Fe3+, Mg2+, K+
What are 3 microbial responses to nutritional deficiency?
Extracellular molecules collect nutrients, enter semi-starvation state, sporulation
What does a selective growth medium allow?
Can limit growth of unwanted microbes or growth of desired ones
What does differential growth media enable?
Enables differentiation between different microbes
What is a defined and complex medium?
Defined- known amounts of chemicals
Complex- unknown
What can influence bacterial growth?
Temp, Ph, Moisture, Atmosphere, Osmotic pressure
What is the most common temperature for bacteria growth?
37 degrees
What is a mesophile bacterias range of temperature?
20-45 degrees
What temperatures do thermophile and psycrophiles prefer?
Psyco- 15
Thermo- 60
What does a microaerophlile require in terms of O2?
Oxygen in small amounts
What are obligate, aerotolerant and facultative anaerobes?
Obligate- strict killed by O2
Aerotolerant- don’t use O2 but not killed by it
Facultative- can grow with or without
What is a con of refrigeration, freezing, boiling and vacuum packing?
Refrigeration- some still grow
Freeze- survivors multiply rapidly when thawed
Boiling- endospores survive
Vacc- very selective
How is must flash pasteurised and UHT produced?
Flash- 72c for 15 seconds
UHT- 140c for 1 sec
What are the normal conditions of an autoclave?
121.5c dore 15 mins
How can things be sterilised?
Airfiltration, Gamma radiation, UV light, Chemical methods
